Stagefright (2) - 和OpenMAX的運作

 

Stagefright的編解碼功能是利用OpenMAX框架，而且用的還是OpenCORE之OMX的實作，我們 來看一下Stagefright和OMX是如何運作的。(1) OMX_InitOMXClient mClient;AwesomePlayer::AwesomePlayer(){  mClient.connect();}status_t OMXClient::connect(){  mOMX = service->getOMX();}sp<IOMX> MediaPlayerService::getOMX(){  mOMX = new OMX;}OMX::OMX() : mMaster(new OMXMaster)OMXMaster::OMXMaster(){  addPlugin(new OMXPVCodecsPlugin);}OMXPVCodecsPlugin::OMXPVCodecsPlugin(){  OMX_MasterInit();}OMX_ERRORTYPE OMX_MasterInit() <-- under OpenCORE{  return OMX_Init();}(2) OMX_SendCommandOMXCodec::function_name(){  mOMX->sendCommand(mNode, OMX_CommandStateSet, OMX_StateIdle);}status_t OMX::sendCommand(node, cmd, param){  return findInstance(node)->sendCommand(cmd, param);}status_t OMXNodeInstance::sendCommand(cmd, param){  OMX_SendCommand(mHandle, cmd, param, NULL);}(3) 其他作用在 OMX 元件的指令其他 作用在OMX元件的指令也和OMX_SendCommand的call path一樣，請見下表：

OMXCodecOMXOMXNodeInstance useBufferuseBuffer (OMX_UseBuffer) getParametergetParameter (OMX_GetParameter) fillBufferfillBuffer (OMX_FillThisBuffer) emptyBufferemptyBuffer (OMX_EmptyThisBuffer)

 

 

(4) Callback FunctionsOMX_CALLBACKTYPE OMXNodeInstance::kCallbacks ={  &OnEvent, <--------------- omx_message::EVENT  &OnEmptyBufferDone, <----- omx_message::EMPTY_BUFFER_DONE  &OnFillBufferDone <------- omx_message::FILL_BUFFER_DONE}