Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

12 files changed, 3387 insertions, 0 deletions

diff --git a/dom/media/webm/EbmlComposer.cpp b/dom/media/webm/EbmlComposer.cpp
new file mode 100644
index 0000000000..e3f04fd89b
--- /dev/null
+++ b/dom/media/webm/EbmlComposer.cpp
@@ -0,0 +1,185 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "EbmlComposer.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/EndianUtils.h"
+#include "libmkv/EbmlIDs.h"
+#include "libmkv/EbmlWriter.h"
+#include "libmkv/WebMElement.h"
+#include "prtime.h"
+#include "limits.h"
+
+namespace mozilla {
+
+// Timecode scale in nanoseconds
+constexpr unsigned long TIME_CODE_SCALE = 1000000;
+// The WebM header size without audio CodecPrivateData
+constexpr int32_t DEFAULT_HEADER_SIZE = 1024;
+// Number of milliseconds after which we flush audio-only clusters
+constexpr int32_t FLUSH_AUDIO_ONLY_AFTER_MS = 1000;
+
+void EbmlComposer::GenerateHeader() {
+  MOZ_RELEASE_ASSERT(!mMetadataFinished);
+  MOZ_RELEASE_ASSERT(mHasAudio || mHasVideo);
+
+  // Write the EBML header.
+  EbmlGlobal ebml;
+  // The WEbM header default size usually smaller than 1k.
+  auto buffer =
+      MakeUnique<uint8_t[]>(DEFAULT_HEADER_SIZE + mCodecPrivateData.Length());
+  ebml.buf = buffer.get();
+  ebml.offset = 0;
+  writeHeader(&ebml);
+  {
+    EbmlLoc segEbmlLoc, ebmlLocseg, ebmlLoc;
+    Ebml_StartSubElement(&ebml, &segEbmlLoc, Segment);
+    {
+      Ebml_StartSubElement(&ebml, &ebmlLocseg, SeekHead);
+      // Todo: We don't know the exact sizes of encoded data and
+      // ignore this section.
+      Ebml_EndSubElement(&ebml, &ebmlLocseg);
+      writeSegmentInformation(&ebml, &ebmlLoc, TIME_CODE_SCALE, 0);
+      {
+        EbmlLoc trackLoc;
+        Ebml_StartSubElement(&ebml, &trackLoc, Tracks);
+        {
+          // Video
+          if (mWidth > 0 && mHeight > 0) {
+            writeVideoTrack(&ebml, 0x1, 0, "V_VP8", mWidth, mHeight,
+                            mDisplayWidth, mDisplayHeight);
+          }
+          // Audio
+          if (mCodecPrivateData.Length() > 0) {
+            // Extract the pre-skip from mCodecPrivateData
+            // then convert it to nanoseconds.
+            // For more details see
+            // https://tools.ietf.org/html/rfc7845#section-4.2
+            uint64_t codecDelay = (uint64_t)LittleEndian::readUint16(
+                                      mCodecPrivateData.Elements() + 10) *
+                                  PR_NSEC_PER_SEC / 48000;
+            // Fixed 80ms, convert into nanoseconds.
+            uint64_t seekPreRoll = 80 * PR_NSEC_PER_MSEC;
+            writeAudioTrack(&ebml, 0x2, 0x0, "A_OPUS", mSampleFreq, mChannels,
+                            codecDelay, seekPreRoll,
+                            mCodecPrivateData.Elements(),
+                            mCodecPrivateData.Length());
+          }
+        }
+        Ebml_EndSubElement(&ebml, &trackLoc);
+      }
+    }
+    // The Recording length is unknown and
+    // ignore write the whole Segment element size
+  }
+  MOZ_ASSERT(ebml.offset <= DEFAULT_HEADER_SIZE + mCodecPrivateData.Length(),
+             "write more data > EBML_BUFFER_SIZE");
+  auto block = mBuffer.AppendElement();
+  block->SetLength(ebml.offset);
+  memcpy(block->Elements(), ebml.buf, ebml.offset);
+  mMetadataFinished = true;
+}
+
+nsresult EbmlComposer::WriteSimpleBlock(EncodedFrame* aFrame) {
+  MOZ_RELEASE_ASSERT(mMetadataFinished);
+  auto frameType = aFrame->mFrameType;
+  const bool isVP8IFrame = (frameType == EncodedFrame::FrameType::VP8_I_FRAME);
+  const bool isVP8PFrame = (frameType == EncodedFrame::FrameType::VP8_P_FRAME);
+  const bool isOpus = (frameType == EncodedFrame::FrameType::OPUS_AUDIO_FRAME);
+
+  MOZ_ASSERT_IF(isVP8IFrame, mHasVideo);
+  MOZ_ASSERT_IF(isVP8PFrame, mHasVideo);
+  MOZ_ASSERT_IF(isOpus, mHasAudio);
+
+  if (isVP8PFrame && !mHasWrittenCluster) {
+    // We ensure there is a cluster header and an I-frame prior to any P-frame.
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  int64_t timeCode = aFrame->mTime.ToMicroseconds() / PR_USEC_PER_MSEC -
+                     mCurrentClusterTimecode;
+
+  const bool needClusterHeader =
+      !mHasWrittenCluster ||
+      (!mHasVideo && timeCode >= FLUSH_AUDIO_ONLY_AFTER_MS) || isVP8IFrame;
+
+  auto block = mBuffer.AppendElement();
+  block->SetLength(aFrame->mFrameData->Length() + DEFAULT_HEADER_SIZE);
+
+  EbmlGlobal ebml;
+  ebml.offset = 0;
+  ebml.buf = block->Elements();
+
+  if (needClusterHeader) {
+    mHasWrittenCluster = true;
+    EbmlLoc ebmlLoc;
+    // This starts the Cluster element. Note that we never end this element
+    // through Ebml_EndSubElement. What the ending would allow us to do is write
+    // the full length of the cluster in the element header. That would also
+    // force us to keep the entire cluster in memory until we know where it
+    // ends. Now it instead ends through the start of the next cluster. This
+    // allows us to stream the muxed data with much lower latency than if we
+    // would have to wait for clusters to end.
+    Ebml_StartSubElement(&ebml, &ebmlLoc, Cluster);
+    // if timeCode didn't under/overflow before, it shouldn't after this
+    mCurrentClusterTimecode = aFrame->mTime.ToMicroseconds() / PR_USEC_PER_MSEC;
+    Ebml_SerializeUnsigned(&ebml, Timecode, mCurrentClusterTimecode);
+
+    // Can't under-/overflow now
+    timeCode = 0;
+  }
+
+  if (MOZ_UNLIKELY(timeCode < SHRT_MIN || timeCode > SHRT_MAX)) {
+    MOZ_CRASH_UNSAFE_PRINTF(
+        "Invalid cluster timecode! audio=%d, video=%d, timeCode=%" PRId64
+        "ms, currentClusterTimecode=%" PRIu64 "ms",
+        mHasAudio, mHasVideo, timeCode, mCurrentClusterTimecode);
+  }
+
+  writeSimpleBlock(&ebml, isOpus ? 0x2 : 0x1, static_cast<short>(timeCode),
+                   isVP8IFrame, 0, 0,
+                   (unsigned char*)aFrame->mFrameData->Elements(),
+                   aFrame->mFrameData->Length());
+  MOZ_ASSERT(ebml.offset <= DEFAULT_HEADER_SIZE + aFrame->mFrameData->Length(),
+             "write more data > EBML_BUFFER_SIZE");
+  block->SetLength(ebml.offset);
+
+  return NS_OK;
+}
+
+void EbmlComposer::SetVideoConfig(uint32_t aWidth, uint32_t aHeight,
+                                  uint32_t aDisplayWidth,
+                                  uint32_t aDisplayHeight) {
+  MOZ_RELEASE_ASSERT(!mMetadataFinished);
+  MOZ_ASSERT(aWidth > 0, "Width should > 0");
+  MOZ_ASSERT(aHeight > 0, "Height should > 0");
+  MOZ_ASSERT(aDisplayWidth > 0, "DisplayWidth should > 0");
+  MOZ_ASSERT(aDisplayHeight > 0, "DisplayHeight should > 0");
+  mWidth = aWidth;
+  mHeight = aHeight;
+  mDisplayWidth = aDisplayWidth;
+  mDisplayHeight = aDisplayHeight;
+  mHasVideo = true;
+}
+
+void EbmlComposer::SetAudioConfig(uint32_t aSampleFreq, uint32_t aChannels) {
+  MOZ_RELEASE_ASSERT(!mMetadataFinished);
+  MOZ_ASSERT(aSampleFreq > 0, "SampleFreq should > 0");
+  MOZ_ASSERT(aChannels > 0, "Channels should > 0");
+  mSampleFreq = aSampleFreq;
+  mChannels = aChannels;
+  mHasAudio = true;
+}
+
+void EbmlComposer::ExtractBuffer(nsTArray<nsTArray<uint8_t> >* aDestBufs,
+                                 uint32_t aFlag) {
+  if (!mMetadataFinished) {
+    return;
+  }
+  aDestBufs->AppendElements(std::move(mBuffer));
+  MOZ_ASSERT(mBuffer.IsEmpty());
+}
+
+}  // namespace mozilla
diff --git a/dom/media/webm/EbmlComposer.h b/dom/media/webm/EbmlComposer.h
new file mode 100644
index 0000000000..a037e4ef8b
--- /dev/null
+++ b/dom/media/webm/EbmlComposer.h
@@ -0,0 +1,81 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef EbmlComposer_h_
+#define EbmlComposer_h_
+#include "nsTArray.h"
+#include "ContainerWriter.h"
+
+namespace mozilla {
+
+/*
+ * A WebM muxer helper for package the valid WebM format.
+ */
+class EbmlComposer {
+ public:
+  EbmlComposer() = default;
+  /*
+   * Assign the parameters which header requires. These can be called multiple
+   * times to change paramter values until GenerateHeader() is called, when this
+   * becomes illegal to call again.
+   */
+  void SetVideoConfig(uint32_t aWidth, uint32_t aHeight, uint32_t aDisplayWidth,
+                      uint32_t aDisplayHeight);
+  void SetAudioConfig(uint32_t aSampleFreq, uint32_t aChannels);
+  /*
+   * Set the CodecPrivateData for writing in header.
+   */
+  void SetAudioCodecPrivateData(nsTArray<uint8_t>& aBufs) {
+    mCodecPrivateData.AppendElements(aBufs);
+  }
+  /*
+   * Generate the whole WebM header with the configured tracks, and make
+   * available to ExtractBuffer. Must only be called once.
+   */
+  void GenerateHeader();
+  /*
+   * Insert media encoded buffer into muxer and it would be package
+   * into SimpleBlock. If no cluster is opened, new cluster will start for
+   * writing. Frames passed to this function should already have any codec delay
+   * applied.
+   */
+  nsresult WriteSimpleBlock(EncodedFrame* aFrame);
+  /*
+   * Get valid cluster data.
+   */
+  void ExtractBuffer(nsTArray<nsTArray<uint8_t>>* aDestBufs,
+                     uint32_t aFlag = 0);
+
+ private:
+  // True once we have written the first cluster header. We cannot serialize any
+  // P-frames until this is true, since we start a new cluster every I-frame.
+  bool mHasWrittenCluster = false;
+  // The timecode of the cluster.
+  uint64_t mCurrentClusterTimecode = 0;
+
+  // Written data to be flushed out by ExtractBuffer().
+  nsTArray<nsTArray<uint8_t>> mBuffer;
+
+  // True when Metadata has been serialized into mBuffer.
+  bool mMetadataFinished = false;
+
+  // Video configuration
+  int mWidth = 0;
+  int mHeight = 0;
+  int mDisplayWidth = 0;
+  int mDisplayHeight = 0;
+  bool mHasVideo = false;
+
+  // Audio configuration
+  float mSampleFreq = 0;
+  int mChannels = 0;
+  bool mHasAudio = false;
+  // Audio codec specific header data.
+  nsTArray<uint8_t> mCodecPrivateData;
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/dom/media/webm/NesteggPacketHolder.h b/dom/media/webm/NesteggPacketHolder.h
new file mode 100644
index 0000000000..7c74f752d3
--- /dev/null
+++ b/dom/media/webm/NesteggPacketHolder.h
@@ -0,0 +1,135 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#if !defined(NesteggPacketHolder_h_)
+#  define NesteggPacketHolder_h_
+
+#  include <deque>
+#  include <stdint.h>
+#  include "nsAutoRef.h"
+#  include "nestegg/nestegg.h"
+
+namespace mozilla {
+
+// Holds a nestegg_packet, and its file offset. This is needed so we
+// know the offset in the file we've played up to, in order to calculate
+// whether it's likely we can play through to the end without needing
+// to stop to buffer, given the current download rate.
+class NesteggPacketHolder {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(NesteggPacketHolder)
+  NesteggPacketHolder()
+      : mPacket(nullptr),
+        mOffset(-1),
+        mTimestamp(-1),
+        mDuration(-1),
+        mTrack(0),
+        mIsKeyframe(false) {}
+
+  bool Init(nestegg_packet* aPacket, int64_t aOffset, unsigned aTrack,
+            bool aIsKeyframe) {
+    uint64_t timestamp_ns;
+    if (nestegg_packet_tstamp(aPacket, &timestamp_ns) == -1) {
+      return false;
+    }
+
+    // We store the timestamp as signed microseconds so that it's easily
+    // comparable to other timestamps we have in the system.
+    mTimestamp = timestamp_ns / 1000;
+    mPacket = aPacket;
+    mOffset = aOffset;
+    mTrack = aTrack;
+    mIsKeyframe = aIsKeyframe;
+
+    uint64_t duration_ns;
+    if (!nestegg_packet_duration(aPacket, &duration_ns)) {
+      mDuration = duration_ns / 1000;
+    }
+    return true;
+  }
+
+  nestegg_packet* Packet() {
+    MOZ_ASSERT(IsInitialized());
+    return mPacket;
+  }
+  int64_t Offset() {
+    MOZ_ASSERT(IsInitialized());
+    return mOffset;
+  }
+  int64_t Timestamp() {
+    MOZ_ASSERT(IsInitialized());
+    return mTimestamp;
+  }
+  int64_t Duration() {
+    MOZ_ASSERT(IsInitialized());
+    return mDuration;
+  }
+  unsigned Track() {
+    MOZ_ASSERT(IsInitialized());
+    return mTrack;
+  }
+  bool IsKeyframe() {
+    MOZ_ASSERT(IsInitialized());
+    return mIsKeyframe;
+  }
+
+ private:
+  ~NesteggPacketHolder() { nestegg_free_packet(mPacket); }
+
+  bool IsInitialized() { return mOffset >= 0; }
+
+  nestegg_packet* mPacket;
+
+  // Offset in bytes. This is the offset of the end of the Block
+  // which contains the packet.
+  int64_t mOffset;
+
+  // Packet presentation timestamp in microseconds.
+  int64_t mTimestamp;
+
+  // Packet duration in microseconds; -1 if unknown or retrieval failed.
+  int64_t mDuration;
+
+  // Track ID.
+  unsigned mTrack;
+
+  // Does this packet contain a keyframe?
+  bool mIsKeyframe;
+
+  // Copy constructor and assignment operator not implemented. Don't use them!
+  NesteggPacketHolder(const NesteggPacketHolder& aOther);
+  NesteggPacketHolder& operator=(NesteggPacketHolder const& aOther);
+};
+
+// Queue for holding nestegg packets.
+class WebMPacketQueue {
+ public:
+  int32_t GetSize() { return mQueue.size(); }
+
+  void Push(NesteggPacketHolder* aItem) { mQueue.push_back(aItem); }
+
+  void PushFront(NesteggPacketHolder* aItem) {
+    mQueue.push_front(std::move(aItem));
+  }
+
+  already_AddRefed<NesteggPacketHolder> PopFront() {
+    RefPtr<NesteggPacketHolder> result = std::move(mQueue.front());
+    mQueue.pop_front();
+    return result.forget();
+  }
+
+  void Reset() {
+    while (!mQueue.empty()) {
+      mQueue.pop_front();
+    }
+  }
+
+ private:
+  std::deque<RefPtr<NesteggPacketHolder>> mQueue;
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/dom/media/webm/WebMBufferedParser.cpp b/dom/media/webm/WebMBufferedParser.cpp
new file mode 100644
index 0000000000..114fd7df89
--- /dev/null
+++ b/dom/media/webm/WebMBufferedParser.cpp
@@ -0,0 +1,676 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WebMBufferedParser.h"
+
+#include <algorithm>
+
+#include "mozilla/CheckedInt.h"
+#include "nsAlgorithm.h"
+#include "nsThreadUtils.h"
+
+extern mozilla::LazyLogModule gMediaDemuxerLog;
+#define WEBM_DEBUG(arg, ...)                          \
+  MOZ_LOG(gMediaDemuxerLog, mozilla::LogLevel::Debug, \
+          ("WebMBufferedParser(%p)::%s: " arg, this, __func__, ##__VA_ARGS__))
+
+namespace mozilla {
+
+static uint32_t VIntLength(unsigned char aFirstByte, uint32_t* aMask) {
+  uint32_t count = 1;
+  uint32_t mask = 1 << 7;
+  while (count < 8) {
+    if ((aFirstByte & mask) != 0) {
+      break;
+    }
+    mask >>= 1;
+    count += 1;
+  }
+  if (aMask) {
+    *aMask = mask;
+  }
+  NS_ASSERTION(count >= 1 && count <= 8, "Insane VInt length.");
+  return count;
+}
+
+constexpr uint8_t EBML_MAX_ID_LENGTH_DEFAULT = 4;
+constexpr uint8_t EBML_MAX_SIZE_LENGTH_DEFAULT = 8;
+
+WebMBufferedParser::WebMBufferedParser(int64_t aOffset)
+    : mStartOffset(aOffset),
+      mCurrentOffset(aOffset),
+      mInitEndOffset(-1),
+      mBlockEndOffset(-1),
+      mState(READ_ELEMENT_ID),
+      mNextState(READ_ELEMENT_ID),
+      mVIntRaw(false),
+      mLastInitStartOffset(-1),
+      mLastInitSize(0),
+      mEBMLMaxIdLength(EBML_MAX_ID_LENGTH_DEFAULT),
+      mEBMLMaxSizeLength(EBML_MAX_SIZE_LENGTH_DEFAULT),
+      mClusterSyncPos(0),
+      mVIntLeft(0),
+      mBlockSize(0),
+      mClusterTimecode(0),
+      mClusterOffset(-1),
+      mClusterEndOffset(-1),
+      mBlockOffset(0),
+      mBlockTimecode(0),
+      mBlockTimecodeLength(0),
+      mSkipBytes(0),
+      mTimecodeScale(1000000),
+      mGotTimecodeScale(false),
+      mGotClusterTimecode(false) {
+  if (mStartOffset != 0) {
+    mState = FIND_CLUSTER_SYNC;
+  }
+}
+
+MediaResult WebMBufferedParser::Append(const unsigned char* aBuffer,
+                                       uint32_t aLength,
+                                       nsTArray<WebMTimeDataOffset>& aMapping) {
+  static const uint32_t EBML_ID = 0x1a45dfa3;
+  static const uint32_t SEGMENT_ID = 0x18538067;
+  static const uint32_t SEGINFO_ID = 0x1549a966;
+  static const uint32_t TRACKS_ID = 0x1654AE6B;
+  static const uint32_t CLUSTER_ID = 0x1f43b675;
+  static const uint32_t TIMECODESCALE_ID = 0x2ad7b1;
+  static const unsigned char TIMECODE_ID = 0xe7;
+  static const unsigned char BLOCKGROUP_ID = 0xa0;
+  static const unsigned char BLOCK_ID = 0xa1;
+  static const unsigned char SIMPLEBLOCK_ID = 0xa3;
+  static const uint16_t EBML_MAX_ID_LENGTH_ID = 0x42f2;
+  static const uint16_t EBML_MAX_SIZE_LENGTH_ID = 0x42f3;
+  static const uint32_t BLOCK_TIMECODE_LENGTH = 2;
+
+  static const unsigned char CLUSTER_SYNC_ID[] = {0x1f, 0x43, 0xb6, 0x75};
+
+  const unsigned char* p = aBuffer;
+
+  // Parse each byte in aBuffer one-by-one, producing timecodes and updating
+  // aMapping as we go.  Parser pauses at end of stream (which may be at any
+  // point within the parse) and resumes parsing the next time Append is
+  // called with new data.
+  while (p < aBuffer + aLength) {
+    switch (mState) {
+      case READ_ELEMENT_ID:
+        mVIntRaw = true;
+        mState = READ_VINT;
+        mNextState = READ_ELEMENT_SIZE;
+        break;
+      case READ_ELEMENT_SIZE:
+        if (mVInt.mLength > mEBMLMaxIdLength) {
+          nsPrintfCString detail("Invalid element id of length %" PRIu64,
+                                 mVInt.mLength);
+          WEBM_DEBUG("%s", detail.get());
+          return MediaResult(NS_ERROR_FAILURE, detail);
+        }
+        mVIntRaw = false;
+        mElement.mID = mVInt;
+        mState = READ_VINT;
+        mNextState = PARSE_ELEMENT;
+        break;
+      case FIND_CLUSTER_SYNC:
+        if (*p++ == CLUSTER_SYNC_ID[mClusterSyncPos]) {
+          mClusterSyncPos += 1;
+        } else {
+          mClusterSyncPos = 0;
+        }
+        if (mClusterSyncPos == sizeof(CLUSTER_SYNC_ID)) {
+          mVInt.mValue = CLUSTER_ID;
+          mVInt.mLength = sizeof(CLUSTER_SYNC_ID);
+          mState = READ_ELEMENT_SIZE;
+        }
+        break;
+      case PARSE_ELEMENT:
+        if (mVInt.mLength > mEBMLMaxSizeLength) {
+          nsPrintfCString detail("Invalid element size of length %" PRIu64,
+                                 mVInt.mLength);
+          WEBM_DEBUG("%s", detail.get());
+          return MediaResult(NS_ERROR_FAILURE, detail);
+        }
+        mElement.mSize = mVInt;
+        switch (mElement.mID.mValue) {
+          case SEGMENT_ID:
+            mState = READ_ELEMENT_ID;
+            break;
+          case SEGINFO_ID:
+            mGotTimecodeScale = true;
+            mState = READ_ELEMENT_ID;
+            break;
+          case TIMECODE_ID:
+            mVInt = VInt();
+            mVIntLeft = mElement.mSize.mValue;
+            mState = READ_VINT_REST;
+            mNextState = READ_CLUSTER_TIMECODE;
+            break;
+          case TIMECODESCALE_ID:
+            mVInt = VInt();
+            mVIntLeft = mElement.mSize.mValue;
+            mState = READ_VINT_REST;
+            mNextState = READ_TIMECODESCALE;
+            break;
+          case CLUSTER_ID:
+            mClusterOffset = mCurrentOffset + (p - aBuffer) -
+                             (mElement.mID.mLength + mElement.mSize.mLength);
+            // Handle "unknown" length;
+            if (mElement.mSize.mValue + 1 !=
+                uint64_t(1) << (mElement.mSize.mLength * 7)) {
+              mClusterEndOffset = mClusterOffset + mElement.mID.mLength +
+                                  mElement.mSize.mLength +
+                                  mElement.mSize.mValue;
+            } else {
+              mClusterEndOffset = -1;
+            }
+            mGotClusterTimecode = false;
+            mState = READ_ELEMENT_ID;
+            break;
+          case BLOCKGROUP_ID:
+            mState = READ_ELEMENT_ID;
+            break;
+          case SIMPLEBLOCK_ID:
+            /* FALLTHROUGH */
+          case BLOCK_ID:
+            if (!mGotClusterTimecode) {
+              WEBM_DEBUG(
+                  "The Timecode element must appear before any Block or "
+                  "SimpleBlock elements in a Cluster");
+              return MediaResult(
+                  NS_ERROR_FAILURE,
+                  "The Timecode element must appear before any Block or "
+                  "SimpleBlock elements in a Cluster");
+            }
+            mBlockSize = mElement.mSize.mValue;
+            mBlockTimecode = 0;
+            mBlockTimecodeLength = BLOCK_TIMECODE_LENGTH;
+            mBlockOffset = mCurrentOffset + (p - aBuffer) -
+                           (mElement.mID.mLength + mElement.mSize.mLength);
+            mState = READ_VINT;
+            mNextState = READ_BLOCK_TIMECODE;
+            break;
+          case TRACKS_ID:
+            mSkipBytes = mElement.mSize.mValue;
+            mState = CHECK_INIT_FOUND;
+            break;
+          case EBML_MAX_ID_LENGTH_ID:
+          case EBML_MAX_SIZE_LENGTH_ID:
+            if (int64_t currentOffset = mCurrentOffset + (p - aBuffer);
+                currentOffset < mLastInitStartOffset ||
+                currentOffset >= mLastInitStartOffset + mLastInitSize) {
+              nsPrintfCString str("Unexpected %s outside init segment",
+                                  mElement.mID.mValue == EBML_MAX_ID_LENGTH_ID
+                                      ? "EBMLMaxIdLength"
+                                      : "EBMLMaxSizeLength");
+              WEBM_DEBUG("%s", str.get());
+              return MediaResult(NS_ERROR_FAILURE, str);
+            }
+            if (mElement.mSize.mValue > 8) {
+              // https://www.rfc-editor.org/rfc/rfc8794.html (EBML):
+              //   An Unsigned Integer Element MUST declare a length from zero
+              //   to eight octets.
+              nsPrintfCString str("Bad length of %s size",
+                                  mElement.mID.mValue == EBML_MAX_ID_LENGTH_ID
+                                      ? "EBMLMaxIdLength"
+                                      : "EBMLMaxSizeLength");
+              WEBM_DEBUG("%s", str.get());
+              return MediaResult(NS_ERROR_FAILURE, str);
+            }
+            mVInt = VInt();
+            mVIntLeft = mElement.mSize.mValue;
+            mState = READ_VINT_REST;
+            mNextState = mElement.mID.mValue == EBML_MAX_ID_LENGTH_ID
+                             ? READ_EBML_MAX_ID_LENGTH
+                             : READ_EBML_MAX_SIZE_LENGTH;
+            break;
+          case EBML_ID:
+            mLastInitStartOffset =
+                mCurrentOffset + (p - aBuffer) -
+                (mElement.mID.mLength + mElement.mSize.mLength);
+            mLastInitSize = mElement.mSize.mValue;
+            mEBMLMaxIdLength = EBML_MAX_ID_LENGTH_DEFAULT;
+            mEBMLMaxSizeLength = EBML_MAX_SIZE_LENGTH_DEFAULT;
+            mState = READ_ELEMENT_ID;
+            break;
+          default:
+            mSkipBytes = mElement.mSize.mValue;
+            mState = SKIP_DATA;
+            mNextState = READ_ELEMENT_ID;
+            break;
+        }
+        break;
+      case READ_VINT: {
+        unsigned char c = *p++;
+        uint32_t mask;
+        mVInt.mLength = VIntLength(c, &mask);
+        mVIntLeft = mVInt.mLength - 1;
+        mVInt.mValue = mVIntRaw ? c : c & ~mask;
+        mState = READ_VINT_REST;
+        break;
+      }
+      case READ_VINT_REST:
+        if (mVIntLeft) {
+          mVInt.mValue <<= 8;
+          mVInt.mValue |= *p++;
+          mVIntLeft -= 1;
+        } else {
+          mState = mNextState;
+        }
+        break;
+      case READ_TIMECODESCALE:
+        if (!mGotTimecodeScale) {
+          WEBM_DEBUG("Should get the SegmentInfo first");
+          return MediaResult(NS_ERROR_FAILURE,
+                             "TimecodeScale appeared before SegmentInfo");
+        }
+        mTimecodeScale = mVInt.mValue;
+        mState = READ_ELEMENT_ID;
+        break;
+      case READ_CLUSTER_TIMECODE:
+        mClusterTimecode = mVInt.mValue;
+        mGotClusterTimecode = true;
+        mState = READ_ELEMENT_ID;
+        break;
+      case READ_BLOCK_TIMECODE:
+        if (mBlockTimecodeLength) {
+          mBlockTimecode <<= 8;
+          mBlockTimecode |= *p++;
+          mBlockTimecodeLength -= 1;
+        } else {
+          // It's possible we've parsed this data before, so avoid inserting
+          // duplicate WebMTimeDataOffset entries.
+          {
+            int64_t endOffset = mBlockOffset + mBlockSize +
+                                mElement.mID.mLength + mElement.mSize.mLength;
+            uint32_t idx = aMapping.IndexOfFirstElementGt(endOffset);
+            if (idx == 0 || aMapping[idx - 1] != endOffset) {
+              // Don't insert invalid negative timecodes.
+              if (mBlockTimecode >= 0 ||
+                  mClusterTimecode >= uint16_t(abs(mBlockTimecode))) {
+                if (!mGotTimecodeScale) {
+                  WEBM_DEBUG("Should get the TimecodeScale first");
+                  return MediaResult(NS_ERROR_FAILURE,
+                                     "Timecode appeared before SegmentInfo");
+                }
+                uint64_t absTimecode = mClusterTimecode + mBlockTimecode;
+                absTimecode *= mTimecodeScale;
+                // Avoid creating an entry if the timecode is out of order
+                // (invalid according to the WebM specification) so that
+                // ordering invariants of aMapping are not violated.
+                if (idx == 0 || aMapping[idx - 1].mTimecode <= absTimecode ||
+                    (idx + 1 < aMapping.Length() &&
+                     aMapping[idx + 1].mTimecode >= absTimecode)) {
+                  WebMTimeDataOffset entry(endOffset, absTimecode,
+                                           mLastInitStartOffset, mClusterOffset,
+                                           mClusterEndOffset);
+                  aMapping.InsertElementAt(idx, entry);
+                } else {
+                  WEBM_DEBUG("Out of order timecode %" PRIu64
+                             " in Cluster at %" PRId64 " ignored",
+                             absTimecode, mClusterOffset);
+                }
+              }
+            }
+          }
+
+          // Skip rest of block header and the block's payload.
+          mBlockSize -= mVInt.mLength;
+          mBlockSize -= BLOCK_TIMECODE_LENGTH;
+          mSkipBytes = uint32_t(mBlockSize);
+          mState = SKIP_DATA;
+          mNextState = READ_ELEMENT_ID;
+        }
+        break;
+      case READ_EBML_MAX_ID_LENGTH:
+        if (mElement.mSize.mLength == 0) {
+          // https://www.rfc-editor.org/rfc/rfc8794.html (EBML):
+          //   If an Empty Element has a default value declared, then the EBML
+          //   Reader MUST interpret the value of the Empty Element as the
+          //   default value.
+          mVInt.mValue = EBML_MAX_ID_LENGTH_DEFAULT;
+        }
+        if (mVInt.mValue < 4 || mVInt.mValue > 5) {
+          // https://www.ietf.org/archive/id/draft-ietf-cellar-matroska-13.html
+          // (Matroska):
+          //   The EBMLMaxIDLength of the EBML Header MUST be "4".
+          //
+          // Also Matroska:
+          //   Element IDs are encoded using the VINT mechanism described in
+          //   Section 4 of [RFC8794] and can be between one and five octets
+          //   long. Five-octet-long Element IDs are possible only if declared
+          //   in the EBML header.
+          nsPrintfCString detail("Invalid EMBLMaxIdLength %" PRIu64,
+                                 mVInt.mValue);
+          WEBM_DEBUG("%s", detail.get());
+          return MediaResult(NS_ERROR_FAILURE, detail);
+        }
+        mEBMLMaxIdLength = mVInt.mValue;
+        mState = READ_ELEMENT_ID;
+        break;
+      case READ_EBML_MAX_SIZE_LENGTH:
+        if (mElement.mSize.mLength == 0) {
+          // https://www.rfc-editor.org/rfc/rfc8794.html (EBML):
+          //   If an Empty Element has a default value declared, then the EBML
+          //   Reader MUST interpret the value of the Empty Element as the
+          //   default value.
+          mVInt.mValue = EBML_MAX_SIZE_LENGTH_DEFAULT;
+        }
+        if (mVInt.mValue < 1 || mVInt.mValue > 8) {
+          // https://www.ietf.org/archive/id/draft-ietf-cellar-matroska-13.html
+          // (Matroska):
+          //   The EBMLMaxSizeLength of the EBML Header MUST be between "1" and
+          //   "8" inclusive.
+          nsPrintfCString detail("Invalid EMBLMaxSizeLength %" PRIu64,
+                                 mVInt.mValue);
+          WEBM_DEBUG("%s", detail.get());
+          return MediaResult(NS_ERROR_FAILURE, detail);
+        }
+        mEBMLMaxSizeLength = mVInt.mValue;
+        mState = READ_ELEMENT_ID;
+        break;
+      case SKIP_DATA:
+        if (mSkipBytes) {
+          uint32_t left = aLength - (p - aBuffer);
+          left = std::min(left, mSkipBytes);
+          p += left;
+          mSkipBytes -= left;
+        }
+        if (!mSkipBytes) {
+          mBlockEndOffset = mCurrentOffset + (p - aBuffer);
+          mState = mNextState;
+        }
+        break;
+      case CHECK_INIT_FOUND:
+        if (mSkipBytes) {
+          uint32_t left = aLength - (p - aBuffer);
+          left = std::min(left, mSkipBytes);
+          p += left;
+          mSkipBytes -= left;
+        }
+        if (!mSkipBytes) {
+          if (mInitEndOffset < 0) {
+            mInitEndOffset = mCurrentOffset + (p - aBuffer);
+            mBlockEndOffset = mCurrentOffset + (p - aBuffer);
+          }
+          mState = READ_ELEMENT_ID;
+        }
+        break;
+    }
+  }
+
+  NS_ASSERTION(p == aBuffer + aLength, "Must have parsed to end of data.");
+  mCurrentOffset += aLength;
+
+  return NS_OK;
+}
+
+int64_t WebMBufferedParser::EndSegmentOffset(int64_t aOffset) {
+  if (mLastInitStartOffset > aOffset || mClusterOffset > aOffset) {
+    return std::min(
+        mLastInitStartOffset >= 0 ? mLastInitStartOffset : INT64_MAX,
+        mClusterOffset >= 0 ? mClusterOffset : INT64_MAX);
+  }
+  return mBlockEndOffset;
+}
+
+int64_t WebMBufferedParser::GetClusterOffset() const { return mClusterOffset; }
+
+// SyncOffsetComparator and TimeComparator are slightly confusing, in that
+// the nsTArray they're used with (mTimeMapping) is sorted by mEndOffset and
+// these comparators are used on the other fields of WebMTimeDataOffset.
+// This is only valid because timecodes are required to be monotonically
+// increasing within a file (thus establishing an ordering relationship with
+// mTimecode), and mEndOffset is derived from mSyncOffset.
+struct SyncOffsetComparator {
+  bool Equals(const WebMTimeDataOffset& a, const int64_t& b) const {
+    return a.mSyncOffset == b;
+  }
+
+  bool LessThan(const WebMTimeDataOffset& a, const int64_t& b) const {
+    return a.mSyncOffset < b;
+  }
+};
+
+struct TimeComparator {
+  bool Equals(const WebMTimeDataOffset& a, const uint64_t& b) const {
+    return a.mTimecode == b;
+  }
+
+  bool LessThan(const WebMTimeDataOffset& a, const uint64_t& b) const {
+    return a.mTimecode < b;
+  }
+};
+
+bool WebMBufferedState::CalculateBufferedForRange(int64_t aStartOffset,
+                                                  int64_t aEndOffset,
+                                                  uint64_t* aStartTime,
+                                                  uint64_t* aEndTime) {
+  MutexAutoLock lock(mMutex);
+
+  // Find the first WebMTimeDataOffset at or after aStartOffset.
+  uint32_t start = mTimeMapping.IndexOfFirstElementGt(aStartOffset - 1,
+                                                      SyncOffsetComparator());
+  if (start == mTimeMapping.Length()) {
+    return false;
+  }
+
+  // Find the first WebMTimeDataOffset at or before aEndOffset.
+  uint32_t end = mTimeMapping.IndexOfFirstElementGt(aEndOffset);
+  if (end > 0) {
+    end -= 1;
+  }
+
+  // Range is empty.
+  if (end <= start) {
+    return false;
+  }
+
+  NS_ASSERTION(mTimeMapping[start].mSyncOffset >= aStartOffset &&
+                   mTimeMapping[end].mEndOffset <= aEndOffset,
+               "Computed time range must lie within data range.");
+  if (start > 0) {
+    NS_ASSERTION(mTimeMapping[start - 1].mSyncOffset < aStartOffset,
+                 "Must have found least WebMTimeDataOffset for start");
+  }
+  if (end < mTimeMapping.Length() - 1) {
+    NS_ASSERTION(mTimeMapping[end + 1].mEndOffset > aEndOffset,
+                 "Must have found greatest WebMTimeDataOffset for end");
+  }
+
+  MOZ_ASSERT(mTimeMapping[end].mTimecode >= mTimeMapping[end - 1].mTimecode);
+  uint64_t frameDuration =
+      mTimeMapping[end].mTimecode - mTimeMapping[end - 1].mTimecode;
+  *aStartTime = mTimeMapping[start].mTimecode;
+  CheckedUint64 endTime{mTimeMapping[end].mTimecode};
+  endTime += frameDuration;
+  if (!endTime.isValid()) {
+    WEBM_DEBUG("End time overflow during CalculateBufferedForRange.");
+    return false;
+  }
+  *aEndTime = endTime.value();
+  return true;
+}
+
+bool WebMBufferedState::GetOffsetForTime(uint64_t aTime, int64_t* aOffset) {
+  MutexAutoLock lock(mMutex);
+
+  if (mTimeMapping.IsEmpty()) {
+    return false;
+  }
+
+  uint64_t time = aTime;
+  if (time > 0) {
+    time = time - 1;
+  }
+  uint32_t idx = mTimeMapping.IndexOfFirstElementGt(time, TimeComparator());
+  if (idx == mTimeMapping.Length()) {
+    // Clamp to end
+    *aOffset = mTimeMapping[mTimeMapping.Length() - 1].mSyncOffset;
+  } else {
+    // Idx is within array or has been clamped to start
+    *aOffset = mTimeMapping[idx].mSyncOffset;
+  }
+  return true;
+}
+
+void WebMBufferedState::NotifyDataArrived(const unsigned char* aBuffer,
+                                          uint32_t aLength, int64_t aOffset) {
+  uint32_t idx = mRangeParsers.IndexOfFirstElementGt(aOffset - 1);
+  if (idx == 0 || !(mRangeParsers[idx - 1] == aOffset)) {
+    // If the incoming data overlaps an already parsed range, adjust the
+    // buffer so that we only reparse the new data.  It's also possible to
+    // have an overlap where the end of the incoming data is within an
+    // already parsed range, but we don't bother handling that other than by
+    // avoiding storing duplicate timecodes when the parser runs.
+    if (idx != mRangeParsers.Length() &&
+        mRangeParsers[idx].mStartOffset <= aOffset) {
+      // Complete overlap, skip parsing.
+      if (aOffset + aLength <= mRangeParsers[idx].mCurrentOffset) {
+        return;
+      }
+
+      // Partial overlap, adjust the buffer to parse only the new data.
+      int64_t adjust = mRangeParsers[idx].mCurrentOffset - aOffset;
+      NS_ASSERTION(adjust >= 0, "Overlap detection bug.");
+      aBuffer += adjust;
+      aLength -= uint32_t(adjust);
+    } else {
+      mRangeParsers.InsertElementAt(idx, WebMBufferedParser(aOffset));
+      if (idx != 0) {
+        mRangeParsers[idx].SetTimecodeScale(
+            mRangeParsers[0].GetTimecodeScale());
+      }
+    }
+  }
+
+  {
+    MutexAutoLock lock(mMutex);
+    mRangeParsers[idx].Append(aBuffer, aLength, mTimeMapping);
+  }
+
+  // Merge parsers with overlapping regions and clean up the remnants.
+  uint32_t i = 0;
+  while (i + 1 < mRangeParsers.Length()) {
+    if (mRangeParsers[i].mCurrentOffset >= mRangeParsers[i + 1].mStartOffset) {
+      mRangeParsers[i + 1].mStartOffset = mRangeParsers[i].mStartOffset;
+      mRangeParsers[i + 1].mInitEndOffset = mRangeParsers[i].mInitEndOffset;
+      mRangeParsers.RemoveElementAt(i);
+    } else {
+      i += 1;
+    }
+  }
+
+  if (mRangeParsers.IsEmpty()) {
+    return;
+  }
+
+  MutexAutoLock lock(mMutex);
+  mLastBlockOffset = mRangeParsers.LastElement().mBlockEndOffset;
+}
+
+void WebMBufferedState::Reset() {
+  MutexAutoLock lock(mMutex);
+  mRangeParsers.Clear();
+  mTimeMapping.Clear();
+}
+
+void WebMBufferedState::UpdateIndex(const MediaByteRangeSet& aRanges,
+                                    MediaResource* aResource) {
+  for (uint32_t index = 0; index < aRanges.Length(); index++) {
+    const MediaByteRange& range = aRanges[index];
+    int64_t offset = range.mStart;
+    uint32_t length = range.mEnd - range.mStart;
+
+    uint32_t idx = mRangeParsers.IndexOfFirstElementGt(offset - 1);
+    if (!idx || !(mRangeParsers[idx - 1] == offset)) {
+      // If the incoming data overlaps an already parsed range, adjust the
+      // buffer so that we only reparse the new data.  It's also possible to
+      // have an overlap where the end of the incoming data is within an
+      // already parsed range, but we don't bother handling that other than by
+      // avoiding storing duplicate timecodes when the parser runs.
+      if (idx != mRangeParsers.Length() &&
+          mRangeParsers[idx].mStartOffset <= offset) {
+        // Complete overlap, skip parsing.
+        if (offset + length <= mRangeParsers[idx].mCurrentOffset) {
+          continue;
+        }
+
+        // Partial overlap, adjust the buffer to parse only the new data.
+        int64_t adjust = mRangeParsers[idx].mCurrentOffset - offset;
+        NS_ASSERTION(adjust >= 0, "Overlap detection bug.");
+        offset += adjust;
+        length -= uint32_t(adjust);
+      } else {
+        mRangeParsers.InsertElementAt(idx, WebMBufferedParser(offset));
+        if (idx) {
+          mRangeParsers[idx].SetTimecodeScale(
+              mRangeParsers[0].GetTimecodeScale());
+        }
+      }
+    }
+
+    MediaResourceIndex res(aResource);
+    while (length > 0) {
+      static const uint32_t BLOCK_SIZE = 1048576;
+      uint32_t block = std::min(length, BLOCK_SIZE);
+      RefPtr<MediaByteBuffer> bytes = res.CachedMediaReadAt(offset, block);
+      if (!bytes) {
+        break;
+      }
+      NotifyDataArrived(bytes->Elements(), bytes->Length(), offset);
+      length -= bytes->Length();
+      offset += bytes->Length();
+    }
+  }
+}
+
+int64_t WebMBufferedState::GetInitEndOffset() {
+  if (mRangeParsers.IsEmpty()) {
+    return -1;
+  }
+  return mRangeParsers[0].mInitEndOffset;
+}
+
+int64_t WebMBufferedState::GetLastBlockOffset() {
+  MutexAutoLock lock(mMutex);
+
+  return mLastBlockOffset;
+}
+
+bool WebMBufferedState::GetStartTime(uint64_t* aTime) {
+  MutexAutoLock lock(mMutex);
+
+  if (mTimeMapping.IsEmpty()) {
+    return false;
+  }
+
+  uint32_t idx = mTimeMapping.IndexOfFirstElementGt(0, SyncOffsetComparator());
+  if (idx == mTimeMapping.Length()) {
+    return false;
+  }
+
+  *aTime = mTimeMapping[idx].mTimecode;
+  return true;
+}
+
+bool WebMBufferedState::GetNextKeyframeTime(uint64_t aTime,
+                                            uint64_t* aKeyframeTime) {
+  MutexAutoLock lock(mMutex);
+  int64_t offset = 0;
+  bool rv = GetOffsetForTime(aTime, &offset);
+  if (!rv) {
+    return false;
+  }
+  uint32_t idx =
+      mTimeMapping.IndexOfFirstElementGt(offset, SyncOffsetComparator());
+  if (idx == mTimeMapping.Length()) {
+    return false;
+  }
+  *aKeyframeTime = mTimeMapping[idx].mTimecode;
+  return true;
+}
+}  // namespace mozilla
+
+#undef WEBM_DEBUG
diff --git a/dom/media/webm/WebMBufferedParser.h b/dom/media/webm/WebMBufferedParser.h
new file mode 100644
index 0000000000..bf553d8f24
--- /dev/null
+++ b/dom/media/webm/WebMBufferedParser.h
@@ -0,0 +1,309 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#if !defined(WebMBufferedParser_h_)
+#  define WebMBufferedParser_h_
+
+#  include "nsISupportsImpl.h"
+#  include "nsTArray.h"
+#  include "mozilla/Mutex.h"
+#  include "MediaResource.h"
+#  include "MediaResult.h"
+
+namespace mozilla {
+
+// Stores a stream byte offset and the scaled timecode of the block at
+// that offset.
+struct WebMTimeDataOffset {
+  WebMTimeDataOffset(int64_t aEndOffset, uint64_t aTimecode,
+                     int64_t aInitOffset, int64_t aSyncOffset,
+                     int64_t aClusterEndOffset)
+      : mEndOffset(aEndOffset),
+        mInitOffset(aInitOffset),
+        mSyncOffset(aSyncOffset),
+        mClusterEndOffset(aClusterEndOffset),
+        mTimecode(aTimecode) {}
+
+  bool operator==(int64_t aEndOffset) const { return mEndOffset == aEndOffset; }
+
+  bool operator!=(int64_t aEndOffset) const { return mEndOffset != aEndOffset; }
+
+  bool operator<(int64_t aEndOffset) const { return mEndOffset < aEndOffset; }
+
+  int64_t mEndOffset;
+  int64_t mInitOffset;
+  int64_t mSyncOffset;
+  int64_t mClusterEndOffset;
+  // In nanoseconds
+  uint64_t mTimecode;
+};
+
+// A simple WebM parser that produces data offset to timecode pairs as it
+// consumes blocks.  A new parser is created for each distinct range of data
+// received and begins parsing from the first WebM cluster within that
+// range.  Old parsers are destroyed when their range merges with a later
+// parser or an already parsed range.  The parser may start at any position
+// within the stream.
+struct WebMBufferedParser {
+  explicit WebMBufferedParser(int64_t aOffset);
+
+  uint32_t GetTimecodeScale() {
+    MOZ_ASSERT(mGotTimecodeScale);
+    return mTimecodeScale;
+  }
+
+  // Use this function when we would only feed media segment for the parser.
+  void AppendMediaSegmentOnly() { mGotTimecodeScale = true; }
+
+  // If this parser is not expected to parse a segment info, it must be told
+  // the appropriate timecode scale to use from elsewhere.
+  void SetTimecodeScale(uint32_t aTimecodeScale) {
+    mTimecodeScale = aTimecodeScale;
+    mGotTimecodeScale = true;
+  }
+
+  // Steps the parser through aLength bytes of data.  Always consumes
+  // aLength bytes.  Updates mCurrentOffset before returning.
+  // Returns false if an error was encountered.
+  MediaResult Append(const unsigned char* aBuffer, uint32_t aLength,
+                     nsTArray<WebMTimeDataOffset>& aMapping);
+
+  bool operator==(int64_t aOffset) const { return mCurrentOffset == aOffset; }
+
+  bool operator<(int64_t aOffset) const { return mCurrentOffset < aOffset; }
+
+  // Returns the start offset of the init (EBML) or media segment (Cluster)
+  // following the aOffset position. If none were found, returns
+  // mBlockEndOffset. This allows to determine the end of the interval containg
+  // aOffset.
+  int64_t EndSegmentOffset(int64_t aOffset);
+
+  // Return the Cluster offset, return -1 if we can't find the Cluster.
+  int64_t GetClusterOffset() const;
+
+  // The offset at which this parser started parsing.  Used to merge
+  // adjacent parsers, in which case the later parser adopts the earlier
+  // parser's mStartOffset.
+  int64_t mStartOffset;
+
+  // Current offset within the stream.  Updated in chunks as Append() consumes
+  // data.
+  int64_t mCurrentOffset;
+
+  // Tracks element's end offset. This indicates the end of the first init
+  // segment. Will only be set if a Segment Information has been found.
+  int64_t mInitEndOffset;
+
+  // End offset of the last block parsed.
+  // Will only be set if a complete block has been parsed.
+  int64_t mBlockEndOffset;
+
+ private:
+  enum State {
+    // Parser start state.  Expects to begin at a valid EBML element.  Move
+    // to READ_VINT with mVIntRaw true, then return to READ_ELEMENT_SIZE.
+    READ_ELEMENT_ID,
+
+    // Store element ID read into mVInt into mElement.mID.  Move to
+    // READ_VINT with mVIntRaw false, then return to PARSE_ELEMENT.
+    READ_ELEMENT_SIZE,
+
+    // Parser start state for parsers started at an arbitrary offset.  Scans
+    // forward for the first cluster, then move to READ_ELEMENT_ID.
+    FIND_CLUSTER_SYNC,
+
+    // Simplistic core of the parser.  Does not pay attention to nesting of
+    // elements.  Checks mElement for an element ID of interest, then moves
+    // to the next state as determined by the element ID.
+    PARSE_ELEMENT,
+
+    // Read the first byte of a variable length integer.  The first byte
+    // encodes both the variable integer's length and part of the value.
+    // The value read so far is stored in mVInt.mValue and the length is
+    // stored in mVInt.mLength.  The number of bytes left to read is stored
+    // in mVIntLeft.
+    READ_VINT,
+
+    // Reads the remaining mVIntLeft bytes into mVInt.mValue.
+    READ_VINT_REST,
+
+    // mVInt holds the parsed timecode scale, store it in mTimecodeScale,
+    // then return READ_ELEMENT_ID.
+    READ_TIMECODESCALE,
+
+    // mVInt holds the parsed cluster timecode, store it in
+    // mClusterTimecode, then return to READ_ELEMENT_ID.
+    READ_CLUSTER_TIMECODE,
+
+    // mBlockTimecodeLength holds the remaining length of the block timecode
+    // left to read.  Read each byte of the timecode into mBlockTimecode.
+    // Once complete, calculate the scaled timecode from the cluster
+    // timecode, block timecode, and timecode scale, and insert a
+    // WebMTimeDataOffset entry into aMapping if one is not already present
+    // for this offset.
+    READ_BLOCK_TIMECODE,
+
+    // mVInt holds the parsed EBMLMaxIdLength, store it in mEBMLMaxIdLength,
+    // then return to READ_ELEMENT_ID.
+    READ_EBML_MAX_ID_LENGTH,
+
+    // mVInt holds the parsed EBMLMaxSizeLength, store it in mEBMLMaxSizeLength,
+    // then return to READ_ELEMENT_ID.
+    READ_EBML_MAX_SIZE_LENGTH,
+
+    // Will skip the current tracks element and set mInitEndOffset if an init
+    // segment has been found.
+    // Currently, only assumes it's the end of the tracks element.
+    CHECK_INIT_FOUND,
+
+    // Skip mSkipBytes of data before resuming parse at mNextState.
+    SKIP_DATA,
+  };
+
+  // Current state machine action.
+  State mState;
+
+  // Next state machine action.  SKIP_DATA and READ_VINT_REST advance to
+  // mNextState when the current action completes.
+  State mNextState;
+
+  struct VInt {
+    VInt() : mValue(0), mLength(0) {}
+    uint64_t mValue;
+    uint64_t mLength;
+  };
+
+  struct EBMLElement {
+    uint64_t Length() { return mID.mLength + mSize.mLength; }
+    VInt mID;
+    VInt mSize;
+  };
+
+  EBMLElement mElement;
+
+  VInt mVInt;
+
+  bool mVIntRaw;
+
+  // EBML start offset. This indicates the start of the last init segment
+  // parsed. Will only be set if an EBML element has been found.
+  int64_t mLastInitStartOffset;
+
+  // EBML element size. This indicates the size of the body of the last init
+  // segment parsed. Will only be set if an EBML element has been found.
+  uint32_t mLastInitSize;
+
+  // EBML max id length is the max number of bytes allowed for an element id
+  // vint.
+  uint8_t mEBMLMaxIdLength;
+
+  // EBML max size length is the max number of bytes allowed for an element size
+  // vint.
+  uint8_t mEBMLMaxSizeLength;
+
+  // Current match position within CLUSTER_SYNC_ID.  Used to find sync
+  // within arbitrary data.
+  uint32_t mClusterSyncPos;
+
+  // Number of bytes of mVInt left to read.  mVInt is complete once this
+  // reaches 0.
+  uint32_t mVIntLeft;
+
+  // Size of the block currently being parsed.  Any unused data within the
+  // block is skipped once the block timecode has been parsed.
+  uint64_t mBlockSize;
+
+  // Cluster-level timecode.
+  uint64_t mClusterTimecode;
+
+  // Start offset of the cluster currently being parsed.  Used as the sync
+  // point offset for the offset-to-time mapping as each block timecode is
+  // been parsed. -1 if unknown.
+  int64_t mClusterOffset;
+
+  // End offset of the cluster currently being parsed. -1 if unknown.
+  int64_t mClusterEndOffset;
+
+  // Start offset of the block currently being parsed.  Used as the byte
+  // offset for the offset-to-time mapping once the block timecode has been
+  // parsed.
+  int64_t mBlockOffset;
+
+  // Block-level timecode.  This is summed with mClusterTimecode to produce
+  // an absolute timecode for the offset-to-time mapping.
+  int16_t mBlockTimecode;
+
+  // Number of bytes of mBlockTimecode left to read.
+  uint32_t mBlockTimecodeLength;
+
+  // Count of bytes left to skip before resuming parse at mNextState.
+  // Mostly used to skip block payload data after reading a block timecode.
+  uint32_t mSkipBytes;
+
+  // Timecode scale read from the segment info and used to scale absolute
+  // timecodes.
+  uint32_t mTimecodeScale;
+
+  // True if we read the timecode scale from the segment info or have
+  // confirmed that the default value is to be used.
+  bool mGotTimecodeScale;
+
+  // True if we've read the cluster time code.
+  bool mGotClusterTimecode;
+};
+
+class WebMBufferedState final {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WebMBufferedState)
+
+ public:
+  WebMBufferedState() : mMutex("WebMBufferedState"), mLastBlockOffset(-1) {
+    MOZ_COUNT_CTOR(WebMBufferedState);
+  }
+
+  void NotifyDataArrived(const unsigned char* aBuffer, uint32_t aLength,
+                         int64_t aOffset);
+  void Reset();
+  void UpdateIndex(const MediaByteRangeSet& aRanges, MediaResource* aResource);
+  bool CalculateBufferedForRange(int64_t aStartOffset, int64_t aEndOffset,
+                                 uint64_t* aStartTime, uint64_t* aEndTime);
+
+  // Returns true if mTimeMapping is not empty and sets aOffset to
+  // the latest offset for which decoding can resume without data
+  // dependencies to arrive at aTime. aTime will be clamped to the start
+  // of mTimeMapping if it is earlier than the first element, and to the end
+  // if later than the last
+  bool GetOffsetForTime(uint64_t aTime, int64_t* aOffset);
+
+  // Returns end offset of init segment or -1 if none found.
+  int64_t GetInitEndOffset();
+  // Returns the end offset of the last complete block or -1 if none found.
+  int64_t GetLastBlockOffset();
+
+  // Returns start time
+  bool GetStartTime(uint64_t* aTime);
+
+  // Returns keyframe for time
+  bool GetNextKeyframeTime(uint64_t aTime, uint64_t* aKeyframeTime);
+
+ private:
+  // Private destructor, to discourage deletion outside of Release():
+  MOZ_COUNTED_DTOR(WebMBufferedState)
+
+  // Synchronizes access to the mTimeMapping array and mLastBlockOffset.
+  Mutex mMutex;
+
+  // Sorted (by offset) map of data offsets to timecodes.  Populated
+  // on the main thread as data is received and parsed by WebMBufferedParsers.
+  nsTArray<WebMTimeDataOffset> mTimeMapping MOZ_GUARDED_BY(mMutex);
+  // The last complete block parsed. -1 if not set.
+  int64_t mLastBlockOffset MOZ_GUARDED_BY(mMutex);
+
+  // Sorted (by offset) live parser instances.  Main thread only.
+  nsTArray<WebMBufferedParser> mRangeParsers;
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/dom/media/webm/WebMDecoder.cpp b/dom/media/webm/WebMDecoder.cpp
new file mode 100644
index 0000000000..814eb8cb64
--- /dev/null
+++ b/dom/media/webm/WebMDecoder.cpp
@@ -0,0 +1,124 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WebMDecoder.h"
+
+#include <utility>
+
+#include "mozilla/Preferences.h"
+#include "VPXDecoder.h"
+#include "mozilla/StaticPrefs_media.h"
+#ifdef MOZ_AV1
+#  include "AOMDecoder.h"
+#endif
+#include "MediaContainerType.h"
+#include "PDMFactory.h"
+#include "PlatformDecoderModule.h"
+#include "VideoUtils.h"
+
+namespace mozilla {
+
+/* static */
+nsTArray<UniquePtr<TrackInfo>> WebMDecoder::GetTracksInfo(
+    const MediaContainerType& aType, MediaResult& aError) {
+  nsTArray<UniquePtr<TrackInfo>> tracks;
+  const bool isVideo = aType.Type() == MEDIAMIMETYPE("video/webm");
+
+  if (aType.Type() != MEDIAMIMETYPE("audio/webm") && !isVideo) {
+    aError = MediaResult(
+        NS_ERROR_DOM_MEDIA_FATAL_ERR,
+        RESULT_DETAIL("Invalid type:%s", aType.Type().AsString().get()));
+    return tracks;
+  }
+
+  aError = NS_OK;
+
+  const MediaCodecs& codecs = aType.ExtendedType().Codecs();
+  if (codecs.IsEmpty()) {
+    return tracks;
+  }
+
+  for (const auto& codec : codecs.Range()) {
+    if (codec.EqualsLiteral("opus") || codec.EqualsLiteral("vorbis")) {
+      tracks.AppendElement(
+          CreateTrackInfoWithMIMETypeAndContainerTypeExtraParameters(
+              "audio/"_ns + NS_ConvertUTF16toUTF8(codec), aType));
+      continue;
+    }
+    if (isVideo) {
+      UniquePtr<TrackInfo> trackInfo;
+      if (IsVP9CodecString(codec)) {
+        trackInfo = CreateTrackInfoWithMIMETypeAndContainerTypeExtraParameters(
+            "video/vp9"_ns, aType);
+      } else if (IsVP8CodecString(codec)) {
+        trackInfo = CreateTrackInfoWithMIMETypeAndContainerTypeExtraParameters(
+            "video/vp8"_ns, aType);
+      }
+      if (trackInfo) {
+        VPXDecoder::SetVideoInfo(trackInfo->GetAsVideoInfo(), codec);
+        tracks.AppendElement(std::move(trackInfo));
+        continue;
+      }
+    }
+#ifdef MOZ_AV1
+    if (StaticPrefs::media_av1_enabled() && IsAV1CodecString(codec)) {
+      auto trackInfo =
+          CreateTrackInfoWithMIMETypeAndContainerTypeExtraParameters(
+              "video/av1"_ns, aType);
+      AOMDecoder::SetVideoInfo(trackInfo->GetAsVideoInfo(), codec);
+      tracks.AppendElement(std::move(trackInfo));
+      continue;
+    }
+#endif
+    // Unknown codec
+    aError = MediaResult(
+        NS_ERROR_DOM_MEDIA_FATAL_ERR,
+        RESULT_DETAIL("Unknown codec:%s", NS_ConvertUTF16toUTF8(codec).get()));
+  }
+  return tracks;
+}
+
+/* static */
+bool WebMDecoder::IsSupportedType(const MediaContainerType& aContainerType) {
+  if (!StaticPrefs::media_webm_enabled()) {
+    return false;
+  }
+
+  MediaResult rv = NS_OK;
+  auto tracks = GetTracksInfo(aContainerType, rv);
+
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  if (tracks.IsEmpty()) {
+    // WebM guarantees that the only codecs it contained are vp8, vp9, opus or
+    // vorbis.
+    return true;
+  }
+
+  // Verify that we have a PDM that supports the whitelisted types, include
+  // color depth
+  RefPtr<PDMFactory> platform = new PDMFactory();
+  for (const auto& track : tracks) {
+    if (!track || platform->Supports(SupportDecoderParams(*track),
+                                     nullptr /* diagnostic */) ==
+                      media::DecodeSupport::Unsupported) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+/* static */
+nsTArray<UniquePtr<TrackInfo>> WebMDecoder::GetTracksInfo(
+    const MediaContainerType& aType) {
+  MediaResult rv = NS_OK;
+  return GetTracksInfo(aType, rv);
+}
+
+}  // namespace mozilla
diff --git a/dom/media/webm/WebMDecoder.h b/dom/media/webm/WebMDecoder.h
new file mode 100644
index 0000000000..9bbe5ce4d2
--- /dev/null
+++ b/dom/media/webm/WebMDecoder.h
@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#if !defined(WebMDecoder_h_)
+#  define WebMDecoder_h_
+
+#  include "mozilla/UniquePtr.h"
+#  include "nsTArray.h"
+
+namespace mozilla {
+
+class MediaContainerType;
+class MediaResult;
+class TrackInfo;
+
+class WebMDecoder {
+ public:
+  // Returns true if aContainerType is a WebM type that we think we can render
+  // with an enabled platform decoder backend.
+  // If provided, codecs are checked for support.
+  static bool IsSupportedType(const MediaContainerType& aContainerType);
+
+  static nsTArray<UniquePtr<TrackInfo>> GetTracksInfo(
+      const MediaContainerType& aType);
+
+ private:
+  static nsTArray<UniquePtr<TrackInfo>> GetTracksInfo(
+      const MediaContainerType& aType, MediaResult& aError);
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/dom/media/webm/WebMDemuxer.cpp b/dom/media/webm/WebMDemuxer.cpp
new file mode 100644
index 0000000000..fce8f0e512
--- /dev/null
+++ b/dom/media/webm/WebMDemuxer.cpp
@@ -0,0 +1,1345 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsError.h"
+#include "MediaResource.h"
+#ifdef MOZ_AV1
+#  include "AOMDecoder.h"
+#endif
+#include "OpusDecoder.h"
+#include "VPXDecoder.h"
+#include "WebMDemuxer.h"
+#include "WebMBufferedParser.h"
+#include "gfx2DGlue.h"
+#include "gfxUtils.h"
+#include "mozilla/EndianUtils.h"
+#include "mozilla/SharedThreadPool.h"
+#include "MediaDataDemuxer.h"
+#include "nsAutoRef.h"
+#include "NesteggPacketHolder.h"
+#include "XiphExtradata.h"
+#include "prprf.h"  // leaving it for PR_vsnprintf()
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/Sprintf.h"
+#include "VideoUtils.h"
+
+#include <algorithm>
+#include <numeric>
+#include <stdint.h>
+
+#define WEBM_DEBUG(arg, ...)                                          \
+  DDMOZ_LOG(gMediaDemuxerLog, mozilla::LogLevel::Debug, "::%s: " arg, \
+            __func__, ##__VA_ARGS__)
+extern mozilla::LazyLogModule gMediaDemuxerLog;
+
+namespace mozilla {
+
+using namespace gfx;
+using media::TimeUnit;
+
+LazyLogModule gNesteggLog("Nestegg");
+
+// How far ahead will we look when searching future keyframe. In microseconds.
+// This value is based on what appears to be a reasonable value as most webm
+// files encountered appear to have keyframes located < 4s.
+#define MAX_LOOK_AHEAD 10000000
+
+// Functions for reading and seeking using WebMDemuxer required for
+// nestegg_io. The 'user data' passed to these functions is the
+// demuxer.
+static int webmdemux_read(void* aBuffer, size_t aLength, void* aUserData) {
+  MOZ_ASSERT(aUserData);
+  MOZ_ASSERT(aLength < UINT32_MAX);
+  WebMDemuxer::NestEggContext* context =
+      reinterpret_cast<WebMDemuxer::NestEggContext*>(aUserData);
+  uint32_t count = aLength;
+  if (context->IsMediaSource()) {
+    int64_t length = context->GetEndDataOffset();
+    int64_t position = context->GetResource()->Tell();
+    MOZ_ASSERT(position <= context->GetResource()->GetLength());
+    MOZ_ASSERT(position <= length);
+    if (length >= 0 && count + position > length) {
+      count = length - position;
+    }
+    MOZ_ASSERT(count <= aLength);
+  }
+  uint32_t bytes = 0;
+  nsresult rv =
+      context->GetResource()->Read(static_cast<char*>(aBuffer), count, &bytes);
+  bool eof = bytes < aLength;
+  return NS_FAILED(rv) ? -1 : eof ? 0 : 1;
+}
+
+static int webmdemux_seek(int64_t aOffset, int aWhence, void* aUserData) {
+  MOZ_ASSERT(aUserData);
+  WebMDemuxer::NestEggContext* context =
+      reinterpret_cast<WebMDemuxer::NestEggContext*>(aUserData);
+  nsresult rv = context->GetResource()->Seek(aWhence, aOffset);
+  return NS_SUCCEEDED(rv) ? 0 : -1;
+}
+
+static int64_t webmdemux_tell(void* aUserData) {
+  MOZ_ASSERT(aUserData);
+  WebMDemuxer::NestEggContext* context =
+      reinterpret_cast<WebMDemuxer::NestEggContext*>(aUserData);
+  return context->GetResource()->Tell();
+}
+
+static void webmdemux_log(nestegg* aContext, unsigned int aSeverity,
+                          char const* aFormat, ...) {
+  if (!MOZ_LOG_TEST(gNesteggLog, LogLevel::Debug)) {
+    return;
+  }
+
+  va_list args;
+  char msg[256];
+  const char* sevStr;
+
+  switch (aSeverity) {
+    case NESTEGG_LOG_DEBUG:
+      sevStr = "DBG";
+      break;
+    case NESTEGG_LOG_INFO:
+      sevStr = "INF";
+      break;
+    case NESTEGG_LOG_WARNING:
+      sevStr = "WRN";
+      break;
+    case NESTEGG_LOG_ERROR:
+      sevStr = "ERR";
+      break;
+    case NESTEGG_LOG_CRITICAL:
+      sevStr = "CRT";
+      break;
+    default:
+      sevStr = "UNK";
+      break;
+  }
+
+  va_start(args, aFormat);
+
+  SprintfLiteral(msg, "%p [Nestegg-%s] ", aContext, sevStr);
+  PR_vsnprintf(msg + strlen(msg), sizeof(msg) - strlen(msg), aFormat, args);
+  MOZ_LOG(gNesteggLog, LogLevel::Debug, ("%s", msg));
+
+  va_end(args);
+}
+
+WebMDemuxer::NestEggContext::~NestEggContext() {
+  if (mContext) {
+    nestegg_destroy(mContext);
+  }
+}
+
+int WebMDemuxer::NestEggContext::Init() {
+  nestegg_io io;
+  io.read = webmdemux_read;
+  io.seek = webmdemux_seek;
+  io.tell = webmdemux_tell;
+  io.userdata = this;
+
+  // While reading the metadata, we do not really care about which nestegg
+  // context is being used so long that they are both initialised.
+  // For reading the metadata however, we will use mVideoContext.
+  return nestegg_init(&mContext, io, &webmdemux_log,
+                      mParent->IsMediaSource() ? mResource.GetLength() : -1);
+}
+
+WebMDemuxer::WebMDemuxer(MediaResource* aResource)
+    : WebMDemuxer(aResource, false) {}
+
+WebMDemuxer::WebMDemuxer(MediaResource* aResource, bool aIsMediaSource)
+    : mVideoContext(this, aResource),
+      mAudioContext(this, aResource),
+      mBufferedState(nullptr),
+      mInitData(nullptr),
+      mVideoTrack(0),
+      mAudioTrack(0),
+      mSeekPreroll(0),
+      mAudioCodec(-1),
+      mVideoCodec(-1),
+      mHasVideo(false),
+      mHasAudio(false),
+      mNeedReIndex(true),
+      mLastWebMBlockOffset(-1),
+      mIsMediaSource(aIsMediaSource) {
+  DDLINKCHILD("resource", aResource);
+  // Audio/video contexts hold a MediaResourceIndex.
+  DDLINKCHILD("video context", mVideoContext.GetResource());
+  DDLINKCHILD("audio context", mAudioContext.GetResource());
+}
+
+WebMDemuxer::~WebMDemuxer() {
+  Reset(TrackInfo::kVideoTrack);
+  Reset(TrackInfo::kAudioTrack);
+}
+
+RefPtr<WebMDemuxer::InitPromise> WebMDemuxer::Init() {
+  InitBufferedState();
+
+  if (NS_FAILED(ReadMetadata())) {
+    return InitPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_METADATA_ERR,
+                                        __func__);
+  }
+
+  if (!GetNumberTracks(TrackInfo::kAudioTrack) &&
+      !GetNumberTracks(TrackInfo::kVideoTrack)) {
+    return InitPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_METADATA_ERR,
+                                        __func__);
+  }
+
+  return InitPromise::CreateAndResolve(NS_OK, __func__);
+}
+
+void WebMDemuxer::InitBufferedState() {
+  MOZ_ASSERT(!mBufferedState);
+  mBufferedState = new WebMBufferedState;
+}
+
+uint32_t WebMDemuxer::GetNumberTracks(TrackInfo::TrackType aType) const {
+  switch (aType) {
+    case TrackInfo::kAudioTrack:
+      return mHasAudio ? 1 : 0;
+    case TrackInfo::kVideoTrack:
+      return mHasVideo ? 1 : 0;
+    default:
+      return 0;
+  }
+}
+
+UniquePtr<TrackInfo> WebMDemuxer::GetTrackInfo(TrackInfo::TrackType aType,
+                                               size_t aTrackNumber) const {
+  switch (aType) {
+    case TrackInfo::kAudioTrack:
+      return mInfo.mAudio.Clone();
+    case TrackInfo::kVideoTrack:
+      return mInfo.mVideo.Clone();
+    default:
+      return nullptr;
+  }
+}
+
+already_AddRefed<MediaTrackDemuxer> WebMDemuxer::GetTrackDemuxer(
+    TrackInfo::TrackType aType, uint32_t aTrackNumber) {
+  if (GetNumberTracks(aType) <= aTrackNumber) {
+    return nullptr;
+  }
+  RefPtr<WebMTrackDemuxer> e = new WebMTrackDemuxer(this, aType, aTrackNumber);
+  DDLINKCHILD("track demuxer", e.get());
+  mDemuxers.AppendElement(e);
+
+  return e.forget();
+}
+
+void WebMDemuxer::Reset(TrackInfo::TrackType aType) {
+  if (aType == TrackInfo::kVideoTrack) {
+    mVideoPackets.Reset();
+  } else {
+    mAudioPackets.Reset();
+  }
+}
+
+nsresult WebMDemuxer::ReadMetadata() {
+  int r = mVideoContext.Init();
+  if (r == -1) {
+    WEBM_DEBUG("mVideoContext::Init failure");
+    return NS_ERROR_FAILURE;
+  }
+  if (mAudioContext.Init() == -1) {
+    WEBM_DEBUG("mAudioContext::Init failure");
+    return NS_ERROR_FAILURE;
+  }
+
+  // For reading the metadata we can only use the video resource/context.
+  MediaResourceIndex& resource = Resource(TrackInfo::kVideoTrack);
+  nestegg* context = Context(TrackInfo::kVideoTrack);
+
+  {
+    // Check how much data nestegg read and force feed it to BufferedState.
+    RefPtr<MediaByteBuffer> buffer = resource.MediaReadAt(0, resource.Tell());
+    if (!buffer) {
+      WEBM_DEBUG("resource.MediaReadAt error");
+      return NS_ERROR_FAILURE;
+    }
+    mBufferedState->NotifyDataArrived(buffer->Elements(), buffer->Length(), 0);
+    if (mBufferedState->GetInitEndOffset() < 0) {
+      WEBM_DEBUG("Couldn't find init end");
+      return NS_ERROR_FAILURE;
+    }
+    MOZ_ASSERT(mBufferedState->GetInitEndOffset() <= resource.Tell());
+  }
+  mInitData = resource.MediaReadAt(0, mBufferedState->GetInitEndOffset());
+  if (!mInitData ||
+      mInitData->Length() != size_t(mBufferedState->GetInitEndOffset())) {
+    WEBM_DEBUG("Couldn't read init data");
+    return NS_ERROR_FAILURE;
+  }
+
+  unsigned int ntracks = 0;
+  r = nestegg_track_count(context, &ntracks);
+  if (r == -1) {
+    WEBM_DEBUG("nestegg_track_count error");
+    return NS_ERROR_FAILURE;
+  }
+
+  for (unsigned int track = 0; track < ntracks; ++track) {
+    int id = nestegg_track_codec_id(context, track);
+    if (id == -1) {
+      WEBM_DEBUG("nestegg_track_codec_id error");
+      return NS_ERROR_FAILURE;
+    }
+    int type = nestegg_track_type(context, track);
+    if (type == NESTEGG_TRACK_VIDEO && !mHasVideo) {
+      nestegg_video_params params;
+      r = nestegg_track_video_params(context, track, &params);
+      if (r == -1) {
+        WEBM_DEBUG("nestegg_track_video_params error");
+        return NS_ERROR_FAILURE;
+      }
+      mVideoCodec = nestegg_track_codec_id(context, track);
+      switch (mVideoCodec) {
+        case NESTEGG_CODEC_VP8:
+          mInfo.mVideo.mMimeType = "video/vp8";
+          break;
+        case NESTEGG_CODEC_VP9:
+          mInfo.mVideo.mMimeType = "video/vp9";
+          break;
+        case NESTEGG_CODEC_AV1:
+          mInfo.mVideo.mMimeType = "video/av1";
+          break;
+        default:
+          NS_WARNING("Unknown WebM video codec");
+          return NS_ERROR_FAILURE;
+      }
+
+      mInfo.mVideo.mColorPrimaries = gfxUtils::CicpToColorPrimaries(
+          static_cast<gfx::CICP::ColourPrimaries>(params.primaries),
+          gMediaDemuxerLog);
+
+      // For VPX, this is our only chance to capture the transfer
+      // characteristics, which we can't get from a VPX bitstream later.
+      // We only need this value if the video is using the BT2020
+      // colorspace, which will be determined on a per-frame basis later.
+      mInfo.mVideo.mTransferFunction = gfxUtils::CicpToTransferFunction(
+          static_cast<gfx::CICP::TransferCharacteristics>(
+              params.transfer_characteristics));
+
+      // Picture region, taking into account cropping, before scaling
+      // to the display size.
+      unsigned int cropH = params.crop_right + params.crop_left;
+      unsigned int cropV = params.crop_bottom + params.crop_top;
+      gfx::IntRect pictureRect(params.crop_left, params.crop_top,
+                               params.width - cropH, params.height - cropV);
+
+      // If the cropping data appears invalid then use the frame data
+      if (pictureRect.width <= 0 || pictureRect.height <= 0 ||
+          pictureRect.x < 0 || pictureRect.y < 0) {
+        pictureRect.x = 0;
+        pictureRect.y = 0;
+        pictureRect.width = params.width;
+        pictureRect.height = params.height;
+      }
+
+      // Validate the container-reported frame and pictureRect sizes. This
+      // ensures that our video frame creation code doesn't overflow.
+      gfx::IntSize displaySize(params.display_width, params.display_height);
+      gfx::IntSize frameSize(params.width, params.height);
+      if (!IsValidVideoRegion(frameSize, pictureRect, displaySize)) {
+        // Video track's frame sizes will overflow. Ignore the video track.
+        continue;
+      }
+
+      mVideoTrack = track;
+      mHasVideo = true;
+
+      mInfo.mVideo.mDisplay = displaySize;
+      mInfo.mVideo.mImage = frameSize;
+      mInfo.mVideo.SetImageRect(pictureRect);
+      mInfo.mVideo.SetAlpha(params.alpha_mode);
+
+      switch (params.stereo_mode) {
+        case NESTEGG_VIDEO_MONO:
+          mInfo.mVideo.mStereoMode = StereoMode::MONO;
+          break;
+        case NESTEGG_VIDEO_STEREO_LEFT_RIGHT:
+          mInfo.mVideo.mStereoMode = StereoMode::LEFT_RIGHT;
+          break;
+        case NESTEGG_VIDEO_STEREO_BOTTOM_TOP:
+          mInfo.mVideo.mStereoMode = StereoMode::BOTTOM_TOP;
+          break;
+        case NESTEGG_VIDEO_STEREO_TOP_BOTTOM:
+          mInfo.mVideo.mStereoMode = StereoMode::TOP_BOTTOM;
+          break;
+        case NESTEGG_VIDEO_STEREO_RIGHT_LEFT:
+          mInfo.mVideo.mStereoMode = StereoMode::RIGHT_LEFT;
+          break;
+      }
+      uint64_t duration = 0;
+      r = nestegg_duration(context, &duration);
+      if (!r) {
+        mInfo.mVideo.mDuration = TimeUnit::FromNanoseconds(duration);
+      }
+      WEBM_DEBUG("stream duration: %lf\n", mInfo.mVideo.mDuration.ToSeconds());
+      mInfo.mVideo.mCrypto = GetTrackCrypto(TrackInfo::kVideoTrack, track);
+      if (mInfo.mVideo.mCrypto.IsEncrypted()) {
+        MOZ_ASSERT(mInfo.mVideo.mCrypto.mCryptoScheme == CryptoScheme::Cenc,
+                   "WebM should only use cenc scheme");
+        mCrypto.AddInitData(u"webm"_ns, mInfo.mVideo.mCrypto.mKeyId);
+      }
+    } else if (type == NESTEGG_TRACK_AUDIO && !mHasAudio) {
+      nestegg_audio_params params;
+      r = nestegg_track_audio_params(context, track, &params);
+      if (r == -1) {
+        WEBM_DEBUG("nestegg_track_audio_params error");
+        return NS_ERROR_FAILURE;
+      }
+      if (params.rate >
+              static_cast<decltype(params.rate)>(AudioInfo::MAX_RATE) ||
+          params.rate <= static_cast<decltype(params.rate)>(0) ||
+          params.channels > AudioConfig::ChannelLayout::MAX_CHANNELS) {
+        WEBM_DEBUG("Invalid audio param rate: %lf channel count: %d",
+                   params.rate, params.channels);
+        return NS_ERROR_DOM_MEDIA_METADATA_ERR;
+      }
+
+      mAudioTrack = track;
+      mHasAudio = true;
+      mAudioCodec = nestegg_track_codec_id(context, track);
+      if (mAudioCodec == NESTEGG_CODEC_VORBIS) {
+        mInfo.mAudio.mCodecSpecificConfig =
+            AudioCodecSpecificVariant{VorbisCodecSpecificData{}};
+        mInfo.mAudio.mMimeType = "audio/vorbis";
+      } else if (mAudioCodec == NESTEGG_CODEC_OPUS) {
+        uint64_t codecDelayUs = params.codec_delay / 1000;
+        mInfo.mAudio.mMimeType = "audio/opus";
+        OpusCodecSpecificData opusCodecSpecificData;
+        opusCodecSpecificData.mContainerCodecDelayMicroSeconds =
+            AssertedCast<int64_t>(codecDelayUs);
+        mInfo.mAudio.mCodecSpecificConfig =
+            AudioCodecSpecificVariant{std::move(opusCodecSpecificData)};
+        WEBM_DEBUG("Preroll for Opus: %" PRIu64, codecDelayUs);
+      }
+      mSeekPreroll = params.seek_preroll;
+      mInfo.mAudio.mRate = AssertedCast<uint32_t>(params.rate);
+      mInfo.mAudio.mChannels = params.channels;
+
+      unsigned int nheaders = 0;
+      r = nestegg_track_codec_data_count(context, track, &nheaders);
+      if (r == -1) {
+        WEBM_DEBUG("nestegg_track_codec_data_count error");
+        return NS_ERROR_FAILURE;
+      }
+
+      AutoTArray<const unsigned char*, 4> headers;
+      AutoTArray<size_t, 4> headerLens;
+      for (uint32_t header = 0; header < nheaders; ++header) {
+        unsigned char* data = 0;
+        size_t length = 0;
+        r = nestegg_track_codec_data(context, track, header, &data, &length);
+        if (r == -1) {
+          WEBM_DEBUG("nestegg_track_codec_data error");
+          return NS_ERROR_FAILURE;
+        }
+        headers.AppendElement(data);
+        headerLens.AppendElement(length);
+      }
+
+      // Vorbis has 3 headers, convert to Xiph extradata format to send them to
+      // the demuxer.
+      // TODO: This is already the format WebM stores them in. Would be nice
+      // to avoid having libnestegg split them only for us to pack them again,
+      // but libnestegg does not give us an API to access this data directly.
+      RefPtr<MediaByteBuffer> audioCodecSpecificBlob =
+          GetAudioCodecSpecificBlob(mInfo.mAudio.mCodecSpecificConfig);
+      if (nheaders > 1) {
+        if (!XiphHeadersToExtradata(audioCodecSpecificBlob, headers,
+                                    headerLens)) {
+          WEBM_DEBUG("Couldn't parse Xiph headers");
+          return NS_ERROR_FAILURE;
+        }
+      } else {
+        audioCodecSpecificBlob->AppendElements(headers[0], headerLens[0]);
+      }
+      uint64_t duration = 0;
+      r = nestegg_duration(context, &duration);
+      if (!r) {
+        mInfo.mAudio.mDuration = TimeUnit::FromNanoseconds(duration);
+        WEBM_DEBUG("audio track duration: %lf",
+                   mInfo.mAudio.mDuration.ToSeconds());
+      }
+      mInfo.mAudio.mCrypto = GetTrackCrypto(TrackInfo::kAudioTrack, track);
+      if (mInfo.mAudio.mCrypto.IsEncrypted()) {
+        MOZ_ASSERT(mInfo.mAudio.mCrypto.mCryptoScheme == CryptoScheme::Cenc,
+                   "WebM should only use cenc scheme");
+        mCrypto.AddInitData(u"webm"_ns, mInfo.mAudio.mCrypto.mKeyId);
+      }
+    }
+  }
+  WEBM_DEBUG("Read metadata OK");
+  return NS_OK;
+}
+
+bool WebMDemuxer::IsSeekable() const {
+  return Context(TrackInfo::kVideoTrack) &&
+         nestegg_has_cues(Context(TrackInfo::kVideoTrack));
+}
+
+bool WebMDemuxer::IsSeekableOnlyInBufferedRanges() const {
+  return Context(TrackInfo::kVideoTrack) &&
+         !nestegg_has_cues(Context(TrackInfo::kVideoTrack));
+}
+
+void WebMDemuxer::EnsureUpToDateIndex() {
+  if (!mNeedReIndex || !mInitData) {
+    return;
+  }
+  AutoPinned<MediaResource> resource(
+      Resource(TrackInfo::kVideoTrack).GetResource());
+  MediaByteRangeSet byteRanges;
+  nsresult rv = resource->GetCachedRanges(byteRanges);
+  if (NS_FAILED(rv) || byteRanges.IsEmpty()) {
+    return;
+  }
+  mBufferedState->UpdateIndex(byteRanges, resource);
+
+  mNeedReIndex = false;
+
+  if (!mIsMediaSource) {
+    return;
+  }
+  mLastWebMBlockOffset = mBufferedState->GetLastBlockOffset();
+  MOZ_ASSERT(mLastWebMBlockOffset <= resource->GetLength());
+}
+
+void WebMDemuxer::NotifyDataArrived() {
+  WEBM_DEBUG("");
+  mNeedReIndex = true;
+}
+
+void WebMDemuxer::NotifyDataRemoved() {
+  mBufferedState->Reset();
+  if (mInitData) {
+    mBufferedState->NotifyDataArrived(mInitData->Elements(),
+                                      mInitData->Length(), 0);
+  }
+  mNeedReIndex = true;
+}
+
+UniquePtr<EncryptionInfo> WebMDemuxer::GetCrypto() {
+  return mCrypto.IsEncrypted() ? MakeUnique<EncryptionInfo>(mCrypto) : nullptr;
+}
+
+CryptoTrack WebMDemuxer::GetTrackCrypto(TrackInfo::TrackType aType,
+                                        size_t aTrackNumber) {
+  const int WEBM_IV_SIZE = 16;
+  const unsigned char* contentEncKeyId;
+  size_t contentEncKeyIdLength;
+  CryptoTrack crypto;
+  nestegg* context = Context(aType);
+
+  int r = nestegg_track_content_enc_key_id(
+      context, aTrackNumber, &contentEncKeyId, &contentEncKeyIdLength);
+
+  if (r == -1) {
+    WEBM_DEBUG("nestegg_track_content_enc_key_id failed r=%d", r);
+    return crypto;
+  }
+
+  uint32_t i;
+  nsTArray<uint8_t> initData;
+  for (i = 0; i < contentEncKeyIdLength; i++) {
+    initData.AppendElement(contentEncKeyId[i]);
+  }
+
+  if (!initData.IsEmpty()) {
+    // Webm only uses a cenc style scheme.
+    crypto.mCryptoScheme = CryptoScheme::Cenc;
+    crypto.mIVSize = WEBM_IV_SIZE;
+    crypto.mKeyId = std::move(initData);
+  }
+
+  return crypto;
+}
+
+nsresult WebMDemuxer::GetNextPacket(TrackInfo::TrackType aType,
+                                    MediaRawDataQueue* aSamples) {
+  if (mIsMediaSource) {
+    // To ensure mLastWebMBlockOffset is properly up to date.
+    EnsureUpToDateIndex();
+  }
+
+  RefPtr<NesteggPacketHolder> holder;
+  nsresult rv = NextPacket(aType, holder);
+
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  int r = 0;
+  unsigned int count = 0;
+  r = nestegg_packet_count(holder->Packet(), &count);
+  if (r == -1) {
+    return NS_ERROR_DOM_MEDIA_DEMUXER_ERR;
+  }
+  int64_t tstamp = holder->Timestamp();
+  int64_t duration = holder->Duration();
+
+  // The end time of this frame is the start time of the next frame. Fetch
+  // the timestamp of the next packet for this track.  If we've reached the
+  // end of the resource, use the file's duration as the end time of this
+  // video frame.
+  RefPtr<NesteggPacketHolder> next_holder;
+  rv = NextPacket(aType, next_holder);
+  if (NS_FAILED(rv) && rv != NS_ERROR_DOM_MEDIA_END_OF_STREAM) {
+    return rv;
+  }
+
+  int64_t next_tstamp = INT64_MIN;
+  auto calculateNextTimestamp = [&](auto&& pushPacket, auto&& lastFrameTime,
+                                    int64_t trackEndTime) {
+    if (next_holder) {
+      next_tstamp = next_holder->Timestamp();
+      (this->*pushPacket)(next_holder);
+    } else if (duration >= 0) {
+      next_tstamp = tstamp + duration;
+    } else if (lastFrameTime.isSome()) {
+      next_tstamp = tstamp + (tstamp - lastFrameTime.ref());
+    } else if (mIsMediaSource) {
+      (this->*pushPacket)(holder);
+    } else {
+      // If we can't get frame's duration, it means either we need to wait for
+      // more data for MSE case or this is the last frame for file resource
+      // case.
+      if (tstamp > trackEndTime) {
+        // This shouldn't happen, but some muxers give incorrect durations to
+        // segments, then have samples appear beyond those durations.
+        WEBM_DEBUG("Found tstamp=%" PRIi64 " > trackEndTime=%" PRIi64
+                   " while calculating next timestamp! Indicates a bad mux! "
+                   "Will use tstamp value.",
+                   tstamp, trackEndTime);
+      }
+      next_tstamp = std::max<int64_t>(tstamp, trackEndTime);
+    }
+    lastFrameTime = Some(tstamp);
+  };
+
+  if (aType == TrackInfo::kAudioTrack) {
+    calculateNextTimestamp(&WebMDemuxer::PushAudioPacket, mLastAudioFrameTime,
+                           mInfo.mAudio.mDuration.ToMicroseconds());
+  } else {
+    calculateNextTimestamp(&WebMDemuxer::PushVideoPacket, mLastVideoFrameTime,
+                           mInfo.mVideo.mDuration.ToMicroseconds());
+  }
+
+  if (mIsMediaSource && next_tstamp == INT64_MIN) {
+    return NS_ERROR_DOM_MEDIA_END_OF_STREAM;
+  }
+
+  int64_t discardPadding = 0;
+  if (aType == TrackInfo::kAudioTrack) {
+    (void)nestegg_packet_discard_padding(holder->Packet(), &discardPadding);
+  }
+
+  int packetEncryption = nestegg_packet_encryption(holder->Packet());
+
+  for (uint32_t i = 0; i < count; ++i) {
+    unsigned char* data = nullptr;
+    size_t length;
+    r = nestegg_packet_data(holder->Packet(), i, &data, &length);
+    if (r == -1) {
+      WEBM_DEBUG("nestegg_packet_data failed r=%d", r);
+      return NS_ERROR_DOM_MEDIA_DEMUXER_ERR;
+    }
+    unsigned char* alphaData = nullptr;
+    size_t alphaLength = 0;
+    // Check packets for alpha information if file has declared alpha frames
+    // may be present.
+    if (mInfo.mVideo.HasAlpha()) {
+      r = nestegg_packet_additional_data(holder->Packet(), 1, &alphaData,
+                                         &alphaLength);
+      if (r == -1) {
+        WEBM_DEBUG(
+            "nestegg_packet_additional_data failed to retrieve alpha data r=%d",
+            r);
+      }
+    }
+    bool isKeyframe = false;
+    if (aType == TrackInfo::kAudioTrack) {
+      isKeyframe = true;
+    } else if (aType == TrackInfo::kVideoTrack) {
+      if (packetEncryption == NESTEGG_PACKET_HAS_SIGNAL_BYTE_ENCRYPTED ||
+          packetEncryption == NESTEGG_PACKET_HAS_SIGNAL_BYTE_PARTITIONED) {
+        // Packet is encrypted, can't peek, use packet info
+        isKeyframe = nestegg_packet_has_keyframe(holder->Packet()) ==
+                     NESTEGG_PACKET_HAS_KEYFRAME_TRUE;
+      } else {
+        MOZ_ASSERT(
+            packetEncryption == NESTEGG_PACKET_HAS_SIGNAL_BYTE_UNENCRYPTED ||
+                packetEncryption == NESTEGG_PACKET_HAS_SIGNAL_BYTE_FALSE,
+            "Unencrypted packet expected");
+        auto sample = Span(data, length);
+        auto alphaSample = Span(alphaData, alphaLength);
+
+        switch (mVideoCodec) {
+          case NESTEGG_CODEC_VP8:
+            isKeyframe = VPXDecoder::IsKeyframe(sample, VPXDecoder::Codec::VP8);
+            if (isKeyframe && alphaLength) {
+              isKeyframe =
+                  VPXDecoder::IsKeyframe(alphaSample, VPXDecoder::Codec::VP8);
+            }
+            break;
+          case NESTEGG_CODEC_VP9:
+            isKeyframe = VPXDecoder::IsKeyframe(sample, VPXDecoder::Codec::VP9);
+            if (isKeyframe && alphaLength) {
+              isKeyframe =
+                  VPXDecoder::IsKeyframe(alphaSample, VPXDecoder::Codec::VP9);
+            }
+            break;
+#ifdef MOZ_AV1
+          case NESTEGG_CODEC_AV1:
+            isKeyframe = AOMDecoder::IsKeyframe(sample);
+            if (isKeyframe && alphaLength) {
+              isKeyframe = AOMDecoder::IsKeyframe(alphaSample);
+            }
+            break;
+#endif
+          default:
+            NS_WARNING("Cannot detect keyframes in unknown WebM video codec");
+            return NS_ERROR_FAILURE;
+        }
+      }
+    }
+
+    WEBM_DEBUG("push sample tstamp: %" PRId64 " next_tstamp: %" PRId64
+               " length: %zu kf: %d",
+               tstamp, next_tstamp, length, isKeyframe);
+    RefPtr<MediaRawData> sample;
+    if (mInfo.mVideo.HasAlpha() && alphaLength != 0) {
+      sample = new MediaRawData(data, length, alphaData, alphaLength);
+      if ((length && !sample->Data()) ||
+          (alphaLength && !sample->AlphaData())) {
+        // OOM.
+        return NS_ERROR_OUT_OF_MEMORY;
+      }
+    } else {
+      sample = new MediaRawData(data, length);
+      if (length && !sample->Data()) {
+        // OOM.
+        return NS_ERROR_OUT_OF_MEMORY;
+      }
+    }
+    sample->mTimecode = TimeUnit::FromMicroseconds(tstamp);
+    sample->mTime = TimeUnit::FromMicroseconds(tstamp);
+    if (next_tstamp > tstamp) {
+      sample->mDuration = TimeUnit::FromMicroseconds(next_tstamp - tstamp);
+    }
+    sample->mOffset = holder->Offset();
+    sample->mKeyframe = isKeyframe;
+    if (discardPadding && i == count - 1) {
+      CheckedInt64 discardFrames;
+      if (discardPadding < 0) {
+        // This is an invalid value as discard padding should never be negative.
+        // Set to maximum value so that the decoder will reject it as it's
+        // greater than the number of frames available.
+        discardFrames = INT32_MAX;
+        WEBM_DEBUG("Invalid negative discard padding");
+      } else {
+        discardFrames = TimeUnitToFrames(
+            TimeUnit::FromNanoseconds(discardPadding), mInfo.mAudio.mRate);
+      }
+      if (discardFrames.isValid()) {
+        sample->mDiscardPadding = discardFrames.value();
+      }
+    }
+
+    if (packetEncryption == NESTEGG_PACKET_HAS_SIGNAL_BYTE_ENCRYPTED ||
+        packetEncryption == NESTEGG_PACKET_HAS_SIGNAL_BYTE_PARTITIONED) {
+      UniquePtr<MediaRawDataWriter> writer(sample->CreateWriter());
+      unsigned char const* iv;
+      size_t ivLength;
+      nestegg_packet_iv(holder->Packet(), &iv, &ivLength);
+      writer->mCrypto.mCryptoScheme = CryptoScheme::Cenc;
+      writer->mCrypto.mIVSize = ivLength;
+      if (ivLength == 0) {
+        // Frame is not encrypted. This shouldn't happen as it means the
+        // encryption bit is set on a frame with no IV, but we gracefully
+        // handle incase.
+        MOZ_ASSERT_UNREACHABLE(
+            "Unencrypted packets should not have the encryption bit set!");
+        WEBM_DEBUG("Unencrypted packet with encryption bit set");
+        writer->mCrypto.mPlainSizes.AppendElement(length);
+        writer->mCrypto.mEncryptedSizes.AppendElement(0);
+      } else {
+        // Frame is encrypted
+        writer->mCrypto.mIV.AppendElements(iv, 8);
+        // Iv from a sample is 64 bits, must be padded with 64 bits more 0s
+        // in compliance with spec
+        for (uint32_t i = 0; i < 8; i++) {
+          writer->mCrypto.mIV.AppendElement(0);
+        }
+
+        if (packetEncryption == NESTEGG_PACKET_HAS_SIGNAL_BYTE_ENCRYPTED) {
+          writer->mCrypto.mPlainSizes.AppendElement(0);
+          writer->mCrypto.mEncryptedSizes.AppendElement(length);
+        } else if (packetEncryption ==
+                   NESTEGG_PACKET_HAS_SIGNAL_BYTE_PARTITIONED) {
+          uint8_t numPartitions = 0;
+          const uint32_t* partitions = NULL;
+          nestegg_packet_offsets(holder->Packet(), &partitions, &numPartitions);
+
+          // WebM stores a list of 'partitions' in the data, which alternate
+          // clear, encrypted. The data in the first partition is always clear.
+          // So, and sample might look as follows:
+          // 00|XXXX|000|XX, where | represents a partition, 0 a clear byte and
+          // X an encrypted byte. If the first bytes in sample are unencrypted,
+          // the first partition will be at zero |XXXX|000|XX.
+          //
+          // As GMP expects the lengths of the clear and encrypted chunks of
+          // data, we calculate these from the difference between the last two
+          // partitions.
+          uint32_t lastOffset = 0;
+          bool encrypted = false;
+
+          for (uint8_t i = 0; i < numPartitions; i++) {
+            uint32_t partition = partitions[i];
+            uint32_t currentLength = partition - lastOffset;
+
+            if (encrypted) {
+              writer->mCrypto.mEncryptedSizes.AppendElement(currentLength);
+            } else {
+              writer->mCrypto.mPlainSizes.AppendElement(currentLength);
+            }
+
+            encrypted = !encrypted;
+            lastOffset = partition;
+
+            MOZ_ASSERT(lastOffset <= length);
+          }
+
+          // Add the data between the last offset and the end of the data.
+          // 000|XXX|000
+          //        ^---^
+          if (encrypted) {
+            writer->mCrypto.mEncryptedSizes.AppendElement(length - lastOffset);
+          } else {
+            writer->mCrypto.mPlainSizes.AppendElement(length - lastOffset);
+          }
+
+          // Make sure we have an equal number of encrypted and plain sizes (GMP
+          // expects this). This simple check is sufficient as there are two
+          // possible cases at this point:
+          // 1. The number of samples are even (so we don't need to do anything)
+          // 2. There is one more clear sample than encrypted samples, so add a
+          // zero length encrypted chunk.
+          // There can never be more encrypted partitions than clear partitions
+          // due to the alternating structure of the WebM samples and the
+          // restriction that the first chunk is always clear.
+          if (numPartitions % 2 == 0) {
+            writer->mCrypto.mEncryptedSizes.AppendElement(0);
+          }
+
+          // Assert that the lengths of the encrypted and plain samples add to
+          // the length of the data.
+          MOZ_ASSERT(
+              ((size_t)(std::accumulate(writer->mCrypto.mPlainSizes.begin(),
+                                        writer->mCrypto.mPlainSizes.end(), 0) +
+                        std::accumulate(writer->mCrypto.mEncryptedSizes.begin(),
+                                        writer->mCrypto.mEncryptedSizes.end(),
+                                        0)) == length));
+        }
+      }
+    }
+    aSamples->Push(sample);
+  }
+  return NS_OK;
+}
+
+nsresult WebMDemuxer::NextPacket(TrackInfo::TrackType aType,
+                                 RefPtr<NesteggPacketHolder>& aPacket) {
+  bool isVideo = aType == TrackInfo::kVideoTrack;
+
+  // Flag to indicate that we do need to playback these types of
+  // packets.
+  bool hasType = isVideo ? mHasVideo : mHasAudio;
+
+  if (!hasType) {
+    return NS_ERROR_DOM_MEDIA_DEMUXER_ERR;
+  }
+
+  // The packet queue for the type that we are interested in.
+  WebMPacketQueue& packets = isVideo ? mVideoPackets : mAudioPackets;
+
+  if (packets.GetSize() > 0) {
+    aPacket = packets.PopFront();
+    return NS_OK;
+  }
+
+  // Track we are interested in
+  uint32_t ourTrack = isVideo ? mVideoTrack : mAudioTrack;
+
+  do {
+    RefPtr<NesteggPacketHolder> holder;
+    nsresult rv = DemuxPacket(aType, holder);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+    if (!holder) {
+      return NS_ERROR_DOM_MEDIA_DEMUXER_ERR;
+    }
+
+    if (ourTrack == holder->Track()) {
+      aPacket = holder;
+      return NS_OK;
+    }
+  } while (true);
+}
+
+nsresult WebMDemuxer::DemuxPacket(TrackInfo::TrackType aType,
+                                  RefPtr<NesteggPacketHolder>& aPacket) {
+  nestegg_packet* packet;
+  int r = nestegg_read_packet(Context(aType), &packet);
+  if (r == 0) {
+    nestegg_read_reset(Context(aType));
+    return NS_ERROR_DOM_MEDIA_END_OF_STREAM;
+  } else if (r < 0) {
+    return NS_ERROR_DOM_MEDIA_DEMUXER_ERR;
+  }
+
+  unsigned int track = 0;
+  r = nestegg_packet_track(packet, &track);
+  if (r == -1) {
+    return NS_ERROR_DOM_MEDIA_DEMUXER_ERR;
+  }
+
+  int64_t offset = Resource(aType).Tell();
+  RefPtr<NesteggPacketHolder> holder = new NesteggPacketHolder();
+  if (!holder->Init(packet, offset, track, false)) {
+    return NS_ERROR_DOM_MEDIA_DEMUXER_ERR;
+  }
+
+  aPacket = holder;
+  return NS_OK;
+}
+
+void WebMDemuxer::PushAudioPacket(NesteggPacketHolder* aItem) {
+  mAudioPackets.PushFront(aItem);
+}
+
+void WebMDemuxer::PushVideoPacket(NesteggPacketHolder* aItem) {
+  mVideoPackets.PushFront(aItem);
+}
+
+nsresult WebMDemuxer::SeekInternal(TrackInfo::TrackType aType,
+                                   const TimeUnit& aTarget) {
+  EnsureUpToDateIndex();
+  uint32_t trackToSeek = mHasVideo ? mVideoTrack : mAudioTrack;
+  MOZ_ASSERT(aTarget.ToNanoseconds() >= 0, "Seek time can't be negative");
+  uint64_t target = static_cast<uint64_t>(aTarget.ToNanoseconds());
+  WEBM_DEBUG("Seeking to %lf", aTarget.ToSeconds());
+
+  Reset(aType);
+
+  if (mSeekPreroll) {
+    uint64_t startTime = 0;
+    if (!mBufferedState->GetStartTime(&startTime)) {
+      startTime = 0;
+    }
+    WEBM_DEBUG("Seek Target: %f",
+               TimeUnit::FromNanoseconds(target).ToSeconds());
+    if (target < mSeekPreroll || target - mSeekPreroll < startTime) {
+      target = startTime;
+    } else {
+      target -= mSeekPreroll;
+    }
+    WEBM_DEBUG("SeekPreroll: %f StartTime: %f Adjusted Target: %f",
+               TimeUnit::FromNanoseconds(mSeekPreroll).ToSeconds(),
+               TimeUnit::FromNanoseconds(startTime).ToSeconds(),
+               TimeUnit::FromNanoseconds(target).ToSeconds());
+  }
+  int r = nestegg_track_seek(Context(aType), trackToSeek, target);
+  if (r == -1) {
+    WEBM_DEBUG("track_seek for track %u to %f failed, r=%d", trackToSeek,
+               TimeUnit::FromNanoseconds(target).ToSeconds(), r);
+    // Try seeking directly based on cluster information in memory.
+    int64_t offset = 0;
+    bool rv = mBufferedState->GetOffsetForTime(target, &offset);
+    if (!rv) {
+      WEBM_DEBUG("mBufferedState->GetOffsetForTime failed too");
+      return NS_ERROR_FAILURE;
+    }
+
+    if (offset < 0) {
+      WEBM_DEBUG("Unknow byte offset time for seek target %" PRIu64 "ns",
+                 target);
+      return NS_ERROR_FAILURE;
+    }
+
+    r = nestegg_offset_seek(Context(aType), static_cast<uint64_t>(offset));
+    if (r == -1) {
+      WEBM_DEBUG("and nestegg_offset_seek to %" PRIu64 " failed", offset);
+      return NS_ERROR_FAILURE;
+    }
+    WEBM_DEBUG("got offset from buffered state: %" PRIu64 "", offset);
+  }
+
+  if (aType == TrackInfo::kAudioTrack) {
+    mLastAudioFrameTime.reset();
+  } else {
+    mLastVideoFrameTime.reset();
+  }
+
+  return NS_OK;
+}
+
+bool WebMDemuxer::IsBufferedIntervalValid(uint64_t start, uint64_t end) {
+  if (start > end) {
+    // Buffered ranges are clamped to the media's start time and duration. Any
+    // frames with timestamps outside that range are ignored, see bug 1697641
+    // for more info.
+    WEBM_DEBUG("Ignoring range %" PRIu64 "-%" PRIu64
+               ", due to invalid interval (start > end).",
+               start, end);
+    return false;
+  }
+
+  auto startTime = TimeUnit::FromNanoseconds(start);
+  auto endTime = TimeUnit::FromNanoseconds(end);
+
+  if (startTime.IsNegative() || endTime.IsNegative()) {
+    // We can get timestamps that are conceptually valid, but become
+    // negative due to uint64 -> int64 conversion from TimeUnit. We should
+    // not get negative timestamps, so guard against them.
+    WEBM_DEBUG(
+        "Invalid range %f-%f, likely result of uint64 -> int64 conversion.",
+        startTime.ToSeconds(), endTime.ToSeconds());
+    return false;
+  }
+
+  return true;
+}
+
+media::TimeIntervals WebMDemuxer::GetBuffered() {
+  EnsureUpToDateIndex();
+  AutoPinned<MediaResource> resource(
+      Resource(TrackInfo::kVideoTrack).GetResource());
+
+  media::TimeIntervals buffered;
+
+  MediaByteRangeSet ranges;
+  nsresult rv = resource->GetCachedRanges(ranges);
+  if (NS_FAILED(rv)) {
+    return media::TimeIntervals();
+  }
+  uint64_t duration = 0;
+  uint64_t startOffset = 0;
+  if (!nestegg_duration(Context(TrackInfo::kVideoTrack), &duration)) {
+    if (mBufferedState->GetStartTime(&startOffset)) {
+      duration += startOffset;
+    }
+    WEBM_DEBUG("Duration: %f StartTime: %f",
+               TimeUnit::FromNanoseconds(duration).ToSeconds(),
+               TimeUnit::FromNanoseconds(startOffset).ToSeconds());
+  }
+  for (uint32_t index = 0; index < ranges.Length(); index++) {
+    uint64_t start, end;
+    bool rv = mBufferedState->CalculateBufferedForRange(
+        ranges[index].mStart, ranges[index].mEnd, &start, &end);
+    if (rv) {
+      NS_ASSERTION(startOffset <= start,
+                   "startOffset negative or larger than start time");
+
+      if (duration && end > duration) {
+        WEBM_DEBUG("limit range to duration, end: %f duration: %f",
+                   TimeUnit::FromNanoseconds(end).ToSeconds(),
+                   TimeUnit::FromNanoseconds(duration).ToSeconds());
+        end = duration;
+      }
+
+      if (!IsBufferedIntervalValid(start, end)) {
+        WEBM_DEBUG("Invalid interval, bailing");
+        break;
+      }
+
+      auto startTime = TimeUnit::FromNanoseconds(start);
+      auto endTime = TimeUnit::FromNanoseconds(end);
+
+      WEBM_DEBUG("add range %f-%f", startTime.ToSeconds(), endTime.ToSeconds());
+      buffered += media::TimeInterval(startTime, endTime);
+    }
+  }
+  return buffered;
+}
+
+bool WebMDemuxer::GetOffsetForTime(uint64_t aTime, int64_t* aOffset) {
+  EnsureUpToDateIndex();
+  return mBufferedState && mBufferedState->GetOffsetForTime(aTime, aOffset);
+}
+
+// WebMTrackDemuxer
+WebMTrackDemuxer::WebMTrackDemuxer(WebMDemuxer* aParent,
+                                   TrackInfo::TrackType aType,
+                                   uint32_t aTrackNumber)
+    : mParent(aParent), mType(aType), mNeedKeyframe(true) {
+  mInfo = mParent->GetTrackInfo(aType, aTrackNumber);
+  MOZ_ASSERT(mInfo);
+}
+
+WebMTrackDemuxer::~WebMTrackDemuxer() { mSamples.Reset(); }
+
+UniquePtr<TrackInfo> WebMTrackDemuxer::GetInfo() const {
+  return mInfo->Clone();
+}
+
+RefPtr<WebMTrackDemuxer::SeekPromise> WebMTrackDemuxer::Seek(
+    const TimeUnit& aTime) {
+  // Seeks to aTime. Upon success, SeekPromise will be resolved with the
+  // actual time seeked to. Typically the random access point time
+
+  auto seekTime = aTime;
+  bool keyframe = false;
+
+  mNeedKeyframe = true;
+
+  do {
+    mSamples.Reset();
+    mParent->SeekInternal(mType, seekTime);
+    nsresult rv = mParent->GetNextPacket(mType, &mSamples);
+    if (NS_FAILED(rv)) {
+      if (rv == NS_ERROR_DOM_MEDIA_END_OF_STREAM) {
+        // Ignore the error for now, the next GetSample will be rejected with
+        // EOS.
+        return SeekPromise::CreateAndResolve(TimeUnit::Zero(), __func__);
+      }
+      return SeekPromise::CreateAndReject(rv, __func__);
+    }
+
+    // Check what time we actually seeked to.
+    if (mSamples.GetSize() == 0) {
+      // We can't determine if the seek succeeded at this stage, so break the
+      // loop.
+      break;
+    }
+
+    for (const auto& sample : mSamples) {
+      seekTime = sample->mTime;
+      keyframe = sample->mKeyframe;
+      if (keyframe) {
+        break;
+      }
+    }
+    if (mType == TrackInfo::kVideoTrack &&
+        !mInfo->GetAsVideoInfo()->HasAlpha()) {
+      // We only perform a search for a keyframe on videos with alpha layer to
+      // prevent potential regression for normal video (even though invalid)
+      break;
+    }
+    if (!keyframe) {
+      // We didn't find any keyframe, attempt to seek to the previous cluster.
+      seekTime = mSamples.First()->mTime - TimeUnit::FromMicroseconds(1);
+    }
+  } while (!keyframe && seekTime >= TimeUnit::Zero());
+
+  SetNextKeyFrameTime();
+
+  return SeekPromise::CreateAndResolve(seekTime, __func__);
+}
+
+nsresult WebMTrackDemuxer::NextSample(RefPtr<MediaRawData>& aData) {
+  nsresult rv = NS_ERROR_DOM_MEDIA_END_OF_STREAM;
+  while (mSamples.GetSize() < 1 &&
+         NS_SUCCEEDED((rv = mParent->GetNextPacket(mType, &mSamples)))) {
+  }
+  if (mSamples.GetSize()) {
+    aData = mSamples.PopFront();
+    return NS_OK;
+  }
+  return rv;
+}
+
+RefPtr<WebMTrackDemuxer::SamplesPromise> WebMTrackDemuxer::GetSamples(
+    int32_t aNumSamples) {
+  RefPtr<SamplesHolder> samples = new SamplesHolder;
+  MOZ_ASSERT(aNumSamples);
+
+  nsresult rv = NS_ERROR_DOM_MEDIA_END_OF_STREAM;
+
+  while (aNumSamples) {
+    RefPtr<MediaRawData> sample;
+    rv = NextSample(sample);
+    if (NS_FAILED(rv)) {
+      break;
+    }
+    // Ignore empty samples.
+    if (sample->Size() == 0) {
+      WEBM_DEBUG(
+          "0 sized sample encountered while getting samples, skipping it");
+      continue;
+    }
+    if (mNeedKeyframe && !sample->mKeyframe) {
+      continue;
+    }
+    if (!sample->HasValidTime()) {
+      return SamplesPromise::CreateAndReject(NS_ERROR_DOM_MEDIA_DEMUXER_ERR,
+                                             __func__);
+    }
+    mNeedKeyframe = false;
+    samples->AppendSample(sample);
+    aNumSamples--;
+  }
+
+  if (samples->GetSamples().IsEmpty()) {
+    return SamplesPromise::CreateAndReject(rv, __func__);
+  } else {
+    UpdateSamples(samples->GetSamples());
+    return SamplesPromise::CreateAndResolve(samples, __func__);
+  }
+}
+
+void WebMTrackDemuxer::SetNextKeyFrameTime() {
+  if (mType != TrackInfo::kVideoTrack || mParent->IsMediaSource()) {
+    return;
+  }
+
+  auto frameTime = TimeUnit::Invalid();
+
+  mNextKeyframeTime.reset();
+
+  MediaRawDataQueue skipSamplesQueue;
+  bool foundKeyframe = false;
+  while (!foundKeyframe && mSamples.GetSize()) {
+    RefPtr<MediaRawData> sample = mSamples.PopFront();
+    if (sample->mKeyframe) {
+      frameTime = sample->mTime;
+      foundKeyframe = true;
+    }
+    skipSamplesQueue.Push(sample.forget());
+  }
+  Maybe<int64_t> startTime;
+  if (skipSamplesQueue.GetSize()) {
+    const RefPtr<MediaRawData>& sample = skipSamplesQueue.First();
+    startTime.emplace(sample->mTimecode.ToMicroseconds());
+  }
+  // Demux and buffer frames until we find a keyframe.
+  RefPtr<MediaRawData> sample;
+  nsresult rv = NS_OK;
+  while (!foundKeyframe && NS_SUCCEEDED((rv = NextSample(sample)))) {
+    if (sample->mKeyframe) {
+      frameTime = sample->mTime;
+      foundKeyframe = true;
+    }
+    int64_t sampleTimecode = sample->mTimecode.ToMicroseconds();
+    skipSamplesQueue.Push(sample.forget());
+    if (!startTime) {
+      startTime.emplace(sampleTimecode);
+    } else if (!foundKeyframe &&
+               sampleTimecode > startTime.ref() + MAX_LOOK_AHEAD) {
+      WEBM_DEBUG("Couldn't find keyframe in a reasonable time, aborting");
+      break;
+    }
+  }
+  // We may have demuxed more than intended, so ensure that all frames are kept
+  // in the right order.
+  mSamples.PushFront(std::move(skipSamplesQueue));
+
+  if (frameTime.IsValid()) {
+    mNextKeyframeTime.emplace(frameTime);
+    WEBM_DEBUG(
+        "Next Keyframe %f (%u queued %.02fs)",
+        mNextKeyframeTime.value().ToSeconds(), uint32_t(mSamples.GetSize()),
+        (mSamples.Last()->mTimecode - mSamples.First()->mTimecode).ToSeconds());
+  } else {
+    WEBM_DEBUG("Couldn't determine next keyframe time  (%u queued)",
+               uint32_t(mSamples.GetSize()));
+  }
+}
+
+void WebMTrackDemuxer::Reset() {
+  mSamples.Reset();
+  media::TimeIntervals buffered = GetBuffered();
+  mNeedKeyframe = true;
+  if (!buffered.IsEmpty()) {
+    WEBM_DEBUG("Seek to start point: %f", buffered.Start(0).ToSeconds());
+    mParent->SeekInternal(mType, buffered.Start(0));
+    SetNextKeyFrameTime();
+  } else {
+    mNextKeyframeTime.reset();
+  }
+}
+
+void WebMTrackDemuxer::UpdateSamples(
+    const nsTArray<RefPtr<MediaRawData>>& aSamples) {
+  for (const auto& sample : aSamples) {
+    if (sample->mCrypto.IsEncrypted()) {
+      UniquePtr<MediaRawDataWriter> writer(sample->CreateWriter());
+      writer->mCrypto.mIVSize = mInfo->mCrypto.mIVSize;
+      writer->mCrypto.mKeyId.AppendElements(mInfo->mCrypto.mKeyId);
+    }
+  }
+  if (mNextKeyframeTime.isNothing() ||
+      aSamples.LastElement()->mTime >= mNextKeyframeTime.value()) {
+    SetNextKeyFrameTime();
+  }
+}
+
+nsresult WebMTrackDemuxer::GetNextRandomAccessPoint(TimeUnit* aTime) {
+  if (mNextKeyframeTime.isNothing()) {
+    // There's no next key frame.
+    *aTime = TimeUnit::FromInfinity();
+  } else {
+    *aTime = mNextKeyframeTime.ref();
+  }
+  return NS_OK;
+}
+
+RefPtr<WebMTrackDemuxer::SkipAccessPointPromise>
+WebMTrackDemuxer::SkipToNextRandomAccessPoint(const TimeUnit& aTimeThreshold) {
+  uint32_t parsed = 0;
+  bool found = false;
+  RefPtr<MediaRawData> sample;
+  nsresult rv = NS_OK;
+
+  WEBM_DEBUG("TimeThreshold: %f", aTimeThreshold.ToSeconds());
+  while (!found && NS_SUCCEEDED((rv = NextSample(sample)))) {
+    parsed++;
+    if (sample->mKeyframe && sample->mTime >= aTimeThreshold) {
+      WEBM_DEBUG("next sample: %f (parsed: %d)", sample->mTime.ToSeconds(),
+                 parsed);
+      found = true;
+      mSamples.Reset();
+      mSamples.PushFront(sample.forget());
+    }
+  }
+  if (NS_SUCCEEDED(rv)) {
+    SetNextKeyFrameTime();
+  }
+  if (found) {
+    return SkipAccessPointPromise::CreateAndResolve(parsed, __func__);
+  } else {
+    SkipFailureHolder failure(NS_ERROR_DOM_MEDIA_END_OF_STREAM, parsed);
+    return SkipAccessPointPromise::CreateAndReject(std::move(failure),
+                                                   __func__);
+  }
+}
+
+media::TimeIntervals WebMTrackDemuxer::GetBuffered() {
+  return mParent->GetBuffered();
+}
+
+void WebMTrackDemuxer::BreakCycles() { mParent = nullptr; }
+
+int64_t WebMTrackDemuxer::GetEvictionOffset(const TimeUnit& aTime) {
+  int64_t offset;
+  int64_t nanos = aTime.ToNanoseconds();
+  if (nanos < 0 ||
+      !mParent->GetOffsetForTime(static_cast<uint64_t>(nanos), &offset)) {
+    return 0;
+  }
+
+  return offset;
+}
+}  // namespace mozilla
+
+#undef WEBM_DEBUG
diff --git a/dom/media/webm/WebMDemuxer.h b/dom/media/webm/WebMDemuxer.h
new file mode 100644
index 0000000000..3d8ff67f9e
--- /dev/null
+++ b/dom/media/webm/WebMDemuxer.h
@@ -0,0 +1,288 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef WebMDemuxer_h_
+#define WebMDemuxer_h_
+
+#include "nsTArray.h"
+#include "MediaDataDemuxer.h"
+#include "MediaResource.h"
+#include "NesteggPacketHolder.h"
+
+#include <deque>
+#include <stdint.h>
+#include <utility>
+
+typedef struct nestegg nestegg;
+
+namespace mozilla {
+
+class WebMBufferedState;
+
+// Queue for holding MediaRawData samples
+class MediaRawDataQueue {
+  typedef std::deque<RefPtr<MediaRawData>> ContainerType;
+
+ public:
+  uint32_t GetSize() { return mQueue.size(); }
+
+  void Push(MediaRawData* aItem) { mQueue.push_back(aItem); }
+
+  void Push(already_AddRefed<MediaRawData>&& aItem) {
+    mQueue.push_back(std::move(aItem));
+  }
+
+  void PushFront(MediaRawData* aItem) { mQueue.push_front(aItem); }
+
+  void PushFront(already_AddRefed<MediaRawData>&& aItem) {
+    mQueue.push_front(std::move(aItem));
+  }
+
+  void PushFront(MediaRawDataQueue&& aOther) {
+    while (!aOther.mQueue.empty()) {
+      PushFront(aOther.Pop());
+    }
+  }
+
+  already_AddRefed<MediaRawData> PopFront() {
+    RefPtr<MediaRawData> result = std::move(mQueue.front());
+    mQueue.pop_front();
+    return result.forget();
+  }
+
+  already_AddRefed<MediaRawData> Pop() {
+    RefPtr<MediaRawData> result = std::move(mQueue.back());
+    mQueue.pop_back();
+    return result.forget();
+  }
+
+  void Reset() {
+    while (!mQueue.empty()) {
+      mQueue.pop_front();
+    }
+  }
+
+  MediaRawDataQueue& operator=(const MediaRawDataQueue& aOther) = delete;
+
+  const RefPtr<MediaRawData>& First() const { return mQueue.front(); }
+
+  const RefPtr<MediaRawData>& Last() const { return mQueue.back(); }
+
+  // Methods for range-based for loops.
+  ContainerType::iterator begin() { return mQueue.begin(); }
+
+  ContainerType::const_iterator begin() const { return mQueue.begin(); }
+
+  ContainerType::iterator end() { return mQueue.end(); }
+
+  ContainerType::const_iterator end() const { return mQueue.end(); }
+
+ private:
+  ContainerType mQueue;
+};
+
+class WebMTrackDemuxer;
+
+DDLoggedTypeDeclNameAndBase(WebMDemuxer, MediaDataDemuxer);
+DDLoggedTypeNameAndBase(WebMTrackDemuxer, MediaTrackDemuxer);
+
+class WebMDemuxer : public MediaDataDemuxer,
+                    public DecoderDoctorLifeLogger<WebMDemuxer> {
+ public:
+  explicit WebMDemuxer(MediaResource* aResource);
+  // Indicate if the WebMDemuxer is to be used with MediaSource. In which
+  // case the demuxer will stop reads to the last known complete block.
+  WebMDemuxer(MediaResource* aResource, bool aIsMediaSource);
+
+  RefPtr<InitPromise> Init() override;
+
+  uint32_t GetNumberTracks(TrackInfo::TrackType aType) const override;
+
+  UniquePtr<TrackInfo> GetTrackInfo(TrackInfo::TrackType aType,
+                                    size_t aTrackNumber) const;
+
+  already_AddRefed<MediaTrackDemuxer> GetTrackDemuxer(
+      TrackInfo::TrackType aType, uint32_t aTrackNumber) override;
+
+  bool IsSeekable() const override;
+
+  bool IsSeekableOnlyInBufferedRanges() const override;
+
+  UniquePtr<EncryptionInfo> GetCrypto() override;
+
+  bool GetOffsetForTime(uint64_t aTime, int64_t* aOffset);
+
+  // Demux next WebM packet and append samples to MediaRawDataQueue
+  nsresult GetNextPacket(TrackInfo::TrackType aType,
+                         MediaRawDataQueue* aSamples);
+
+  void Reset(TrackInfo::TrackType aType);
+
+  // Pushes a packet to the front of the audio packet queue.
+  void PushAudioPacket(NesteggPacketHolder* aItem);
+
+  // Pushes a packet to the front of the video packet queue.
+  void PushVideoPacket(NesteggPacketHolder* aItem);
+
+  // Public accessor for nestegg callbacks
+  bool IsMediaSource() const { return mIsMediaSource; }
+
+  int64_t LastWebMBlockOffset() const { return mLastWebMBlockOffset; }
+
+  struct NestEggContext {
+    NestEggContext(WebMDemuxer* aParent, MediaResource* aResource)
+        : mParent(aParent), mResource(aResource), mContext(nullptr) {}
+
+    ~NestEggContext();
+
+    int Init();
+
+    // Public accessor for nestegg callbacks
+
+    bool IsMediaSource() const { return mParent->IsMediaSource(); }
+    MediaResourceIndex* GetResource() { return &mResource; }
+
+    int64_t GetEndDataOffset() const {
+      return (!mParent->IsMediaSource() || mParent->LastWebMBlockOffset() < 0)
+                 ? mResource.GetLength()
+                 : mParent->LastWebMBlockOffset();
+    }
+
+    WebMDemuxer* mParent;
+    MediaResourceIndex mResource;
+    nestegg* mContext;
+  };
+
+ private:
+  friend class WebMTrackDemuxer;
+
+  ~WebMDemuxer();
+  void InitBufferedState();
+  nsresult ReadMetadata();
+  void NotifyDataArrived() override;
+  void NotifyDataRemoved() override;
+  void EnsureUpToDateIndex();
+
+  // A helper to catch bad intervals during `GetBuffered`.
+  // Verifies if the interval given by start and end is valid, returning true if
+  // it is, or false if not. Logs failure reason if the interval is invalid.
+  bool IsBufferedIntervalValid(uint64_t start, uint64_t end);
+
+  media::TimeIntervals GetBuffered();
+  nsresult SeekInternal(TrackInfo::TrackType aType,
+                        const media::TimeUnit& aTarget);
+  CryptoTrack GetTrackCrypto(TrackInfo::TrackType aType, size_t aTrackNumber);
+
+  // Read a packet from the nestegg file. Returns nullptr if all packets for
+  // the particular track have been read. Pass TrackInfo::kVideoTrack or
+  // TrackInfo::kVideoTrack to indicate the type of the packet we want to read.
+  nsresult NextPacket(TrackInfo::TrackType aType,
+                      RefPtr<NesteggPacketHolder>& aPacket);
+
+  // Internal method that demuxes the next packet from the stream. The caller
+  // is responsible for making sure it doesn't get lost.
+  nsresult DemuxPacket(TrackInfo::TrackType aType,
+                       RefPtr<NesteggPacketHolder>& aPacket);
+
+  // libnestegg audio and video context for webm container.
+  // Access on reader's thread only.
+  NestEggContext mVideoContext;
+  NestEggContext mAudioContext;
+  MediaResourceIndex& Resource(TrackInfo::TrackType aType) {
+    return aType == TrackInfo::kVideoTrack ? mVideoContext.mResource
+                                           : mAudioContext.mResource;
+  }
+  nestegg* Context(TrackInfo::TrackType aType) const {
+    return aType == TrackInfo::kVideoTrack ? mVideoContext.mContext
+                                           : mAudioContext.mContext;
+  }
+
+  MediaInfo mInfo;
+  nsTArray<RefPtr<WebMTrackDemuxer>> mDemuxers;
+
+  // Parser state and computed offset-time mappings.  Shared by multiple
+  // readers when decoder has been cloned.  Main thread only.
+  RefPtr<WebMBufferedState> mBufferedState;
+  RefPtr<MediaByteBuffer> mInitData;
+
+  // Queue of video and audio packets that have been read but not decoded.
+  WebMPacketQueue mVideoPackets;
+  WebMPacketQueue mAudioPackets;
+
+  // Index of video and audio track to play
+  uint32_t mVideoTrack;
+  uint32_t mAudioTrack;
+
+  // Nanoseconds to discard after seeking.
+  uint64_t mSeekPreroll;
+
+  // Calculate the frame duration from the last decodeable frame using the
+  // previous frame's timestamp.  In NS.
+  Maybe<int64_t> mLastAudioFrameTime;
+  Maybe<int64_t> mLastVideoFrameTime;
+
+  // Codec ID of audio track
+  int mAudioCodec;
+  // Codec ID of video track
+  int mVideoCodec;
+
+  // Booleans to indicate if we have audio and/or video data
+  bool mHasVideo;
+  bool mHasAudio;
+  bool mNeedReIndex;
+
+  // The last complete block parsed by the WebMBufferedState. -1 if not set.
+  // We cache those values rather than retrieving them for performance reasons
+  // as nestegg only performs 1-byte read at a time.
+  int64_t mLastWebMBlockOffset;
+  const bool mIsMediaSource;
+
+  EncryptionInfo mCrypto;
+};
+
+class WebMTrackDemuxer : public MediaTrackDemuxer,
+                         public DecoderDoctorLifeLogger<WebMTrackDemuxer> {
+ public:
+  WebMTrackDemuxer(WebMDemuxer* aParent, TrackInfo::TrackType aType,
+                   uint32_t aTrackNumber);
+
+  UniquePtr<TrackInfo> GetInfo() const override;
+
+  RefPtr<SeekPromise> Seek(const media::TimeUnit& aTime) override;
+
+  RefPtr<SamplesPromise> GetSamples(int32_t aNumSamples = 1) override;
+
+  void Reset() override;
+
+  nsresult GetNextRandomAccessPoint(media::TimeUnit* aTime) override;
+
+  RefPtr<SkipAccessPointPromise> SkipToNextRandomAccessPoint(
+      const media::TimeUnit& aTimeThreshold) override;
+
+  media::TimeIntervals GetBuffered() override;
+
+  int64_t GetEvictionOffset(const media::TimeUnit& aTime) override;
+
+  void BreakCycles() override;
+
+ private:
+  friend class WebMDemuxer;
+  ~WebMTrackDemuxer();
+  void UpdateSamples(const nsTArray<RefPtr<MediaRawData>>& aSamples);
+  void SetNextKeyFrameTime();
+  nsresult NextSample(RefPtr<MediaRawData>& aData);
+  RefPtr<WebMDemuxer> mParent;
+  TrackInfo::TrackType mType;
+  UniquePtr<TrackInfo> mInfo;
+  Maybe<media::TimeUnit> mNextKeyframeTime;
+  bool mNeedKeyframe;
+
+  // Queued samples extracted by the demuxer, but not yet returned.
+  MediaRawDataQueue mSamples;
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/dom/media/webm/WebMWriter.cpp b/dom/media/webm/WebMWriter.cpp
new file mode 100644
index 0000000000..96c4169091
--- /dev/null
+++ b/dom/media/webm/WebMWriter.cpp
@@ -0,0 +1,112 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WebMWriter.h"
+#include "EbmlComposer.h"
+#include "mozilla/ProfilerLabels.h"
+#include "OpusTrackEncoder.h"
+
+namespace mozilla {
+
+WebMWriter::WebMWriter()
+    : ContainerWriter(), mEbmlComposer(new EbmlComposer()) {}
+
+WebMWriter::~WebMWriter() {
+  // Out-of-line dtor so mEbmlComposer UniquePtr can delete a complete type.
+}
+
+nsresult WebMWriter::WriteEncodedTrack(
+    const nsTArray<RefPtr<EncodedFrame>>& aData, uint32_t aFlags) {
+  AUTO_PROFILER_LABEL("WebMWriter::WriteEncodedTrack", OTHER);
+  for (uint32_t i = 0; i < aData.Length(); i++) {
+    nsresult rv = mEbmlComposer->WriteSimpleBlock(aData.ElementAt(i).get());
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+  return NS_OK;
+}
+
+nsresult WebMWriter::GetContainerData(nsTArray<nsTArray<uint8_t>>* aOutputBufs,
+                                      uint32_t aFlags) {
+  AUTO_PROFILER_LABEL("WebMWriter::GetContainerData", OTHER);
+  mEbmlComposer->ExtractBuffer(aOutputBufs, aFlags);
+  if (aFlags & ContainerWriter::FLUSH_NEEDED) {
+    mIsWritingComplete = true;
+  }
+  return NS_OK;
+}
+
+nsresult WebMWriter::SetMetadata(
+    const nsTArray<RefPtr<TrackMetadataBase>>& aMetadata) {
+  AUTO_PROFILER_LABEL("WebMWriter::SetMetadata", OTHER);
+  MOZ_DIAGNOSTIC_ASSERT(!aMetadata.IsEmpty());
+
+  // Integrity checks
+  bool bad = false;
+  for (const RefPtr<TrackMetadataBase>& metadata : aMetadata) {
+    MOZ_ASSERT(metadata);
+
+    if (metadata->GetKind() == TrackMetadataBase::METADATA_VP8) {
+      VP8Metadata* meta = static_cast<VP8Metadata*>(metadata.get());
+      if (meta->mWidth == 0 || meta->mHeight == 0 || meta->mDisplayWidth == 0 ||
+          meta->mDisplayHeight == 0) {
+        bad = true;
+      }
+    }
+
+    if (metadata->GetKind() == TrackMetadataBase::METADATA_VORBIS) {
+      VorbisMetadata* meta = static_cast<VorbisMetadata*>(metadata.get());
+      if (meta->mSamplingFrequency == 0 || meta->mChannels == 0 ||
+          meta->mData.IsEmpty()) {
+        bad = true;
+      }
+    }
+
+    if (metadata->GetKind() == TrackMetadataBase::METADATA_OPUS) {
+      OpusMetadata* meta = static_cast<OpusMetadata*>(metadata.get());
+      if (meta->mSamplingFrequency == 0 || meta->mChannels == 0 ||
+          meta->mIdHeader.IsEmpty()) {
+        bad = true;
+      }
+    }
+  }
+  if (bad) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Storing
+  DebugOnly<bool> hasAudio = false;
+  DebugOnly<bool> hasVideo = false;
+  for (const RefPtr<TrackMetadataBase>& metadata : aMetadata) {
+    MOZ_ASSERT(metadata);
+
+    if (metadata->GetKind() == TrackMetadataBase::METADATA_VP8) {
+      MOZ_ASSERT(!hasVideo);
+      VP8Metadata* meta = static_cast<VP8Metadata*>(metadata.get());
+      mEbmlComposer->SetVideoConfig(meta->mWidth, meta->mHeight,
+                                    meta->mDisplayWidth, meta->mDisplayHeight);
+      hasVideo = true;
+    }
+
+    if (metadata->GetKind() == TrackMetadataBase::METADATA_VORBIS) {
+      MOZ_ASSERT(!hasAudio);
+      VorbisMetadata* meta = static_cast<VorbisMetadata*>(metadata.get());
+      mEbmlComposer->SetAudioConfig(meta->mSamplingFrequency, meta->mChannels);
+      mEbmlComposer->SetAudioCodecPrivateData(meta->mData);
+      hasAudio = true;
+    }
+
+    if (metadata->GetKind() == TrackMetadataBase::METADATA_OPUS) {
+      MOZ_ASSERT(!hasAudio);
+      OpusMetadata* meta = static_cast<OpusMetadata*>(metadata.get());
+      mEbmlComposer->SetAudioConfig(meta->mSamplingFrequency, meta->mChannels);
+      mEbmlComposer->SetAudioCodecPrivateData(meta->mIdHeader);
+      hasAudio = true;
+    }
+  }
+  mEbmlComposer->GenerateHeader();
+  return NS_OK;
+}
+
+}  // namespace mozilla
diff --git a/dom/media/webm/WebMWriter.h b/dom/media/webm/WebMWriter.h
new file mode 100644
index 0000000000..71d2e18311
--- /dev/null
+++ b/dom/media/webm/WebMWriter.h
@@ -0,0 +1,69 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WebMWriter_h_
+#define WebMWriter_h_
+
+#include "ContainerWriter.h"
+
+namespace mozilla {
+
+class EbmlComposer;
+
+// Vorbis meta data structure
+class VorbisMetadata : public TrackMetadataBase {
+ public:
+  nsTArray<uint8_t> mData;
+  int32_t mChannels;
+  float mSamplingFrequency;
+  MetadataKind GetKind() const override { return METADATA_VORBIS; }
+};
+
+// VP8 meta data structure
+class VP8Metadata : public TrackMetadataBase {
+ public:
+  int32_t mWidth;
+  int32_t mHeight;
+  int32_t mDisplayWidth;
+  int32_t mDisplayHeight;
+  MetadataKind GetKind() const override { return METADATA_VP8; }
+};
+
+/**
+ * WebM writer helper
+ * This class accepts encoder to set audio or video meta data or
+ * encoded data to ebml Composer, and get muxing data through GetContainerData.
+ * The ctor/dtor run in the MediaRecorder thread, others run in MediaEncoder
+ * thread.
+ */
+class WebMWriter : public ContainerWriter {
+ public:
+  // Run in MediaRecorder thread
+  WebMWriter();
+  virtual ~WebMWriter();
+
+  // WriteEncodedTrack inserts raw packets into WebM stream. Does not accept
+  // any flags: any specified will be ignored. Writing is finalized via
+  // flushing via GetContainerData().
+  nsresult WriteEncodedTrack(const nsTArray<RefPtr<EncodedFrame>>& aData,
+                             uint32_t aFlags = 0) override;
+
+  // GetContainerData outputs multiplexing data.
+  // aFlags indicates the muxer should enter into finished stage and flush out
+  // queue data.
+  nsresult GetContainerData(nsTArray<nsTArray<uint8_t>>* aOutputBufs,
+                            uint32_t aFlags = 0) override;
+
+  // Assign metadata into muxer
+  nsresult SetMetadata(
+      const nsTArray<RefPtr<TrackMetadataBase>>& aMetadata) override;
+
+ private:
+  UniquePtr<EbmlComposer> mEbmlComposer;
+};
+
+}  // namespace mozilla
+
+#endif
diff --git a/dom/media/webm/moz.build b/dom/media/webm/moz.build
new file mode 100644
index 0000000000..f65fe5bc6b
--- /dev/null
+++ b/dom/media/webm/moz.build
@@ -0,0 +1,28 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXPORTS += [
+    "NesteggPacketHolder.h",
+    "WebMBufferedParser.h",
+    "WebMDecoder.h",
+    "WebMDemuxer.h",
+    "WebMWriter.h",
+]
+
+UNIFIED_SOURCES += [
+    "EbmlComposer.cpp",
+    "WebMBufferedParser.cpp",
+    "WebMDecoder.cpp",
+    "WebMDemuxer.cpp",
+    "WebMWriter.cpp",
+]
+
+CXXFLAGS += CONFIG["MOZ_LIBVPX_CFLAGS"]
+
+FINAL_LIBRARY = "xul"
+
+# Add libFuzzer configuration directives
+include("/tools/fuzzing/libfuzzer-config.mozbuild")