stagefright框架_启动stagefright_stagefright怎么解决(3)

(1) Video decoder是在onPrepareAsyncEvent中的initVideoDecoder被決定的OMXCodec::Create()會回傳video decoder給mVideoSource。status_t AwesomePlayer::initVideoDecoder(){mVideoSource = OMXCodec::Create(mClient.intece(),mVideoTrack->getFormat(),false,mVideoTrack);}sp<MediaSource> OMXCodec::Create(&omx, &meta, createEncoder, &source, matchComponentName){meta->findCString(kKeyMIMEType, &mime);findMatchingCodecs(mime, ..., &matchingCodecs); ........ (2)for (size_t i = 0; i < matchingCodecs.size(); ++i){componentName = matchingCodecs[i].string();softwareCodec =InstantiateSoftwareCodec(componentName, ...); ..... (3)if (softwareCodec != NULL) return softwareCodec;err = omx->allocateNode(componentName, ..., &node); ... (4)if (err == OK){codec = new OMXCodec(..., componentName, ...); ...... (5)return codec;}}}(2) 根據mVideoTrack的MIME從kDecoderInfo挑出合適的componentsvoid OMXCodec::findMatchingCodecs(mime, ..., matchingCodecs){for (int index = 0;; ++index){componentName = GetCodec(kDecoderInfo,sizeof(kDecoderInfo)/sizeof(kDecoderInfo[0]),mime,index);matchingCodecs->push(String8(componentName));}}static const CodecInfo kDecoderInfo[] ={...{ MEDIA_MIMETYPE_VIDEO_MPEG4, "OMX.qcom.video.decoder.mpeg4" },{ MEDIA_MIMETYPE_VIDEO_MPEG4, "OMX.TI.Video.Decoder" },{ MEDIA_MIMETYPE_VIDEO_MPEG4, "M4vH263Decoder" },...}GetCodec會依據mime從kDecoderInfo挑出所有的component name，然後存到matchingCodecs中。

(3) 根據matchingCodecs中component的順序，我們會先去檢查其是否為software decoderstatic sp<MediaSource> InstantiateSoftwareCodec(name, ...){FactoryInfo kFactoryInfo[] ={...FACTORY_REF(M4vH263Decoder)...};for (i = 0; i < sizeof(kFactoryInfo)/sizeof(kFactoryInfo[0]); ++i){if (!strcmp(name, kFactoryInfo[i].name))return (*kFactoryInfo[i].CreateFunc)(source);}}所有的software decoder都會被列在kFactoryInfo中，我們藉由傳進來的name來對應到適合的decoder。stagefright框架(4) 如果該component不是software decoder，則試著去配置對應的OMX componentstatus_t OMX::allocateNode(name, ..., node){mMaster->makeComponentInstance(name,&OMXNodeInstance::kCallbacks,instance,handle);}OMX_ERRORTYPE OMXMaster::makeComponentInstance(name, ...){plugin->makeComponentInstance(name, ...);}OMX_ERRORTYPE OMXPVCodecsPlugin::makeComponentInstance(name, ...){return OMX_MasterGetHandle(..., name, ...);}OMX_ERRORTYPE OMX_MasterGetHandle(...){return OMX_GetHandle(...);}(5) 若該component為OMX deocder，則回傳；否則繼續檢查下一個componentstagefright框架（四）-Video Buffer傳輸流程這篇文章將介紹Stagefright中是如何和OMX video decoder傳遞buffer。stagefright框架

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