tor-browser

MediaEncoder.h (14519B)

---

/* -*- 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 MediaEncoder_h_
#define MediaEncoder_h_

#include "ContainerWriter.h"
#include "CubebUtils.h"
#include "MediaQueue.h"
#include "MediaTrackGraph.h"
#include "MediaTrackListener.h"
#include "TrackEncoder.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/MozPromise.h"
#include "mozilla/UniquePtr.h"
#include "nsIMemoryReporter.h"

namespace mozilla {

class DriftCompensator;
class Muxer;
class Runnable;
class TaskQueue;

namespace dom {
class AudioNode;
class AudioStreamTrack;
class BlobImpl;
class MediaStreamTrack;
class MutableBlobStorage;
class VideoStreamTrack;
}  // namespace dom

class DriftCompensator;

/**
* MediaEncoder is the framework of encoding module, it controls and manages
* procedures between Muxer, ContainerWriter and TrackEncoder. ContainerWriter
* writes the encoded track data into a specific container (e.g. ogg, webm).
* AudioTrackEncoder and VideoTrackEncoder are subclasses of TrackEncoder, and
* are responsible for encoding raw data coming from MediaStreamTracks.
*
* MediaEncoder solves threading issues by doing message passing to a TaskQueue
* (the "encoder thread") as passed in to the constructor. Each
* MediaStreamTrack to be recorded is set up with a MediaTrackListener.
* Typically there are a non-direct track listeners for audio, direct listeners
* for video, and there is always a non-direct listener on each track for
* time-keeping. The listeners forward data to their corresponding TrackEncoders
* on the encoder thread.
*
* The MediaEncoder listens to events from all TrackEncoders, and in turn
* signals events to interested parties. Typically a MediaRecorder::Session.
* The MediaEncoder automatically encodes incoming data, muxes it, writes it
* into a container and stores the container data into a MutableBlobStorage.
* It is timeslice-aware so that it can notify listeners when it's time to
* expose a blob due to filling the timeslice.
*
* MediaEncoder is designed to be a passive component, neither does it own or is
* in charge of managing threads. Instead this is done by its owner.
*
* For example, usage from MediaRecorder of this component would be:
* 1) Create an encoder with a valid MIME type. Note that there are more
*    configuration options, see the docs on MediaEncoder::CreateEncoder.
*    => encoder = MediaEncoder::CreateEncoder(aMIMEType);
*    It then creates track encoders and the appropriate ContainerWriter
*    according to the MIME type
*
* 2) Connect handlers through MediaEventListeners to the MediaEncoder's
*    MediaEventSources, StartedEvent(), DataAvailableEvent(), ErrorEvent() and
*    ShutdownEvent().
*    => listener = encoder->DataAvailableEvent().Connect(mainThread, &OnBlob);
*
* 3) Connect the sources to be recorded. Either through:
*    => encoder->ConnectAudioNode(node);
*    or
*    => encoder->ConnectMediaStreamTrack(track);
*    These should not be mixed. When connecting MediaStreamTracks there is
*    support for at most one of each kind.
*
* 4) MediaEncoder automatically encodes data from the connected tracks, muxes
*    them and writes it all into a blob, including metadata. When the blob
*    contains at least `timeslice` worth of data it notifies the
*    DataAvailableEvent that was connected in step 2.
*    => void OnBlob(RefPtr<BlobImpl> aBlob) {
*    =>   DispatchBlobEvent(Blob::Create(GetOwnerGlobal(), aBlob));
*    => };
*
* 5) To stop encoding, there are multiple options:
*
*    5.1) Stop() for a graceful stop.
*         => encoder->Stop();
*
*    5.2) Cancel() for an immediate stop, if you don't need the data currently
*         buffered.
*         => encoder->Cancel();
*
*    5.3) When all input tracks end, the MediaEncoder will automatically stop
*         and shut down.
*/
class MediaEncoder {
private:
 class AudioTrackListener;
 class VideoTrackListener;
 class EncoderListener;

public:
 using BlobPromise =
     MozPromise<RefPtr<dom::BlobImpl>, nsresult, false /* IsExclusive */>;
 using SizeOfPromise = MozPromise<size_t, size_t, true /* IsExclusive */>;

 NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MediaEncoder)

private:
 MediaEncoder(RefPtr<TaskQueue> aEncoderThread,
              RefPtr<DriftCompensator> aDriftCompensator,
              UniquePtr<ContainerWriter> aWriter,
              UniquePtr<AudioTrackEncoder> aAudioEncoder,
              UniquePtr<VideoTrackEncoder> aVideoEncoder,
              UniquePtr<MediaQueue<EncodedFrame>> aEncodedAudioQueue,
              UniquePtr<MediaQueue<EncodedFrame>> aEncodedVideoQueue,
              TrackRate aTrackRate, const nsAString& aMIMEType,
              uint64_t aMaxMemory, TimeDuration aTimeslice);

public:
 /**
  * Called on main thread from MediaRecorder::Pause.
  */
 void Suspend();

 /**
  * Called on main thread from MediaRecorder::Resume.
  */
 void Resume();

 /**
  * Disconnects the input tracks, causing the encoding to stop.
  */
 void DisconnectTracks();

 /**
  * Connects an AudioNode with the appropriate encoder.
  */
 void ConnectAudioNode(dom::AudioNode* aNode, uint32_t aOutput);

 /**
  * Connects a MediaStreamTrack with the appropriate encoder.
  */
 void ConnectMediaStreamTrack(dom::MediaStreamTrack* aTrack);

 /**
  * Removes a connected MediaStreamTrack.
  */
 void RemoveMediaStreamTrack(dom::MediaStreamTrack* aTrack);

 /**
  * Creates an encoder with the given MIME type. This must be a valid MIME type
  * or we will crash hard.
  * Bitrates are given either explicit, or with 0 for defaults.
  * aTrackRate is the rate in which data will be fed to the TrackEncoders.
  * aMaxMemory is the maximum number of bytes of muxed data allowed in memory.
  * Beyond that the blob is moved to a temporary file.
  * aTimeslice is the minimum duration of muxed data we gather before
  * automatically issuing a dataavailable event.
  */
 static already_AddRefed<MediaEncoder> CreateEncoder(
     RefPtr<TaskQueue> aEncoderThread, const nsAString& aMimeType,
     uint32_t aAudioBitrate, uint32_t aVideoBitrate, uint8_t aTrackTypes,
     TrackRate aTrackRate, uint64_t aMaxMemory, TimeDuration aTimeslice);

 /**
  * Encodes raw data for all tracks to aOutputBufs. The buffer of container
  * data is allocated in ContainerWriter::GetContainerData().
  *
  * On its first call, metadata is also encoded. TrackEncoders must have been
  * initialized before this is called.
  */
 nsresult GetEncodedData(nsTArray<nsTArray<uint8_t>>* aOutputBufs);

 /**
  * Asserts that Shutdown() has been called. Reasons are encoding
  * complete, encounter an error, or being canceled by its caller.
  */
 void AssertShutdownCalled() { MOZ_ASSERT(mShutdownPromise); }

 /**
  * Stops (encoding any data currently buffered) the encoding and shuts down
  * the encoder using Shutdown().
  */
 RefPtr<GenericNonExclusivePromise> Stop();

 /**
  * Cancels (discarding any data currently buffered) the encoding and shuts
  * down the encoder using Shutdown().
  */
 RefPtr<GenericNonExclusivePromise> Cancel();

 bool HasError();

 static bool IsWebMEncoderEnabled();

 /**
  * Updates internal state when track encoders are all initialized.
  */
 void UpdateInitialized();

 /**
  * Updates internal state when track encoders are all initialized, and
  * notifies listeners that this MediaEncoder has been started.
  */
 void UpdateStarted();

 MOZ_DEFINE_MALLOC_SIZE_OF(MallocSizeOf)
 /*
  * Measure the size of the buffer, and heap memory in bytes occupied by
  * mAudioEncoder and mVideoEncoder.
  */
 RefPtr<SizeOfPromise> SizeOfExcludingThis(
     mozilla::MallocSizeOf aMallocSizeOf);

 /**
  * Encode, mux and store into blob storage what has been buffered until now,
  * then return the blob backed by that storage.
  */
 RefPtr<BlobPromise> RequestData();

 // Event that gets notified when all track encoders have received data.
 MediaEventSource<void>& StartedEvent() { return mStartedEvent; }
 // Event that gets notified when there was an error preventing continued
 // recording somewhere in the MediaEncoder stack.
 MediaEventSource<void>& ErrorEvent() { return mErrorEvent; }
 // Event that gets notified when the MediaEncoder stack has been shut down.
 MediaEventSource<void>& ShutdownEvent() { return mShutdownEvent; }
 // Event that gets notified after we have muxed at least mTimeslice worth of
 // data into the current blob storage.
 MediaEventSource<RefPtr<dom::BlobImpl>>& DataAvailableEvent() {
   return mDataAvailableEvent;
 }

protected:
 ~MediaEncoder();

private:
 /**
  * Registers listeners.
  */
 void RegisterListeners();

 /**
  * Sets mGraphTrack if not already set, using a new stream from aTrack's
  * graph.
  */
 void EnsureGraphTrackFrom(MediaTrack* aTrack);

 /**
  * Shuts down gracefully if there is no remaining live track encoder.
  */
 void MaybeShutdown();

 /**
  * Waits for TrackEncoders to shut down, then shuts down the MediaEncoder and
  * cleans up track encoders.
  */
 RefPtr<GenericNonExclusivePromise> Shutdown();

 /**
  * Sets mError to true, notifies listeners of the error if mError changed,
  * and stops encoding.
  */
 void SetError();

 /**
  * Creates a new MutableBlobStorage if one doesn't exist.
  */
 void MaybeCreateMutableBlobStorage();

 /**
  * Called when an encoded audio frame has been pushed by the audio encoder.
  */
 void OnEncodedAudioPushed(const RefPtr<EncodedFrame>& aFrame);

 /**
  * Called when an encoded video frame has been pushed by the video encoder.
  */
 void OnEncodedVideoPushed(const RefPtr<EncodedFrame>& aFrame);

 /**
  * If enough data has been pushed to the muxer, extract it into the current
  * blob storage. If more than mTimeslice data has been pushed to the muxer
  * since the last DataAvailableEvent was notified, also gather the blob and
  * notify MediaRecorder.
  */
 void MaybeExtractOrGatherBlob();

 // Extracts encoded and muxed data into the current blob storage, creating one
 // if it doesn't exist. The returned promise resolves when data has been
 // stored into the blob.
 RefPtr<GenericPromise> Extract();

 // Stops gathering data into the current blob and resolves when the current
 // blob is available. Future data will be stored in a new blob.
 // Should a previous async GatherBlob() operation still be in progress, we'll
 // wait for it to finish before starting this one.
 RefPtr<BlobPromise> GatherBlob();

 RefPtr<BlobPromise> GatherBlobImpl();

 const RefPtr<nsISerialEventTarget> mMainThread;
 const RefPtr<TaskQueue> mEncoderThread;
 const RefPtr<DriftCompensator> mDriftCompensator;

 const UniquePtr<MediaQueue<EncodedFrame>> mEncodedAudioQueue;
 const UniquePtr<MediaQueue<EncodedFrame>> mEncodedVideoQueue;

 const UniquePtr<Muxer> mMuxer;
 const UniquePtr<AudioTrackEncoder> mAudioEncoder;
 const RefPtr<AudioTrackListener> mAudioListener;
 const UniquePtr<VideoTrackEncoder> mVideoEncoder;
 const RefPtr<VideoTrackListener> mVideoListener;
 const RefPtr<EncoderListener> mEncoderListener;

public:
 const nsString mMimeType;

 // Max memory to use for the MutableBlobStorage.
 const uint64_t mMaxMemory;

 // The interval of passing encoded data from MutableBlobStorage to
 // onDataAvailable handler.
 const TimeDuration mTimeslice;

private:
 MediaEventListener mAudioPushListener;
 MediaEventListener mAudioFinishListener;
 MediaEventListener mVideoPushListener;
 MediaEventListener mVideoFinishListener;

 MediaEventProducer<void> mStartedEvent;
 MediaEventProducer<void> mErrorEvent;
 MediaEventProducer<void> mShutdownEvent;
 MediaEventProducer<RefPtr<dom::BlobImpl>> mDataAvailableEvent;

 // The AudioNode we are encoding.
 // Will be null when input is media stream or destination node.
 RefPtr<dom::AudioNode> mAudioNode;
 // Pipe-track for allowing a track listener on a non-destination AudioNode.
 // Will be null when input is media stream or destination node.
 RefPtr<AudioNodeTrack> mPipeTrack;
 // Input port that connect mAudioNode to mPipeTrack.
 // Will be null when input is media stream or destination node.
 RefPtr<MediaInputPort> mInputPort;
 // An audio track that we are encoding. Will be null if the input stream
 // doesn't contain audio on start() or if the input is an AudioNode.
 RefPtr<dom::AudioStreamTrack> mAudioTrack;
 // A video track that we are encoding. Will be null if the input stream
 // doesn't contain video on start() or if the input is an AudioNode.
 RefPtr<dom::VideoStreamTrack> mVideoTrack;

 // A stream to keep the MediaTrackGraph alive while we're recording.
 RefPtr<SharedDummyTrack> mGraphTrack;

 // A buffer to cache muxed encoded data.
 RefPtr<dom::MutableBlobStorage> mMutableBlobStorage;
 // If set, is a promise for the latest GatherBlob() operation. Allows
 // GatherBlob() operations to be serialized in order to avoid races.
 RefPtr<BlobPromise> mBlobPromise;
 // The end time of the muxed data in the last gathered blob. If more than one
 // track is present, this is the end time of the track that ends the earliest
 // in the last blob. Encoder thread only.
 media::TimeUnit mLastBlobTime;
 // The end time of the muxed data in the current blob storage. If more than
 // one track is present, this is the end time of the track that ends the
 // earliest in the current blob storage. Encoder thread only.
 media::TimeUnit mLastExtractTime;
 // The end time of encoded audio data sent to the muxer. Positive infinity if
 // there is no audio encoder. Encoder thread only.
 media::TimeUnit mMuxedAudioEndTime;
 // The end time of encoded video data sent to the muxer. Positive infinity if
 // there is no video encoder. Encoder thread only.
 media::TimeUnit mMuxedVideoEndTime;

 TimeStamp mStartTime;
 bool mInitialized;
 bool mStarted;
 bool mCompleted;
 bool mError;
 // Set when shutdown starts.
 RefPtr<GenericNonExclusivePromise> mShutdownPromise;
 // Get duration from create encoder, for logging purpose
 double GetEncodeTimeStamp() {
   TimeDuration decodeTime;
   decodeTime = TimeStamp::Now() - mStartTime;
   return decodeTime.ToMilliseconds();
 }
};

}  // namespace mozilla

#endif