Stagefright (5) - Video Rendering

AwesomePlayer::onVideoEvent除了透過OMXCodec::read取得解碼後的資料外，還必須將這些資料 (mVideoBuffer)傳給video renderer，以便畫到螢幕上去。(1) 要將mVideoBuffer中的資料畫出來之前，必須先建立mVideoRenderervoid AwesomePlayer::onVideoEvent(){  ...  if (mVideoRenderer == NULL)  {    initRenderer_l();  }  ...}void AwesomePlayer::initRenderer_l(){  if (!strncmp("OMX.", component, 4))  {    mVideoRenderer = new AwesomeRemoteRenderer(                           mClient.interface()->createRenderer(                                                  mISurface,                                                  component,                                                  ...)); .......... (2)  }  else  {    mVideoRenderer = new AwesomeLocalRenderer(                           ...,                           component,                           mISurface); ............................ (3)  }}(2) 如果video decoder是OMX component，則建立一個AwesomeRemoteRenderer作為mVideoRenderer從 上段的程式碼(1)來看，AwesomeRemoteRenderer的本質是由OMX::createRenderer所創建的。 createRenderer會先建立一個hardware renderer -- SharedVideoRenderer (libstagefrighthw.so)；若失敗，則建立software renderer -- SoftwareRenderer (surface)。sp<IOMXRenderer> OMX::createRenderer(...){  VideoRenderer *impl = NULL;  libHandle = dlopen("libstagefrighthw.so", RTLD_NOW);  if (libHandle)  {    CreateRendererFunc func = dlsym(libHandle, ...);    impl = (*func)(...); <----------------- Hardware Renderer  }  if (!impl)  {    impl = new SoftwareRenderer(...); <---- Software Renderer  }}(3) 如果video decoder是software component，則建立一個AwesomeLocalRenderer作為mVideoRendererAwesomeLocalRenderer 的constructor會呼叫本身的init函式，其所做的事和OMX::createRenderer一模一樣。void AwesomeLocalRenderer::init(...){  mLibHandle = dlopen("libstagefrighthw.so", RTLD_NOW);  if (mLibHandle)  {    CreateRendererFunc func = dlsym(...);    mTarget = (*func)(...); <---------------- Hardware Renderer  }  if (mTarget == NULL)  {    mTarget = new SoftwareRenderer(...); <--- Software Renderer  }}(4) mVideoRenderer一經建立就可以開始將解碼後的資料傳給它void AwesomePlayer::onVideoEvent(){  if (!mVideoBuffer)  {    mVideoSource->read(&mVideoBuffer, ...);  }  [Check Timestamp]  if (mVideoRenderer == NULL)  {    initRenderer_l();  }  mVideoRenderer->render(mVideoBuffer); <----- Render Data}