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音频 PCM 数据的采集和播放
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PCM（Pulse Code Modulation）脉冲编码调制 —— 音频的采集与量化过程。
PCM数据是最原始的音频数据完全无损 ，所以PCM数据虽然音质优秀但体积庞大。
为了解决这个问题先后诞生了一系列的音频格式，这些音频格式运用不同的方法对音频数据进行压缩，其中有无损压缩（ALAC、APE、FLAC）和有损压缩（MP3、AAC、OGG、WMA）两种。
代码实现逻辑过程：
使用
AudioRecord
录制pcm音频 ——> PCM转WAV（只要加上wav头文件即可）——> 使用
AudioTrack
播放pcm音频
——> 使用 AudioTrack 播放音频
使用AudioRecord录制PCM音频代码：
/**
* 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。
*/
private 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。
*/
private 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.
*/
private static final int AUDIO_FORMAT = AudioFormat.ENCODING_PCM_16BIT;
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;
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();
PCM转WAV：
// 音频数据的大小
long totalAudioLen = fileInputStream.getChannel().size();
// wav总区块大小
long totalDataLen = totalAudioLen + 36;
// 声道数量
int channels;
// 采样率
long longSampleRate;
// 位元率
long byteRate = 16 * longSampleRate * channels / 8;
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);
使用AudioTrack 播放音频
/**
* 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);
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);
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
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);
Log.d(TAG, "Writing audio data...");
audioTrack.write(audioData, 0, audioData.length);
Log.d(TAG, "Starting playback");
audioTrack.play();
Log.d(TAG, "Playing");
}
}.execute();
}
使用AudioRecord录制PCM音频代码：
/**
* 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。
*/
private 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。
*/
private 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.
*/
private static final int AUDIO_FORMAT = AudioFormat.ENCODING_PCM_16BIT; 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; 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();
PCM转WAV：
// 音频数据的大小
long totalAudioLen = fileInputStream.getChannel().size();
// wav总区块大小
long totalDataLen = totalAudioLen + 36;
// 声道数量
int channels;
// 采样率
long longSampleRate;
// 位元率
long byteRate = 16 * longSampleRate * channels / 8; 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);
使用AudioTrack 播放音频
/**
* 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);
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);
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
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);
Log.d(TAG, "Writing audio data...");
audioTrack.write(audioData, 0, audioData.length);
Log.d(TAG, "Starting playback");
audioTrack.play();
Log.d(TAG, "Playing");
} }.execute(); }
demo 代码： https://i.cnblogs.com/Files.aspx
