Stagefright框架解读（—）音视频Playback流程

　

stagefright

转载请注明出处：http://blog.csdn.net/itachi85/article/details/7216639

从Android 2.0，Google引进了Stagefright，并在android2.3时用Stagefright在Android中是以shared library的形式存在(libstagefright.so)，其中AwesomePlayer可用來播放video/audio。AwesomePlayer提供許多API，可以让上层的应用用程式(java/JNI)來呼叫，我在这里简单说明一下video playback的流程（采用的是android2.2的源码）。

在Java中，若要播放一个影片，我們通常会这样写：

[java] view plain copy print?

1. mediaplayermp=newMediaPlayer();
2. mp.setdatasource(PATH_TO_FILE);
3. mp.prepare()；
4. mp.start();

MediaPlayer mp = new MediaPlayer();
mp.setDataSource(PATH_TO_FILE);
mp.prepare()；
mp.start();

在Stagefright中，会看到如下的处理：

1.将影片文件的绝对路径指定给uri:

[cpp] view plain copy print?

1. status_tAwesomePlayer::setDataSource(
2. constchar*uri,constKeyedvector<String8,String8>*headers){
3. mutex::AutolockautoLock(mLock);
4. returnsetDataSource_l(uri,headers);
5. }
7. status_tAwesomePlayer::setDataSource_l(
8. constchar*uri,constKeyedVector<String8,String8>*headers){
9. reset_l();
11. mUri=uri;
13. if(headers){
14. mUriHeaders=*headers;
15. }
17. //Theactualworkwillbedoneduringpreparationinthecallto
18. //::finishSetDataSource_ltoavoidblockingthecallingthreadin
19. //setDataSourceforanysignificanttime.
21. returnOK;
22. }

status_t AwesomePlayer::setDataSource(
        const char *uri, const KeyedVector<String8, String8> *headers) {
    Mutex::Autolock autoLock(mLock);
    return setDataSource_l(uri, headers);
}

status_t AwesomePlayer::setDataSource_l(
        const char *uri, const KeyedVector<String8, String8> *headers) {
    reset_l();

    mUri = uri;

    if (headers) {
        mUriHeaders = *headers;
    }

    // The actual work will be done during preparation in the call to
    // ::finishSetDataSource_l to avoid blocking the calling thread in
    // setDataSource for any significant time.

    return OK;
}

2.启动mqueue:

[cpp] view plain copy print?

1. status_tAwesomePlayer::prepare(){
2. Mutex::AutolockautoLock(mLock);
3. returnprepare_l();
4. }
6. status_tAwesomePlayer::prepare_l(){
7. if(mFlags&PREPARED){
8. returnOK;
9. }
11. if(mFlags&PREPARING){
12. returnUNKNOWN_ERROR;
13. }
15. mIsAsyncPrepare=false;
16. status_terr=prepareAsync_l();
18. if(err!=OK){
19. returnerr;
20. }
22. while(mFlags&PREPARING){
23. mPreparedCondition.wait(mLock);
24. }
26. returnmPrepareResult;
27. }
30. status_tAwesomePlayer::prepareAsync(){
31. Mutex::AutolockautoLock(mLock);
33. if(mFlags&PREPARING){
34. returnUNKNOWN_ERROR;//asyncpreparealreadypending
35. }
37. mIsAsyncPrepare=true;
38. returnprepareAsync_l();
39. }
41. status_tAwesomePlayer::prepareAsync_l(){
42. if(mFlags&PREPARING){
43. returnUNKNOWN_ERROR;//asyncpreparealreadypending
44. }
46. if(!mQueueStarted){
47. mQueue.start();
48. mQueueStarted=true;
49. }
51. mFlags|=PREPARING;
52. mAsyncPrepareEvent=newAwesomeEvent(
53. this,&AwesomePlayer::onPrepareAsyncEvent);
55. mQueue.postEvent(mAsyncPrepareEvent);
57. returnOK;
58. }

status_t AwesomePlayer::prepare() {
    Mutex::Autolock autoLock(mLock);
    return prepare_l();
}

status_t AwesomePlayer::prepare_l() {
    if (mFlags & PREPARED) {
        return OK;
    }

    if (mFlags & PREPARING) {
        return UNKNOWN_ERROR;
    }

    mIsAsyncPrepare = false;
    status_t err = prepareAsync_l();

    if (err != OK) {
        return err;
    }

    while (mFlags & PREPARING) {
        mPreparedCondition.wait(mLock);
    }

    return mPrepareResult;
}


status_t AwesomePlayer::prepareAsync() {
    Mutex::Autolock autoLock(mLock);

    if (mFlags & PREPARING) {
        return UNKNOWN_ERROR;  // async prepare already pending
    }

    mIsAsyncPrepare = true;
    return prepareAsync_l();
}

status_t AwesomePlayer::prepareAsync_l() {
    if (mFlags & PREPARING) {
        return UNKNOWN_ERROR;  // async prepare already pending
    }

    if (!mQueueStarted) {
        mQueue.start();
        mQueueStarted = true;
    }

    mFlags |= PREPARING;
    mAsyncPrepareEvent = new AwesomeEvent(
            this, &AwesomePlayer::onPrepareAsyncEvent);

    mQueue.postEvent(mAsyncPrepareEvent);

    return OK;
}

3.onprepareAsyncEvent被触发，根据传来文件的header来创建相应的解析器，并初始化音视频解码器：

[cpp] view plain copy print?

1. voidAwesomePlayer::onPrepareAsyncEvent(){
2. sp<prefetcher>prefetcher;
4. {
5. Mutex::AutolockautoLock(mLock);
7. if(mFlags&PREPARE_CANCELLED){
8. LOGI(”preparewascancelledbeforedoinganything”);
9. abortPrepare(UNKNOWN_ERROR);
10. return;
11. }
13. if(mUri.size()>0){
14. //在这个方法中创建解析器
15. <strong>status_terr=finishSetDataSource_l();</strong>
17. if(err!=OK){
18. abortPrepare(err);
19. return;
20. }
21. }
23. if(mVideoTrack!=NULL&&mVideoSource==NULL){
24. //初始化视频解码器
25. <strong>status_terr=initVideoDecoder();</strong>
27. if(err!=OK){
28. abortPrepare(err);
29. return;
30. }
31. }
33. if(mAudioTrack!=NULL&&mAudiOSource==NULL){
34. //初始化音频解码器
35. <strong>status_terr=initAudioDecoder();
36. </strong>
37. if(err!=OK){
38. abortPrepare(err);
39. return;
40. }
41. }
43. prefetcher=mPrefetcher;
44. }
45. if(prefetcher!=NULL){
46. {
47. Mutex::AutolockautoLock(mLock);
48. if(mFlags&PREPARE_CANCELLED){
49. LOGI(”preparewascancelledbeforepreparingtheprefetcher”);
51. prefetcher.clear();
52. abortPrepare(UNKNOWN_ERROR);
53. return;
54. }
55. }
57. LOGI(”callingprefetcher->prepare()”);
58. status_tresult=
59. prefetcher->prepare(&AwesomePlayer::ContinuePreparation,this);
61. prefetcher.clear();
63. if(result==OK){
64. LOGI(”prefetcherisdonepreparing”);
65. }else{
66. Mutex::AutolockautoLock(mLock);
68. CHECK_EQ(result,-EINTR);
70. LOGI(”prefetcher->prepare()wascancelledearly.”);
71. abortPrepare(UNKNOWN_ERROR);
72. return;
73. }
74. }
76. Mutex::AutolockautoLock(mLock);
78. if(mIsAsyncPrepare){
79. if(mVideoWidth<0||mVideoHeight<0){
80. notifyListener_l(MEDIA_SET_VIDEO_SIZE,0,0);
81. }else{
82. notifyListener_l(MEDIA_SET_VIDEO_SIZE,mVideoWidth,mVideoHeight);
83. }
85. notifyListener_l(MEDIA_PREPARED);
86. }
88. mPrepareResult=OK;
89. mFlags&=~(PREPARING|PREPARE_CANCELLED);
90. mFlags|=PREPARED;
91. mAsyncPrepareEvent=NULL;
92. mPreparedCondition.broadcast();
94. postBufferingEvent_l();
95. }

void AwesomePlayer::onPrepareAsyncEvent() {
    sp<Prefetcher> prefetcher;

    {
        Mutex::Autolock autoLock(mLock);

        if (mFlags & PREPARE_CANCELLED) {
            LOGI("prepare was cancelled before doing anything");
            abortPrepare(UNKNOWN_ERROR);
            return;
        }

        if (mUri.size() > 0) {
           //在这个方法中创建解析器
          <strong>status_t err = finishSetDataSource_l();</strong>

            if (err != OK) {
                abortPrepare(err);
                return;
            }
        }

        if (mVideoTrack != NULL && mVideoSource == NULL) {
            //初始化视频解码器
           <strong>status_t err = initVideoDecoder();</strong>

            if (err != OK) {
                abortPrepare(err);
                return;
            }
        }

        if (mAudioTrack != NULL && mAudioSource == NULL) {
            //初始化音频解码器
           <strong>status_t err = initAudioDecoder();
</strong>
            if (err != OK) {
                abortPrepare(err);
                return;
            }
        }

        prefetcher = mPrefetcher;
    }
 if (prefetcher != NULL) {
        {
            Mutex::Autolock autoLock(mLock);
            if (mFlags & PREPARE_CANCELLED) {
                LOGI("prepare was cancelled before preparing the prefetcher");

                prefetcher.clear();
                abortPrepare(UNKNOWN_ERROR);
                return;
            }
        }

        LOGI("calling prefetcher->prepare()");
        status_t result =
            prefetcher->prepare(&AwesomePlayer::ContinuePreparation, this);

        prefetcher.clear();

        if (result == OK) {
            LOGI("prefetcher is done preparing");
        } else {
            Mutex::Autolock autoLock(mLock);

            CHECK_EQ(result, -EINTR);

            LOGI("prefetcher->prepare() was cancelled early.");
            abortPrepare(UNKNOWN_ERROR);
            return;
        }
    }

 Mutex::Autolock autoLock(mLock);

    if (mIsAsyncPrepare) {
        if (mVideoWidth < 0 || mVideoHeight < 0) {
            notifyListener_l(MEDIA_SET_VIDEO_SIZE, 0, 0);
        } else {
            notifyListener_l(MEDIA_SET_VIDEO_SIZE, mVideoWidth, mVideoHeight);
        }

        notifyListener_l(MEDIA_PREPARED);
    }

    mPrepareResult = OK;
    mFlags &= ~(PREPARING|PREPARE_CANCELLED);
    mFlags |= PREPARED;
    mAsyncPrepareEvent = NULL;
    mPreparedCondition.broadcast();

    postBufferingEvent_l();
}

[cpp] view plain copy print?

1. status_tAwesomePlayer::finishSetDataSource_l(){
2. sp<DataSource>dataSource;
4. if(!strncasecmp(“http://”,mUri.string(),7)){
5. mconnectingDataSource=newHTTPDataSource(mUri,&mUriHeaders);
7. mLock.unlock();
8. status_terr=mConnectingDataSource->connect();
9. mLock.lock();
11. if(err!=OK){
12. mConnectingDataSource.clear();
14. LOGI(”mConnectingDataSource->connect()returned%d”,err);
15. returnerr;
16. }
18. dataSource=newCachingDataSource(
19. mConnectingDataSource,64*1024,10);
21. mConnectingDataSource.clear();
22. }else{
23. dataSource=DataSource::CreateFromURI(mUri.string(),&mUriHeaders);
24. }
26. if(dataSource==NULL){
27. returnUNKNOWN_ERROR;
28. }
30. <strong>sp<Mediaextractor>extractor=MediaExtractor::Create(dataSource);
31. </strong>
32. if(extractor==NULL){
33. returnUNKNOWN_ERROR;
34. }
36. dataSource->getDrmInfo(&mDecrypthandle,&mDrmManagerClient);
37. if(mDecryptHandle!=NULL
38. &&RightsStatus::RIGHTS_valid!=mDecryptHandle->status){
39. notifyListener_l(MEDIA_ERROR,MEDIA_ERROR_UNKNOWN,ERROR_NO_LICENSE);
40. }
42. if(dataSource->flags()&DataSource::kWantsPrefetching){
43. mPrefetcher=newPrefetcher;
44. }
46. <strong>returnsetDataSource_l(extractor)</strong>;
47. }

status_t AwesomePlayer::finishSetDataSource_l() {
    sp<DataSource> dataSource;

    if (!strncasecmp("http://", mUri.string(), 7)) {
        mConnectingDataSource = new HTTPDataSource(mUri, &mUriHeaders);

        mLock.unlock();
        status_t err = mConnectingDataSource->connect();
        mLock.lock();

        if (err != OK) {
            mConnectingDataSource.clear();

            LOGI("mConnectingDataSource->connect() returned %d", err);
            return err;
        }

        dataSource = new CachingDataSource(
                mConnectingDataSource, 64 * 1024, 10);

        mConnectingDataSource.clear();
    } else {
        dataSource = DataSource::CreateFromURI(mUri.string(), &mUriHeaders);
    }

    if (dataSource == NULL) {
        return UNKNOWN_ERROR;
    }

    <strong>sp<MediaExtractor> extractor = MediaExtractor::Create(dataSource);
</strong>
    if (extractor == NULL) {
        return UNKNOWN_ERROR;
    }

    dataSource->getDrmInfo(&mDecryptHandle, &mDrmManagerClient);
    if (mDecryptHandle != NULL
            && RightsStatus::RIGHTS_VALID != mDecryptHandle->status) {
        notifyListener_l(MEDIA_ERROR, MEDIA_ERROR_UNKNOWN, ERROR_NO_LICENSE);
    }

    if (dataSource->flags() & DataSource::kWantsPrefetching) {
        mPrefetcher = new Prefetcher;
    }

   <strong> return setDataSource_l(extractor)</strong>;
}

4.使用extractor对文件进行A/V分离：

[cpp] view plain copy print?

1. status_tAwesomePlayer::setDataSource_l(constsp<MediaExtractor>&extractor){
2. boolhaveAudio=false;
3. boolhaveVideo=false;
4. for(size_ti=0;i<extractor->countTracks();++i){
5. sp<MetaData>meta=extractor->getTrackMetaData(i);
7. constchar*mime;
8. CHECK(meta->findCString(kKeyMIMEType,&mime));
10. if(!haveVideo&&!strncasecmp(mime,“video/”,6)){
11. setVideoSource(extractor->getTrack(i));
12. haveVideo=true;
13. }elseif(!haveAudio&&!strncasecmp(mime,“audio/”,6)){
14. setAudioSource(extractor->getTrack(i));
15. haveAudio=true;
16. }
18. if(haveAudio&&haveVideo){
19. break;
20. }
21. }
23. if(!haveAudio&&!haveVideo){
24. returnUNKNOWN_ERROR;
25. }
27. mExtractorFlags=extractor->flags();
29. returnOK;
30. }

status_t AwesomePlayer::setDataSource_l(const sp<MediaExtractor> &extractor) {
    bool haveAudio = false;
    bool haveVideo = false;
    for (size_t i = 0; i < extractor->countTracks(); ++i) {
        sp<MetaData> meta = extractor->getTrackMetaData(i);

        const char *mime;
        CHECK(meta->findCString(kKeyMIMEType, &mime));

        if (!haveVideo && !strncasecmp(mime, "video/", 6)) {
            setVideoSource(extractor->getTrack(i));
            haveVideo = true;
        } else if (!haveAudio && !strncasecmp(mime, "audio/", 6)) {
            setAudioSource(extractor->getTrack(i));
            haveAudio = true;
        }

        if (haveAudio && haveVideo) {
            break;
        }
    }

    if (!haveAudio && !haveVideo) {
        return UNKNOWN_ERROR;
    }

    mExtractorFlags = extractor->flags();

    return OK;
}

5.将解析后的音视频数据分别交给VideoTrack和AudioTrack:

[cpp] view plain copy print?

1. voidAwesomePlayer::setVideoSource(sp<MediaSource>source){
2. CHECK(source!=NULL);
4. if(mPrefetcher!=NULL){
5. source=mPrefetcher->addSource(source);
6. }
8. mVideoTrack=source;
9. }
11. voidAwesomePlayer::setAudioSource(sp<MediaSource>source){
12. CHECK(source!=NULL);
14. if(mPrefetcher!=NULL){
15. source=mPrefetcher->addSource(source);
16. }
18. mAudioTrack=source;
19. }

void AwesomePlayer::setVideoSource(sp<MediaSource> source) {
    CHECK(source != NULL);

    if (mPrefetcher != NULL) {
        source = mPrefetcher->addSource(source);
    }

    mVideoTrack = source;
}

void AwesomePlayer::setAudioSource(sp<MediaSource> source) {
 CHECK(source != NULL);

 if (mPrefetcher != NULL) {
 source = mPrefetcher->addSource(source);
 }

 mAudioTrack = source;
}

6.根据mVideoTrck中的编码类型来选择 video decoder 同理根据mAudioTrack中的编码类型来选择 audio decoder:

[cpp] view plain copy print?

1. status_tAwesomePlayer::initVideoDecoder(){
2. mVideoSource=OMXCodec::Create(
3. mClient.interface(),mVideoTrack->getFormat(),
4. false,//createEncoder
5. mVideoTrack);
7. if(mVideoSource!=NULL){
8. int64_tdurationUs;
9. if(mVideoTrack->getFormat()->findInt64(kKeyDuration,&durationUs)){
10. Mutex::AutolockautoLock(mMiscStateLock);
11. if(mDurationUs<0||durationUs>mDurationUs){
12. mDurationUs=durationUs;
13. }
14. }
16. CHECK(mVideoTrack->getFormat()->findInt32(kKeyWidth,&mVideoWidth));
17. CHECK(mVideoTrack->getFormat()->findInt32(kKeyHeight,&mVideoHeight));
19. status_terr=mVideoSource->start();
21. if(err!=OK){
22. mVideoSource.clear();
23. returnerr;
24. }
25. }
27. returnmVideoSource!=NULL?OK:UNKNOWN_ERROR;
28. }

status_t AwesomePlayer::initVideoDecoder() {
    mVideoSource = OMXCodec::Create(
            mClient.interface(), mVideoTrack->getFormat(),
            false, // createEncoder
            mVideoTrack);

    if (mVideoSource != NULL) {
        int64_t durationUs;
        if (mVideoTrack->getFormat()->findInt64(kKeyDuration, &durationUs)) {
            Mutex::Autolock autoLock(mMiscStateLock);
            if (mDurationUs < 0 || durationUs > mDurationUs) {
                mDurationUs = durationUs;
            }
        }

        CHECK(mVideoTrack->getFormat()->findInt32(kKeyWidth, &mVideoWidth));
        CHECK(mVideoTrack->getFormat()->findInt32(kKeyHeight, &mVideoHeight));

        status_t err = mVideoSource->start();

        if (err != OK) {
            mVideoSource.clear();
            return err;
        }
    }

    return mVideoSource != NULL ? OK : UNKNOWN_ERROR;
}

7.将mVideoEvent放入mQueue中，开始解码播放，并交由mvideoRenderer来画出 audio的数据则交由audioplayer来管理，它最终将解码的数据交给audioTrack并由audioTrack和audioFlinger进行交互，最终将数据交给audio hal层，这个我们以后会做讲解：

[cpp] view plain copy print?

1. status_tAwesomePlayer::play(){
2. Mutex::AutolockautoLock(mLock);
3. returnplay_l();
4. }
5. status_tAwesomePlayer::play_l(){
6. if(mFlags&PLAYING){
7. returnOK;
8. }
10. if(!(mFlags&PREPARED)){
11. status_terr=prepare_l();
13. if(err!=OK){
14. returnerr;
15. }
16. }
18. mFlags|=PLAYING;
19. mFlags|=FIRST_FRAME;
21. booldeferredAudioSeek=false;
23. if(mAudioSource!=NULL){
24. if(mAudioPlayer==NULL){
25. if(mAudioSink!=NULL){
26. //音频数据由audioplayer进行管理
27. mAudioPlayer=newAudioPlayer(mAudioSink);
28. mAudioPlayer->setSource(mAudioSource);
30. //We’vealreadystartedtheMediaSourceinordertoenable
31. //theprefetchertoreaditsdata.
32. //调用audioPlayer的start方法则是调用audioSource对数据进行解码
33. //并将解码似得数据最终交给audioTrack,并调用audioTrack的start方法与audioFlinger进行交互
34. status_terr=mAudioPlayer->start(
35. true/*sourceAlreadyStarted*/);
37. if(err!=OK){
38. deletemAudioPlayer;
39. mAudioPlayer=NULL;
41. mFlags&=~(PLAYING|FIRST_FRAME);
43. returnerr;
44. }
46. deletemTimeSource;
47. mTimeSource=mAudioPlayer;
49. deferredAudioSeek=true;
51. mWatchForAudioSeekComplete=false;
52. mWatchForAudioEOS=true;
53. }
54. }else{
55. mAudioPlayer->resume();
56. }
58. postCheckAudioStatusEvent_l();
59. }
61. if(mTimeSource==NULL&&mAudioPlayer==NULL){
62. mTimeSource=newSystemTimeSource;
63. }
65. if(mVideoSource!=NULL){
66. //Kickoffvideoplayback
67. //将mVideoEvent放入queue中
68. postVideoEvent_l();
69. }
71. if(deferredAudioSeek){
72. //Iftherewasaseekrequestwhilewewerepaused
73. //andwe’rejuststartingupagain,honortherequestnow.
74. seekAudioIfNecessary_l();
75. }
77. if(mFlags&AT_EOS){
78. //Legacybehaviour,ifastreamfinishesplayingandthen
79. //isstartedagain,weplayfromthestart…
80. seekto_l(0);
81. }
83. if(mDecryptHandle!=NULL){
84. int64_tposition;
85. getPosition(&position);
86. mDrmManagerClient->setPlaybackStatus(mDecryptHandle,
87. Playback::START,position/1000);
88. }
90. returnOK;
91. }
93. voidAwesomePlayer::postVideoEvent_l(int64_tdelayUs){
94. if(mVideoEventPending){
95. return;
96. }
98. mVideoEventPending=true;
99. mQueue.postEventwithDelay(mVideoEvent,delayUs<0?10000:delayUs);
100. }

status_t AwesomePlayer::play() {
    Mutex::Autolock autoLock(mLock);
    return play_l();
}
status_t AwesomePlayer::play_l() {
    if (mFlags & PLAYING) {
        return OK;
    }

    if (!(mFlags & PREPARED)) {
        status_t err = prepare_l();

        if (err != OK) {
            return err;
        }
    }

    mFlags |= PLAYING;
    mFlags |= FIRST_FRAME;

    bool deferredAudioSeek = false;

    if (mAudioSource != NULL) {
        if (mAudioPlayer == NULL) {
            if (mAudioSink != NULL) {
                //音频数据由audioplayer进行管理
               mAudioPlayer = new AudioPlayer(mAudioSink);
                mAudioPlayer->setSource(mAudioSource);

                // We've already started the MediaSource in order to enable
                // the prefetcher to read its data.
                  //调用audioPlayer的start方法则是调用audioSource对数据进行解码
                   //并将解码似得数据最终交给audioTrack,并调用audioTrack的start方法与audioFlinger进行交互
                  status_t err = mAudioPlayer->start(
                        true /* sourceAlreadyStarted */);

                if (err != OK) {
                    delete mAudioPlayer;
                    mAudioPlayer = NULL;

                    mFlags &= ~(PLAYING | FIRST_FRAME);

                    return err;
                }

                delete mTimeSource;
                mTimeSource = mAudioPlayer;

                deferredAudioSeek = true;

                mWatchForAudioSeekComplete = false;
                mWatchForAudioEOS = true;
            }
        } else {
            mAudioPlayer->resume();
        }

        postCheckAudioStatusEvent_l();
    }

    if (mTimeSource == NULL && mAudioPlayer == NULL) {
        mTimeSource = new SystemTimeSource;
    }

    if (mVideoSource != NULL) {
        // Kick off video playback
        //将mVideoEvent放入queue中
         postVideoEvent_l();
    }

    if (deferredAudioSeek) {
        // If there was a seek request while we were paused
        // and we're just starting up again, honor the request now.
        seekAudioIfNecessary_l();
    }

    if (mFlags & AT_EOS) {
        // Legacy behaviour, if a stream finishes playing and then
        // is started again, we play from the start...
        seekTo_l(0);
    }

    if (mDecryptHandle != NULL) {
        int64_t position;
        getPosition(&position);
        mDrmManagerClient->setPlaybackStatus(mDecryptHandle,
                Playback::START, position / 1000);
    }

    return OK;
}

void AwesomePlayer::postVideoEvent_l(int64_t delayUs) {
 if (mVideoEventPending) {
 return;
 }

 mVideoEventPending = true;
 mQueue.postEventWithDelay(mVideoEvent, delayUs < 0 ? 10000 : delayUs);
}

[cpp] view plain copy print?

1. voidAwesomePlayer::onVideoEvent()
2. {
3. mVideoSource->read(&mVideoBuffer,&options);
4. mVideoRenderer->render(mVideoBuffer);
6. postVideoEvent_l();
7. }

void AwesomePlayer::onVideoEvent()
{
  mVideoSource->read(&mVideoBuffer, &options);
  mVideoRenderer->render(mVideoBuffer);

  postVideoEvent_l();
}

转自:https://blog.csdn.net/itachi85/article/details/7216639

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