转载 ADROID 2.1 架构解析 10 声音

10 声音
10.1 音频管理
文件： frameworks/base/media/java/android/media/AudioManager.java

10.1.1 音量控制

/**  @hide Default volume index values for audio streams */ 

    public static final int[] DEFAULT_STREAM_VOLUME = new int[] { 

        4,  // STREAM_VOICE_CALL 

         7,  // STREAM_SYSTEM 

        5,  // STREAM_RING 

        11, // STREAM_MUSIC 

        6,  // STREAM_ALARM 

        5,  // STREAM_NOTIFICATION 

        7,  // STREAM_BLUETOOTH_SCO 

        7,  // STREAM_SYSTEM_ENFORCED 

        11, // STREAM_DTMF 

        11  // STREAM_TTS 

}; 

以上结构定义了默认音量。

public void adjustStreamVolume(int streamType, int direction, int flags) { 

        IAudioService service = getService(); 

        try { 

            service.adjustStreamVolume(streamType, direction, flags); 

        } catch (RemoteException e) { 

            Log.e(TAG, "Dead object in adjustStreamVolume", e); 

        } 

} 

public void setStreamVolume(int streamType, int index, int flags) { 

        IAudioService service = getService(); 

        try { 

            service.setStreamVolume(streamType, index, flags); 

        } catch (RemoteException e) { 

            Log.e(TAG, "Dead object in setStreamVolume", e); 

        } 

    } 

将音量控制参数转给音频服务去处理。

10.1.2 播放控制

@Deprecated public void setParameter(String key, String value) { 

        setParameters(key+"="+value); 

    } 



    /** 

     * Sets a variable number of parameter values to audio hardware. 

     * 

     * @param keyValuePairs list of parameters key value pairs in the form: 

     *    key1=value1;key2=value2;... 

     * 

     */ 

    public void setParameters(String keyValuePairs) { 

        AudioSystem.setParameters(keyValuePairs); 

} 

cupcake 的播放控制采用的是 setrouting() 方式进行， eclaire 的播放控制改用 setParameter 方式，用参数设置的方式进行。

以上代码的功能是：将参数传给音频系统去进行处理。

10.2 音频服务
文件： frameworks/base/media/java/android/media/AudioService.java

10.2.1 音效

 
private static final String SOUND_EFFECTS_PATH = "/media/audio/ui/"; 

    private static final String[] SOUND_EFFECT_FILES = new String[] { 

        "Effect_Tick.ogg", 

        "KeypressStandard.ogg", 

        "KeypressSpacebar.ogg", 

        "KeypressDelete.ogg", 

        "KeypressReturn.ogg" 

}; 

public boolean loadSoundEffects() { 

        ... 

String filePath = Environment.getRootDirectory() + SOUND_EFFECTS_PATH + SOUND_EFFECT_FILES[SOUND_EFFECT_FILES_MAP[effect][0]]; 

              ... 

        return true; 

} 

音效文件放在： /system/media/audio/ui/ 目录下。

10.2.2 音量

public void setStreamVolume(int streamType, int index, int flags) { 

        ensureValidStreamType(streamType); 

        index = rescaleIndex(index * 10, streamType, STREAM_VOLUME_ALIAS[streamType]); 

        setStreamVolumeInt(STREAM_VOLUME_ALIAS[streamType], index, false, true); 



        // UI, etc. 

        mVolumePanel.postVolumeChanged(streamType, flags); 

        // Broadcast Intent 

        sendVolumeUpdate(streamType); 

} 

private void setStreamVolumeInt(int streamType, int index, boolean force, boolean lastAudible) { 

        VolumeStreamState streamState = mStreamStates[streamType]; 

        if (streamState.setIndex(index, lastAudible) || force) { 

            // Post message to set system volume (it in turn will post a message 

            // to persist). Do not change volume if stream is muted. 

            if (streamState.muteCount() == 0) { 

                 sendMsg(mAudioHandler, MSG_SET_SYSTEM_VOLUME, streamType, SENDMSG_NOOP, 0, 0, 

                        streamState, 0); 

            } 

        } 

} 

private class AudioHandler extends Handler { 

private void setStreamVolumeIndex(int stream, int index) { 

         AudioSystem.setStreamVolumeIndex(s tream, (index + 5)/10); 

} 



        private void setSystemVolume(VolumeStreamState streamState) { 



            // Adjust volume 

            setStreamVolumeIndex (streamState.mStreamType, streamState.mIndex); 

... 

         } 

public void handleMessage(Message msg) { 

            int baseMsgWhat = getMsgBase(msg.what); 



            switch (baseMsgWhat) { 



                case MSG_SET_SYSTEM_VOLUME: 

                    setSystemVolume((VolumeStreamState) msg.obj); 

                     break; 

... 

音量设置通过消息发给消息处理，然后再转向音频系统进行处理：

AudioSystem.setStreamVolumeIndex

10.3 音频系统
文件： frameworks/base/media/java/android/media/AudioSystem.java

10.3.1 音频类型

/* The audio stream for phone calls */ 

    public static final int STREAM_VOICE_CALL = 0; 

     /* The audio stream for system sounds */ 

    public static final int STREAM_SYSTEM = 1; 

    /* The audio stream for the phone ring and message alerts */ 

    public static final int STREAM_RING = 2; 

    /* The audio stream for music playback */ 

    public static final int STREAM_MUSIC = 3; 

    /* The audio stream for alarms */ 

    public static final int STREAM_ALARM = 4; 

    /* The audio stream for notifications */ 

    public static final int STREAM_NOTIFICATION = 5; 

    /* @hide The audio stream for phone calls when connected on bluetooth */ 

    public static final int STREAM_BLUETOOTH_SCO = 6; 

    /* @hide The audio stream for enforced system sounds in certain countries (e.g camera in Japan) */ 

    public static final int STREAM_SYSTEM_ENFORCED = 7; 

    /* @hide The audio stream for DTMF tones */ 

     public static final int STREAM_DTMF = 8; 

    /* @hide The audio stream for text to speech (TTS) */ 

public static final int STREAM_TTS = 9; 

10.3.2 输入输出设备

// output devices 

    public static final int DEVICE_OUT_EARPIECE = 0x1; 

    public static final int DEVICE_OUT_SPEAKER = 0x2; 

    public static final int DEVICE_OUT_WIRED_HEADSET = 0x4; 

    public static final int DEVICE_OUT_WIRED_HEADPHONE = 0x8; 

    public static final int DEVICE_OUT_BLUETOOTH_SCO = 0x10; 

     public static final int DEVICE_OUT_BLUETOOTH_SCO_HEADSET = 0x20; 

    public static final int DEVICE_OUT_BLUETOOTH_SCO_CARKIT = 0x40; 

    public static final int DEVICE_OUT_BLUETOOTH_A2DP = 0x80; 

    public static final int DEVICE_OUT_BLUETOOTH_A2DP_HEADPHONES = 0x100; 

    public static final int DEVICE_OUT_BLUETOOTH_A2DP_SPEAKER = 0x200; 

    public static final int DEVICE_OUT_AUX_DIGITAL = 0x400; 

    public static final int DEVICE_OUT_DEFAULT = 0x8000; 

    // input devices 

    public static final int DEVICE_IN_COMMUNICATION = 0x10000; 

    public static final int DEVICE_IN_AMBIENT = 0x20000; 

    public static final int DEVICE_IN_BUILTIN_MIC1 = 0x40000; 

    public static final int DEVICE_IN_BUILTIN_MIC2 = 0x80000; 

    public static final int DEVICE_IN_MIC_ARRAY = 0x100000; 

    public static final int DEVICE_IN_BLUETOOTH_SCO_HEADSET = 0x200000; 

    public static final int DEVICE_IN_WIRED_HEADSET = 0x400000; 

    public static final int DEVICE_IN_AUX_DIGITAL = 0x800000; 

public static final int DEVICE_IN_DEFAULT = 0x80000000; 

10.3.3 转向底层处理

public static native int setParameters(String keyValuePairs); 

public static native int setStreamVolumeIndex(int stream, int index); 

对于参数设置和音量设置都转向 C/C++ 文件进行处理。

10.4 音频系统底层处理
文件： frameworks/base/media/libmedia/AudioSystem.cpp

10.4.1 音量设置

const sp<IAudioPolicyService>& AudioSystem::get_audio_policy_service() 

{ 

    ... 

        sp<IServiceManager> sm = defaultServiceManager(); 

              ... 

        binder = sm->getService(String16("media.audio_policy")); 

           ... 

} 

status_t AudioSystem::setStreamVolumeIndex(stream_type stream, int index) 

{ 

    const sp<IAudioPolicyService>& aps = AudioSystem::get_audio_policy_service(); 

    if (aps == 0) return PERMISSION_DENIED; 

     return aps->setStreamVolumeIndex(stream, index); 

} 

将参数传给音频策略进行处理。

10.4.1 参数设置

const sp<IAudioFlinger>& AudioSystem::get_audio_flinger() 

{ 

    ... 

        sp<IServiceManager> sm = defaultServiceManager(); 

       .. 

            binder = sm->getService(String16("media.audio_flinger")); 

        ... 

} 

status_t AudioSystem::setParameters(audio_io_handle_t ioHandle, const String8& keyValuePairs) { 

    const sp<IAudioFlinger>& af = AudioSystem::get_audio_flinger(); 

    if (af == 0) return PERMISSION_DENIED; 

    return af->setParameters(ioHandle, keyValuePairs); 

} 

将参数传给音频投掷进行处理。

主参数：

const char *AudioParameter::keyRouting = "routing"; 

const char *AudioParameter::keySamplingRate = "sampling_rate"; 

const char *AudioParameter::keyFormat = "format"; 

const char *AudioParameter::keyChannels = "channels"; 

const char *AudioParameter::keyFrameCount = "frame_count"; 

10.5 音频策略
文件： frameworks/base/libs/audioflinger/AudioPolicyService.cpp

void AudioPolicyService::instantiate() { 

    defaultServiceManager()->addService( 

            String16("media.audio_policy"), new AudioPolicyService()); 

} 

注册名为 media.audio_policy 的服务。

AudioPolicyService::AudioPolicyService() 

    : BnAudioPolicyService() , mpPolicyManager(NULL) 

{ 

    ... 

        mpPolicyManager = createAudioPolicyManager(this); 

    ... 

} 

调用音频策略管理器。

status_t AudioPolicyService::setStreamVolumeIndex(AudioSystem::stream_type stream, int index) 

{ 

    ... 



    return mpPolicyManager->setStreamVolumeIndex(stream, index); 

} 

将音量控制参数传给音频策略管理器。

10.6 音频投掷
文件： frameworks/base/libs/audioflinger/AudioFlinger.cpp

void AudioFlinger::instantiate() { 

    defaultServiceManager()->addService( 

            String16("media.audio_flinger"), new AudioFlinger()); 

} 

注册名为 media.audio_flinger 的服务

AudioFlinger::AudioFlinger() 

    : BnAudioFlinger(), 

        mAudioHardware(0), mMasterVolume(1.0f), mMasterMute(false), mNextThreadId(0) 

{ 

    ... 

mAudioHardware = AudioHardwareInterface::create(); 

... 

} 

status_t AudioFlinger::setParameters(int ioHandle, const String8& keyValuePairs) 

{ 

    ... 

        result = mAudioHardware->setParameters(keyValuePairs); 

    ... 

} 

将参数转向硬件接口去进行处理。

10.6.1 硬件接口
文件： frameworks/base/libs/audioflinger/AudioHardwareInterface.cpp

AudioHardwareInterface* AudioHardwareInterface::create() 

{ 

   ... 

   hw = createAudioHardware(); 

   ... 

} 

调用音频设备。

10.7 音频策略管理器
文件： hardware/msm7k/libaudio/AudioPolicyManager.cpp

extern "C" AudioPolicyInterface* createAudioPolicyManager(AudioPolicyClientInterface *clientInterface) 

{ 

    return new AudioPolicyManager(clientInterface); 

} 

status_t AudioPolicyManager::setStreamVolumeIndex(AudioSystem::stream_type stream, int index) 

{ 



   ... 

    for (size_t i = 0; i < mOutputs.size(); i++) { 

         status_t volStatus = checkAndSetVolume(stream, index, mOutputs.keyAt(i), mOutputs.valueAt(i)->device()); 

        if (volStatus != NO_ERROR) { 

            status = volStatus; 

        } 

    } 

    return status; 

} 

设置音量。

10.8 音频设备
文件： hardware/msm7k/libaudio/AudioHardware.cpp

extern "C" AudioHardwareInterface* createAudioHardware (void) { 

    return new AudioHardware(); 

} 

status_t AudioHardware::setParameters(const String8& keyValuePairs) 

{ 

    AudioParameter param = AudioParameter(keyValuePairs); 

    String8 value; 

    String8 key; 

... 

    key = String8(BT_NAME_KEY); 

    if (param.get(key, value) == NO_ERROR) { 

       ... 

    } 

    return NO_ERROR; 

} 

处理 setParameters 参数。