gecko-dev/content/media/encoder/MediaEncoder.h

135 lines
4.6 KiB
C++

/* -*- 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 "mozilla/DebugOnly.h"
#include "TrackEncoder.h"
#include "ContainerWriter.h"
#include "MediaStreamGraph.h"
namespace mozilla {
/**
* MediaEncoder is the framework of encoding module, it controls and manages
* procedures between ContainerWriter and TrackEncoder. ContainerWriter packs
* the encoded track data with a specific container (e.g. ogg, mp4).
* AudioTrackEncoder and VideoTrackEncoder are subclasses of TrackEncoder, and
* are responsible for encoding raw data coming from MediaStreamGraph.
*
* Also, MediaEncoder is a type of MediaStreamListener, it starts to receive raw
* segments after itself is added to the source stream. In the mean time,
* encoded track data is pulled by its owner periodically on a worker thread. A
* reentrant monitor is used to protect the push and pull of resource.
*
* MediaEncoder is designed to be a passive component, neither it owns nor in
* charge of managing threads. However, a monitor is used in function
* TrackEncoder::GetEncodedTrack() for the purpose of thread safety (e.g.
* between callbacks of MediaStreamListener and others), a call to this function
* might block. Therefore, MediaEncoder should not run on threads that forbid
* blocking, such as main thread or I/O thread.
*
* For example, an usage from MediaRecorder of this component would be:
* 1) Create an encoder with a valid MIME type.
* => encoder = MediaEncoder::CreateEncoder(aMIMEType);
* It then generate a ContainerWriter according to the MIME type, and an
* AudioTrackEncoder (or a VideoTrackEncoder too) associated with the media
* type.
*
* 2) Dispatch the task GetEncodedData() to a worker thread.
*
* 3) To start encoding, add this component to its source stream.
* => sourceStream->AddListener(encoder);
*
* 4) To stop encoding, remove this component from its source stream.
* => sourceStream->RemoveListener(encoder);
*/
class MediaEncoder : public MediaStreamListener
{
public :
enum {
ENCODE_HEADER,
ENCODE_TRACK,
ENCODE_DONE,
};
MediaEncoder(ContainerWriter* aWriter,
AudioTrackEncoder* aAudioEncoder,
VideoTrackEncoder* aVideoEncoder,
const nsAString& aMIMEType)
: mWriter(aWriter)
, mAudioEncoder(aAudioEncoder)
, mVideoEncoder(aVideoEncoder)
, mMIMEType(aMIMEType)
, mState(MediaEncoder::ENCODE_HEADER)
, mShutdown(false)
{}
~MediaEncoder() {};
/**
* Notified by the control loop of MediaStreamGraph; aQueueMedia is the raw
* track data in form of MediaSegment.
*/
virtual void NotifyQueuedTrackChanges(MediaStreamGraph* aGraph, TrackID aID,
TrackRate aTrackRate,
TrackTicks aTrackOffset,
uint32_t aTrackEvents,
const MediaSegment& aQueuedMedia);
/**
* Notified the stream is being removed.
*/
virtual void NotifyRemoved(MediaStreamGraph* aGraph);
/**
* Creates an encoder with a given MIME type. Returns null if we are unable
* to create the encoder. For now, default aMIMEType to "audio/ogg" and use
* Ogg+Opus if it is empty.
*/
static already_AddRefed<MediaEncoder> CreateEncoder(const nsAString& aMIMEType);
/**
* Encodes the raw track data and returns the final container data. Assuming
* it is called on a single worker thread. The buffer of container data is
* allocated in ContainerWriter::GetContainerData(), and is appended to
* aOutputBufs. aMIMEType is the valid mime-type of this returned container
* data.
*/
void GetEncodedData(nsTArray<nsTArray<uint8_t> >* aOutputBufs,
nsAString& aMIMEType);
/**
* Return true if MediaEncoder has been shutdown. Reasons are encoding
* complete, encounter an error, or being canceled by its caller.
*/
bool IsShutdown()
{
return mShutdown;
}
/**
* Cancel the encoding, and wakes up the lock of reentrant monitor in encoder.
*/
void Cancel()
{
if (mAudioEncoder) {
mAudioEncoder->NotifyCancel();
}
}
private:
nsAutoPtr<ContainerWriter> mWriter;
nsAutoPtr<AudioTrackEncoder> mAudioEncoder;
nsAutoPtr<VideoTrackEncoder> mVideoEncoder;
nsString mMIMEType;
int mState;
bool mShutdown;
};
}
#endif