video/audio playback:prepare & start
prepare:启动mQueue，对http://，rtsp://gtalk/，fmradio://rx 之类的url进行mAudioTrack/mVideoTrack分离，并根据mAudioTrack/mVideoTrack编码类型选择相应的decode
1.framework/base/media/libmediaplayerservice/MediaPlayerService.cpp
status_t MediaPlayerService::Client::prepareAsync()
{….
sp<MediaPlayerBase> p = getPlayer(); …….. setDataSource时创建的stagefrightplayer
if (p == 0) return UNKNOWN_ERROR;
status_t ret = p->prepareAsync();
……
return ret;
}
2.framework/base/media/libmediaplayerservice/stagefrightplayer
status_t StagefrightPlayer::prepareAsync() {
return mPlayer->prepareAsync();…………mPlayer--->AwesomePlayer
}
3:framework/base/media/libstagefright/awesomePlayer
status_t AwesomePlayer::prepareAsync() {
…….
return prepareAsync_l();
}
启动mQueue，onPrepareAsyncEvent被触发
status_t AwesomePlayer::prepareAsync_l() {……
if (!mQueueStarted) {
mQueue.start();
mQueueStarted = true;
}
….
mAsyncPrepareEvent = new AwesomeEvent(
this, &AwesomePlayer::onPrepareAsyncEvent);
mQueue.postEvent(mAsyncPrepareEvent);
return OK;
}
void AwesomePlayer::onPrepareAsyncEvent() {
….
if (mUri.size() > 0) {
status_t err = finishSetDataSource_l();………….对http://之类的url进行mAudioTrack/mVideoTrack分离
if (mVideoTrack != NULL && mVideoSource == NULL) {
status_t err = initVideoDecoder();……………………decode video
}
if (mAudioTrack != NULL && mAudioSource == NULL) {
status_t err = initAudioDecoder();…………………….decode audio
return;
}
}
if (mCachedSource != NULL || mRTSPController != NULL) {
postBufferingEvent_l();………………..触发mBufferingEvent，对应的实现在void AwesomePlayer::onBufferingUpdate()
}
}
start：解码并播放
1,framework/base/media/libmedia/mediaPlayer.cpp
status_t MediaPlayer::start()
{……
if ( (mPlayer != 0) && ( mCurrentState & ( MEDIA_PLAYER_PREPARED |
MEDIA_PLAYER_PLAYBACK_COMPLETE | MEDIA_PLAYER_PAUSED ) ) ) {
mPlayer->setLooping(mLoop);
mPlayer->setVolume(mLeftVolume, mRightVolume);
mPlayer->setAuxEffectSendLevel(mSendLevel);
mCurrentState = MEDIA_PLAYER_STARTED;
status_t ret = mPlayer->start();
……….
}
2,framework/base/media/libmediaPlayerService /mediaPlayerService.cpp
status_t MediaPlayerService::Client::start()
{..
sp<MediaPlayerBase> p = getPlayer();
…
p->setLooping(mLoop);
return p->start();
}
3,framework/base/media/libmediaPlayerService/stagefrightplayer.cpp
status_t StagefrightPlayer::start() {
return mPlayer->play();
}
4,framework/base/media/libstagefright/awesomePlayer.cpp
tatus_t AwesomePlayer::play() {
………..
return play_l();
}
status_t AwesomePlayer::play_l() {
……
if (mVideoSource != NULL) {
// Kick off video playback
postVideoEvent_l();……..把videoEvent放入mQueue中
…
}
开始解码播放，并由mVideoRenderer输出，video playback 完成
void AwesomePlayer::onVideoEvent() {……………
status_t err = mVideoSource->read(&mVideoBuffer[mVideoQueueBack], &options);
……….
if (mVideoRenderer != NULL) {
mVideoRenderer->render(mVideoBuffer[mVideoQueueBack]);
}
…..
postVideoEvent_l();
}
audio playerback
1,framework/base/media/libstagefright/awesomePlayer.cpp
status_t AwesomePlayer::play_l() {
if (mAudioSource != NULL) {
if (mAudioPlayer == NULL) {
if (mAudioSink != NULL) {
mWatchForAudioSeekComplete = false;
mAudioPlayer = new AudioPlayer(mAudioSink, this);
mAudioPlayer->setSource(mAudioSource);
…………..
}
}
status_t err = mAudioPlayer->start(
true /* sourceAlreadyStarted */);
………………..
}
2,framework/base/media/libstagefright/audioplayer.cpp
读第一手解析的数据，并开启audio output
status_t AudioPlayer::start(bool sourceAlreadyStarted) {
if (mAudioSink.get() != NULL) {
status_t err = mAudioSink->open(
mSampleRate, numChannels, AudioSystem::PCM_16_BIT,
DEFAULT_AUDIOSINK_BUFFERCOUNT,
&AudioPlayer::AudioSinkCallback, this);
……
mAudioSink->start();
} else {
mAudioTrack = new AudioTrack(
AudioSystem::MUSIC, mSampleRate, AudioSystem::PCM_16_BIT,
(numChannels == 2)
? AudioSystem::CHANNEL_OUT_STEREO
: AudioSystem::CHANNEL_OUT_MONO,
0, 0, &AudioCallback, this, 0);
….
mAudioTrack->start();
}
mStarted = true;
return OK;
}
开启audio output 时后把AudioSinkCallback传给它，每当调用callback时，audioplayer都回去decode 获取解码后的数据
size_t AudioPlayer::AudioSinkCallback(
MediaPlayerBase::AudioSink *audioSink,
void *buffer, size_t size, void *cookie) {
AudioPlayer *me = (AudioPlayer *)cookie;
return me->fillBuffer(buffer, size);
}
size_t AudioPlayer::fillBuffer(void *data, size_t size) {
…..
err = mSource->read(&mInputBuffer, &options);
…..
memcpy((char *)data + size_done,
(const char *)mInputBuffer->data() + mInputBuffer->range_offset(),
copy);
…….
return size_done;
}