解释：
AudioTrack是什么？
AudioRecord是可以播放原始音频数据pcm的api，pcm一般的播放器都是无法播放的，AudioRecord可以播放pcm，不过需要制定播放时候的采样率、声道数位宽，现在在android下面做了一个demo，主要是播放pcm录音文件。pcm录音时候需要制定几个重要参数，播放的时候还需要设置录制缓冲区大小，缓存区越大，内存溢出风险越小。
pcm参数：
1、采样率
2、声道数
3、位宽
详细代码：
public class MyAudio extends AppCompatActivity implements View.OnClickListener {
private static final int MY_PERMISSIONS_REQUEST = 1001;
private static final String TAG = "jqd";
private Button mBtnControl;
private Button mBtnPlay;
/**
* 需要申请的运行时权限
*/
private String[] permissions = new String[]{
Manifest.permission.RECORD_AUDIO,
Manifest.permission.WRITE_EXTERNAL_STORAGE
};
/**
* 被用户拒绝的权限列表
*/
private List<String> mPermissionList = new ArrayList<>();
private boolean isRecording;
private AudioRecord audioRecord;
private Button mBtnConvert;
private AudioTrack audioTrack;
private byte[] audioData;
private FileInputStream fileInputStream;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mBtnControl = (Button) findViewById(R.id.btn_control);
mBtnControl.setOnClickListener(this);
mBtnConvert = (Button) findViewById(R.id.btn_convert);
mBtnConvert.setOnClickListener(this);
mBtnPlay = (Button) findViewById(R.id.btn_play);
mBtnPlay.setOnClickListener(this);
checkPermissions();
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.btn_control:
Button button = (Button) view;
if (button.getText().toString().equals(getString(R.string.start_record))) {
button.setText(getString(R.string.stop_record));
startRecord();
} else {
button.setText(getString(R.string.start_record));
stopRecord();
}
break;
case R.id.btn_convert:
PcmToWavUtil pcmToWavUtil = new PcmToWavUtil(SAMPLE_RATE_INHZ, CHANNEL_CONFIG, AUDIO_FORMAT);
File pcmFile = new File(getExternalFilesDir(Environment.DIRECTORY_MUSIC), "test.pcm");
File wavFile = new File(getExternalFilesDir(Environment.DIRECTORY_MUSIC), "test.wav");
if (!wavFile.mkdirs()) {
Log.e(TAG, "wavFile Directory not created");
}
if (wavFile.exists()) {
wavFile.delete();
}
pcmToWavUtil.pcmToWav(pcmFile.getAbsolutePath(), wavFile.getAbsolutePath());
break;
case R.id.btn_play:
Button btn = (Button) view;
String string = btn.getText().toString();
if (string.equals(getString(R.string.start_play))) {
btn.setText(getString(R.string.stop_play));
playInModeStream();
//playInModeStatic();
} else {
btn.setText(getString(R.string.start_play));
stopPlay();
}
break;
default:
break;
}
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
if (requestCode == MY_PERMISSIONS_REQUEST) {
for (int i = 0; i < grantResults.length; i++) {
if (grantResults[i] != PackageManager.PERMISSION_GRANTED) {
Log.i(TAG, permissions[i] + " 权限被用户禁止！");
}
}
// 运行时权限的申请不是本demo的重点，所以不再做更多的处理，请同意权限申请。
}
}
public void startRecord() {
final int minBufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE_INHZ, CHANNEL_CONFIG, AUDIO_FORMAT);
audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, SAMPLE_RATE_INHZ,
CHANNEL_CONFIG, AUDIO_FORMAT, minBufferSize);
final byte data[] = new byte[minBufferSize];
final File file = new File(getExternalFilesDir(Environment.DIRECTORY_MUSIC), "test.pcm");
if (!file.mkdirs()) {
Log.e(TAG, "Directory not created");
}
if (file.exists()) {
file.delete();
}
audioRecord.startRecording();
isRecording = true;
// TODO: 2018/3/10 pcm数据无法直接播放，保存为WAV格式。
new Thread(new Runnable() {
@Override
public void run() {
FileOutputStream os = null;
try {
os = new FileOutputStream(file);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
if (null != os) {
while (isRecording) {
int read = audioRecord.read(data, 0, minBufferSize);
// 如果读取音频数据没有出现错误，就将数据写入到文件
if (AudioRecord.ERROR_INVALID_OPERATION != read) {
try {
os.write(data);
} catch (IOException e) {
e.printStackTrace();
}
}
}
try {
Log.i(TAG, "run: close file output stream !");
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}).start();
}
public void stopRecord() {
isRecording = false;
// 释放资源
if (null != audioRecord) {
audioRecord.stop();
audioRecord.release();
audioRecord = null;
//recordingThread = null;
}
}
private void checkPermissions() {
// Marshmallow开始才用申请运行时权限
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
for (int i = 0; i < permissions.length; i++) {
if (ContextCompat.checkSelfPermission(this, permissions[i]) !=
PackageManager.PERMISSION_GRANTED) {
mPermissionList.add(permissions[i]);
}
}
if (!mPermissionList.isEmpty()) {
String[] permissions = mPermissionList.toArray(new String[mPermissionList.size()]);
ActivityCompat.requestPermissions(this, permissions, MY_PERMISSIONS_REQUEST);
}
}
}
/**
* 播放，使用stream模式
*/
private void playInModeStream() {
/*
* SAMPLE_RATE_INHZ 对应pcm音频的采样率
* channelConfig 对应pcm音频的声道
* AUDIO_FORMAT 对应pcm音频的格式
* */
int channelConfig = AudioFormat.CHANNEL_OUT_MONO;
final int minBufferSize = AudioTrack.getMinBufferSize(SAMPLE_RATE_INHZ, channelConfig, AUDIO_FORMAT);
if (Build.VERSION.SDK_INT > Build.VERSION_CODES.KITKAT) {
audioTrack = new AudioTrack(
new AudioAttributes.Builder()
.setUsage(AudioAttributes.USAGE_MEDIA)
.setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
.build(),
new AudioFormat.Builder().setSampleRate(SAMPLE_RATE_INHZ)
.setEncoding(AUDIO_FORMAT)
.setChannelMask(channelConfig)
.build(),
minBufferSize,
AudioTrack.MODE_STREAM,
AudioManager.AUDIO_SESSION_ID_GENERATE);
} else {
audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
48000,
channelConfig,
AudioFormat.ENCODING_PCM_16BIT,
minBufferSize,
AudioTrack.MODE_STREAM);
}
audioTrack.play();
File file = new File(getExternalFilesDir(Environment.DIRECTORY_MUSIC), "test.pcm");
try {
fileInputStream = new FileInputStream(file);
new Thread(new Runnable() {
@Override
public void run() {
try {
byte[] tempBuffer = new byte[minBufferSize];
while (fileInputStream.available() > 0) {
int readCount = fileInputStream.read(tempBuffer);
if (readCount == AudioTrack.ERROR_INVALID_OPERATION ||
readCount == AudioTrack.ERROR_BAD_VALUE) {
continue;
}
if (readCount != 0 && readCount != -1) {
audioTrack.write(tempBuffer, 0, readCount);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 播放，使用static模式
*/
private void playInModeStatic() {
// static模式，需要将音频数据一次性write到AudioTrack的内部缓冲区
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... params) {
try {
InputStream in = getResources().openRawResource(R.raw.ding);
try {
ByteArrayOutputStream out = new ByteArrayOutputStream();
for (int b; (b = in.read()) != -1; ) {
out.write(b);
}
Log.d(TAG, "Got the data");
audioData = out.toByteArray();
} finally {
in.close();
}
} catch (IOException e) {
Log.wtf(TAG, "Failed to read", e);
}
return null;
}
@Override
protected void onPostExecute(Void v) {
Log.i(TAG, "Creating track...audioData.length = " + audioData.length);
// R.raw.ding铃声文件的相关属性为 22050Hz, 8-bit, Mono
if (Build.VERSION.SDK_INT >Build.VERSION_CODES.KITKAT) {
audioTrack = new AudioTrack(
new AudioAttributes.Builder()
.setUsage(AudioAttributes.USAGE_MEDIA)
.setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
.build(),
new AudioFormat.Builder().setSampleRate(22050)
.setEncoding(AudioFormat.ENCODING_PCM_8BIT)
.setChannelMask(AudioFormat.CHANNEL_OUT_MONO)
.build(),
audioData.length,
AudioTrack.MODE_STATIC,
AudioManager.AUDIO_SESSION_ID_GENERATE);
} else {
audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
48000,
AudioFormat.CHANNEL_OUT_MONO,
AudioFormat.ENCODING_PCM_16BIT,
audioData.length,
AudioTrack.MODE_STREAM);
}
Log.d(TAG, "Writing audio data...");
audioTrack.write(audioData, 0, audioData.length);
Log.d(TAG, "Starting playback");
audioTrack.play();
Log.d(TAG, "Playing");
}
}.execute();
}
/**
* 停止播放
*/
private void stopPlay() {
if (audioTrack != null) {
Log.d(TAG, "Stopping");
audioTrack.stop();
Log.d(TAG, "Releasing");
audioTrack.release();
Log.d(TAG, "Nulling");
}
}
}
工具类：
/**
* 将pcm音频文件转换为wav音频文件
*/
public class PcmToWavUtil {
/**
* 缓存的音频大小
*/
private int mBufferSize;
/**
* 采样率
*/
private int mSampleRate;
/**
* 声道数
*/
private int mChannel;
/**
* @param sampleRate sample rate、采样率
* @param channel channel、声道
* @param encoding Audio data format、音频格式
*/
public PcmToWavUtil(int sampleRate, int channel, int encoding) {
this.mSampleRate = sampleRate;
this.mChannel = channel;
this.mBufferSize = AudioRecord.getMinBufferSize(mSampleRate, mChannel, encoding);
}
/**
* pcm文件转wav文件
*
* @param inFilename 源文件路径
* @param outFilename 目标文件路径
*/
public void pcmToWav(String inFilename, String outFilename) {
FileInputStream in;
FileOutputStream out;
long totalAudioLen;
long totalDataLen;
long longSampleRate = mSampleRate;
int channels = mChannel == AudioFormat.CHANNEL_IN_MONO ? 1 : 2;
long byteRate = 16 * mSampleRate * channels / 8;
byte[] data = new byte[mBufferSize];
try {
in = new FileInputStream(inFilename);
out = new FileOutputStream(outFilename);
totalAudioLen = in.getChannel().size();
totalDataLen = totalAudioLen + 36;
writeWaveFileHeader(out, totalAudioLen, totalDataLen,
longSampleRate, channels, byteRate);
while (in.read(data) != -1) {
out.write(data);
}
in.close();
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 加入wav文件头
*/
private void writeWaveFileHeader(FileOutputStream out, long totalAudioLen,
long totalDataLen, long longSampleRate, int channels, long byteRate)
throws IOException {
byte[] header = new byte[44];
// RIFF/WAVE header
header[0] = 'R';
header[1] = 'I';
header[2] = 'F';
header[3] = 'F';
header[4] = (byte) (totalDataLen & 0xff);
header[5] = (byte) ((totalDataLen >> 8) & 0xff);
header[6] = (byte) ((totalDataLen >> 16) & 0xff);
header[7] = (byte) ((totalDataLen >> 24) & 0xff);
//WAVE
header[8] = 'W';
header[9] = 'A';
header[10] = 'V';
header[11] = 'E';
// 'fmt ' chunk
header[12] = 'f';
header[13] = 'm';
header[14] = 't';
header[15] = ' ';
// 4 bytes: size of 'fmt ' chunk
header[16] = 16;
header[17] = 0;
header[18] = 0;
header[19] = 0;
// format = 1
header[20] = 1;
header[21] = 0;
header[22] = (byte) channels;
header[23] = 0;
header[24] = (byte) (longSampleRate & 0xff);
header[25] = (byte) ((longSampleRate >> 8) & 0xff);
header[26] = (byte) ((longSampleRate >> 16) & 0xff);
header[27] = (byte) ((longSampleRate >> 24) & 0xff);
header[28] = (byte) (byteRate & 0xff);
header[29] = (byte) ((byteRate >> 8) & 0xff);
header[30] = (byte) ((byteRate >> 16) & 0xff);
header[31] = (byte) ((byteRate >> 24) & 0xff);
// block align
header[32] = (byte) (2 * 16 / 8);
header[33] = 0;
// bits per sample
header[34] = 16;
header[35] = 0;
//data
header[36] = 'd';
header[37] = 'a';
header[38] = 't';
header[39] = 'a';
header[40] = (byte) (totalAudioLen & 0xff);
header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
header[43] = (byte) ((totalAudioLen >> 24) & 0xff);
out.write(header, 0, 44);
}
}
config类
public class Config {
/**
* 采样率，现在能够保证在所有设备上使用的采样率是44100Hz, 但是其他的采样率（22050, 16000, 11025）在一些设备上也可以使用。
*/
public static final int SAMPLE_RATE_INHZ = 44100;
/**
* 声道数。CHANNEL_IN_MONO and CHANNEL_IN_STEREO. 其中CHANNEL_IN_MONO是可以保证在所有设备能够使用的。
*/
public static final int CHANNEL_CONFIG = AudioFormat.CHANNEL_IN_MONO;
/**
* 返回的音频数据的格式。 ENCODING_PCM_8BIT, ENCODING_PCM_16BIT, and ENCODING_PCM_FLOAT.
*/
public static final int AUDIO_FORMAT = AudioFormat.ENCODING_PCM_16BIT;
}
总结： android相对底层的录制、播放api，了解用法即可。建议先学习音频基础知识，再学会使用api。