Android的Audio子系统
2019-07-13 17:56发布
生成海报
原址
Android边录边播应用
AP（Application Processor主处理器）<——>DSP（Codec）<——>BP（Baseband Processor基带处理器，猫）
一、AudioTrack播放基本流程
1.初始化new AudioTrack完成通路创建，也在MixerThread线程中创建Track。getOutput（以及openOutput）
frameworks/av/media/libmedia/AudioTrack.cpp
AudioTrack::AudioTrack(){
mStatus = set();
}
status_t AudioTrack::set(){
audio_io_handle_t output = AudioSystem::getOutput(); //重要！！！！！后边AudioPolicyService部分展开；获取工作线程
mAudioTrackThread = new AudioTrackThread();
mAudioTrackThread->run();
status_t status = createTrack_l(streamType,sampleRate,format,frameCount,sharedBuffer,output,0);//在output对应工作线程中创建Track
}
status_t AudioTrack::createTrack_l(){
const sp& audioFlinger = AudioSystem::get_audio_flinger();
sp track = audioFlinger->createTrack();
sp cblk = track->getCblk();
mAudioTrack = track; //AudioFlinger中的Track
mCblkMemory = iMem;
audio_track_cblk_t* cblk = static_cast(iMem->pointer());//共享内存头部
mCblk = cbkl;
mCblk->buffers = (char*)mCblk + sizeof(audio_track_cblk_t); //共享内存实际数据
}
先看getOutput
frameworks/av/media/libmedia/AudioSystem.cpp
audio_io_handle_t AudioSystem::getOutput(){
return aps->getOutput();
}
frameworks/av/services/audio/audioflinger/AudioPolicyService.cpp
audio_io_handle_t AudioPolicyService::getOutput(){
return mpAudioPolicy->get_output();
}
hardware/libhardware_legacy/audio/audio_policy_hal.cpp
static audio_io_handle_t ap_get_output(){
return lap->apm->getOutput();
}
hardware/libhardware_legacy/audio/AudioPolicyManagerBase.cpp
audio_io_handle_t AudioPolicyManagerBase::getOutput(){
routing_strategy strategy = getStrategy();//根据streamtype获取路由策略
audio_device_t device = getDeviceForStrategy();//根据路由策略选择设备
output = mpClientInterface->openOutput();//返回该设备的audio_io_handle_t
}
hardware/libhardware_legacy/audio/AudioPolicyCompatClient::openOutput(){
return mServiceOps->open_output_on_module();
}
frameworks/av/services/audio/audioflinger/AudioPolicyService.cpp
static audio_io_handle_t aps_open_output_on_module(){
return af->openOutput();
}
frameworks/av/services/audio/audioflinger/AudioFlinger.cpp
audio_io_handle_t AudioFlinger::openOutput(){
audio_hw_device_t *hwDevHal = outHwDev->hwDevice();
status_t status = hwDevHal->open_output_stream();
AudioStreamOut *output = new AudioStreamOut();
thread = new MixerThread(this, output, id, *pDevices);
mPlaybackThreads.add(id, thread);
hwDevHal->set_mode();
}
在看createTrack
frameworks/av/services/audio/audioflinger/AudioFlinger.cpp
sp AudioFlinger::createTrack() {
track = thread->createTrack_l();
}
frameworks/av/services/audio/audioflinger/Threads.cpp
sp AudioFlinger::PlaybackThread::createTrack_l() {
track = new Track();
mTracks.add(track);
}
frameworks/av/services/audio/audioflinger/Tracks.cpp
AudioFlinger::PlaybackThread::Track::Track() {
/*
AudioFlinger::ThreadBase::TrackBase::TrackBase() {
mCblkMemory = client->heap()->allocate(size);
mCblk = static_cast (mCblkMemory->pointer());
}
*/
}
2.开始播放AudioTrack.play()完成通路切换；也就是完成实际硬件设备的切换startOutput
frameworks/av/media/libmedia/AudioTrack.cpp
status_t AudioTrack::start(){
status = mAudioTrack->start();
}
frameworks/av/services/audio/audioflinger/Tracks.cpp
AudioFlinger::PlaybackThread::Track::start() {
PlaybackThread *playbackThread = (PlaybackThread *)thread.get();
status = playbackThread->addTrack_l(this);
}
frameworks/av/services/audio/audioflinger/Threads.cpp
status_t AudioFlinger::PlaybackThread::addTrack_l() {
status = AudioSystem::startOutput(mId, track->streamType(), track->sessionId());
mActiveTracks.add(track);
boradcast_l();//通知PlaybackThread线程
}
bool AudioFlinger::PlaybackThread::threadLoop(){
mWaitWorkCV.wait(mLock);
mMixerStatus = prepareTracks_l(&tracksToRemove);//设置混音参数，删除tracksToRemove中的track
threadLoop_mix(); //混音
ssize_t ret = threadLoop_write();//输出
}
frameworks/av/services/audio/audioflinger/AudioPolicyService.cpp
status_t AudioPolicyService::startOutput(audio_io_handle_t output, audio_stream_type_t stream, int session){
return mpAudioPolicy->start_output(mpAudioPolicy, output, stream, session);
}
hardware/libhardware_legacy/audio/AudioPolicyManagerBase.cpp
status_t AudioPolicyManagerBase::startOutput(audio_io_handle_t output, AudioSystem::stream_type stream, int session){
audio_device_t newDevice = getNewDevice(output, false);
setOutputDevice(output, newDevice, force);
}
uint32_t AudioPolicyManagerBase::setOutputDevice(audio_io_handle_t output, audio_device_t device, bool force, int delayMs){
AudioOutputDescriptor *outputDesc = mOutputs.valueFor(output);
outputDesc->mDevice = device;
param.addInt(String8(AudioParameter::keyRouting), (int)device);
mpClientInterface->setParameters(output, param.toString(), delayMs);
}
hardware/libhardware_legacy/audio/AudioPolicyCompatClient.cpp
void AudioPolicyCompatClient::setParameters(){
mServiceOps->set_parameters();
}
frameworks/av/services/audio/audioflinger/AudioPolicyService.cpp
void AudioPolicyService::setParameters(){
mAudioCommandThread->parametersCommand();
}
status_t AudioPolicyService::AudioCommandThread::parametersCommand(){
}
bool AudioPolicyService::AudioCommandThread::threadLoop(){
command->mStatus = AudioSystem::setParameters();
}
frameworks/av/media/libmedia/AudioSystem.cpp
status_t AudioSystem::setParameters(){
return af->setParameters();
}
frameworks/av/services/audio/audioflinger/AudioFlinger.cpp
status_t AudioFlinger::setParameters(){
audio_hw_device_t *dev = mPrimaryHardwareDev->hwDevice();
final_result = dev->set_parameters(dev, keyValuePairs.string());
}
3.开始写入write；向该设备写入数据
frameworks/av/media/libmedia/AudioTrack.cpp
ssize_t AudioTrack::write(){
while (userSize >= mFrameSize){
status_t err = obtainBuffer(&audioBuffer, &ClientProxy::kForever);
memcpy(audioBuffer.i8, buffer, toWrite);
releaseBuffer(&audioBuffer);
}
}
status_t AudioTrack::obtainBuffer() {
status = proxy->obtainBuffer(0;
}
frameworks/av/media/libmedia/AudioTrackShared.cpp
status_t ClientProxy::obtainBuffer() {
buffer->mRaw = part1 >0 ?
}
服务端
frameworks/av/services/audio/audioflinger/Threads.cpp
ssize_t AudioFlinger::PlaybackThread::threadLoop_write() {
}
二、耳机热插拔
1.
frameworks/base/services/java/com/android/server/WiredAccessoryManager.java
mAudioManager.setWiredDeviceConnectionState(device, state, headsetName);
2.
frameworks/base/media/java/android/media/AudioManager.java
frameworks/base/media/java/android/media/AudioService.java
handleDeviceConnection
AudioSystem.setDeviceConnectionState
3.
hardware/libhardware_legacy/audio/AudioPolicyManagerBase.cpp
setDeviceConnectionState
checkOutputsForDevice
三、AudioPolicy专项
frameworks/av/media/libmedia/AudioSystem.cpp
audio_io_handle_t AudioSystem::getOutput(){
return aps->getOutput();
}
frameworks/av/services/audio/audioflinger/AudioPolicyService.cpp
audio_io_handle_t AudioPolicyService::getOutput(){
return mpAudioPolicy->get_output();
}
AudioPolicyService::AudioPolicyService(){
mTonePlaybackThread = new AudioCommandThread(String8("ApmTone"),this);
mAudioCommandThread = new AudioCommandThread(String8("ApmAudio"),this);
mOutputCommandThread = new AudioCommandThread(String8("ApmOutput"),this);
rc = hw_get_module(AUDIO_POLICY_HARDWARE_MODULE_ID, &module);
rc = audio_policy_dev_open(module, &mpAudioPolicyDev);
rc = mpAudioPolicyDev->create_audio_policy(mpAudioPolicyDev, &aps_ops, this, &mpAudioPolicy);
rc = mpAudioPolicy->init_check(mpAudioPolicy); //audio_policy的HAL
}
hardware/libhardware_legacy/audio/AudioPolicyManagerBase.cpp
audio_io_handle_t AudioPolicyManagerBase::getOutput(){
routing_strategy strategy = getStrategy();//根据streamtype获取路由策略
audio_device_t device = getDeviceForStrategy();//根据路由策略选择设备
output = mpClientInterface->openOutput();//返回该设备的audio_io_handle_t
}
void AudioPolicyManagerBase::addOutput(audio_io_handle_t id, AudioOutputDescriptor *outputDesc){
outputDesc->mId = id;
mOutputs.add(id, outputDesc);
}
audio_io_handle_t AudioPolicyManagerBase::selectOutput() {
}
uint32_t AudioPolicyManagerBase::setOutputDevice(audio_io_handle_t output, audio_device_t device, bool force, int delayMs) {
}
路由策略
AudioPolicyManagerBase::routing_strategy AudioPolicyMannagerBase::getStrategy(AudioSystem::stream_type stream){
//根据streamtype选择路由策略
}
audio_devices_t AudioPolicyManagerBase::getDeviceForStrategy(routing_strategy strategy, bool fromCache) {
//根据路由策略获得设备
}
audio_device_t AudioPolicyManagerBase::getDevicesForStream(){
//根据streamtype获得设备
getStrategy();
getDeviceForStrategy();
}
打开微信“扫一扫”，打开网页后点击屏幕右上角分享按钮
{var%20f='http://v.t.sina.com.cn/share/share.php?appkey=1515056452',u=z||d.location,p=['&url=',e(u),'&title=',e(t||d.title),'&source=',e(r),'&sourceUrl=',e(l),'&content=',c||'gb2312','&pic=',e(p||'')].join('');function%20a(){if(!window.open([f,p].join(''),'mb',['toolbar=0,status=0,resizable=1,width=440,height=430,left=',(s.width-440)/2,',top=',(s.height-430)/2].join('')))u.href=[f,p].join('');};if(/Firefox/.test(navigator.userAgent))setTimeout(a,0);else%20a();})(screen,document,encodeURIComponent,'','','https://www.xiaopingtou.cn//data/attach/topic/topicKPo7gB.jpg', '推荐 huyu0427 的文章《Android的Audio子系统》','https://www.xiaopingtou.net/article-82119.html','页面编码gb2312|utf-8默认gb2312'));){kind=link}