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diff --git a/dom/media/encoder/OpusTrackEncoder.h b/dom/media/encoder/OpusTrackEncoder.h
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+/* -*- 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 OpusTrackEncoder_h_
+#define OpusTrackEncoder_h_
+
+#include <stdint.h>
+#include <speex/speex_resampler.h>
+#include "TimeUnits.h"
+#include "TrackEncoder.h"
+
+struct OpusEncoder;
+
+namespace mozilla {
+
+// Opus meta data structure
+class OpusMetadata : public TrackMetadataBase {
+ public:
+  // The ID Header of OggOpus. refer to http://wiki.xiph.org/OggOpus.
+  nsTArray<uint8_t> mIdHeader;
+  // The Comment Header of OggOpus.
+  nsTArray<uint8_t> mCommentHeader;
+  int32_t mChannels;
+  float mSamplingFrequency;
+  MetadataKind GetKind() const override { return METADATA_OPUS; }
+};
+
+class OpusTrackEncoder : public AudioTrackEncoder {
+ public:
+  OpusTrackEncoder(TrackRate aTrackRate,
+                   MediaQueue<EncodedFrame>& aEncodedDataQueue);
+  virtual ~OpusTrackEncoder();
+
+  already_AddRefed<TrackMetadataBase> GetMetadata() override;
+
+  /**
+   * The encoder lookahead at 48k rate.
+   */
+  int GetLookahead() const;
+
+ protected:
+  /**
+   * The number of frames, in the input rate mTrackRate, needed to fill an
+   * encoded opus packet. A frame is a sample per channel.
+   */
+  int NumInputFramesPerPacket() const override;
+
+  nsresult Init(int aChannels) override;
+
+  /**
+   * Encodes buffered data and pushes it to mEncodedDataQueue.
+   */
+  nsresult Encode(AudioSegment* aSegment) override;
+
+  /**
+   * The number of frames, in the output rate (see GetOutputSampleRate), needed
+   * to fill an encoded opus packet. A frame is a sample per channel.
+   */
+  int NumOutputFramesPerPacket() const;
+
+  /**
+   * True if the input needs to be resampled to be fed to the underlying opus
+   * encoder.
+   */
+  bool NeedsResampler() const;
+
+ public:
+  /**
+   * Get the samplerate of the data to be fed to the Opus encoder. This might be
+   * different from the input samplerate if resampling occurs.
+   */
+  const TrackRate mOutputSampleRate;
+
+ private:
+  /**
+   * The Opus encoder from libopus.
+   */
+  OpusEncoder* mEncoder;
+
+  /**
+   * Total samples of delay added by codec (in rate mOutputSampleRate), can
+   * be queried by the encoder. From the perspective of decoding, real data
+   * begins this many samples late, so the encoder needs to append this many
+   * null samples to the end of stream, in order to align the time of input and
+   * output.
+   */
+  int mLookahead;
+
+  /**
+   * Number of mLookahead samples that has been written. When non-zero and equal
+   * to mLookahead, encoding is complete.
+   */
+  int mLookaheadWritten;
+
+  /**
+   * If the input sample rate does not divide 48kHz evenly, the input data are
+   * resampled.
+   */
+  SpeexResamplerState* mResampler;
+
+  /**
+   * Store the resampled frames that don't fit into an Opus packet duration.
+   * They will be prepended to the resampled frames next encoding cycle.
+   */
+  nsTArray<AudioDataValue> mResampledLeftover;
+
+  /**
+   * Number of audio frames encoded, in kOpusSamplingRate.
+   */
+  uint64_t mNumOutputFrames;
+};
+
+}  // namespace mozilla
+
+#endif