转自http://blog.****.net/ameyume/article/details/7618820
播放声音可以用MediaPlayer和AudioTrack,两者都提供了java API供应用开发者使用。虽然都可以播放声音,但两者还是有很大的区别的。 其中最大的区别是MediaPlayer可以播放多种格式的声音文件,例如MP3,AAC,WAV,OGG,MIDI等。MediaPlayer会在framework层创建对应的音频解码器。 而AudioTrack只能播放已经解码的PCM流,如果是文件的话只支持wav格式的音频文件,因为wav格式的音频文件大部分都是PCM流。AudioTrack不创建解码器,所以只能播放不需要解码的wav文件。
当然两者之间还是有紧密的联系的,MediaPlayer在framework层还是会创建AudioTrack,把解码后的PCM数流传递给AudioTrack,AudioTrack再传递给AudioFlinger进行混音,然后才传递给硬件播放。 所以是MediaPlayer包含了AudioTRack。 通过查看API可以知道,MediaPlayer提供了5个setDataSource方法,分为三类,一类是传递播放文件的字符串路径作为参数,例如直接取sd卡里mp3文件的路径,一类是传递播放文件的FileDescriptor文件描述符作为播放的id,例例如从db中查询的音频文件的id,就可以直接赋给MediaPlayer进行播放。还有一类是Uri类型的资源文件,用于播放content uri文件。
下面是一个用MediaPlayer播放音乐的示例,音乐文件是从数据库中取出的。
- if (mMediaPlayer == null) {
- mMediaPlayer = new MediaPlayer(); // 创建MediaPlayer对象
- }
- mMediaPlayer.reset();
- String dataSource = getDataByPosition(mCursor, mPlayPosition);
- mMediaPlayer.setDataSource(dataSource); // 设置需要播放的数据源
- mMediaPlayer.prepare(); // 准备播放,如果是流媒体需要调用prepareAsync进行异步准备
- if (Common.PLAY_MODE_SINGLE_LOOP == mPlayMode) {
- mMediaPlayer.setLooping(true); // 单曲循环
- } else {
- mMediaPlayer.setLooping(false); // 不循环播放
- }
- mMediaPlayer.start(); // 开始播放,如果是播放流媒体,需要等到流媒体准备完成才能播放(在prepare的callback函数中调用start进行播放)
- // 根据位置来获取歌曲位置
- public String getDataByPosition(Cursor c, int position) {
- c.moveToPosition(position);
- int dataColumn = c.getColumnIndex(MediaStore.Audio.Media.DATA);
- String data = c.getString(dataColumn);
- return data;
- }
if (mMediaPlayer == null) {
mMediaPlayer = new MediaPlayer(); // 创建MediaPlayer对象
} mMediaPlayer.reset();
String dataSource = getDataByPosition(mCursor, mPlayPosition);
mMediaPlayer.setDataSource(dataSource); // 设置需要播放的数据源
mMediaPlayer.prepare(); // 准备播放,如果是流媒体需要调用prepareAsync进行异步准备
if (Common.PLAY_MODE_SINGLE_LOOP == mPlayMode) {
mMediaPlayer.setLooping(true); // 单曲循环
} else {
mMediaPlayer.setLooping(false); // 不循环播放
}
mMediaPlayer.start(); // 开始播放,如果是播放流媒体,需要等到流媒体准备完成才能播放(在prepare的callback函数中调用start进行播放) // 根据位置来获取歌曲位置
public String getDataByPosition(Cursor c, int position) {
c.moveToPosition(position);
int dataColumn = c.getColumnIndex(MediaStore.Audio.Media.DATA);
String data = c.getString(dataColumn);
return data;
}
AudioTrack播放声音时不能直接把wav文件传递给AudioTrack进行播放,必须传递buffer,通过write函数把需要播放的缓冲区buffer传递给AudioTrack,然后才能播放。
AudioTrack使用的例子参考下面: 此示例转自:http://samyou.iteye.com/blog/1125872
- public class AndroidTest extends Activity implements View.OnClickListener,SurfaceHolder.Callback
- {
- private SurfaceHolder surfaceHolder = null;
- private SurfaceView surfaceView = null;
- private AudioTrack audioTrack = null;
- private Thread writePCMThread = null;
- private File audioFile = null;
- private FileInputStream fileInputStream = null;
- private byte buffer[] = new byte[16*10000];
- // The Handler that gets information back from the other threads
- private final Handler msgHandler = new Handler()
- {
- public void handleMessage(Message msg)
- {
- switch (msg.what)
- {
- default:
- break;
- }
- }
- };
- /** Called when the activity is first created. */
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- surfaceView = (SurfaceView) findViewById(R.id.surface);
- SurfaceHolder surfaceHolder = surfaceView.getHolder();
- surfaceHolder.addCallback(this);
- surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
- findViewById(R.id.button1).setOnClickListener(this);
- findViewById(R.id.button2).setOnClickListener(this);
- }
- public void finish() {
- super.finish();
- System.out.println("finish");
- try {
- writePCMThread.interrupt();
- } catch (Exception e) {
- }
- try {
- fileInputStream.close();
- } catch (Exception e) {
- }
- try {
- audioTrack.stop();
- audioTrack.release();
- } catch (Exception e) {
- }
- }
- protected void onResume()
- {
- super.onResume();
- System.out.println("back on!!!!!!!!!!!");
- initAudioTrack();
- audioFile = new File(Environment.getExternalStorageDirectory(),"test.wav");
- System.out.println(audioFile.length());
- try {
- fileInputStream = new FileInputStream(audioFile);
- fileInputStream.skip(0x2c);
- } catch (Exception e) {
- }
- writePCMThread = new Thread(new Runnable(){
- public void run() {
- try
- {
- while(fileInputStream.read(buffer)>=0)
- {
- System.out.println("write pcm data");
- audioTrack.write(buffer, 0, buffer.length);
- }
- }
- catch (Exception e) {
- e.printStackTrace();
- }
- }
- });
- }
- private void initAudioTrack()
- {
- int minBufferSize = AudioTrack.getMinBufferSize(0xac44, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT);
- System.out.println("minBufferSize = "+minBufferSize);
- audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 0xac44,
- AudioFormat.CHANNEL_CONFIGURATION_STEREO, AudioFormat.ENCODING_PCM_16BIT, minBufferSize*2,AudioTrack.MODE_STREAM);
- audioTrack.setStereoVolume(1.0f, 1.0f);// 设置当前音量大小
- System.out.println("initAudioTrack over");
- audioTrack.play();
- }
- public void onClick(View v)
- {
- switch (v.getId()) {
- case R.id.button1:
- writePCMThread.start();
- break;
- case R.id.button2:
- break;
- default:
- break;
- }
- }
- public void surfaceCreated(SurfaceHolder holder) {
- System.out.println("surfaceCreated()");
- this.surfaceHolder = holder;
- }
- public void surfaceDestroyed(SurfaceHolder holder) {
- }
- public void surfaceChanged(SurfaceHolder holder, int format, int width,
- int height) {
- this.surfaceHolder = holder;
- }
- public void onActivityResult(int requestCode, int resultCode, Intent data) {
- }
- }
public class AndroidTest extends Activity implements View.OnClickListener,SurfaceHolder.Callback
{
private SurfaceHolder surfaceHolder = null;
private SurfaceView surfaceView = null;
private AudioTrack audioTrack = null;
private Thread writePCMThread = null;
private File audioFile = null;
private FileInputStream fileInputStream = null;
private byte buffer[] = new byte[16*10000]; // The Handler that gets information back from the other threads
private final Handler msgHandler = new Handler()
{
public void handleMessage(Message msg)
{
switch (msg.what)
{
default:
break;
}
}
}; /** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
surfaceView = (SurfaceView) findViewById(R.id.surface);
SurfaceHolder surfaceHolder = surfaceView.getHolder();
surfaceHolder.addCallback(this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
findViewById(R.id.button1).setOnClickListener(this);
findViewById(R.id.button2).setOnClickListener(this);
} public void finish() {
super.finish();
System.out.println("finish");
try {
writePCMThread.interrupt();
} catch (Exception e) {
}
try {
fileInputStream.close();
} catch (Exception e) {
}
try {
audioTrack.stop();
audioTrack.release();
} catch (Exception e) {
}
} protected void onResume()
{
super.onResume();
System.out.println("back on!!!!!!!!!!!");
initAudioTrack();
audioFile = new File(Environment.getExternalStorageDirectory(),"test.wav");
System.out.println(audioFile.length());
try {
fileInputStream = new FileInputStream(audioFile);
fileInputStream.skip(0x2c);
} catch (Exception e) {
} writePCMThread = new Thread(new Runnable(){
public void run() {
try
{
while(fileInputStream.read(buffer)>=0)
{
System.out.println("write pcm data");
audioTrack.write(buffer, 0, buffer.length);
}
}
catch (Exception e) {
e.printStackTrace();
}
}
}); } private void initAudioTrack()
{
int minBufferSize = AudioTrack.getMinBufferSize(0xac44, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT);
System.out.println("minBufferSize = "+minBufferSize);
audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 0xac44,
AudioFormat.CHANNEL_CONFIGURATION_STEREO, AudioFormat.ENCODING_PCM_16BIT, minBufferSize*2,AudioTrack.MODE_STREAM);
audioTrack.setStereoVolume(1.0f, 1.0f);// 设置当前音量大小
System.out.println("initAudioTrack over");
audioTrack.play();
} public void onClick(View v)
{
switch (v.getId()) {
case R.id.button1:
writePCMThread.start();
break;
case R.id.button2:
break;
default:
break;
} } public void surfaceCreated(SurfaceHolder holder) {
System.out.println("surfaceCreated()");
this.surfaceHolder = holder;
} public void surfaceDestroyed(SurfaceHolder holder) {
} public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
this.surfaceHolder = holder;
} public void onActivityResult(int requestCode, int resultCode, Intent data) {
} }
注:PCM和WAV
以下摘自:http://www.erji.net/read.php?tid=227570
简单来说,pcm是一种数据编码格式,CD唱盘上刻录的就直接用pcm格式编码的数据文件; wav是一种声音文件格式,wav里面包含的声音数据可以是采用pcm格式编码的声音数据,也可以是采用其它格式编码的声音数据,但目前一般采用pcm编码的声音数据 两者区别就是这些
pcm是一个通信上的概念,脉冲编码调制。wav是媒体概念,体现的是封装。wav文件可以封装pcm编码信息,也可以封装其他编码格式,例如mp3等。