codec编码传输流程是怎么样的

codec编码传输流程是怎么样的，很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。

1. SurfaceMediaSource::read()锁控制从IGraphicBufferConsumer处读取buffer,当graphic产生数据
   Overrun时等待

   while (mStarted && mNumPendingBuffers == mMaxAcquiredBufferCount) {

   mMediaBuffersAvailableCondition.wait(mMutex);

   }
   

2. MediaPuller拿到该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() 中拷贝buffer数据到codec的mEncoderInputBuffers
   通过这个while循环来等待拷贝

   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. 上面流程传递的是主要是共享内存buffer_handle_t，当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（）让graphic consumer来真正释放

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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