【stagefrightplayer】4 OMX Codec介绍 （2/2）

4.1 看下 drainInputBuffers();实现

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1. <PREclass=htmlname="code">void OMXCodec::drainInputBuffers() {
2. for (size_t i = 0; i< buffers->size(); ++i) {
3. BufferInfo *info = &buffers->editItemAt(i);
4. if (info->mStatus != OWNED_BY_US) {
5. continue;
6. }
7. if (!drainInputBuffer(info)) {
8. break;
9. }
10. if (mFlags & kOnlySubmitOneInputBufferAtOneTime) {
11. break;
12. }
13. }
14. }</PRE>

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void OMXCodec::drainInputBuffers() {  
       for (size_t i = 0; i < buffers->size(); ++i) {  
           BufferInfo *info = &buffers->editItemAt(i);  
           if (info->mStatus != OWNED_BY_US) {  
               continue;  
           }  
           if (!drainInputBuffer(info)) {  
               break;  
           }  
           if (mFlags & kOnlySubmitOneInputBufferAtOneTime) {  
               break;  
           }     
       }  
}  
void OMXCodec::drainInputBuffers() {       for (size_t i = 0; i < buffers->size(); ++i) {           BufferInfo *info = &buffers->editItemAt(i);           if (info->mStatus != OWNED_BY_US) {               continue;           }           if (!drainInputBuffer(info)) {               break;           }           if (mFlags & kOnlySubmitOneInputBufferAtOneTime) {               break;           }          }}
这里解释下，我们可能申请了多个输入缓冲区，因此是一个循环，先检查我们有没有权限使用即OWNED_BY_US，这一缓冲区获取完数据后会检测
kOnlySubmitOneInputBufferAtOneTime即每次只允许读一个包，否则循环都读满。
下面继续跟进drainInputBuffer(info),忽略无关代码：
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bool OMXCodec::drainInputBuffer(BufferInfo *info) { 
********** 
status_t err; 
bool signalEOS = false;
int64_t timestampUs =0; 
size_t offset = 0;
int32_t n = 0; 
for (;;) { 
MediaBuffer *srcBuffer; 
err = mSource->read(&srcBuffer);
size_t remainingBytes =info->mSize - offset;
下面是判断从extractor读取到的数据是不是超过了总大小 
if (srcBuffer->range_length()> remainingBytes) { 
if (offset == 0) { 
srcBuffer->release();
srcBuffer = NULL;
setState(ERROR); 
return false; 
} 
mLeftOverBuffer =srcBuffer; 
break; 
} memcpy((uint8_t *)info->mData + offset,
(const uint8_t *)srcBuffer->data()
+ srcBuffer->range_offset(),
srcBuffer->range_length()); 
offset += srcBuffer->range_length();
if (releaseBuffer) { 
srcBuffer->release();
srcBuffer = NULL;
} 
数据读取完毕后将srcBufferrelease掉 
} 
err = mOMX->emptyBuffer(
mNode, info->mBuffer, 0, offset,
flags, timestampUs); 
info->mStatus =OWNED_BY_COMPONENT; 
} 
这里读取完毕后将缓冲区的状态设置成OWNED_BY_COMPONENT 解码器就可以解码了 
这里可以看出来读取数据时实现了一次拷贝~~，而不是用的同一块缓冲区，注意下
读取数据可以参考前面介绍的extractor的内容，比较简单不说了。
下面看读取数据完毕后调用mOMX->emptyBuffer都干了些啥
通过前面我们很容易的理解实际调用的是
omx::emptybufferèOMXNodeInstance::emptyBuffer,
从代码可以看到最终调用的是
((OMX_COMPONENTTYPE*)hComponent)->EmptyThisBuffer()
实际代码在SimpleSoftOMXComponent.cpp中，具体如下
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OMX_ERRORTYPE SimpleSoftOMXComponent::emptyThisBuffer(
OMX_BUFFERHEADERTYPE *buffer) { 
sp<AMessage>msg = new AMessage(kWhatEmptyThisBuffer, mHandler->id());
msg->setPointer("header", buffer);
msg->post(); 
return OMX_ErrorNone; 
} 
OMX_ERRORTYPE SimpleSoftOMXComponent::emptyThisBuffer(       OMX_BUFFERHEADERTYPE *buffer) {   sp<AMessage> msg = new AMessage(kWhatEmptyThisBuffer, mHandler->id());   msg->setPointer("header", buffer);   msg->post();   return OMX_ErrorNone;}
可以看到就是发了一条命令kWhatEmptyThisBuffer
通过handler->id确定了自己发的还得自己收，处理函数如下：
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void SimpleSoftOMXComponent::onMessageReceived(const sp<AMessage> &msg) {
Mutex::Autolock autoLock(mLock); 
uint32_t msgType =msg->what();
ALOGV("msgType = %d", msgType);
switch (msgType) { 
******** 
case kWhatEmptyThisBuffer: 
case kWhatFillThisBuffer: 
{ 
OMX_BUFFERHEADERTYPE *header; 
CHECK(msg->findPointer("header", (void **)&header));
CHECK(mState == OMX_StateExecuting &&mTargetState == mState); 
bool found = false; 
size_t portIndex = (kWhatEmptyThisBuffer == msgType)? header->nInputPortIndex: header->nOutputPortIndex;
PortInfo *port = &mPorts.editItemAt(portIndex);
for (size_t j = 0; j< port->mBuffers.size(); ++j) {
BufferInfo *buffer = &port->mBuffers.editItemAt(j);
if (buffer->mHeader == header) {
CHECK(!buffer->mOwnedByUs); 
buffer->mOwnedByUs =true; 
CHECK((msgType == kWhatEmptyThisBuffer
&& port->mDef.eDir == OMX_DirInput)|| (port->mDef.eDir == OMX_DirOutput));
port->mQueue.push_back(buffer); 
onQueueFilled(portIndex); 
found = true;
break; 
} 
} 
CHECK(found); 
break; 
} 
default: 
TRESPASS(); 
break; 
} 
} 
void SimpleSoftOMXComponent::onMessageReceived(const sp<AMessage> &msg) {   Mutex::Autolock autoLock(mLock);   uint32_t msgType = msg->what();   ALOGV("msgType = %d", msgType);   switch (msgType) {********       case kWhatEmptyThisBuffer:       case kWhatFillThisBuffer:       {           OMX_BUFFERHEADERTYPE *header;           CHECK(msg->findPointer("header", (void **)&header));           CHECK(mState == OMX_StateExecuting && mTargetState == mState);           bool found = false;           size_t portIndex = (kWhatEmptyThisBuffer == msgType)?                   header->nInputPortIndex: header->nOutputPortIndex;           PortInfo *port = &mPorts.editItemAt(portIndex);           for (size_t j = 0; j < port->mBuffers.size(); ++j) {               BufferInfo *buffer = &port->mBuffers.editItemAt(j);                 if (buffer->mHeader == header) {                   CHECK(!buffer->mOwnedByUs);                   buffer->mOwnedByUs = true;                   CHECK((msgType == kWhatEmptyThisBuffer                           && port->mDef.eDir == OMX_DirInput)|| (port->mDef.eDir == OMX_DirOutput));                   port->mQueue.push_back(buffer);                   onQueueFilled(portIndex);               found = true;                   break;               }           }           CHECK(found);           break;       }       default:           TRESPASS();           break;   }}

从代码这里来看这两个case都走同一套代码，而且都是通过onQueueFilled来处理，这样我们就引出了实际的处理函数，也就是onQueueFilled，
以mp3为例这里具体实现在SoftMP3中。
具体解释看代码中注释
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void SoftMP3::onQueueFilled(OMX_U32 portIndex) { 
if (mSignalledError || mOutputPortSettingsChange != NONE) { 
return; 
} 
获取输入输出链表 
List<BufferInfo *> &inQueue =getPortQueue(0); 
List<BufferInfo *> &outQueue =getPortQueue(1); 
while (!inQueue.empty() && !outQueue.empty()) { 
各自取输入输出缓冲区中的第一个缓冲区 
BufferInfo *inInfo = *inQueue.begin();
OMX_BUFFERHEADERTYPE *inHeader =inInfo->mHeader;
BufferInfo *outInfo = *outQueue.begin();
OMX_BUFFERHEADERTYPE *outHeader =outInfo->mHeader;
判断缓冲区是不是没有数据，若果第一个都没有那就是没有 
if (inHeader->nFlags & OMX_BUFFERFLAG_EOS) {
inQueue.erase(inQueue.begin()); 
inInfo->mOwnedByUs =false; 
notifyEmptyBufferDone(inHeader); 
if (!mIsFirst) { 
// pad the end of the stream with 529 samples, since that many samples 
// were trimmed off the beginning when decoding started 
outHeader->nFilledLen =
kPVMP3DecoderDelay * mNumChannels * sizeof(int16_t);
memset(outHeader->pBuffer, 0, outHeader->nFilledLen);
} else { 
// Since we never discarded frames from the start, we won't have
// to add any padding at the end either. 
outHeader->nFilledLen =0; 
} 
outHeader->nFlags =OMX_BUFFERFLAG_EOS; 
outQueue.erase(outQueue.begin()); 
outInfo->mOwnedByUs =false; 
notifyFillBufferDone(outHeader); 
return; 
} 
如果offset==0说明是第一包的开头，需要读取pts，请结合extractor理解
if (inHeader->nOffset == 0) {
mAnchorTimeUs =inHeader->nTimeStamp;
mNumFramesOutput = 0;
} 
mConfig->pInputBuffer =
inHeader->pBuffer + inHeader->nOffset;
mConfig->inputBufferCurrentLength =inHeader->nFilledLen;
mConfig->inputBufferMaxLength =0; 
mConfig->inputBufferUsedLength =0; 
mConfig->outputFrameSize =kOutputBufferSize / sizeof(int16_t);
mConfig->pOutputBuffer =
reinterpret_cast<int16_t *>(outHeader->pBuffer);
ERROR_CODE decoderErr; 
上面是配置参数 下面调用自己的解码器进行解码 
if ((decoderErr = pvmp3_framedecoder(mConfig, mDecoderBuf))
!= NO_DECODING_ERROR) { 
***出错处理* 
这里注意如果解码失败，则填充0数据，也就是静音帧 
// play silence instead. 
memset(outHeader->pBuffer, 
0, 
mConfig->outputFrameSize * sizeof(int16_t));
mConfig->inputBufferUsedLength =inHeader->nFilledLen;
} else if (mConfig->samplingRate != mSamplingRate
|| mConfig->num_channels != mNumChannels) {
这里说明参数发生了改变，即采样率等改变了，需要重新设置输出 
mSamplingRate =mConfig->samplingRate;
mNumChannels = mConfig->num_channels;
notify(OMX_EventPortSettingsChanged, 1, 0, NULL); 
mOutputPortSettingsChange =AWAITING_DISABLED; 
return; 
} 
if (mIsFirst) { 
mIsFirst = false;
// The decoder delay is 529 samples, so trim that many samples off
// the start of the first output buffer. This essentially makes this 
// decoder have zero delay, which the rest of the pipeline assumes.
outHeader->nOffset =
kPVMP3DecoderDelay * mNumChannels * sizeof(int16_t);
outHeader->nFilledLen =
mConfig->outputFrameSize * sizeof(int16_t) - outHeader->nOffset;
} else { 
outHeader->nOffset =0; 
outHeader->nFilledLen =mConfig->outputFrameSize * sizeof(int16_t);
} 
outHeader->nTimeStamp =
mAnchorTimeUs
+ (mNumFramesOutput * 1000000ll) / mConfig->samplingRate;
outHeader->nFlags =0; 
CHECK_GE(inHeader->nFilledLen, mConfig->inputBufferUsedLength);
inHeader->nOffset += mConfig->inputBufferUsedLength;
inHeader->nFilledLen -= mConfig->inputBufferUsedLength;
mNumFramesOutput += mConfig->outputFrameSize / mNumChannels;
如果输入缓冲区数据都解码完了，则调用notifyEmptyBufferDone 
if (inHeader->nFilledLen == 0) {
inInfo->mOwnedByUs =false; 
inQueue.erase(inQueue.begin()); 
inInfo = NULL;
notifyEmptyBufferDone(inHeader); 
inHeader = NULL;
} 
outInfo->mOwnedByUs =false; 
outQueue.erase(outQueue.begin()); 
outInfo = NULL; 
这是将解码出来的数据告诉外部，通过调用notifyFillBufferDone 
notifyFillBufferDone(outHeader); 
outHeader = NULL;
} 
} 
void SoftMP3::onQueueFilled(OMX_U32 portIndex) {    if (mSignalledError || mOutputPortSettingsChange != NONE) {        return;    }      获取输入输出链表      List<BufferInfo *> &inQueue = getPortQueue(0);    List<BufferInfo *> &outQueue = getPortQueue(1);      while (!inQueue.empty() && !outQueue.empty()) {          各自取输入输出缓冲区中的第一个缓冲区         BufferInfo *inInfo = *inQueue.begin();        OMX_BUFFERHEADERTYPE *inHeader = inInfo->mHeader;          BufferInfo *outInfo = *outQueue.begin();        OMX_BUFFERHEADERTYPE *outHeader = outInfo->mHeader;                  判断缓冲区是不是没有数据，若果第一个都没有那就是没有           if (inHeader->nFlags & OMX_BUFFERFLAG_EOS) {            inQueue.erase(inQueue.begin());            inInfo->mOwnedByUs = false;            notifyEmptyBufferDone(inHeader);              if (!mIsFirst) {                // pad the end of the stream with 529 samples, since that many samples                // were trimmed off the beginning when decoding started                outHeader->nFilledLen =                    kPVMP3DecoderDelay * mNumChannels * sizeof(int16_t);                  memset(outHeader->pBuffer, 0, outHeader->nFilledLen);            } else {                // Since we never discarded frames from the start, we won't have                // to add any padding at the end either.                outHeader->nFilledLen = 0;            }              outHeader->nFlags = OMX_BUFFERFLAG_EOS;              outQueue.erase(outQueue.begin());            outInfo->mOwnedByUs = false;            notifyFillBufferDone(outHeader);            return;        }              如果offset==0说明是第一包的开头，需要读取pts，请结合extractor理解          if (inHeader->nOffset == 0) {            mAnchorTimeUs = inHeader->nTimeStamp;            mNumFramesOutput = 0;        }          mConfig->pInputBuffer =            inHeader->pBuffer + inHeader->nOffset;          mConfig->inputBufferCurrentLength = inHeader->nFilledLen;        mConfig->inputBufferMaxLength = 0;        mConfig->inputBufferUsedLength = 0;          mConfig->outputFrameSize = kOutputBufferSize / sizeof(int16_t);          mConfig->pOutputBuffer =            reinterpret_cast<int16_t *>(outHeader->pBuffer);          ERROR_CODE decoderErr;          上面是配置参数 下面调用自己的解码器进行解码        if ((decoderErr = pvmp3_framedecoder(mConfig, mDecoderBuf))                != NO_DECODING_ERROR) {                   ***出错处理*              这里注意如果解码失败，则填充0数据，也就是静音帧            // play silence instead.            memset(outHeader->pBuffer,                   0,                   mConfig->outputFrameSize * sizeof(int16_t));              mConfig->inputBufferUsedLength = inHeader->nFilledLen;        } else if (mConfig->samplingRate != mSamplingRate                || mConfig->num_channels != mNumChannels) {              这里说明参数发生了改变，即采样率等改变了，需要重新设置输出            mSamplingRate = mConfig->samplingRate;            mNumChannels = mConfig->num_channels;              notify(OMX_EventPortSettingsChanged, 1, 0, NULL);            mOutputPortSettingsChange = AWAITING_DISABLED;            return;        }          if (mIsFirst) {            mIsFirst = false;            // The decoder delay is 529 samples, so trim that many samples off            // the start of the first output buffer. This essentially makes this            // decoder have zero delay, which the rest of the pipeline assumes.            outHeader->nOffset =                kPVMP3DecoderDelay * mNumChannels * sizeof(int16_t);              outHeader->nFilledLen =                mConfig->outputFrameSize * sizeof(int16_t) - outHeader->nOffset;        } else {            outHeader->nOffset = 0;            outHeader->nFilledLen = mConfig->outputFrameSize * sizeof(int16_t);        }          outHeader->nTimeStamp =            mAnchorTimeUs                + (mNumFramesOutput * 1000000ll) / mConfig->samplingRate;          outHeader->nFlags = 0;          CHECK_GE(inHeader->nFilledLen, mConfig->inputBufferUsedLength);          inHeader->nOffset += mConfig->inputBufferUsedLength;        inHeader->nFilledLen -= mConfig->inputBufferUsedLength;          mNumFramesOutput += mConfig->outputFrameSize / mNumChannels;          如果输入缓冲区数据都解码完了，则调用notifyEmptyBufferDone          if (inHeader->nFilledLen == 0) {            inInfo->mOwnedByUs = false;            inQueue.erase(inQueue.begin());            inInfo = NULL;            notifyEmptyBufferDone(inHeader);            inHeader = NULL;        }          outInfo->mOwnedByUs = false;        outQueue.erase(outQueue.begin());        outInfo = NULL;          这是将解码出来的数据告诉外部，通过调用notifyFillBufferDone          notifyFillBufferDone(outHeader);        outHeader = NULL;    }}
下面分析下，如何将输入缓冲区释放和将输出缓冲区中的数据传递出去
A、输入部分的清空
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void SoftOMXComponent::notifyEmptyBufferDone(OMX_BUFFERHEADERTYPE *header) {
(*mCallbacks->EmptyBufferDone)(
mComponent, mComponent->pApplicationPrivate, header);
} 
void SoftOMXComponent::notifyEmptyBufferDone(OMX_BUFFERHEADERTYPE *header) {     (*mCallbacks->EmptyBufferDone)(             mComponent, mComponent->pApplicationPrivate, header);  }
通知外面我们emptythisbuffer完工了，具体调用的是OMXNodeInstance中的方法，具体怎么传进去的，大家可以自己分析下：
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OMX_ERRORTYPE OMXNodeInstance::OnEmptyBufferDone( 
OMX_IN OMX_HANDLETYPE hComponent, 
OMX_IN OMX_PTR pAppData, 
OMX_IN OMX_BUFFERHEADERTYPE* pBuffer) { 
OMXNodeInstance *instance =static_cast<OMXNodeInstance *>(pAppData);
if (instance->mDying) { 
return OMX_ErrorNone; 
} 
return instance->owner()->OnEmptyBufferDone(instance->nodeID(), pBuffer);
} 
OMX_ERRORTYPE OMXNodeInstance::OnEmptyBufferDone(         OMX_IN OMX_HANDLETYPE hComponent,         OMX_IN OMX_PTR pAppData,         OMX_IN OMX_BUFFERHEADERTYPE* pBuffer) {     OMXNodeInstance *instance = static_cast<OMXNodeInstance *>(pAppData);     if (instance->mDying) {         return OMX_ErrorNone;     }    return instance->owner()->OnEmptyBufferDone(instance->nodeID(), pBuffer);  }
OMXNodeInstance的ownner是OMX，因此代码为
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OMX_ERRORTYPE OMX::OnEmptyBufferDone( 
node_id node, OMX_IN OMX_BUFFERHEADERTYPE *pBuffer) { 
ALOGV("OnEmptyBufferDone buffer=%p", pBuffer);
omx_message msg; 
msg.type = omx_message::EMPTY_BUFFER_DONE; 
msg.node = node; 
msg.u.buffer_data.buffer =pBuffer; 
findDispatcher(node)->post(msg);
return OMX_ErrorNone; 
} 
OMX_ERRORTYPE OMX::OnEmptyBufferDone(          node_id node, OMX_IN OMX_BUFFERHEADERTYPE *pBuffer) {      ALOGV("OnEmptyBufferDone buffer=%p", pBuffer);      omx_message msg;      msg.type = omx_message::EMPTY_BUFFER_DONE;      msg.node = node;      msg.u.buffer_data.buffer = pBuffer;     findDispatcher(node)->post(msg);     return OMX_ErrorNone;   }
其中findDispatcher定义如下
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sp<OMX::CallbackDispatcher> OMX::findDispatcher(node_id node) {
Mutex::Autolock autoLock(mLock); 
ssize_t index =mDispatchers.indexOfKey(node); 
return index < 0 ? NULL : mDispatchers.valueAt(index);
} 
sp<OMX::CallbackDispatcher> OMX::findDispatcher(node_id node) {    Mutex::Autolock autoLock(mLock);    ssize_t index = mDispatchers.indexOfKey(node);    return index < 0 ? NULL : mDispatchers.valueAt(index);}
这里mDispatcher在之前allocateNode中通过mDispatchers.add(*node, new CallbackDispatcher(instance)); 创建的
看下实际的实现可知道，CallbackDispatcher的post方法最终会调用dispatch
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void OMX::CallbackDispatcher::dispatch(const omx_message &msg) {
if (mOwner == NULL) { 
ALOGV("Would have dispatched a message to a node that's already gone.");
return; 
} 
mOwner->onMessage(msg); 
} 
void OMX::CallbackDispatcher::dispatch(const omx_message &msg) {    if (mOwner == NULL) {        ALOGV("Would have dispatched a message to a node that's already gone.");        return;    }    mOwner->onMessage(msg);}
而owner是OMXNodeInstance，因此消息饶了一圈还是到了OMXNodeInstance的OnMessage方法接收了
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void OMXNodeInstance::onMessage(const omx_message &msg) {
if (msg.type == omx_message::FILL_BUFFER_DONE) {
OMX_BUFFERHEADERTYPE *buffer =
static_cast<OMX_BUFFERHEADERTYPE *>(
msg.u.extended_buffer_data.buffer); 
BufferMeta *buffer_meta =
static_cast<BufferMeta *>(buffer->pAppPrivate);
buffer_meta->CopyFromOMX(buffer);
} 
mObserver->onMessage(msg);
} 
void OMXNodeInstance::onMessage(const omx_message &msg) {    if (msg.type == omx_message::FILL_BUFFER_DONE) {        OMX_BUFFERHEADERTYPE *buffer =            static_cast<OMX_BUFFERHEADERTYPE *>(                    msg.u.extended_buffer_data.buffer);          BufferMeta *buffer_meta =            static_cast<BufferMeta *>(buffer->pAppPrivate);          buffer_meta->CopyFromOMX(buffer);    }      mObserver->onMessage(msg);}
而onMessage又将消息传递到 mObserver中，也就是在OMXCodec::Create中构造的OMXCodecObserver对象，其OnMessage实现如下
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virtual void onMessage(const omx_message &msg) { 
sp<OMXCodec>codec = mTarget.promote();
if (codec.get() != NULL) { 
Mutex::Autolock autoLock(codec->mLock);
codec->on_message(msg); 
codec.clear(); 
} 
} 
virtual void onMessage(const omx_message &msg) {    sp<OMXCodec> codec = mTarget.promote();      if (codec.get() != NULL) {        Mutex::Autolock autoLock(codec->mLock);        codec->on_message(msg);        codec.clear();    }}
最终还是传递给了OMXCodec里，具体看下：
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void OMXCodec::on_message(const omx_message &msg) { 
switch (msg.type) { 
************ 
case omx_message::EMPTY_BUFFER_DONE: 
{ 
IOMX::buffer_id buffer = msg.u.extended_buffer_data.buffer; 
Vector<BufferInfo> *buffers = &mPortBuffers[kPortIndexInput];
size_t i = 0;
while (i < buffers->size() && (*buffers)[i].mBuffer != buffer) {
++i; 
} 
BufferInfo* info = &buffers->editItemAt(i);
info->mStatus =OWNED_BY_US; 
// Buffer could not be released until empty buffer done is called. 
if (info->mMediaBuffer != NULL) {
info->mMediaBuffer->release();
info->mMediaBuffer =NULL; 
} 
drainInputBuffer(&buffers->editItemAt(i));
break; 
} 
**************** 
} 
void OMXCodec::on_message(const omx_message &msg) {  switch (msg.type) {  ************        case omx_message::EMPTY_BUFFER_DONE:         {             IOMX::buffer_id buffer = msg.u.extended_buffer_data.buffer;             Vector<BufferInfo> *buffers = &mPortBuffers[kPortIndexInput];             size_t i = 0;             while (i < buffers->size() && (*buffers)[i].mBuffer != buffer) {                 ++i;             }             BufferInfo* info = &buffers->editItemAt(i);             info->mStatus = OWNED_BY_US;             // Buffer could not be released until empty buffer done is called.             if (info->mMediaBuffer != NULL) {                 info->mMediaBuffer->release();                 info->mMediaBuffer = NULL;             }             drainInputBuffer(&buffers->editItemAt(i));            break;         }  ****************  }

这部分很绕，但搞清楚就好了，请大家仔细阅读，此处虽然调用了info->mMediaBuffer->release();但是由于其引用始终大于0，因此不会真正的release
二是当release完毕后，会调用drainInputBuffer(&buffers->editItemAt(i));来填充数据
也就是说当我们启动一次解码播放后，会在此处循环读取数和据解码数据。而输出数据在后面的filloutbuffer中。
B、输出数据的清空notifyFillBufferDone(outHeader);
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void SoftOMXComponent::notifyFillBufferDone(OMX_BUFFERHEADERTYPE *header) {
(*mCallbacks->FillBufferDone)( 
mComponent, mComponent->pApplicationPrivate, header);
} 
void SoftOMXComponent::notifyFillBufferDone(OMX_BUFFERHEADERTYPE *header) {   (*mCallbacks->FillBufferDone)(           mComponent, mComponent->pApplicationPrivate, header);}
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OMX_ERRORTYPE OMX::OnFillBufferDone( 
node_id node, OMX_IN OMX_BUFFERHEADERTYPE *pBuffer) { 
ALOGV("OnFillBufferDone buffer=%p", pBuffer);
omx_message msg; 
msg.type = omx_message::FILL_BUFFER_DONE; 
msg.node = node;
msg.u.extended_buffer_data.buffer =pBuffer; 
msg.u.extended_buffer_data.range_offset =pBuffer->nOffset;
msg.u.extended_buffer_data.range_length =pBuffer->nFilledLen;
msg.u.extended_buffer_data.flags =pBuffer->nFlags;
msg.u.extended_buffer_data.timestamp =pBuffer->nTimeStamp;
msg.u.extended_buffer_data.platform_private =pBuffer->pPlatformPrivate;
msg.u.extended_buffer_data.data_ptr =pBuffer->pBuffer;
findDispatcher(node)->post(msg); 
return OMX_ErrorNone; 
} 
OMX_ERRORTYPE OMX::OnFillBufferDone(        node_id node, OMX_IN OMX_BUFFERHEADERTYPE *pBuffer) {    ALOGV("OnFillBufferDone buffer=%p", pBuffer);    omx_message msg;    msg.type = omx_message::FILL_BUFFER_DONE;    msg.node = node;    msg.u.extended_buffer_data.buffer = pBuffer;    msg.u.extended_buffer_data.range_offset = pBuffer->nOffset;    msg.u.extended_buffer_data.range_length = pBuffer->nFilledLen;    msg.u.extended_buffer_data.flags = pBuffer->nFlags;    msg.u.extended_buffer_data.timestamp = pBuffer->nTimeStamp;    msg.u.extended_buffer_data.platform_private = pBuffer->pPlatformPrivate;    msg.u.extended_buffer_data.data_ptr = pBuffer->pBuffer;   findDispatcher(node)->post(msg);     return OMX_ErrorNone; }
最终处理在OMXCodec.cpp中
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void OMXCodec::on_message(const omx_message &msg) { 
{ 
case omx_message::FILL_BUFFER_DONE: 
info->mStatus =OWNED_BY_US; 
mFilledBuffers.push_back(i); 
mBufferFilled.signal(); 
break; 
} 
} 
void OMXCodec::on_message(const omx_message &msg) {{case omx_message::FILL_BUFFER_DONE:               info->mStatus = OWNED_BY_US;               mFilledBuffers.push_back(i);               mBufferFilled.signal();                   break;       }}

主体就这么几句，先将mStatus设置成OWNED_BY_US，这样component便不能操作了，后面将这个buffer push到mFilledBuffers中。
4.2 fillOutputBuffers
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void OMXCodec::fillOutputBuffers() { 
CHECK_EQ((int)mState, (int)EXECUTING); 
Vector<BufferInfo> *buffers = &mPortBuffers[kPortIndexOutput];
for (size_t i = 0; i< buffers->size(); ++i) {
BufferInfo *info = &buffers->editItemAt(i);
if (info->mStatus == OWNED_BY_US) {
fillOutputBuffer(&buffers->editItemAt(i));
} 
} 
} 
void OMXCodec::fillOutputBuffers() {   CHECK_EQ((int)mState, (int)EXECUTING);   Vector<BufferInfo> *buffers = &mPortBuffers[kPortIndexOutput];   for (size_t i = 0; i < buffers->size(); ++i) {       BufferInfo *info = &buffers->editItemAt(i);       if (info->mStatus == OWNED_BY_US) {           fillOutputBuffer(&buffers->editItemAt(i));       }   }}
找到一个输出缓冲区bufferinfo，启动输出
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void OMXCodec::fillOutputBuffer(BufferInfo *info) { 
************** 
status_t err = mOMX->fillBuffer(mNode, info->mBuffer);
info->mStatus =OWNED_BY_COMPONENT; 
} 
void OMXCodec::fillOutputBuffer(BufferInfo *info) {   **************   status_t err = mOMX->fillBuffer(mNode, info->mBuffer);   info->mStatus = OWNED_BY_COMPONENT;}
下面和解码流程类似，我们依次来看：
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status_t OMXNodeInstance::fillBuffer(OMX::buffer_id buffer) {
Mutex::Autolock autoLock(mLock); 
OMX_BUFFERHEADERTYPE *header = (OMX_BUFFERHEADERTYPE *)buffer;
header->nFilledLen =0; 
header->nOffset =0; 
header->nFlags =0; 
OMX_ERRORTYPE err =OMX_FillThisBuffer(mHandle, header);
return StatusFromOMXError(err); 
} 
status_t OMXNodeInstance::fillBuffer(OMX::buffer_id buffer) {    Mutex::Autolock autoLock(mLock);   OMX_BUFFERHEADERTYPE *header = (OMX_BUFFERHEADERTYPE *)buffer;   header->nFilledLen = 0;    header->nOffset = 0;    header->nFlags = 0;    OMX_ERRORTYPE err = OMX_FillThisBuffer(mHandle, header);    return StatusFromOMXError(err); }
进行一些初始化后，调用进入了softMP3中，也就是
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OMX_ERRORTYPE SimpleSoftOMXComponent::fillThisBuffer(
OMX_BUFFERHEADERTYPE *buffer) { 
sp<AMessage>msg = new AMessage(kWhatFillThisBuffer, mHandler->id());
msg->setPointer("header", buffer);
msg->post(); 
return OMX_ErrorNone; 
} 
OMX_ERRORTYPE SimpleSoftOMXComponent::fillThisBuffer(        OMX_BUFFERHEADERTYPE *buffer) {    sp<AMessage> msg = new AMessage(kWhatFillThisBuffer, mHandler->id());    msg->setPointer("header", buffer);   msg->post();   return OMX_ErrorNone;}
同理，接收程序也在本文件中：
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void SimpleSoftOMXComponent::onMessageReceived(const sp<AMessage> &msg) {
Mutex::Autolock autoLock(mLock); 
uint32_t msgType =msg->what();
ALOGV("msgType = %d", msgType);
switch (msgType) { 
case kWhatEmptyThisBuffer: 
case kWhatFillThisBuffer: 
{ 
OMX_BUFFERHEADERTYPE *header; 
CHECK(msg->findPointer("header", (void **)&header));
CHECK(mState == OMX_StateExecuting &&mTargetState == mState); 
bool found = false;
size_t portIndex = (kWhatEmptyThisBuffer == msgType)?
header->nInputPortIndex: header->nOutputPortIndex;
PortInfo *port = &mPorts.editItemAt(portIndex);
for (size_t j = 0; j< port->mBuffers.size(); ++j) {
BufferInfo *buffer = &port->mBuffers.editItemAt(j);
if (buffer->mHeader == header) {
CHECK(!buffer->mOwnedByUs);
buffer->mOwnedByUs =true; 
CHECK((msgType == kWhatEmptyThisBuffer
&& port->mDef.eDir == OMX_DirInput)
|| (port->mDef.eDir == OMX_DirOutput));
port->mQueue.push_back(buffer); 
onQueueFilled(portIndex); 
found = true;
break; 
} 
} 
CHECK(found); 
break; 
} 
default: 
TRESPASS(); 
break; 
} 
} 
void SimpleSoftOMXComponent::onMessageReceived(const sp<AMessage> &msg) {    Mutex::Autolock autoLock(mLock);    uint32_t msgType = msg->what();    ALOGV("msgType = %d", msgType);    switch (msgType) {        case kWhatEmptyThisBuffer:        case kWhatFillThisBuffer:       {            OMX_BUFFERHEADERTYPE *header;            CHECK(msg->findPointer("header", (void **)&header));            CHECK(mState == OMX_StateExecuting && mTargetState == mState);           bool found = false;            size_t portIndex = (kWhatEmptyThisBuffer == msgType)?                    header->nInputPortIndex: header->nOutputPortIndex;            PortInfo *port = &mPorts.editItemAt(portIndex);           for (size_t j = 0; j < port->mBuffers.size(); ++j) {                BufferInfo *buffer = &port->mBuffers.editItemAt(j);                if (buffer->mHeader == header) {                    CHECK(!buffer->mOwnedByUs);                    buffer->mOwnedByUs = true;                 CHECK((msgType == kWhatEmptyThisBuffer                            && port->mDef.eDir == OMX_DirInput)                            || (port->mDef.eDir == OMX_DirOutput));                    port->mQueue.push_back(buffer);                  onQueueFilled(portIndex);                    found = true;                    break;                }            }            CHECK(found);            break;        }       default:            TRESPASS();            break;    }   }

也会调用void SoftMP3::onQueueFilled执行一次解码操作，然后再通过 
notifyEmptyBufferDone(inHeader);
notifyFillBufferDone(outHeader);
两个函数来推进播放进度。
【结束】

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