标签:android awesomeplayer play mediaplayer 多媒体
这一篇文章接着之前的prepare,讲play的流程
前面的流程省略,直接从AwesomePlayer的Play()开始讲。
status_t AwesomePlayer::play() { …… return play_l(); } status_t AwesomePlayer::play_l() { …… if (mAudioSource != NULL) { if (mAudioPlayer == NULL) { createAudioPlayer_l(); } if (mVideoSource == NULL) { status_t err = startAudioPlayer_l( false /* sendErrorNotification */); ……; } } if (mVideoSource != NULL) { // Kick off video playback postVideoEvent_l(); if (mAudioSource != NULL && mVideoSource != NULL) { postVideoLagEvent_l(); } } …… }
如果是播放AVI、MP4等视频文件,则m_AudioSource和mVideoSource都不为null,如果是播放MP3文件,则m_AudioSource不为null而mVideoSource为null。现在按照播放视频文件的流程来分析。
先看createAudioPlayer_1();void AwesomePlayer::createAudioPlayer_l() { …… mAudioPlayer = new AudioPlayer(mAudioSink, flags, this); mAudioPlayer->setSource(mAudioSource); …… }
可以看到,创建了audioPlayer,且把mAudioSource传给了创建的mAudioPlayer。
接着看postVideoEvent_lvoid AwesomePlayer::postVideoEvent_l(int64_t delayUs) { ATRACE_CALL(); if (mVideoEventPending) { return; } mVideoEventPending = true; mQueue.postEventWithDelay(mVideoEvent, delayUs < 0 ? 10000 : delayUs); }
有关TimedEventQueue的介绍,在上一篇TimedEventQueue分析。mVideoEvent在AwesomePlayer的构造函数中定义,如下:
mVideoEvent = new AwesomeEvent(this,&AwesomePlayer::onVideoEvent);
所以,mQueue.postEventWithDelay()后,将会执行到onVideoEventvoid AwesomePlayer::onVideoEvent() { …… if (!mVideoBuffer) { …… for (;;) { status_t err = mVideoSource->read(&mVideoBuffer, &options); …… if (mVideoBuffer->range_length() == 0) { mVideoBuffer->release(); mVideoBuffer = NULL; continue; } break; } { Mutex::Autolock autoLock(mStatsLock); ++mStats.mNumVideoFramesDecoded; } } …… if (mAudioPlayer != NULL && !(mFlags & (AUDIO_RUNNING | SEEK_PREVIEW))) { status_t err = startAudioPlayer_l(); } if ((mFlags & TEXTPLAYER_INITIALIZED) && !(mFlags & (TEXT_RUNNING | SEEK_PREVIEW))) { mTextDriver->start(); modifyFlags(TEXT_RUNNING, SET); } …… if ((mNativeWindow != NULL) && (mVideoRendererIsPreview || mVideoRenderer == NULL)) { mVideoRendererIsPreview = false; initRenderer_l(); } if (mVideoRenderer != NULL) { mSinceLastDropped++; mVideoRenderer->render(mVideoBuffer); if (!mVideoRenderingStarted) { mVideoRenderingStarted = true; notifyListener_l(MEDIA_INFO, MEDIA_INFO_RENDERING_START); } if (mFlags & PLAYING) { notifyIfMediaStarted_l(); } } …… postVideoEvent_l(); }
接下来分步分析
step1 : status_t err= mVideoSource->read(&mVideoBuffer, &options); 这个方法的作用就是从数据源读取数据,然后将数据送给解码器解码,最后解码器将解码好的数据输出,并通过输出参数buffer传出,为后面的render所用。status_t OMXCodec::read( MediaBuffer **buffer, const ReadOptions *options) { …… if (mInitialBufferSubmit) { // only run once,之后通过解码器调用之前设置的回调函数来调用drainInputBuffers来获取原始视频数据 mInitialBufferSubmit = false; …… drainInputBuffers(); // 通过videoTrack读取数据后将数据送给解码器处理 if (mState == EXECUTING) { // Otherwise mState == RECONFIGURING and this code will trigger // after the output port is reenabled. fillOutputBuffers(); // 向解码器请求输出数据 } } …… // 等待解码器输出解码完成 while (mState != ERROR && !mNoMoreOutputData && mFilledBuffers.empty()) { if ((err = waitForBufferFilled_l()) != OK) { return err; } } …… *buffer = info->mMediaBuffer; // 输出数据给AwesomePlayer return OK; }drainInputBuffers()和fillOutputBuffers()这两个函数后面再分析,先接着看onVideoEvent里面的step2 : status_t err = startAudioPlayer_l();
status_t AwesomePlayer::startAudioPlayer_l(bool sendErrorNotification) { …… err = mAudioPlayer->start( true /* sourceAlreadyStarted */); …… return err; } status_t AudioPlayer::start(bool sourceAlreadyStarted) { …… mAudioTrack = new AudioTrack(AUDIO_STREAM_MUSIC, mSampleRate, AUDIO_FORMAT_PCM_16_BIT, audioMask, 0, AUDIO_OUTPUT_FLAG_NONE, &AudioCallback, this, 0); …… // start之后,mAudioTrack开始播放并通过回调函数AudioCallback来获取音频数据 mAudioTrack->start(); …… return OK; } void AudioPlayer::AudioCallback(int event, void *info) { switch (event) { case AudioTrack::EVENT_MORE_DATA: { AudioTrack::Buffer *buffer = (AudioTrack::Buffer *)info; // fillBuffer通过mSource->read(&mInputBuffer, &options)读取数据,mSource为audioTrack size_t numBytesWritten = fillBuffer(buffer->raw, buffer->size); buffer->size = numBytesWritten; } break; case AudioTrack::EVENT_STREAM_END: mReachedEOS = true; notifyAudioEOS(); break; } }Step3 : initRenderer_l() 创建render
void AwesomePlayer::initRenderer_l() { …… if (USE_SURFACE_ALLOC && !strncmp(component, "OMX.", 4) && strncmp(component, "OMX.google.", 11)) { // Hardware decoders avoid the CPU color conversion by decoding // directly to ANativeBuffers, so we must use a renderer that // just pushes those buffers to the ANativeWindow. // 创建硬件加速渲染的render mVideoRenderer = new AwesomeNativeWindowRenderer(mNativeWindow, rotationDegrees); } else { // Other decoders are instantiated locally and as a consequence // allocate their buffers in local address space. This renderer // then performs a color conversion and copy to get the data // into the ANativeBuffer. // 创建软件渲染的render mVideoRenderer = new AwesomeLocalRenderer(mNativeWindow, meta); } }
Step4 : mVideoRenderer->render(mVideoBuffer);
就是将mVideoBuffer的内容输出到屏幕
到现在为止,onVideoEvent流程分析完成,接下来详细分析drainInputBuffers和fillOutputBuffers,这两个函数都是通过OMX和解码器通讯的函数。bool OMXCodec::drainInputBuffer(BufferInfo *info) { …… // mSource为mVideoTrack,通过read方法读取原始视频数据 err = mSource->read(&srcBuffer); …… // 通过OMX的emptyBuffer调用解码库解码数据 err = mOMX->emptyBuffer( mNode, info->mBuffer, 0, offset, flags, timestampUs); info->mStatus = OWNED_BY_COMPONENT; return true; } void OMXCodec::fillOutputBuffer(BufferInfo *info) { // 通过调用OMX的fillBuffer来获取解码后的帧数据 status_t err = mOMX->fillBuffer(mNode, info->mBuffer); info->mStatus = OWNED_BY_COMPONENT; }
貌似很简单,其实调用解码器的这个流程还是蛮复杂的,下面以emptyBuffer为例来梳理一下:
首先,mOMX为OMX的Bp端,其Bn端的实现在OMX.cpp里面status_t OMX::emptyBuffer( node_id node, buffer_id buffer, OMX_U32 range_offset, OMX_U32 range_length, OMX_U32 flags, OMX_TICKS timestamp) { return findInstance(node)->emptyBuffer( buffer, range_offset, range_length, flags, timestamp); }再看findInstance(node),node是prepare时调用OMX的allocateNode方法得到的,findInstance将会根据这个node值返回之前创建的OMXNodeInstance对象,其emptyBuffer定义如下:
status_t OMXNodeInstance::emptyBuffer( OMX::buffer_id buffer, OMX_U32 rangeOffset, OMX_U32 rangeLength, OMX_U32 flags, OMX_TICKS timestamp) { Mutex::Autolock autoLock(mLock); OMX_BUFFERHEADERTYPE *header = (OMX_BUFFERHEADERTYPE *)buffer; header->nFilledLen = rangeLength; header->nOffset = rangeOffset; header->nFlags = flags; header->nTimeStamp = timestamp; BufferMeta *buffer_meta = static_cast<BufferMeta *>(header->pAppPrivate); buffer_meta->CopyToOMX(header); OMX_ERRORTYPE err = OMX_EmptyThisBuffer(mHandle, header); return StatusFromOMXError(err); } #define OMX_EmptyThisBuffer( hComponent, pBuffer) ((OMX_COMPONENTTYPE*)hComponent)->EmptyThisBuffer( hComponent, pBuffer) /* Macro End */从代码中,我们可以看出实际上是调用了mHandle的EmptyThisBuffer方法,mHandle是什么呢?在prepare过程中,我们调用了OMX的allocateNode方法,在这个方法里面,我们通过调用OMXNodeInstance的setHandle方法设置了其值。再回顾一下其实现:
status_t OMX::allocateNode( const char *name, const sp<IOMXObserver> &observer, node_id *node) { Mutex::Autolock autoLock(mLock); *node = 0; // 创建instance OMXNodeInstance *instance = new OMXNodeInstance(this, observer); // 创建解码器组件,并将其值赋值给handle OMX_COMPONENTTYPE *handle; OMX_ERRORTYPE err = mMaster->makeComponentInstance( name, &OMXNodeInstance::kCallbacks, instance, &handle); if (err != OMX_ErrorNone) { ALOGV("FAILED to allocate omx component '%s'", name); instance->onGetHandleFailed(); return UNKNOWN_ERROR; } *node = makeNodeID(instance); mDispatchers.add(*node, new CallbackDispatcher(instance)); instance->setHandle(*node, handle); mLiveNodes.add(observer->asBinder(), instance); observer->asBinder()->linkToDeath(this); return OK; } void OMXNodeInstance::setHandle(OMX::node_id node_id, OMX_HANDLETYPE handle) { CHECK(mHandle == NULL); mNodeID = node_id; mHandle = handle; }OK,至此整个发送数据到解码器的流程就跑通了,但是前面也说了,在OMXCodec的read方法中,drainInputBuffers方法只会执行一次,之后要再往解码器送数据该怎么弄呢?就要靠回调了。一起来看一下这个回调的流程是怎么弄的吧?
在OMX的allocateNode方法中
OMX_COMPONENTTYPE *handle; OMX_ERRORTYPE err = mMaster->makeComponentInstance( name, &OMXNodeInstance::kCallbacks, instance, &handle);创建解码器时,就注册了回调函数
OMX_CALLBACKTYPE OMXNodeInstance::kCallbacks = { &OnEvent, &OnEmptyBufferDone, &OnFillBufferDone };当解码器将原始数据全部解码完成后,就会调用OMXNodeInstance 的OnEmptyBufferDone方法
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); }Instance->owner()实际上就是OMX,再看OMX的OnEmptyBufferDone
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; }findDispatcher返回CallbackDispatcher对象,是OMX的内部类,也是在OMX的allocate方法中创建的,CallbackDispatcher在创建时启动了一个线程,不断的获取消息,然后调用dispatch方法执行之,看dispatch方法:
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); }mOwner为OMXNodeInstance对象,所以看OMXNodeInstance的onMessage方法。
void OMXNodeInstance::onMessage(const omx_message &msg) { …… mObserver->onMessage(msg); }mObserver为OMXCodecObserver对象,是在prepare时在OMXCodec::Create中创建,下面看其onMessage方法实现
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(); } }codec的值为OMXCodec对象,看其on_message的实现
void OMXCodec::on_message(const omx_message &msg) { …… switch (msg.type) { …… case omx_message::EMPTY_BUFFER_DONE: { …… if (mPortStatus[kPortIndexInput] == DISABLING) { …… } else if (mState != ERROR && mPortStatus[kPortIndexInput] != SHUTTING_DOWN) { CHECK_EQ((int)mPortStatus[kPortIndexInput], (int)ENABLED); if (mFlags & kUseSecureInputBuffers) { drainAnyInputBuffer(); } else { // 看,数据用完后又开始要新的数据了 drainInputBuffer(&buffers->editItemAt(i)); } } break; } case omx_message::FILL_BUFFER_DONE: { // 可以看到,FILL_BUFFER_DONE的回调流程和EMPTY_BUFFER_DONE基本一样 // 这里做的主要的事情就是通知AwesomePlayer解码库有解码好的帧输出,可以播放了 …… } } }
全文完。
标签:android awesomeplayer play mediaplayer 多媒体
原文地址:http://blog.csdn.net/super_dc/article/details/39484125