高稳定性的网站设计制作,公司网站建设费计入科目,seo搜索引擎优化试题及答案,专门做瑜伽的网站文章目录 前言音频采集音频初始化AudioRecord 分析AudioSource 采集到音频 音频编码音频编码后数据处理MPEG4Writer写入音频编码后数据到文件MPEG4Writer::Track 取编码后的音频编数据结语 本文首发地址 https://blog.csdn.net/CSqingchen/article/details/134896808 最新更新地… 文章目录 前言音频采集音频初始化AudioRecord 分析AudioSource 采集到音频 音频编码音频编码后数据处理MPEG4Writer写入音频编码后数据到文件MPEG4Writer::Track 取编码后的音频编数据结语 本文首发地址 https://blog.csdn.net/CSqingchen/article/details/134896808 最新更新地址 https://gitee.com/chenjim/chenjimblog 前言
通过安卓MediaRecorder(2)录制源码分析我们知道 MediaRecorder 相关接口是在 StagefrightRecorder.cpp 中实现本文进一步分析音频采集、编码、写入文件详细流程。
音频采集
音频初始化
通过前文我们知道 setupAudioEncoder 在 setupMPEG4orWEBMRecording 中初始化相关源码如下
// frameworks/av/media/libmediaplayerservice/StagefrightRecorder.cpp
status_t StagefrightRecorder::setupAudioEncoder() {spMediaCodecSource audioEncoder createAudioSource();return OK;
}
spMediaCodecSource StagefrightRecorder::createAudioSource() {...// 通过 AVFactory 工厂创建 AudioSource,并初始化 spAudioSource audioSource AVFactory::get()-createAudioSource(attr,mAttributionSource,sourceSampleRate,mAudioChannels,mSampleRate,mSelectedDeviceId,mSelectedMicDirection,mSelectedMicFieldDimension);}那 AudioSource 是如何初始化的呢
// frameworks/av/media/libstagefright/AudioSource.cpp
void AudioSource::set(const audio_attributes_t *attr, const AttributionSourceState attributionSource,uint32_t sampleRate, uint32_t channelCount, uint32_t outSampleRate,audio_port_handle_t selectedDeviceId,audio_microphone_direction_t selectedMicDirection,float selectedMicFieldDimension)
{...// 构造了 一个 AudioRecord cpp 对象 mRecord new AudioRecord(AUDIO_SOURCE_DEFAULT, sampleRate, AUDIO_FORMAT_PCM_16_BIT,audio_channel_in_mask_from_count(channelCount),attributionSource,(size_t) (bufCount * frameCount),// 采集的音频数据回调 wpAudioRecord::IAudioRecordCallback{this},frameCount /*notificationFrames*/,AUDIO_SESSION_ALLOCATE,AudioRecord::TRANSFER_DEFAULT,AUDIO_INPUT_FLAG_NONE,attr,selectedDeviceId,selectedMicDirection,selectedMicFieldDimension);...
}AudioRecord.java 底层的实现也是 AudioSource.cpp AudioRecord 主要是负责从麦克风设备采集音频 PCM 帧
AudioRecord 分析
// frameworks/av/media/libaudioclient/AudioRecord.cpp
status_t AudioRecord::set(...) {...if (mCallback ! nullptr) {// 启动录制的线程 mAudioRecordThread new AudioRecordThread(*this);mAudioRecordThread-run(AudioRecord, ANDROID_PRIORITY_AUDIO);}...
}
bool AudioRecord::AudioRecordThread::threadLoop() {...nsecs_t ns mReceiver.processAudioBuffer();...
}nsecs_t AudioRecord::processAudioBuffer() {... // 回调 AudioRecord::IAudioRecordCallback if (newOverrun) {callback-onOverrun();}if (markerReached) {callback-onMarker(markerPosition.value());}while (newPosCount 0) {callback-onNewPos(newPosition.value());newPosition updatePeriod;newPosCount--;}if (mObservedSequence ! sequence) {mObservedSequence sequence;callback-onNewIAudioRecord();}while (mRemainingFrames 0) {// 获取 audioBuffer status_t err obtainBuffer(audioBuffer, requested, NULL, nonContig);// 回调 取到的 buffer 到 AudioSource 中 onMoreData const size_t readSize callback-onMoreData(*buffer);// 释放 buffer releaseBuffer(audioBuffer);}
}AudioSource 采集到音频
// frameworks/av/media/libstagefright/AudioSource.cpp
size_t AudioSource::onMoreData(const AudioRecord::Buffer audioBuffer) { ...// 将AudioRecord::Buffer 放入 MediaBufferMediaBuffer *buffer new MediaBuffer(audioBuffer.size());memcpy((uint8_t *) buffer-data(),audioBuffer.data(), audioBuffer.size());buffer-set_range(0, audioBuffer.size());// 将 buffer 放入缓存queueInputBuffer_l(buffer, timeUs);return audioBuffer.size();
}
void AudioSource::queueInputBuffer_l(MediaBuffer *buffer, int64_t timeUs) {...// 将 buffer 放入缓存 mBuffersReceived 中mBuffersReceived.push_back(buffer);mFrameAvailableCondition.signal();
}// 如下接口可以读取采集到的 buffer
status_t AudioSource::read(MediaBufferBase **out, const ReadOptions * /* options */) {...MediaBuffer *buffer *mBuffersReceived.begin();mBuffersReceived.erase(mBuffersReceived.begin());buffer-setObserver(this);...*out buffer;
}音频编码
编码器创建如下
spMediaCodecSource StagefrightRecorder::createAudioSource() {spMediaCodecSource audioEncoder MediaCodecSource::Create(mLooper, format, audioSource);
}
// MediaCodecSource 构造如下
MediaCodecSource::MediaCodecSource(const spALooper looper,const spAMessage outputFormat,const spMediaSource source,const spPersistentSurface persistentSurface,uint32_t flags){if (!(mFlags FLAG_USE_SURFACE_INPUT)) {// 将 AudioSource 放入 Puller 中mPuller new Puller(source);}
}MediaCodecSource::start 发送 kWhatStart 消息
status_t MediaCodecSource::start(MetaData* params) {spAMessage msg new AMessage(kWhatStart, mReflector);msg-setObject(meta, params);// 发消息 kWhatStart 到 MediaCodecSource::onMessageReceived // 进而传递到 MediaCodecSource::onStart return postSynchronouslyAndReturnError(msg);
}
void MediaCodecSource::onMessageReceived(const spAMessage msg) {switch (msg-what()) {case kWhatStart: {spAMessage response new AMessage;// 调用 MediaCodecSource::onStart response-setInt32(err, onStart(params));response-postReply(replyID);}}
}
status_t MediaCodecSource::onStart(MetaData *params) {...// 创建 kWhatPullerNotify 消息,传入 MediaCodecSource::Puller::start spAMessage notify new AMessage(kWhatPullerNotify, mReflector);err mPuller-start(meta.get(), notify);
}MediaCodecSource::Puller::start 流程如下
status_t MediaCodecSource::Puller::start(const spMetaData meta, const spAMessage notify) {mNotify notify;// 发送 kWhatStart 消息 到 MediaCodecSource::Puller::onMessageReceivedspAMessage msg new AMessage(kWhatStart, this);msg-setObject(meta, meta);return postSynchronouslyAndReturnError(msg);
}
void MediaCodecSource::Puller::onMessageReceived(const spAMessage msg) {switch (msg-what()) {case kWhatStart: {// start后就开始 pull schedulePull();}case kWhatPull:{// 通过上文的 AudioSource::read 读取采集到的数据status_t err mSource-read(mbuf);// 将读取到的 mbuf 放入队列 queue-pushBuffer(mbuf);if (mbuf ! NULL) {// 送到 MediaCodecSource::onMessageReceived 通知编码器 pull 到数据mNotify-post();// 继续 pull msg-post();} else {// 结束 EndOfStream handleEOS();}}
}MediaCodecSource::Puller 读取到数据后mNotify 发消息 kWhatPullerNotify 通知编码
void MediaCodecSource::onMessageReceived(const spAMessage msg) {switch (msg-what()) {case kWhatPullerNotify:{...// 收到 通知送去编码feedEncoderInputBuffers();}}
}
status_t MediaCodecSource::feedEncoderInputBuffers() {// 取数据编码while (!mAvailEncoderInputIndices.empty() mPuller-readBuffer(mbuf)) {...// inbuf 送到编码器status_t err mEncoder-getInputBuffer(bufferIndex, inbuf);...// 编码status_t err mEncoder-queueInputBuffer(bufferIndex, 0, size, timeUs, flags);}
}音频编码后数据处理
在创建编码器时把 mEncoderActivityNotify 设置到编码器的 Callback编码器的消息会通过 kWhatEncoderActivity 发送出来
status_t MediaCodecSource::initEncoder() {...mEncoderActivityNotify new AMessage(kWhatEncoderActivity, mReflector);mEncoder-setCallback(mEncoderActivityNotify);...
}当编码完成、状态变化会收到 kWhatEncoderActivity 消息通知
void MediaCodecSource::onMessageReceived(const spAMessage msg) {switch (msg-what()) {case kWhatEncoderActivity:{if (cbID MediaCodec::CB_INPUT_AVAILABLE) {// 输入不可用继续给编码器送输入} else if (cbID MediaCodec::CB_OUTPUT_FORMAT_CHANGED) {// 输出格式变化} else if (cbID MediaCodec::CB_OUTPUT_AVAILABLE) {// 正常的输出数据// 获取编码器额输出status_t err mEncoder-getOutputBuffer(index, outbuf);// 将输出 buf 转 MediaBufferMediaBuffer *mbuf new MediaBuffer(outbuf-size());// 提取 MetaDataspMetaData meta new MetaData(mbuf-meta_data());...// 将 编码数据 outbuf 填充到 mbufmemcpy(mbuf-data(), outbuf-data(), outbuf-size());// 将编码后的数据添加到队列output-mBufferQueue.push_back(mbuf);} else if (cbID MediaCodec::CB_ERROR) {// ERROR 异常退出signalEOS(err);}}}
}当需要数据时,从输出队列取数据即可
status_t MediaCodecSource::read(MediaBufferBase** buffer, const ReadOptions* /* options */) {MutexedOutput::Locked output(mOutput);*buffer NULL;while (output-mBufferQueue.size() 0 !output-mEncoderReachedEOS) {output.waitForCondition(output-mCond);}if (!output-mEncoderReachedEOS) {*buffer *output-mBufferQueue.begin();output-mBufferQueue.erase(output-mBufferQueue.begin());return OK;}return output-mErrorCode;
}MPEG4Writer写入音频编码后数据到文件
通过如下源码我们知道了 MPEG4Writer 创建和写入线程启动
status_t StagefrightRecorder::setupMPEG4orWEBMRecording() {...writer mp4writer new MPEG4Writer(mOutputFd);
}
status_t StagefrightRecorder::start() {...status mWriter-start(meta.get());
}
status_t MPEG4Writer::start(MetaData *param) {...err startWriterThread();...// 这个 startTracks 主要为 MPEG4Writer::Track 做准备 err startTracks(param);
}
status_t MPEG4Writer::startWriterThread() {mDone false;mIsFirstChunk true;mDriftTimeUs 0;// 将 音、视频 Track 添加到 mChunkInfosfor (ListTrack *::iterator it mTracks.begin();it ! mTracks.end(); it) {ChunkInfo info;info.mTrack *it;info.mPrevChunkTimestampUs 0;info.mMaxInterChunkDurUs 0;mChunkInfos.push_back(info);}...// 启动线程执行 ThreadWrapper pthread_attr_t attr;pthread_attr_init(attr);pthread_attr_setdetachstate(attr, PTHREAD_CREATE_JOINABLE);pthread_create(mThread, attr, ThreadWrapper, this);pthread_attr_destroy(attr);return OK;
}
void *MPEG4Writer::ThreadWrapper(void *me) {MPEG4Writer *writer static_castMPEG4Writer *(me);// 最终执行的是 threadFunc()writer-threadFunc();return NULL;
}写入线程开启后一直循环无数据时等待
void MPEG4Writer::threadFunc() {Mutex::Autolock autoLock(mLock);while (!mDone) {Chunk chunk;bool chunkFound false;// findChunkToWrite 从 mChunkInfos 找到需要写入的 Chunkwhile (!mDone !(chunkFound findChunkToWrite(chunk))) {mChunkReadyCondition.wait(mLock);}// 在实时记录模式下写时不按顺序持有锁, 减少媒体跟踪线程的阻塞时间。// 否则保持锁直到现有的块被写入文件。if (chunkFound) {if (mIsRealTimeRecording) {mLock.unlock();}// 写入 Chunk writeChunkToFile(chunk);if (mIsRealTimeRecording) {mLock.lock();}}}// 写入所有内存writeAllChunks();
}写入到文件是在 writeChunkToFile 中完成
void MPEG4Writer::writeChunkToFile(Chunk* chunk) {while (!chunk-mSamples.empty()) {// 取一个 MediaBuffer ListMediaBuffer *::iterator it chunk-mSamples.begin();...// 写入 MediaBuffer off64_t offset addSample_l(*it, usePrefix, tiffHdrOffset, bytesWritten);...}// 写入后清空chunk-mSamples.clear();
}
off64_t MPEG4Writer::addSample_l(MediaBuffer *buffer, bool usePrefix,uint32_t tiffHdrOffset, size_t *bytesWritten) {...writeOrPostError(mFd, (const uint8_t*)buffer-data() buffer-range_offset(),buffer-range_length());
}
void MPEG4Writer::writeOrPostError(int fd, const void* buf, size_t count) {...// 真正的写入 buf ssize_t bytesWritten ::write(fd, buf, count);...// IO 异常时 抛出 通过消息传递到上层 spAMessage msg new AMessage(kWhatIOError, mReflector);msg-setInt32(err, ERROR_IO);
}MPEG4Writer::Track 取编码后的音频编数据
MPEG4Writer::Track 启动源码如下
status_t MPEG4Writer::startTracks(MetaData *params) {...for (ListTrack *::iterator it mTracks.begin();it ! mTracks.end(); it) {// MPEG4Writer::Track start status_t err (*it)-start(params);...}return OK;
}
status_t MPEG4Writer::Track::start(MetaData *params) {...// 启动线程执行 ThreadWrapper pthread_create(mThread, attr, ThreadWrapper, this);
}
void *MPEG4Writer::Track::ThreadWrapper(void *me) {Track *track static_castTrack *(me);status_t err track-threadEntry();return (void *)(uintptr_t)err;
}MPEG4Writer::Track::threadEntry 读取编码后的数据
status_t MPEG4Writer::Track::threadEntry() {// mSource-read 也就是 上文 MediaCodecSource::read 一直不停的读取数据到 buffer MediaBufferBase *buffer;while (!mDone (err mSource-read(buffer)) OK buffer ! NULL) {...// 将 buffer 转为 MediaBuffer MediaBuffer *copy new MediaBuffer(buffer-range_length());if (sampleFileOffset ! -1) {copy-meta_data().setInt64(kKeySampleFileOffset, sampleFileOffset);} else {memcpy(copy-data(), (uint8_t*)buffer-data() buffer-range_offset(),buffer-range_length());}...// 将 copy 放入队列 mChunkSamplesmChunkSamples.push_back(copy);...// 将 mChunkSamples 转 为 ChunkbufferChunk(timestampUs);}
}
void MPEG4Writer::Track::bufferChunk(int64_t timestampUs) {Chunk chunk(this, timestampUs, mChunkSamples);// 也就是 MPEG4Writer::bufferChunk mOwner-bufferChunk(chunk);mChunkSamples.clear();
}
void MPEG4Writer::bufferChunk(const Chunk chunk) {Mutex::Autolock autolock(mLock);for (ListChunkInfo::iterator it mChunkInfos.begin();it ! mChunkInfos.end(); it) {if (chunk.mTrack it-mTrack) {// 将 Chunk 放入 ChunkInfo.mChunks 中it-mChunks.push_back(chunk);// 数据准备好了通知 mChunkReadyCondition.wait 继续执行// 进而 由 findChunkToWrite 读取写入文件 mChunkReadyCondition.signal();return;}}
}结语
到这里已经完成了 MediaRecorder 音频采集、编码、写入文件详细源码分析。 用一幅图概括如下 #mermaid-svg-3ij6OnkF94m4gjTW {font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}#mermaid-svg-3ij6OnkF94m4gjTW .error-icon{fill:#552222;}#mermaid-svg-3ij6OnkF94m4gjTW .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-3ij6OnkF94m4gjTW .edge-thickness-normal{stroke-width:2px;}#mermaid-svg-3ij6OnkF94m4gjTW .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-3ij6OnkF94m4gjTW .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-3ij6OnkF94m4gjTW .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-3ij6OnkF94m4gjTW .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-3ij6OnkF94m4gjTW .marker{fill:#333333;stroke:#333333;}#mermaid-svg-3ij6OnkF94m4gjTW .marker.cross{stroke:#333333;}#mermaid-svg-3ij6OnkF94m4gjTW svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-3ij6OnkF94m4gjTW g.classGroup text{fill:#9370DB;fill:#131300;stroke:none;font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:10px;}#mermaid-svg-3ij6OnkF94m4gjTW g.classGroup text .title{font-weight:bolder;}#mermaid-svg-3ij6OnkF94m4gjTW .nodeLabel,#mermaid-svg-3ij6OnkF94m4gjTW .edgeLabel{color:#131300;}#mermaid-svg-3ij6OnkF94m4gjTW .edgeLabel .label rect{fill:#ECECFF;}#mermaid-svg-3ij6OnkF94m4gjTW .label text{fill:#131300;}#mermaid-svg-3ij6OnkF94m4gjTW .edgeLabel .label span{background:#ECECFF;}#mermaid-svg-3ij6OnkF94m4gjTW .classTitle{font-weight:bolder;}#mermaid-svg-3ij6OnkF94m4gjTW .node rect,#mermaid-svg-3ij6OnkF94m4gjTW .node circle,#mermaid-svg-3ij6OnkF94m4gjTW .node ellipse,#mermaid-svg-3ij6OnkF94m4gjTW .node polygon,#mermaid-svg-3ij6OnkF94m4gjTW .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-3ij6OnkF94m4gjTW .divider{stroke:#9370DB;stroke:1;}#mermaid-svg-3ij6OnkF94m4gjTW g.clickable{cursor:pointer;}#mermaid-svg-3ij6OnkF94m4gjTW g.classGroup rect{fill:#ECECFF;stroke:#9370DB;}#mermaid-svg-3ij6OnkF94m4gjTW g.classGroup line{stroke:#9370DB;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW .classLabel .box{stroke:none;stroke-width:0;fill:#ECECFF;opacity:0.5;}#mermaid-svg-3ij6OnkF94m4gjTW .classLabel .label{fill:#9370DB;font-size:10px;}#mermaid-svg-3ij6OnkF94m4gjTW .relation{stroke:#333333;stroke-width:1;fill:none;}#mermaid-svg-3ij6OnkF94m4gjTW .dashed-line{stroke-dasharray:3;}#mermaid-svg-3ij6OnkF94m4gjTW #compositionStart,#mermaid-svg-3ij6OnkF94m4gjTW .composition{fill:#333333!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW #compositionEnd,#mermaid-svg-3ij6OnkF94m4gjTW .composition{fill:#333333!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW #dependencyStart,#mermaid-svg-3ij6OnkF94m4gjTW .dependency{fill:#333333!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW #dependencyStart,#mermaid-svg-3ij6OnkF94m4gjTW .dependency{fill:#333333!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW #extensionStart,#mermaid-svg-3ij6OnkF94m4gjTW .extension{fill:#333333!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW #extensionEnd,#mermaid-svg-3ij6OnkF94m4gjTW .extension{fill:#333333!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW #aggregationStart,#mermaid-svg-3ij6OnkF94m4gjTW .aggregation{fill:#ECECFF!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW #aggregationEnd,#mermaid-svg-3ij6OnkF94m4gjTW .aggregation{fill:#ECECFF!important;stroke:#333333!important;stroke-width:1;}#mermaid-svg-3ij6OnkF94m4gjTW .edgeTerminals{font-size:11px;}#mermaid-svg-3ij6OnkF94m4gjTW :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;} MPEG4Writer::Track 读取编码后内容() AudioSource 采集音频() MediaCodecSource 编码() MPEG4Writer 写入编码后内容() 希望对你有所帮助。如果你在使用MediaRecorder的过程中遇到了其他问题欢迎留言讨论。 如果你觉得本文还不错可以点赞收藏。 相关文章 安卓MediaRecorder(1)录制音频的详细使用 安卓MediaRecorder(2)录制源码分析 安卓MediaRecorder(3)音频采集编码写入详细源码分析 安卓MediaRecorder(4)视频采集编码写入详细源码分析
