stagefright框架(二)- 和OpenMAX的運作

Stagefright的編解碼功能是利用OpenMAX框架,而且用的還是OpenCOREOMX的實作,我們來看一下StagefrightOMX是如何運作的。

(1) OMX_Init


OMXClient 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_SendCommand


OMXCodec::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_SendCommandcall path一樣,請見下表:

OMXCodec

OMX

OMXNodeInstance

useBuffer

useBuffer (OMX_UseBuffer)

getParameter

getParameter (OMX_GetParameter)

fillBuffer

fillBuffer (OMX_FillThisBuffer)

emptyBuffer

emptyBuffer (OMX_EmptyThisBuffer)











(4) Callback Functions


OMX_CALLBACKTYPE OMXNodeInstance::kCallbacks =
{
&OnEvent, <--------------- omx_message::EVENT
&OnEmptyBufferDone, <----- omx_message::EMPTY_BUFFER_DONE
&OnFillBufferDone <------- omx_message::FILL_BUFFER_DONE
}

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