做it的兼职网站有哪些,权重2的网站,网站建设发展状况,南京建设网站公司网站这里是他们自己的源代码阅读点滴总结属性#xff0c;转请注明出处#xff0c;谢谢。欢迎和大家分享。qq:1037701636 email:gzzaigcn2012gmail.comAndroid源代码版本号Version#xff1a;4.2.2; 硬件平台 全志A31前沿#xff1a;在前面的博文中#xff0c;基本提到的是stag… 这里是他们自己的源代码阅读点滴总结属性转请注明出处谢谢。欢迎和大家分享。qq:1037701636 email:gzzaigcn2012gmail.comAndroid源代码版本号Version4.2.2; 硬件平台 全志A31 前沿在前面的博文中基本提到的是stagefright相关的控制流详细分析了android架构中的MediaExtractor、AwesomePlayer、StagefrightPlayer、OMXCodec等的创建。底层OMXNodinstance实例的创建。分析了OMX最底层插件库、编解码器组件的架构以及怎样创建属于我们自己的OMX Plugin。分析源代码架构的还有一个关键是数据流的分析从这里開始。我们将对stagefright中的编解码缓存区进行分析1.回到OMXCodec的创建过程的源代码status_t AwesomePlayer::initVideoDecoder(uint32_t flags) {
.......mVideoSource OMXCodec::Create(mClient.interface(), mVideoTrack-getFormat(),//提取视频流的格式, mClient:BpOMXmVideoTrack-getFormat()false, // createEncoder不创建编码器falsemVideoTrack,NULL, flags, USE_SURFACE_ALLOC ? mNativeWindow : NULL);//创建一个解码器mVideoSourceif (mVideoSource ! NULL) {int64_t durationUs;if (mVideoTrack-getFormat()-findInt64(kKeyDuration, durationUs)) {Mutex::Autolock autoLock(mMiscStateLock);if (mDurationUs 0 || durationUs mDurationUs) {mDurationUs durationUs;}}status_t err mVideoSource-start();//启动解码器OMXCodec。完毕解码器的init初始化操作
.............
}在Android4.2.2下Stagefright多媒体架构中的A31的OMX插件和Codec组件 博文我们对于OMXCodec::create已经做了具体的分析。这里来关注mVideoSource-start的相关功能即OMXCodec::start的处理status_t OMXCodec::start(MetaData *meta) {Mutex::Autolock autoLock(mLock);
........return init();//进行初始化操作
}这里调用init()的过程。将会进行buffer的申请操作。为兴许的流操作打下基础status_t OMXCodec::init() {// mLock is held.
.........err allocateBuffers();//缓存区的分配if (err ! (status_t)OK) {return err;}if (mQuirks kRequiresLoadedToIdleAfterAllocation) {err mOMX-sendCommand(mNode, OMX_CommandStateSet, OMX_StateIdle);CHECK_EQ(err, (status_t)OK);setState(LOADED_TO_IDLE);}
............
}我们来看allocateBuffers的实现 2.关注allocateBuffersOnPort的实现status_t OMXCodec::allocateBuffers() {status_t err allocateBuffersOnPort(kPortIndexInput);//输入缓存input口分配if (err ! OK) {return err;}return allocateBuffersOnPort(kPortIndexOutput);//输出缓存input口分配
}这里分别将对输入和输出口进行Buffer的申请与分配。对于解码器须要输入口来存储待解码的数据源须要将解码后的数据源存储到输出口而这也符合硬件的实现逻辑。以输入缓存区分配为例展开分析status_t OMXCodec::allocateBuffersOnPort(OMX_U32 portIndex) {
.......OMX_PARAM_PORTDEFINITIONTYPE def;InitOMXParams(def);def.nPortIndex portIndex;//输入口err mOMX-getParameter(mNode, OMX_IndexParamPortDefinition, def, sizeof(def));//获取输入口參数到def
..........err mOMX-allocateBuffer(mNode, portIndex, def.nBufferSize, buffer,info.mData);
........info.mBuffer buffer;//获取相应的buffer_id。有保存有底层的buffer的相关信息info.mStatus OWNED_BY_US;info.mMem mem;info.mMediaBuffer NULL;...........mPortBuffers[portIndex].push(info);//把当前的buffer恢复到mPortBuffers[2]中去
上述过程主要分为step1先是获取底层解码器组件的当前的參数熟悉一般这些參数都在建立OMX_Codec时完毕的初始配置前一博文中已经提到过。step2:进行allocateBuffer的处理这个函数的调用终于交给底层的OMX组件来完毕相关的实现将集成到A31的底层OMX编解码组件的处理流中进行分析。step3:完毕对分配好的buffer信息info。维护在mPortBuffers[0]这个port中。上述过程完毕了输入与输出的Buffer分配。为兴许解码操作buffer打下了基础。 3.mediaplay启动播放器通过start的API调用。进入MediaplayerService::Client再依次经过stagefrightplayerAwesomePlayer。触发play的videoevent的发生.void AwesomePlayer::postVideoEvent_l(int64_t delayUs) {ATRACE_CALL();if (mVideoEventPending) {return;}mVideoEventPending true;mQueue.postEventWithDelay(mVideoEvent, delayUs 0 ? 10000 : delayUs);
}依据前一博文的分析可知该事件相应的处理函数为AwesomePlayer::onVideoEvent()该部分代码量较大。提取核心内容read的处理进行分析 status_t err mVideoSource-read(mVideoBuffer, options);//循环读数据实际的OMX_CODEC::read,读取到mVideoBufferread的核心是获取能够用于render的视频数据这表明了read函数主要完毕了从视频源读取元数据并调用解码器完毕解码生成可送显的数据。 4. read函数的实现能够想象read函数的应该是一个比較复杂的过程。我们从OMX_Codec的read函数入手来分析status_t OMXCodec::read(MediaBuffer **buffer, const ReadOptions *options) {status_t err OK;*buffer NULL;Mutex::Autolock autoLock(mLock);drainInputBuffers();//buffer填充数据源if (mState EXECUTING) {// Otherwise mState RECONFIGURING and this code will trigger// after the output port is reenabled.fillOutputBuffers();}}...........
}read的核心逻辑总结为drainInputBuffers()和fillOutputBuffers()我们对其依次进行深入的分析 5. drainInputBuffers()读取待解码的视频数据源到解码器的Inport这里贴出其较为复杂的处理过程代码。主要分为下面3个部分进行分析1bool OMXCodec::drainInputBuffer(BufferInfo *info) { if (mCodecSpecificDataIndex mCodecSpecificData.size()) {CHECK(!(mFlags kUseSecureInputBuffers));const CodecSpecificData *specific mCodecSpecificData[mCodecSpecificDataIndex];size_t size specific-mSize;if (!strcasecmp(MEDIA_MIMETYPE_VIDEO_AVC, mMIME) !(mQuirks kWantsNALFragments)) {static const uint8_t kNALStartCode[4] { 0x00, 0x00, 0x00, 0x01 };CHECK(info-mSize specific-mSize 4);size 4;memcpy(info-mData, kNALStartCode, 4);memcpy((uint8_t *)info-mData 4,specific-mData, specific-mSize);} else {CHECK(info-mSize specific-mSize);memcpy(info-mData, specific-mData, specific-mSize);//copy前面的数据字段}mNoMoreOutputData false;CODEC_LOGV(calling emptyBuffer with codec specific data);status_t err mOMX-emptyBuffer(mNode, info-mBuffer, 0, size,OMX_BUFFERFLAG_ENDOFFRAME | OMX_BUFFERFLAG_CODECCONFIG,0);//处理bufferCHECK_EQ(err, (status_t)OK);info-mStatus OWNED_BY_COMPONENT;mCodecSpecificDataIndex;return true;}...............(1)这部分的内容主要是提取一部分解码器字段填充到info-mData的存储空间中去。这部分主要基于视频源的格式如mp4等在创建OXMCodec病configureCodec时就完毕了这个mCodecSpecificData字段的加入应该些解码须要的特殊字段吧。是否须要要看其视频源的格式。获取完这个字段信息后就是正式读取视频源的数据了。 (2) for (;;) {MediaBuffer *srcBuffer;if (mSeekTimeUs 0) {if (mLeftOverBuffer) {mLeftOverBuffer-release();mLeftOverBuffer NULL;}MediaSource::ReadOptions options;options.setSeekTo(mSeekTimeUs, mSeekMode);mSeekTimeUs -1;mSeekMode ReadOptions::SEEK_CLOSEST_SYNC;mBufferFilled.signal();err mSource-read(srcBuffer, options);//读取视频源中的真实数据这里是MPEG4Source的readif (err OK) {int64_t targetTimeUs;if (srcBuffer-meta_data()-findInt64(kKeyTargetTime, targetTimeUs) targetTimeUs 0) {CODEC_LOGV(targetTimeUs %lld us, targetTimeUs);mTargetTimeUs targetTimeUs;} else {mTargetTimeUs -1;}}} else if (mLeftOverBuffer) {srcBuffer mLeftOverBuffer;mLeftOverBuffer NULL;err OK;} else {err mSource-read(srcBuffer);}if (err ! OK) {signalEOS true;mFinalStatus err;mSignalledEOS true;mBufferFilled.signal();break;}if (mFlags kUseSecureInputBuffers) {info findInputBufferByDataPointer(srcBuffer-data());CHECK(info ! NULL);}size_t remainingBytes info-mSize - offset;//buffer中剩余的能够存储视频数据的空间if (srcBuffer-range_length() remainingBytes) {//当前读取的数据已经达到解码的数据量if (offset 0) {CODEC_LOGE(Codecs input buffers are too small to accomodate buffer read from source (info-mSize %d, srcLength %d),info-mSize, srcBuffer-range_length());srcBuffer-release();srcBuffer NULL;setState(ERROR);return false;}mLeftOverBuffer srcBuffer;//把没读取的buffer记录下来break;}bool releaseBuffer true;if (mFlags kStoreMetaDataInVideoBuffers) {releaseBuffer false;info-mMediaBuffer srcBuffer;}if (mFlags kUseSecureInputBuffers) {// Data in info is already provided at this time.releaseBuffer false;CHECK(info-mMediaBuffer NULL);info-mMediaBuffer srcBuffer;} else {CHECK(srcBuffer-data() ! NULL) ;memcpy((uint8_t *)info-mData offset,(const uint8_t *)srcBuffer-data() srcBuffer-range_offset(),srcBuffer-range_length());//copy数据源数据到输入缓存,数据容量srcBuffer-range_length()}int64_t lastBufferTimeUs;CHECK(srcBuffer-meta_data()-findInt64(kKeyTime, lastBufferTimeUs));CHECK(lastBufferTimeUs 0);if (mIsEncoder mIsVideo) {mDecodingTimeList.push_back(lastBufferTimeUs);}if (offset 0) {timestampUs lastBufferTimeUs;}offset srcBuffer-range_length();//添加偏移量if (!strcasecmp(MEDIA_MIMETYPE_AUDIO_VORBIS, mMIME)) {CHECK(!(mQuirks kSupportsMultipleFramesPerInputBuffer));CHECK_GE(info-mSize, offset sizeof(int32_t));int32_t numPageSamples;if (!srcBuffer-meta_data()-findInt32(kKeyValidSamples, numPageSamples)) {numPageSamples -1;}memcpy((uint8_t *)info-mData offset,numPageSamples,sizeof(numPageSamples));offset sizeof(numPageSamples);}if (releaseBuffer) {srcBuffer-release();srcBuffer NULL;}n;if (!(mQuirks kSupportsMultipleFramesPerInputBuffer)) {break;}int64_t coalescedDurationUs lastBufferTimeUs - timestampUs;if (coalescedDurationUs 250000ll) {// Dont coalesce more than 250ms worth of encoded data at once.break;}}...........该部分是提取视频源数据的关键主要通过 err mSource-read(srcBuffer, options)来完毕mSource是在创建编解码器传入的实际是一个相应于视频源格式的一个解析器MediaExtractor。比方在建立MP4的解析器MPEG4Extractor通过新建一个new MPEG4Source。故终于这里调用的是MPEG4Source的read成员函数事实上际也维护着整个待解码的原始视频流。我们能够看大在read函数后。会将待解码的数据流以for循环依次读入究竟层的buffer空间中。仅仅有当满足当前读取的原始数据片段比底层的input口的buffer剩余空间小srcBuffer-range_length() remainingBytes。那就能够继续读取否则直接break后去进行下一步操作。或者假设一次待解码的数据时张是大于250ms也直接跳出。这处理体现了处理的高效性。终于视频原始数据存储在info-mData的底层输入空间中。 (3) err mOMX-emptyBuffer(mNode, info-mBuffer, 0, offset,flags, timestampUs);触发底层的解码器组件进行处理。这部分留在兴许对A31的底层编解码API操作时进行分析。6.fillOutputBuffers对输出buffer口的填充即实现解码过程void OMXCodec::fillOutputBuffers() {CHECK_EQ((int)mState, (int)EXECUTING);
...........VectorBufferInfo *buffers mPortBuffers[kPortIndexOutput];输出portfor (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::fillOutputBuffer(BufferInfo *info) {CHECK_EQ((int)info-mStatus, (int)OWNED_BY_US);if (mNoMoreOutputData) {CODEC_LOGV(There is no more output data available, not calling fillOutputBuffer);return;}CODEC_LOGV(Calling fillBuffer on buffer %p, info-mBuffer);status_t err mOMX-fillBuffer(mNode, info-mBuffer);if (err ! OK) {CODEC_LOGE(fillBuffer failed w/ error 0x%08x, err);setState(ERROR);return;}info-mStatus OWNED_BY_COMPONENT;
}
从上面的代码看来fillOutputBuffer的实现比drainInputBuffers简单了非常多。但同样的是。两者终于都讲控制权交给底层的解码器来完毕。 7.等待解码数据被fill到outbuffer中OMXCodecObserver完毕回调处理等待解码完毕的这部分内容在read函数中通过下面函数来实现 while (mState ! ERROR !mNoMoreOutputData mFilledBuffers.empty()) {if ((err waitForBufferFilled_l()) ! OK) {//进入等待buffer被填充return err;}}上述表明仅仅要mFilledBuffers为空则进入等待填充pthread_cond_timedwait。而这个线程被唤醒是通过底层的组件回调来完毕的。回调函数的注冊哎底层编解码器Node完毕的。实际终于的回调是交给OMXCodecObserver来完毕的struct OMXCodecObserver : public BnOMXObserver {OMXCodecObserver() {}void setCodec(const spOMXCodec target) {mTarget target;}// from IOMXObservervirtual void onMessage(const omx_message msg) {spOMXCodec codec mTarget.promote();if (codec.get() ! NULL) {Mutex::Autolock autoLock(codec-mLock);codec-on_message(msg);//OMX_Codec的on_message处理codec.clear();}}
终于能够看到是由OMX_Codec-on_message来进行消息的处理。这部分的内容主要包含EMPTY_BUFFER_DONE和FILL_BUFFER_DONE两个message处理。对FILL_BUFFER_DONE完毕后的消息回调进行分析void OMXCodec::on_message(const omx_message msg) {if (mState ERROR) {/** only drop EVENT messages, EBD and FBD are still* processed for bookkeeping purposes*/if (msg.type omx_message::EVENT) {ALOGW(Dropping OMX EVENT message - were in ERROR state.);return;}}switch (msg.type) { case omx_message::FILL_BUFFER_DONE://底层回调callback告知当前 ..............mFilledBuffers.push_back(i);//当前的输出buffer信息维护在mFilledBuffersmBufferFilled.signal();//发出信息用于渲染
能够看到这里对read线程进行了唤醒。8.提取一个可用的解码后的数据帧 size_t index *mFilledBuffers.begin();mFilledBuffers.erase(mFilledBuffers.begin());BufferInfo *info mPortBuffers[kPortIndexOutput].editItemAt(index);//从获取解码后的视频源CHECK_EQ((int)info-mStatus, (int)OWNED_BY_US);info-mStatus OWNED_BY_CLIENT;info-mMediaBuffer-add_ref();//if (mSkipCutBuffer ! NULL) {mSkipCutBuffer-submit(info-mMediaBuffer);}*buffer info-mMediaBuffer;
获得了线程唤醒后的buffer从这里获取到输出port相应的Bufferinfo。作为终于的BufferInfo信息返回给read函数9经过5、6、7、8的处理过程。read终于返回可用于显示的mVideoBuffer接下去就是怎样送显的过程了。能够看到以下的代码。将会创建一个渲染器mVideoRenderer来完毕这个解码后视频源的显示 if ((mNativeWindow ! NULL) (mVideoRendererIsPreview || mVideoRenderer NULL)) {//首次创建渲染器 mVideoRendererIsPreview false; initRenderer_l();//初始化渲染器。新建一个AwesomeLocalRenderer } if (mVideoRenderer ! NULL) { mSinceLastDropped; mVideoRenderer-render(mVideoBuffer);//启动渲染。即显示当前buffer if (!mVideoRenderingStarted) { mVideoRenderingStarted true; notifyListener_l(MEDIA_INFO, MEDIA_INFO_RENDERING_START); } }void AwesomePlayer::initRenderer_l() {ATRACE_CALL();if (mNativeWindow NULL) {return;}spMetaData meta mVideoSource-getFormat();int32_t format;const char *component;int32_t decodedWidth, decodedHeight;CHECK(meta-findInt32(kKeyColorFormat, format));CHECK(meta-findCString(kKeyDecoderComponent, component));CHECK(meta-findInt32(kKeyWidth, decodedWidth));CHECK(meta-findInt32(kKeyHeight, decodedHeight));int32_t rotationDegrees;if (!mVideoTrack-getFormat()-findInt32(kKeyRotation, rotationDegrees)) {rotationDegrees 0;}mVideoRenderer.clear();// Must ensure that mVideoRenderers destructor is actually executed// before creating a new one.IPCThreadState::self()-flushCommands();// Even if set scaling mode fails, we will continue anywaysetVideoScalingMode_l(mVideoScalingMode);if (USE_SURFACE_ALLOC !strncmp(component, OMX., 4) strncmp(component, OMX.google., 11) strcmp(component, OMX.Nvidia.mpeg2v.decode)) {//使用硬件渲染器。除去上述的解码器// 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.mVideoRenderer new AwesomeNativeWindowRenderer(mNativeWindow, rotationDegrees);//通常是使用硬件渲染机制} 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.mVideoRenderer new AwesomeLocalRenderer(mNativeWindow, meta);}
}能够看到这里有2个渲染器的创建分支OMX和OMX.google说明底层的解码器用的是软解码。那么他渲染器也使用所谓的本地渲染器实际是软渲染器。故这里我们使用的是AwesomeNativeWindowRenderer渲染器其结构例如以下所述struct AwesomeNativeWindowRenderer : public AwesomeRenderer {AwesomeNativeWindowRenderer(const spANativeWindow nativeWindow,int32_t rotationDegrees): mNativeWindow(nativeWindow) {applyRotation(rotationDegrees);}virtual void render(MediaBuffer *buffer) {ATRACE_CALL();int64_t timeUs;CHECK(buffer-meta_data()-findInt64(kKeyTime, timeUs));native_window_set_buffers_timestamp(mNativeWindow.get(), timeUs * 1000);status_t err mNativeWindow-queueBuffer(mNativeWindow.get(), buffer-graphicBuffer().get(), -1);//直接使用queuebuffer进行渲染显示if (err ! 0) {ALOGE(queueBuffer failed with error %s (%d), strerror(-err),-err);return;}spMetaData metaData buffer-meta_data();metaData-setInt32(kKeyRendered, 1);}
不是非常复杂仅仅是实现了AwesomeRenderer渲染接口render。终于调用这个函数来实现对buffer的显示。这里看到非常熟悉的queueBuffer大家能够回看我的博文Android4.2.2 SurfaceFlinger之图形渲染queueBuffer实现和VSYNC的存在感 这是通过应用程序的本地窗体mNativeWindow由于播放器videoview继承了sufaceview,surfaceview类会创建一个本地的surface其继承了本地窗体类将当前buffer提交给SurfaceFlinger服务进行显示。具体内容不在展开。至此我们完毕了stagefright下的编解码的数据流的相关操作程序上复杂主要体如今emptybuffer和fillbuffer为主。当然由于能力有限。在非常多细节上也没有进行非常具体的分析。也希望大家多交流。多学习。 版权声明本文博主原创文章。博客未经同意不得转载。 转载于:https://www.cnblogs.com/hrhguanli/p/4827324.html
