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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(stream, (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。
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