Android(安卓)Audio 数据流详解

Android Audio Architecture 图如下所示

详细调用路径如下

1. 音频播放
示例代码
MediaPlayer mp = new MediaPlayer();
mp.setDataSource(PATH_TO_FILE);
mp.prepare();
mp.start();

1.1 MediaPlayer mp = new MediaPlayer()

实现流程如下表：

函数名	文件名
MediaPlayer:: MediaPlayer	MediaPlayer.Java
MediaPlayer::native_setup	MediaPlayer.Java
android_media_MediaPlayer_native_setup	android_media_MediaPlayer.cpp
MediaPlayer::MediaPlayer	MediaPlayer.cpp

1.2 mp.setDataSource(PATH_TO_FILE);

实现流程如下：

函数名	文件名
MediaPlayer::setDataSource	MediaPlayer.Java
android_media_MediaPlayer_setDataSource	android_media_MediaPlayer.cpp
MediaPlayer::setDataSource	MediaPlayer.cpp
-MediaPlayer::getMediaPlayerService	MediaPlayer.cpp
-IMediaPlayerService	IMediaPlayerService.h
-IMediaPlayerService::create	MediaPlayer.cpp
--MediaPlayerService::create	MediaPlayerService.cpp
-IMediaPlayer::setDataSource	MediaPlayer.cpp
--BpMediaPlayer::setDataSource	IMediaPlayer.cpp
--MediaPlayerService::Client::setDataSource(真正执行操作)	MediaPlayerService.cpp
--android::createPlayer	MediaPlayerService.cpp
-- new StagefrightPlayer	MediaPlayerService.cpp
--new AudioOutput	MediaPlayerService.cpp
--StagefrightPlayer::setDataSource	StagefrightPlayer.cpp
--AwesomePlayer::setDataSource	AwesomePlayer.cpp
--AwesomePlayer::setDataSource_l	AwesomePlayer.cpp

1.3 mp.prepare()

函数名	文件名
MediaPlayer:: prepare	MediaPlayer.Java
android_media_MediaPlayer_prepare	android_media_MediaPlayer.cpp
MediaPlayer:: prepare	MediaPlayer.cpp
MidiFile:: prepare	MidiFile.cpp
VorbisPlayer:: prepare	VorbisPlayer.cpp
VorbisPlayer::createOutputTrack	VorbisPlayer.cpp
AudioOutput::open	MediaPlayerService.cpp
AudioTrack::AudioTrack	AudioTrack.cpp
AudioSystem::get_audio_flinger	AudioSystem.cpp
AudioFlinger::createTrack	AudioFlinger.cpp

1.4 mp.start()

函数名	文件名
MediaPlayer:: start	MediaPlayer.Java
android_media_MediaPlayer_start	android_media_MediaPlayer.cpp
MediaPlayer::start	MediaPlayer.cpp
PVPlayer:: start	PVPlayer.h
MidiFile:: start	MidiFile.cpp
VorbisPlayer:: start	VorbisPlayer.cpp
AudioTrack::start	AudioTrack.cpp

MediaPlayerService:: MediaPlayerService(MediaPlayerService.cpp)由systemserver进程创建，在文件system_init.cpp里的函数system_init()调用MediaPlayerService::instantiate创建

getPlayerType(MediaPlayerService.cpp)返回3种player:
1) PV_PLAYER:播放mp3
2) SONIVOX_PLAYER:播放midi
3) VORBIS_PLAYER:播放ogg,

简单说来，播放流程如下：
Java端发起调用，MediaPlayer会转至MediaPlayerService,然后会调用相应的解码工具解码后创建AudioTrack，所有待输出的AudioTrack在AudioFlinger::AudioMixer里合成，然后通过AudioHAL(AudioHardwareInterface的实际实现者)传至实际的硬件来实现播放

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