codec編碼傳輸流程是怎么樣的，很多新手對(duì)此不是很清楚，為了幫助大家解決這個(gè)難題，下面小編將為大家詳細(xì)講解，有這方面需求的人可以來(lái)學(xué)習(xí)下，希望你能有所收獲。

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1.  SurfaceMediaSource::read()鎖控制從IGraphicBufferConsumer處讀取buffer,當(dāng)graphic產(chǎn)生數(shù)據(jù)
   Overrun時(shí)等待

    while (mStarted && mNumPendingBuffers == mMaxAcquiredBufferCount) {

       mMediaBuffersAvailableCondition.wait(mMutex);

     }

   
   

2. MediaPuller拿到該buffer后
   status_t err = mSource->read(&mbuf);

   
   
   

   notify->setInt32("what", kWhatAccessUnit);

   notify->setBuffer("accessUnit", accessUnit);

   notify->post();

3. Converter 接收CHECK_EQ(what, MediaPuller::kWhatAccessUnit);
   后

   mInputBufferQueue.push_back(accessUnit);

   feedEncoderInputBuffers();

4. Converter::feedEncoderInputBuffers() 中拷貝buffer數(shù)據(jù)到codec的mEncoderInputBuffers
   通過(guò)這個(gè)while循環(huán)來(lái)等待拷貝

   while (!mInputBufferQueue.empty()&& !mAvailEncoderInputIndices.empty()){

   memcpy(mEncoderInputBuffers.itemAt(bufferIndex)->data(),

             buffer->data(),

             buffer->size());

  status_t err = mEncoder->queueInputBuffer(

        bufferIndex, 0, (buffer == NULL) ? 0 : buffer->size(),

        timeUs, flags);

5. 上面流程傳遞的是主要是共享內(nèi)存buffer_handle_t，當(dāng)codec 完成ACodec::BaseState::onOMXEmptyBufferDone后

 // We're in "store-metadata-in-buffers" mode, the underlying

  // OMX component had access to data that's implicitly refcounted

  // by this "MediaBuffer" object. Now that the OMX component has

  // told us that it's done with the input buffer, we can decrement

  // the mediaBuffer's reference count.

  info->mData->setMediaBufferBase(NULL);

  才通知SurfaceMediaSource::signalBufferReturned（）讓graphic consumer來(lái)真正釋放

     mConsumer->releaseBuffer(）；

Stack 信息

 #06 pc 000f4583  /system/lib/libstagefright.so (android::SurfaceMediaSource::signalBufferReturned(android::MediaBuffer*)+38)

 #07 pc 000f45a5  /system/lib/libstagefright.so (non-virtual thunk to android::SurfaceMediaSource::signalBufferReturned(android::MediaBuffer*)+4)

 #08 pc 0000b011  /system/lib/libstagefright_foundation.so (android::ABuffer::setMediaBufferBase(android::MediaBufferBase*)+16)

 #09 pc 0008adeb  /system/lib/libstagefright.so (android::ACodec::BaseState::onOMXEmptyBufferDone(unsigned int, int)+78)

 #10 pc 0008aab5  /system/lib/libstagefright.so (android::ACodec::BaseState::onOMXMessage(android::sp const&)+228)

 #11 pc 0008a731  /system/lib/libstagefright.so (android::ACodec::BaseState::onMessageReceived(android::sp const&)+744)

 #12 pc 0008e779  /system/lib/libstagefright.so (android::ACodec::ExecutingState::onMessageReceived(android::sp const&)+508)

 #13 pc 0000b5a1  /system/lib/libstagefright_foundation.so (android::AHierarchicalStateMachine::handleMessage(android::sp const&)+64)

 #14 pc 0008a917  /system/lib/libstagefright.so (android::ACodec::BaseState::onOMXMessageList(android::sp const&)+106)

 #15 pc 0008a5e7  /system/lib/libstagefright.so (android::ACodec::BaseState::onMessageReceived(android::sp const&)+414)

 #16 pc 0008e779  /system/lib/libstagefright.so (android::ACodec::ExecutingState::onMessageReceived(android::sp const&)+508)

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