stagefright框架_启动stagefright_stagefright怎么解决

stagefright框架（一）Video Playback的流程在Android上，預設的多媒體框架(multimedia framework)是OpenCORE。OpenCORE的優點是兼顧了跨平台的移植性，而且已經過多方驗證，所以相對來說較為穩定；但是其缺點是過於龐大複雜，需要耗費相當多的時間去維護。從Android 2.0開始，Google引進了架構稍為簡潔的Stagefright，並且有逐漸取代OpenCORE的趨勢(註1)。[圖1] Stagefright在Android多媒體架構中的位置。[圖2] Stagefright所涵蓋的模組 (註2)。以下我們就先來看看Stagefright是如何播放一個影片檔。Stagefright在Android中是以shared library的形式存在(libstagefright.so)，其中的module -- AwesomePlayer可用來播放video/audio (註3)。AwesomePlayer提供許多API，可以讓上層的應用程式(Java/JNI)來呼叫，我們以一個簡單的程式來說明video playback的流程。在Java中，若要播放一個影片檔，我們會這樣寫：MediaPlayer mp = new MediaPlayer();mp.setDataSource(PATH_TO_FILE); ...... (1)mp.prepare(); ........................ (2)、(3)mp.start(); .......................... (4)在Stagefright中，則會看到相對應的處理；(1) 將檔案的絕對路徑指定給mUristatus_t AwesomePlayer::setDataSource(const char* uri, ...){return setDataSource_l(uri, ...);}status_t AwesomePlayer::setDataSource_l(const char* uri, ...){mUri = uri;}(2) 啟動mQueue，作為event handlerstatus_t AwesomePlayer::prepare(){return prepare_l();}status_t AwesomePlayer::prepare_l(){prepareAsync_l();while (mFlags & PREPARING){mPreparedCondition.wait(mLock);}}status_t AwesomePlayer::prepareAsync_l(){mQueue.start();mFlags |= PREPARING;mAsyncPrepareEvent = new AwesomeEvent(this&AwesomePlayer::onPrepareAsyncEvent);mQueue.postEvent(mAsyncPrepareEvent);}(3) onPrepareAsyncEvent被觸發void AwesomePlayer::onPrepareAsyncEvent(){finishSetDataSource_l();initVideoDecoder(); ...... (3.3)initAudioDecoder();}status_t AwesomePlayer::finishSetDataSource_l(){dataSource = DataSource::CreateFromURI(mUri.string(), ...);sp<MediaExtractor> extractor =MediaExtractor::Create(dataSource); ..... (3.1)return setDataSource_l(extractor); ......................... (3.2)}(3.1) 解析mUri所指定的檔案，並且根據其header來選擇對應的extractorsp<MediaExtractor> MediaExtractor::Create(const sp<DataSource> &source, ...){source->sniff(&tmp, ...);mime = tmp.string();if (!strcasecmp(mime, MEDIA_MIMETYPE_CONTAINER_MPEG4){return new MPEG4Extractor(source);}else if (!strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_MPEG)){return new MP3Extractor(source);}else if (!strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_AMR_NB){return new AMRExtractor(source);}}(3.2) 使用extractor對檔案做A/V的分離 (mVideoTrack/mAudioTrack)status_t AwesomePlayer::setDataSource_l(const sp<MediaExtractor> &extractor){for (size_t i = 0; i < extractor->countTracks(); ++i){sp<MetaData> meta = extractor->getTrackMetaData(i);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;}}}void AwesomePlayer::setVideoSource(sp<MediaSource> source){mVideoTrack = source;}(3.3) 根據mVideoTrack中的編碼類型來選擇video decoder (mVideoSource)status_t AwesomePlayer::initVideoDecoder(){mVideoSource = OMXCodec::Create(mClient.intece(),mVideoTrack->getFormat(),false,mVideoTrack);}(4)將mVideoEvent放入mQueue中，開始解碼播放，並交由mVideoRenderer來畫出 status_t AwesomePlayer::play(){return play_l();}status_t AwesomePlayer::play_l(){postVideoEvent_l();}void AwesomePlayer::postVideoEvent_l(int64_t delayUs){mQueue.postEventWithDelay(mVideoEvent, delayUs);}void AwesomePlayer::onVideoEvent(){mVideoSource->read(&mVideoBuffer, &options);[Check Timestamp]mVideoRenderer->render(mVideoBuffer);postVideoEvent_l();}(註1) 從Android2.3 (Gingerbread) 開始，預設的多媒體框架為 Stagefright。

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