Android(安卓)Audio音量设置流程

转载自http://blog.axlecho.com/audioyin-liang-she-zhi-liu-cheng/

Audio音量调节是一级一级调节，而且分不同的流类型，如响铃，通话，多媒体等。不同的设备(蓝牙设备)的设置方法有所区别。

sdk的api，设置相应流的音量。不同的流index的范围不一样

//--->frameworks/base/media/java/android/media/AudioManager.javapublic void setStreamVolume(int streamType, int index, int flags) {    IAudioService service = getService();    try {        service.setStreamVolume(streamType, index, flags,             getContext().getOpPackageName());    } catch (RemoteException e) {        Log.e(TAG, "Dead object in setStreamVolume", e);    }}

java层Service实现,volume的调节的实现是用state模式来实现，可能需要原子性或不同的模式下调节音量的操作不同。

//--->frameworks/base/services/core/java/com/android/server/audio/AudioService.javaprivate void setStreamVolume(int streamType, int index, int flags,     String callingPackage,String caller, int uid) {    ...(检查参数)    ...(转换参数)    // 获取设备    final int device = getDeviceForStream(streamType);    ...(特殊处理a2dp)    ...(检查uid，实体按键调节音量需要判断当前用户？)    synchronized (mSafeMediaVolumeState) {        mPendingVolumeCommand = null;        oldIndex = streamState.getIndex(device);        index = rescaleIndex(index * 10, streamType, streamTypeAlias);        ...(特殊处理a2dp)        ...(特殊处理HDMI)        ...(设置一些标志位，如标记一些不可调节音量的设备)        //检查当前是否可设置音量        if (!checkSafeMediaVolume(streamTypeAlias, index, device)) {            // 不可以则生成PendingCommand，等待合适的时机            mVolumeController.postDisplaySafeVolumeWarning(flags);            mPendingVolumeCommand = new StreamVolumeCommand(                streamType, index, flags, device);        } else {            // 设置音量            onSetStreamVolume(streamType, index, flags, device,                 caller);            index = mStreamStates[streamType].getIndex(device);        }    }    // 发送更新音量信息    sendVolumeUpdate(streamType, oldIndex, index, flags);}private void onSetStreamVolume(int streamType, int index, int flags,     int device,String caller) {    final int stream = mStreamVolumeAlias[streamType];    // 设置音量    setStreamVolumeInt(stream, index, device, false, caller);    ...(判断音量是否为0，调节模式(静音或响铃))    mStreamStates[stream].mute(index == 0);}private void setStreamVolumeInt(int streamType,int index,int device,    boolean force,String caller) {    VolumeStreamState streamState = mStreamStates[streamType];    if (streamState.setIndex(index, device, caller) || force) {        // Post message to set system volume (it in turn will post a message        // to persist).        sendMsg(mAudioHandler,MSG_SET_DEVICE_VOLUME,SENDMSG_QUEUE,device,            0,streamState,0);    }}  @Overridepublic void handleMessage(Message msg) {    ...    switch (msg.what) {        case MSG_SET_DEVICE_VOLUME:            setDeviceVolume((VolumeStreamState) msg.obj, msg.arg1);            break;        ...    }    ...}private void setDeviceVolume(VolumeStreamState streamState, int device) {    synchronized (VolumeStreamState.class) {        // 设置音量        streamState.applyDeviceVolume_syncVSS(device);        ...(Apply change to all streams using this one as alias)    }    // Post a persist volume msg    sendMsg(mAudioHandler,MSG_PERSIST_VOLUME,SENDMSG_QUEUE,device,0,        streamState,PERSIST_DELAY);}public void applyDeviceVolume_syncVSS(int device) {    int index;    if (mIsMuted) {        index = 0;    } else if (((device & AudioSystem.DEVICE_OUT_ALL_A2DP) != 0         && mAvrcpAbsVolSupported) || ((device & mFullVolumeDevices) != 0)) {        index = (mIndexMax + 5)/10;    } else {        index = (getIndex(device) + 5)/10;    }    AudioSystem.setStreamVolumeIndex(mStreamType, index, device);}

AudioSystem的setStreamVolumeIndex是个native函数，从这里到跳到c++代码

//--->frameworks/base/media/java/android/media/AudioSystem.javapublic static native int setStreamVolumeIndex(int stream, int index,    int device);

jni的代码没做处理，直接转发给c++层的AudioSystem

//--->frameworks/base/core/jni/android_media_AudioSystem.cppstatic JNINativeMethod gMethods[] = { ... {"setStreamVolumeIndex","(III)I",   (void *)android_media_AudioSystem_setStreamVolumeIndex},...};static jint android_media_AudioSystem_setStreamVolumeIndex(    JNIEnv *env,jobject thiz,jint stream,jint index,jint device){    return (jint) check_AudioSystem_Command(AudioSystem::setStreamVolumeIndex(        static_cast <audio_stream_type_t>(stream),index,(audio_devices_t)device));}

AudioSystem又踢给AudioPolicyService(这里是binder通信，从这里跳到服务端处理)

//--->frameworks/av/media/libmedia/AudioSystem.cppstatus_t AudioSystem::setStreamVolumeIndex(audio_stream_type_t stream,    int index,audio_devices_t device){    const sp<IAudioPolicyService>& aps = AudioSystem::get_audio_policy_service();    if (aps == 0) return PERMISSION_DENIED;    return aps->setStreamVolumeIndex(stream, index, device);}

AudioPolicyService做了些权限和参数检查，转发给AudioPolicyManager

//---frameworks/av/services/audiopolicy/service/AudioPolicyService.cppstatus_t AudioPolicyService::setStreamVolumeIndex(audio_stream_type_t stream,    int index,audio_devices_t device){    if (mAudioPolicyManager == NULL) return NO_INIT;    if (!settingsAllowed()) return PERMISSION_DENIED;    if (uint32_t(stream) >= AUDIO_STREAM_PUBLIC_CNT) return BAD_VALUE;    Mutex::Autolock _l(mLock);    return mAudioPolicyManager->setStreamVolumeIndex(stream,index,device);}

AudioPolicyManager的处理比较复杂，主要是包括了音频策略的判断

//--->frameworks/av/services/audiopolicy/managerdefault/AudioPolicyManager.cppstatus_t AudioPolicyManager::setStreamVolumeIndex(audio_stream_type_t stream,    int index,audio_devices_t device){    ...(检查音量及设备是否为audio设备)    ...(策略判断)    if ((device != AUDIO_DEVICE_OUT_DEFAULT) &&         (device & (strategyDevice | accessibilityDevice)) == 0) {        return NO_ERROR;    }    ...(设置每个输出设备的音量)    status_t volStatus = checkAndSetVolume(stream, index, desc, curDevice);    ...}status_t AudioPolicyManager::checkAndSetVolume(audio_stream_type_t stream,int index,    const sp<AudioOutputDescriptor>& outputDesc,audio_devices_t device,int delayMs,bool force){    ...(do not change actual stream volume if the stream is muted)    ...(do not change in call volume if bluetooth is connected and vice versa)    // 声音等级与真正参数的转换    float volumeDb = computeVolume(stream, index, device);      // 设置输出设备的声音    outputDesc->setVolume(volumeDb, stream, device, delayMs, force);    // 设置通话的音量？？    if (stream == AUDIO_STREAM_VOICE_CALL || stream == AUDIO_STREAM_BLUETOOTH_SCO) {            ...            mpClientInterface->setVoiceVolume(voiceVolume, delayMs);            ...        }    }    return NO_ERROR;}

AudioOutputDescriptor是音频设备描述符，outputDesc是SwAudioOutputDescriptor类型。

//--->/frameworks/av/services/audiopolicy/common/managerdefinitions/src/AudioOutputDescriptor.cpp bool AudioOutputDescriptor::setVolume(float volume,audio_stream_type_t stream,    audio_devices_t device __unused,uint32_t delayMs,bool force){    // We actually change the volume if:    // - the float value returned by computeVolume() changed    // - the force flag is set    if (volume != mCurVolume[stream] || force) {        ALOGV("setVolume() for stream %d, volume %f, delay %d", stream, volume, delayMs);        mCurVolume[stream] = volume;        return true;    }    return false;}bool SwAudioOutputDescriptor::setVolume(float volume,audio_stream_type_t stream,    audio_devices_t device,uint32_t delayMs,bool force){    bool changed = AudioOutputDescriptor::setVolume(volume, stream, device,         delayMs, force);    if (changed) {        // Force VOICE_CALL to track BLUETOOTH_SCO stream volume when bluetooth audio is        // enabled        float volume = Volume::DbToAmpl(mCurVolume[stream]);        if (stream == AUDIO_STREAM_BLUETOOTH_SCO) {            mClientInterface->setStreamVolume(AUDIO_STREAM_VOICE_CALL, volume,                mIoHandle, delayMs);        }        mClientInterface->setStreamVolume(stream, volume, mIoHandle, delayMs);    }    return changed;}

AudioOutputDescriptor的mClientInterface是AudioPolicyService，所以会转到AudioPolicyService的setStreamVolume
AudioPolicyService异步执行这个操作,最后会转到AudioSystem的setStreamVolume。

//--->frameworks/av/services/audiopolicy/service/AudioPolicyService.cppint AudioPolicyService::setStreamVolume(audio_stream_type_t stream,float volume,    audio_io_handle_t output,int delayMs){    return (int)mAudioCommandThread->volumeCommand(stream, volume,output, delayMs);}status_t AudioPolicyService::AudioCommandThread::volumeCommand(audio_stream_type_t stream,    float volume,audio_io_handle_t output,int delayMs){    ...(封装了一下data跟command)    return sendCommand(command, delayMs);}status_t AudioPolicyService::AudioCommandThread::sendCommand(sp<AudioCommand>& command, int delayMs) {...(一些命令队列的操作)}// 处理函数bool AudioPolicyService::AudioCommandThread::threadLoop(){    ...    while (!exitPending())    {        ...        switch (command->mCommand) {        ...        case SET_VOLUME:             ...(Lock)            VolumeData *data = (VolumeData *)command->mParam.get();            command->mStatus = AudioSystem::setStreamVolume(data->mStream,                data->mVolume,data->mIO);        break;        ...    }}

AudioSystem又转到AudioFlinger

//--->frameworks/av/media/libmedia/AudioSystem.cpp status_t AudioSystem::setStreamVolume(audio_stream_type_t stream, float value,    audio_io_handle_t output){    ...(权限参数检查)    af->setStreamVolume(stream, value, output);    return NO_ERROR;}

AudioFlinger会去获取output对应的PlaybackThread并设置PlaybackThread的音量，如果output == AUDIOIOHANDLE_NONE，则设置所有PlaybackThread的音量。

//--->frameworks/av/services/audioflinger/AudioFlinger.cppstatus_t AudioFlinger::setStreamVolume(audio_stream_type_t stream, float value,        audio_io_handle_t output){    ...(权限检查)    ...(流类型检查)    AutoMutex lock(mLock);    ...(获取对应设备的PlaybackTread)    // ???    mStreamTypes[stream].volume = value;    if (thread == NULL) {   // output == AUDIO_IO_HANDLE_NONE        for (size_t i = 0; i < mPlaybackThreads.size(); i++) {            mPlaybackThreads.valueAt(i)->setStreamVolume(stream, value);        }    } else {        thread->setStreamVolume(stream, value);    }    return NO_ERROR;}

PlaybackThread设置mStreamTypes的volume。并唤醒PlaybackThread线程

void AudioFlinger::PlaybackThread::setStreamVolume(audio_stream_type_t stream, float value){    Mutex::Autolock _l(mLock);    mStreamTypes[stream].volume = value;    broadcast_l();}

不同类型的Thread貌似有不同使用方法 MixerThread是在prepareTracks_l里使用，最后会设置AudioMixer的参数

//--->frameworks/av/services/audioflinger/Threads.cppAudioFlinger::PlaybackThread::mixer_state AudioFlinger::MixerThread::prepareTracks_l(    Vector< sp<Track> > *tracksToRemove) {    ...    // FastTrack    track->mCachedVolume = masterVolume * mStreamTypes[track->streamType()].volume;    ...    // NormalTrack    // 这里涉及到了左右声道的音量的计算    // compute volume for this track    uint32_t vl, vr;       // in U8.24 integer format    float vlf, vrf, vaf;   // in [0.0, 1.0] float format    float typeVolume = mStreamTypes[track->streamType()].volume;    float v = masterVolume * typeVolume;    ...    //计算完设置混音器的参数    mAudioMixer->setParameter(name, param, AudioMixer::VOLUME0, &vlf);    mAudioMixer->setParameter(name, param, AudioMixer::VOLUME1, &vrf);    mAudioMixer->setParameter(name, param, AudioMixer::AUXLEVEL, &vaf);    ...}// 最后会调用到mAudioMixer的setVolumeRampVariablesstatic inline bool setVolumeRampVariables(float newVolume, int32_t ramp,    int16_t *pIntSetVolume, int32_t *pIntPrevVolume, int32_t *pIntVolumeInc,    float *pSetVolume, float *pPrevVolume, float *pVolumeInc){...}

DirectOutputThread在processVolumel里使用(processVolumel在prepareTracksl中被调用)
processVolumel直接设置了输出设备的volume

//--->frameworks/av/services/audioflinger/Threads.cpp   void AudioFlinger::DirectOutputThread::processVolume_l(Track *track, bool lastTrack) {    ...    float typeVolume = mStreamTypes[track->streamType()].volume;    float v = mMasterVolume * typeVolume;    ...(一系列的设置)    if (mOutput->stream->set_volume) {        mOutput->stream->set_volume(mOutput->stream, left, right);    }}

还有其他的几种Thread都是上面两种Thread的子类，处理方式是一致的

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