AudioPolicyService负责音频策略处理,包括根据手机的各种状态和器件的存在、插拔状态、用户使能状态,给不同的audio stream选择不同的输入输出设备,控制不同设备的增益等。
代码层面,该类则主要是维护3个线程looper,通过不同的辅助类,向client提供服务。
AudioPolicyService的相关类关系如下,
同AudioFlinger,APS在audioServer里启动。AudioPolicyService有两种实现方案,由USE_LEGACY_AUDIO_POLICY控制,
如果是LEGACY方法,使用一个ops函数集操作接口,类似驱动模块的写法,在AudioPolicyClientImplLegacy.cpp实现所有函数功能,这些函数实际上就是对AF的功能封装,在其构造函数中初始,这种方法以及废弃,我们就不具体分析。
另外一种方法,在AudioPolicyService的onFirstRef中,创建了如下几个重要的线程和实例。
void AudioPolicyService::onFirstRef() {
// start tone playback thread mTonePlaybackThread = new AudioCommandThread(String8("ApmTone"), this); // start audio commands thread mAudioCommandThread = new AudioCommandThread(String8("ApmAudio"), this); // start output activity command thread mOutputCommandThread = new AudioCommandThread(String8("ApmOutput"), this);
mAudioPolicyClient = new AudioPolicyClient(this); mAudioPolicyManager = createAudioPolicyManager(mAudioPolicyClient);
sp } |
AudioCommandThread是AudioPolicyService的内部类,继承自Thread,在其onFirstRef启动线程,
void AudioPolicyService::AudioCommandThread::onFirstRef() { run(mName.string(), ANDROID_PRIORITY_AUDIO); } |
它对外提供各种接口,如startOutputCommand,向其队列发消息,如START_OUTPUT,然后由其threadLoop处理这些消息,这样的好处是避免消息拥塞,避免调用栈过长,阻塞系统等,代码结构清晰,系统耦合性也低。
bool AudioPolicyService::AudioCommandThread::threadLoop() { nsecs_t waitTime = -1;
mLock.lock(); while (!exitPending()) { sp while (!mAudioCommands.isEmpty() && !exitPending()) { nsecs_t curTime = systemTime(); // commands are sorted by increasing time stamp: execute them from index 0 and up if (mAudioCommands[0]->mTime <= curTime) { sp mAudioCommands.removeAt(0); mLastCommand = command;
switch (command->mCommand) { … case START_OUTPUT: { StartOutputData *data = (StartOutputData *)command->mParam.get(); ALOGV("AudioCommandThread() processing start output %d", data->mIO); svc = mService.promote(); if (svc == 0) { command->mStatus = UNKNOWN_ERROR; break; } mLock.unlock(); command->mStatus = svc->doStartOutput(data->mIO, data->mStream, data->mSession); mLock.lock(); …
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threadLoop主要调用ToneGenerator,AudioSystem,AF,还有自身的功能实现函数AudioPolicyIntefaceImpl来完成相应的消息处理。实际上,APII也只是封装了对APM(AudioPolicyManager)的调用而已。
AudioPolicyService还有一个NotificationClient子类,提供接口registerClient让客户端注册,貌似只有AS一个客户,和AF类似。
AudioSystem.cpp(frameworks\av\media\libmedia): af->registerClient(afc);
AudioSystem.cpp(frameworks\av\media\libmedia): ap->registerClient(apc);
AudioSystem.cpp(frameworks\av\media\libmedia): af->registerClient(afc);
I
void AudioPolicyService::registerClient(const sp {
sp client, uid); ALOGV("registerClient() client %p, uid %d", client.get(), uid);
mNotificationClients.add(uid, notificationClient);
} |
AudioPolicyClient : publicAudioPolicyClientInterface,代码实现在AudioPolicyClientImpl.cpp,这个类也只是一个功能封装类,调用了AF,AudioSystem,APS的接口。在APS的构造函数中作为APM的构造参数传入,所以它是APM调用AF,AudioSystem,APS的桥梁。
mAudioPolicyClient = new AudioPolicyClient(this); mAudioPolicyManager = createAudioPolicyManager(mAudioPolicyClient); |
对于APM类,
APS创建了它的实例,自己的文件不怎么使用它,但通过looper,使用APII来调用APM的功能。我们先分析这些表面的调用关系,之后要思考其背后的设计意图。
通过后面分析APM,会发现前面围绕APS讲了一堆的策略、架构、汇报关系的东西,其实真正干活的只有APM,它就是APS架构里面的码农,干了个体力活还不显眼,毕竟大家喜欢看架构和策略方面的东西。
APM还是有些技能的,首先他有几个工具,他把他们交给AudioPolicyConfig去管理(在AudioPolicyConfig.h中),
HwModuleCollection &mHwModules; DeviceVector &mAvailableOutputDevices; DeviceVector &mAvailableInputDevices; sp VolumeCurvesCollection *mVolumeCurves; |
在APM的构造函数里,
首先从/system/etc/audio_policy_configuration.xml加载相关配置信息,并序列化、以及初始,不再使用/system/etc/audio_policy.conf文件,这里会用到PolicySerializer和EngineInstance。
后面就是围绕AudioPolicyConfig管理的几个类,根据配置文件进行初始化,如,代码太多,不一一细化。
AudioPolicyManager::AudioPolicyManager(AudioPolicyClientInterface *clientInterface) {
1.加载配置信息 #ifdef USE_XML_AUDIO_POLICY_CONF mVolumeCurves = new VolumeCurvesCollection(); AudioPolicyConfig config(mHwModules, mAvailableOutputDevices, mAvailableInputDevices, mDefaultOutputDevice, speakerDrcEnabled, static_cast PolicySerializer serializer; if (serializer.deserialize(AUDIO_POLICY_XML_CONFIG_FILE, config) != NO_ERROR) { config.setDefault(); } #endif
audio_policy::EngineInstance *engineInstance = audio_policy::EngineInstance::getInstance(); mEngine = engineInstance->queryInterface mEngine->setObserver(this); status_t status = mEngine->initCheck(); … 2. 加载配置文件里的模块,并一一初始化 for (size_t i = 0; i < mHwModules.size(); i++) { mHwModules[i]->mHandle = mpClientInterface->loadHwModule(mHwModules[i]->getName());
2.1 打开输出流设备 for (size_t j = 0; j < mHwModules[i]->mOutputProfiles.size(); j++) { const sp sp mpClientInterface); audio_io_handle_t output = AUDIO_IO_HANDLE_NONE; status_t status = mpClientInterface->openOutput(outProfile->getModuleHandle(), &output, &config, &outputDesc->mDevice, address, &outputDesc->mLatency, outputDesc->mFlags); addOutput(output, outputDesc); setOutputDevice(outputDesc, outputDesc->mDevice, true, 0, NULL, address.string()); } 2.2 打开输入流设备 for (size_t j = 0; j < mHwModules[i]->mInputProfiles.size(); j++) { const sp sp new AudioInputDescriptor(inProfile); audio_io_handle_t input = AUDIO_IO_HANDLE_NONE; status_t status = mpClientInterface->openInput(inProfile->getModuleHandle(), &input, &config, &inputDesc->mDevice, address, AUDIO_SOURCE_MIC, AUDIO_INPUT_FLAG_NONE); }
3.设置输入输出状态和设备使能专题 // make sure all attached devices have been allocated a unique ID for (size_t i = 0; i < mAvailableOutputDevices.size();) { if (!mAvailableOutputDevices[i]->isAttached()) { ALOGW("Output device %08x unreachable", mAvailableOutputDevices[i]->type()); mAvailableOutputDevices.remove(mAvailableOutputDevices[i]); continue; } // The device is now validated and can be appended to the available devices of the engine mEngine->setDeviceConnectionState(mAvailableOutputDevices[i], AUDIO_POLICY_DEVICE_STATE_AVAILABLE); i++; } for (size_t i = 0; i < mAvailableInputDevices.size();) { if (!mAvailableInputDevices[i]->isAttached()) { ALOGW("Input device %08x unreachable", mAvailableInputDevices[i]->type()); mAvailableInputDevices.remove(mAvailableInputDevices[i]); continue; } // The device is now validated and can be appended to the available devices of the engine mEngine->setDeviceConnectionState(mAvailableInputDevices[i], AUDIO_POLICY_DEVICE_STATE_AVAILABLE); i++; }
updateDevicesAndOutputs(); } |
一份完整的audio_policy_configuration.xml如下,可对照这个配置分解来分析APM的构造过程,
samplingRates="48000" channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
flags="AUDIO_OUTPUT_FLAG_FAST|AUDIO_OUTPUT_FLAG_RAW"> samplingRates="48000" channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
flags="AUDIO_OUTPUT_FLAG_DEEP_BUFFER"> samplingRates="48000" channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
flags="AUDIO_OUTPUT_FLAG_DIRECT"> samplingRates="8000,11025,16000,22050,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="dynamic"/>
flags="AUDIO_OUTPUT_FLAG_DIRECT|AUDIO_OUTPUT_FLAG_DIRECT_PCM"> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_2POINT1,AUDIO_CHANNEL_OUT_QUAD,AUDIO_CHANNEL_OUT_PENTA,AUDIO_CHANNEL_OUT_5POINT1,AUDIO_CHANNEL_OUT_6POINT1,AUDIO_CHANNEL_OUT_7POINT1"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_2POINT1,AUDIO_CHANNEL_OUT_QUAD,AUDIO_CHANNEL_OUT_PENTA,AUDIO_CHANNEL_OUT_5POINT1,AUDIO_CHANNEL_OUT_6POINT1,AUDIO_CHANNEL_OUT_7POINT1"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_2POINT1,AUDIO_CHANNEL_OUT_QUAD,AUDIO_CHANNEL_OUT_PENTA,AUDIO_CHANNEL_OUT_5POINT1,AUDIO_CHANNEL_OUT_6POINT1,AUDIO_CHANNEL_OUT_7POINT1"/>
flags="AUDIO_OUTPUT_FLAG_DIRECT|AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD|AUDIO_OUTPUT_FLAG_NON_BLOCKING"> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_2POINT1,AUDIO_CHANNEL_OUT_QUAD,AUDIO_CHANNEL_OUT_PENTA,AUDIO_CHANNEL_OUT_5POINT1,AUDIO_CHANNEL_OUT_6POINT1,AUDIO_CHANNEL_OUT_7POINT1"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_2POINT1,AUDIO_CHANNEL_OUT_QUAD,AUDIO_CHANNEL_OUT_PENTA,AUDIO_CHANNEL_OUT_5POINT1,AUDIO_CHANNEL_OUT_6POINT1,AUDIO_CHANNEL_OUT_7POINT1"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_2POINT1,AUDIO_CHANNEL_OUT_QUAD,AUDIO_CHANNEL_OUT_PENTA,AUDIO_CHANNEL_OUT_5POINT1,AUDIO_CHANNEL_OUT_6POINT1,AUDIO_CHANNEL_OUT_7POINT1"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/> samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000,64000,88200,96000" channelMasks="AUDIO_CHANNEL_OUT_STEREO,AUDIO_CHANNEL_OUT_MONO"/>
samplingRates="8000,16000,48000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO"/>
flags="AUDIO_OUTPUT_FLAG_DIRECT|AUDIO_OUTPUT_FLAG_VOIP_RX"> samplingRates="8000,16000" channelMasks="AUDIO_CHANNEL_OUT_MONO"/>
samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000" channelMasks="AUDIO_CHANNEL_IN_MONO,AUDIO_CHANNEL_IN_STEREO,AUDIO_CHANNEL_IN_FRONT_BACK"/>
samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000" channelMasks="AUDIO_CHANNEL_IN_MONO,AUDIO_CHANNEL_IN_STEREO,AUDIO_CHANNEL_IN_FRONT_BACK,AUDIO_CHANNEL_INDEX_MASK_3,AUDIO_CHANNEL_INDEX_MASK_4,AUDIO_CHANNEL_IN_5POINT1"/>
samplingRates="8000,16000,48000" channelMasks="AUDIO_CHANNEL_IN_MONO,AUDIO_CHANNEL_IN_STEREO"/>
samplingRates="48000" channelMasks="AUDIO_CHANNEL_IN_MONO"/>
samplingRates="48000" channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
samplingRates="48000" channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
samplingRates="48000" channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
samplingRates="48000" channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
samplingRates="8000,16000" channelMasks="AUDIO_CHANNEL_OUT_MONO"/>
samplingRates="8000,16000" channelMasks="AUDIO_CHANNEL_OUT_MONO"/>
samplingRates="8000,16000" channelMasks="AUDIO_CHANNEL_OUT_MONO"/>
samplingRates="8000,16000" channelMasks="AUDIO_CHANNEL_OUT_MONO"/>
samplingRates="8000,16000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO"/>
samplingRates="8000,11025,16000,22050,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="dynamic"/>
samplingRates="8000,11025,16000,22050,32000,44100,48000,64000,88200,96000,128000,176400,192000" channelMasks="dynamic"/>
samplingRates="48000" channelMasks="AUDIO_CHANNEL_OUT_MONO,AUDIO_CHANNEL_OUT_STEREO"/>
samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000" channelMasks="AUDIO_CHANNEL_IN_MONO,AUDIO_CHANNEL_IN_STEREO,AUDIO_CHANNEL_IN_FRONT_BACK"/>
samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000" channelMasks="AUDIO_CHANNEL_IN_MONO,AUDIO_CHANNEL_IN_STEREO,AUDIO_CHANNEL_IN_FRONT_BACK"/>
samplingRates="48000" channelMasks="AUDIO_CHANNEL_IN_MONO,AUDIO_CHANNEL_IN_STEREO"/>
samplingRates="8000,11025,12000,16000,22050,24000,32000,44100,48000" channelMasks="AUDIO_CHANNEL_IN_MONO,AUDIO_CHANNEL_IN_STEREO,AUDIO_CHANNEL_IN_FRONT_BACK"/>
samplingRates="8000,16000" channelMasks="AUDIO_CHANNEL_IN_MONO"/>
samplingRates="8000,16000,48000" channelMasks="AUDIO_CHANNEL_IN_MONO"/>
sources="primary output,raw,deep_buffer,direct_pcm,compressed_offload,voip_rx"/> sources="primary output,raw,deep_buffer,direct_pcm,compressed_offload,voip_rx"/> sources="primary output,raw,deep_buffer,direct_pcm,compressed_offload,voip_rx"/> sources="primary output,raw,deep_buffer,direct_pcm,compressed_offload,voip_rx"/> sources="primary output,raw,deep_buffer,direct_pcm,compressed_offload,voip_rx"/> sources="primary output,raw,deep_buffer,multichannel,direct_pcm,compressed_offload"/> sources="primary output,raw,deep_buffer,multichannel,direct_pcm,compressed_offload"/> sources="primary output"/> sources="primary output,raw,deep_buffer,direct_pcm,compressed_offload,voip_rx"/> sources="voice_tx"/> sources="Wired Headset Mic,BT SCO Headset Mic,FM Tuner,Telephony Rx"/> sources="Built-In Mic,Built-In Back Mic"/> sources="Telephony Rx"/>
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APM类的继承关系:
AudioPolicyInterface—AudioPolicyManagerBase—AudioPolicyManagerDefault
AudioPolicyInterface—AudioPolicyManager-- AudioPolicyManagerCustom
AudioPolicyClientInterface--
AudioPolicyManagerBase
getDeviceForStrategy 根据路由策略,按一定优先顺序选取不同的设备类型,对应用来讲,不用关心手机的各种状态和器件的存在、插拔状态、用户使能状态。
mAvailableOutputDevices表明了当前device能支持哪些输出设备,在AudioPolicyManagerBase构造时初始,在setDeviceConnectionState中更新。
mAvailableInputDevices表明了当前device能支持哪些输入设备,在defaultAudioPolicyConfig时初始,在setDeviceConnectionState中更新。
代码里还有这样一套APM,应该是legacy的,被废弃了,
AudioPolicyManager.cpp(hardware\qcom\audio\policy_hal)
AudioPolicyInterface.h (hardware\libhardware_legacy\include\hardware_legacy)
Audio_policy_hal.cpp (hardware\libhardware_legacy\audio)
AudioPolicyManagerCustom
APS里各种元素的对应关系(一对一或一对多的关系):
System -- audiointerfaces
Audiointerface -- outputs
Output -- devices
Stream Type -- PlaybackThread --device
APS的概述分析就到这里,细节部分要结合具体的调用流程分析。
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