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| -rw-r--r-- | dom/media/webm/WebMBufferedParser.h | 309 |
1 files changed, 309 insertions, 0 deletions
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 |