在Android中我所知道的音頻編解碼有兩種方式：
（一）使用AudioRecord採集音頻，用這種方式採集的是未經壓縮的音頻流；用AudioTrack播放實時音頻流。用這兩個類的話，如果需要對音頻進行編解碼，就需要自己移植編解碼庫了，比如可以移植ilbc，speex等開源編解碼庫。
ilbc的編解碼實現可以查看這個專欄：http://blog.csdn.net/column/details/media.html
（二）使用MediaRecorder獲取編碼後的AMR音頻，但由於MediaRecorder的特點，只能將流保存到文件中，但通過其他方式是可以獲取到實時音頻流的，這篇文章將介紹用LocalSocket的方法來實現；使用MediaPlayer來播放AMR音頻流，但同樣MediaPlayer也只能播放文件流，因此我用緩存的方式來播放音頻。
以上兩種方式各有利弊，使用方法（一）需移植編解碼庫，但可以播放實時音頻流；使用方法（二）直接硬編硬解碼效率高，但是需要對文件進行操作。
PS：這篇文章只是給大家一個參考，僅供學習之用，如果真正用到項目中還有很多地方需要優化。
我強烈推薦播放音頻時候用方法（一），方法（二）雖然能夠實現功能，但是實現方式不太好。
接下來看代碼：
編碼器：
package cn.edu.xmu.zgy.audio.encoder;
import java.io.DataInputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import cn.edu.xmu.zgy.config.CommonConfig;
import android.app.Activity;
import android.media.MediaRecorder;
import android.net.LocalServerSocket;
import android.net.LocalSocket;
import android.net.LocalSocketAddress;
import android.util.Log;
import android.widget.Toast;
//blog.csdn.net/zgyulongfei
//Email: [email protected]
public class AmrAudioEncoder {
private static final String TAG = "ArmAudioEncoder";
private static AmrAudioEncoder amrAudioEncoder = null;
private Activity activity;
private MediaRecorder audioRecorder;
private boolean isAudioRecording;
private LocalServerSocket lss;
private LocalSocket sender, receiver;
private AmrAudioEncoder() {
}
public static AmrAudioEncoder getArmAudioEncoderInstance() {
if (amrAudioEncoder == null) {
synchronized (AmrAudioEncoder.class) {
if (amrAudioEncoder == null) {
amrAudioEncoder = new AmrAudioEncoder();
}
}
}
return amrAudioEncoder;
}
public void initArmAudioEncoder(Activity activity) {
this.activity = activity;
isAudioRecording = false;
}
public void start() {
if (activity == null) {
showToastText("音頻編碼器未初始化，請先執行init方法");
return;
}
if (isAudioRecording) {
showToastText("音頻已經開始編碼，無需再次編碼");
return;
}
if (!initLocalSocket()) {
showToastText("本地服務開啓失敗");
releaseAll();
return;
}
if (!initAudioRecorder()) {
showToastText("音頻編碼器初始化失敗");
releaseAll();
return;
}
this.isAudioRecording = true;
startAudioRecording();
}
private boolean initLocalSocket() {
boolean ret = true;
try {
releaseLocalSocket();
String serverName = "armAudioServer";
final int bufSize = 1024;
lss = new LocalServerSocket(serverName);
receiver = new LocalSocket();
receiver.connect(new LocalSocketAddress(serverName));
receiver.setReceiveBufferSize(bufSize);
receiver.setSendBufferSize(bufSize);
sender = lss.accept();
sender.setReceiveBufferSize(bufSize);
sender.setSendBufferSize(bufSize);
} catch (IOException e) {
ret = false;
}
return ret;
}
private boolean initAudioRecorder() {
if (audioRecorder != null) {
audioRecorder.reset();
audioRecorder.release();
}
audioRecorder = new MediaRecorder();
audioRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
audioRecorder.setOutputFormat(MediaRecorder.OutputFormat.RAW_AMR);
final int mono = 1;
audioRecorder.setAudioChannels(mono);
audioRecorder.setAudioSamplingRate(8000);
audioRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
audioRecorder.setOutputFile(sender.getFileDescriptor());
boolean ret = true;
try {
audioRecorder.prepare();
audioRecorder.start();
} catch (Exception e) {
releaseMediaRecorder();
showToastText("手機不支持錄音此功能");
ret = false;
}
return ret;
}
private void startAudioRecording() {
new Thread(new AudioCaptureAndSendThread()).start();
}
public void stop() {
if (isAudioRecording) {
isAudioRecording = false;
}
releaseAll();
}
private void releaseAll() {
releaseMediaRecorder();
releaseLocalSocket();
amrAudioEncoder = null;
}
private void releaseMediaRecorder() {
try {
if (audioRecorder == null) {
return;
}
if (isAudioRecording) {
audioRecorder.stop();
isAudioRecording = false;
}
audioRecorder.reset();
audioRecorder.release();
audioRecorder = null;
} catch (Exception err) {
Log.d(TAG, err.toString());
}
}
private void releaseLocalSocket() {
try {
if (sender != null) {
sender.close();
}
if (receiver != null) {
receiver.close();
}
if (lss != null) {
lss.close();
}
} catch (IOException e) {
e.printStackTrace();
}
sender = null;
receiver = null;
lss = null;
}
private boolean isAudioRecording() {
return isAudioRecording;
}
private void showToastText(String msg) {
Toast.makeText(activity, msg, Toast.LENGTH_SHORT).show();
}
private class AudioCaptureAndSendThread implements Runnable {
public void run() {
try {
sendAmrAudio();
} catch (Exception e) {
Log.e(TAG, "sendAmrAudio() 出錯");
}
}
private void sendAmrAudio() throws Exception {
DatagramSocket udpSocket = new DatagramSocket();
DataInputStream dataInput = new DataInputStream(receiver.getInputStream());
skipAmrHead(dataInput);
final int SEND_FRAME_COUNT_ONE_TIME = 10;// 每次發送10幀的數據，1幀大約32B
// AMR格式見博客：http://blog.csdn.net/dinggo/article/details/1966444
final int BLOCK_SIZE[] = { 12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0 };
byte[] sendBuffer = new byte[1024];
while (isAudioRecording()) {
int offset = 0;
for (int index = 0; index < SEND_FRAME_COUNT_ONE_TIME; ++index) {
if (!isAudioRecording()) {
break;
}
dataInput.read(sendBuffer, offset, 1);
int blockIndex = (int) (sendBuffer[offset] >> 3) & 0x0F;
int frameLength = BLOCK_SIZE[blockIndex];
readSomeData(sendBuffer, offset + 1, frameLength, dataInput);
offset += frameLength + 1;
}
udpSend(udpSocket, sendBuffer, offset);
}
udpSocket.close();
dataInput.close();
releaseAll();
}
private void skipAmrHead(DataInputStream dataInput) {
final byte[] AMR_HEAD = new byte[] { 0x23, 0x21, 0x41, 0x4D, 0x52, 0x0A };
int result = -1;
int state = 0;
try {
while (-1 != (result = dataInput.readByte())) {
if (AMR_HEAD[0] == result) {
state = (0 == state) ? 1 : 0;
} else if (AMR_HEAD[1] == result) {
state = (1 == state) ? 2 : 0;
} else if (AMR_HEAD[2] == result) {
state = (2 == state) ? 3 : 0;
} else if (AMR_HEAD[3] == result) {
state = (3 == state) ? 4 : 0;
} else if (AMR_HEAD[4] == result) {
state = (4 == state) ? 5 : 0;
} else if (AMR_HEAD[5] == result) {
state = (5 == state) ? 6 : 0;
}
if (6 == state) {
break;
}
}
} catch (Exception e) {
Log.e(TAG, "read mdat error...");
}
}
private void readSomeData(byte[] buffer, int offset, int length, DataInputStream dataInput) {
int numOfRead = -1;
while (true) {
try {
numOfRead = dataInput.read(buffer, offset, length);
if (numOfRead == -1) {
Log.d(TAG, "amr...no data get wait for data coming.....");
Thread.sleep(100);
} else {
offset += numOfRead;
length -= numOfRead;
if (length <= 0) {
break;
}
}
} catch (Exception e) {
Log.e(TAG, "amr..error readSomeData");
break;
}
}
}
private void udpSend(DatagramSocket udpSocket, byte[] buffer, int sendLength) {
try {
InetAddress ip = InetAddress.getByName(CommonConfig.SERVER_IP_ADDRESS.trim());
int port = CommonConfig.AUDIO_SERVER_UP_PORT;
byte[] sendBuffer = new byte[sendLength];
System.arraycopy(buffer, 0, sendBuffer, 0, sendLength);
DatagramPacket packet = new DatagramPacket(sendBuffer, sendLength);
packet.setAddress(ip);
packet.setPort(port);
udpSocket.send(packet);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
播放器：
package cn.edu.xmu.zgy.audio.player;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.InetAddress;
import java.net.Socket;
import cn.edu.xmu.zgy.config.CommonConfig;
import android.app.Activity;
import android.media.MediaPlayer;
import android.os.Handler;
import android.util.Log;
//blog.csdn.net/zgyulongfei
//Email: [email protected]
public class AmrAudioPlayer {
private static final String TAG = "AmrAudioPlayer";
private static AmrAudioPlayer playerInstance = null;
private long alreadyReadByteCount = 0;
private MediaPlayer audioPlayer;
private Handler handler = new Handler();
private final String cacheFileName = "audioCacheFile";
private File cacheFile;
private int cacheFileCount = 0;
// 用來記錄是否已經從cacheFile中複製數據到另一個cache中
private boolean hasMovedTheCacheFlag;
private boolean isPlaying;
private Activity activity;
private boolean isChaingCacheToAnother;
private AmrAudioPlayer() {
}
public static AmrAudioPlayer getAmrAudioPlayerInstance() {
if (playerInstance == null) {
synchronized (AmrAudioPlayer.class) {
if (playerInstance == null) {
playerInstance = new AmrAudioPlayer();
}
}
}
return playerInstance;
}
public void initAmrAudioPlayer(Activity activity) {
this.activity = activity;
deleteExistCacheFile();
initCacheFile();
}
private void deleteExistCacheFile() {
File cacheDir = activity.getCacheDir();
File[] needDeleteCacheFiles = cacheDir.listFiles();
for (int index = 0; index < needDeleteCacheFiles.length; ++index) {
File cache = needDeleteCacheFiles[index];
if (cache.isFile()) {
if (cache.getName().contains(cacheFileName.trim())) {
Log.e(TAG, "delete cache file: " + cache.getName());
cache.delete();
}
}
}
needDeleteCacheFiles = null;
}
private void initCacheFile() {
cacheFile = null;
cacheFile = new File(activity.getCacheDir(), cacheFileName);
}
public void start() {
isPlaying = true;
isChaingCacheToAnother = false;
setHasMovedTheCacheToAnotherCache(false);
new Thread(new NetAudioPlayerThread()).start();
}
public void stop() {
isPlaying = false;
isChaingCacheToAnother = false;
setHasMovedTheCacheToAnotherCache(false);
releaseAudioPlayer();
deleteExistCacheFile();
cacheFile = null;
handler = null;
}
private void releaseAudioPlayer() {
playerInstance = null;
if (audioPlayer != null) {
try {
if (audioPlayer.isPlaying()) {
audioPlayer.pause();
}
audioPlayer.release();
audioPlayer = null;
} catch (Exception e) {
}
}
}
private boolean hasMovedTheCacheToAnotherCache() {
return hasMovedTheCacheFlag;
}
private void setHasMovedTheCacheToAnotherCache(boolean result) {
hasMovedTheCacheFlag = result;
}
private class NetAudioPlayerThread implements Runnable {
// 從接受數據開始計算，當緩存大於INIT_BUFFER_SIZE時候開始播放
private final int INIT_AUDIO_BUFFER = 2 * 1024;
// 剩1秒的時候播放新的緩存的音樂
private final int CHANGE_CACHE_TIME = 1000;
public void run() {
try {
Socket socket = createSocketConnectToServer();
receiveNetAudioThenPlay(socket);
} catch (Exception e) {
Log.e(TAG, e.getMessage() + "從服務端接受音頻失敗。。。");
}
}
private Socket createSocketConnectToServer() throws Exception {
String hostName = CommonConfig.SERVER_IP_ADDRESS;
InetAddress ipAddress = InetAddress.getByName(hostName);
int port = CommonConfig.AUDIO_SERVER_DOWN_PORT;
Socket socket = new Socket(ipAddress, port);
return socket;
}
private void receiveNetAudioThenPlay(Socket socket) throws Exception {
InputStream inputStream = socket.getInputStream();
FileOutputStream outputStream = new FileOutputStream(cacheFile);
final int BUFFER_SIZE = 100 * 1024;// 100kb buffer size
byte[] buffer = new byte[BUFFER_SIZE];
// 收集了10*350b了之後纔開始更換緩存
int testTime = 10;
try {
alreadyReadByteCount = 0;
while (isPlaying) {
int numOfRead = inputStream.read(buffer);
if (numOfRead <= 0) {
break;
}
alreadyReadByteCount += numOfRead;
outputStream.write(buffer, 0, numOfRead);
outputStream.flush();
try {
if (testTime++ >= 10) {
Log.e(TAG, "cacheFile=" + cacheFile.length());
testWhetherToChangeCache();
testTime = 0;
}
} catch (Exception e) {
// TODO: handle exception
}
// 如果複製了接收網絡流的cache，則執行此操作
if (hasMovedTheCacheToAnotherCache() && !isChaingCacheToAnother) {
if (outputStream != null) {
outputStream.close();
outputStream = null;
}
// 將接收網絡流的cache刪除，然後重0開始存儲
// initCacheFile();
outputStream = new FileOutputStream(cacheFile);
setHasMovedTheCacheToAnotherCache(false);
alreadyReadByteCount = 0;
}
}
} catch (Exception e) {
errorOperator();
e.printStackTrace();
Log.e(TAG, "socket disconnect...:" + e.getMessage());
throw new Exception("socket disconnect....");
} finally {
buffer = null;
if (socket != null) {
socket.close();
}
if (inputStream != null) {
inputStream.close();
inputStream = null;
}
if (outputStream != null) {
outputStream.close();
outputStream = null;
}
stop();
}
}
private void testWhetherToChangeCache() throws Exception {
if (audioPlayer == null) {
firstTimeStartPlayer();
} else {
changeAnotherCacheWhenEndOfCurrentCache();
}
}
private void firstTimeStartPlayer() throws Exception {
// 當緩存已經大於INIT_AUDIO_BUFFER則開始播放
if (alreadyReadByteCount >= INIT_AUDIO_BUFFER) {
Runnable r = new Runnable() {
public void run() {
try {
File firstCacheFile = createFirstCacheFile();
// 設置已經從cache中複製數據，然後會刪除這個cache
setHasMovedTheCacheToAnotherCache(true);
audioPlayer = createAudioPlayer(firstCacheFile);
audioPlayer.start();
} catch (Exception e) {
Log.e(TAG, e.getMessage() + " :in firstTimeStartPlayer() fun");
} finally {
}
}
};
handler.post(r);
}
}
private File createFirstCacheFile() throws Exception {
String firstCacheFileName = cacheFileName + (cacheFileCount++);
File firstCacheFile = new File(activity.getCacheDir(), firstCacheFileName);
// 爲什麼不直接播放cacheFile，而要複製cacheFile到一個新的cache，然後播放此新的cache？
// 是爲了防止潛在的讀/寫錯誤，可能在寫入cacheFile的時候，
// MediaPlayer正試圖讀數據， 這樣可以防止死鎖的發生。
moveFile(cacheFile, firstCacheFile);
return firstCacheFile;
}
private void moveFile(File oldFile, File newFile) throws IOException {
if (!oldFile.exists()) {
throw new IOException("oldFile is not exists. in moveFile() fun");
}
if (oldFile.length() <= 0) {
throw new IOException("oldFile size = 0. in moveFile() fun");
}
BufferedInputStream reader = new BufferedInputStream(new FileInputStream(oldFile));
BufferedOutputStream writer = new BufferedOutputStream(new FileOutputStream(newFile,
false));
final byte[] AMR_HEAD = new byte[] { 0x23, 0x21, 0x41, 0x4D, 0x52, 0x0A };
writer.write(AMR_HEAD, 0, AMR_HEAD.length);
writer.flush();
try {
byte[] buffer = new byte[1024];
int numOfRead = 0;
Log.d(TAG, "POS...newFile.length=" + newFile.length() + " old=" + oldFile.length());
while ((numOfRead = reader.read(buffer, 0, buffer.length)) != -1) {
writer.write(buffer, 0, numOfRead);
writer.flush();
}
Log.d(TAG, "POS..AFTER...newFile.length=" + newFile.length());
} catch (IOException e) {
Log.e(TAG, "moveFile error.. in moveFile() fun." + e.getMessage());
throw new IOException("moveFile error.. in moveFile() fun.");
} finally {
if (reader != null) {
reader.close();
reader = null;
}
if (writer != null) {
writer.close();
writer = null;
}
}
}
private MediaPlayer createAudioPlayer(File audioFile) throws IOException {
MediaPlayer mPlayer = new MediaPlayer();
// It appears that for security/permission reasons, it is better to
// pass
// a FileDescriptor rather than a direct path to the File.
// Also I have seen errors such as "PVMFErrNotSupported" and
// "Prepare failed.: status=0x1" if a file path String is passed to
// setDataSource(). So unless otherwise noted, we use a
// FileDescriptor here.
FileInputStream fis = new FileInputStream(audioFile);
mPlayer.reset();
mPlayer.setDataSource(fis.getFD());
mPlayer.prepare();
return mPlayer;
}
private void changeAnotherCacheWhenEndOfCurrentCache() throws IOException {
// 檢查當前cache剩餘時間
long theRestTime = audioPlayer.getDuration() - audioPlayer.getCurrentPosition();
Log.e(TAG, "theRestTime=" + theRestTime + " isChaingCacheToAnother="
+ isChaingCacheToAnother);
if (!isChaingCacheToAnother && theRestTime <= CHANGE_CACHE_TIME) {
isChaingCacheToAnother = true;
Runnable r = new Runnable() {
public void run() {
try {
File newCacheFile = createNewCache();
// 設置已經從cache中複製數據，然後會刪除這個cache
setHasMovedTheCacheToAnotherCache(true);
transferNewCacheToAudioPlayer(newCacheFile);
} catch (Exception e) {
Log.e(TAG, e.getMessage()
+ ":changeAnotherCacheWhenEndOfCurrentCache() fun");
} finally {
deleteOldCache();
isChaingCacheToAnother = false;
}
}
};
handler.post(r);
}
}
private File createNewCache() throws Exception {
// 將保存網絡數據的cache複製到newCache中進行播放
String newCacheFileName = cacheFileName + (cacheFileCount++);
File newCacheFile = new File(activity.getCacheDir(), newCacheFileName);
Log.e(TAG, "before moveFile............the size=" + cacheFile.length());
moveFile(cacheFile, newCacheFile);
return newCacheFile;
}
private void transferNewCacheToAudioPlayer(File newCacheFile) throws Exception {
MediaPlayer oldPlayer = audioPlayer;
try {
audioPlayer = createAudioPlayer(newCacheFile);
audioPlayer.start();
} catch (Exception e) {
Log.e(TAG, "filename=" + newCacheFile.getName() + " size=" + newCacheFile.length());
Log.e(TAG, e.getMessage() + " " + e.getCause() + " error start..in transfanNer..");
}
try {
oldPlayer.pause();
oldPlayer.reset();
oldPlayer.release();
} catch (Exception e) {
Log.e(TAG, "ERROR release oldPlayer.");
} finally {
oldPlayer = null;
}
}
private void deleteOldCache() {
int oldCacheFileCount = cacheFileCount - 1;
String oldCacheFileName = cacheFileName + oldCacheFileCount;
File oldCacheFile = new File(activity.getCacheDir(), oldCacheFileName);
if (oldCacheFile.exists()) {
oldCacheFile.delete();
}
}
private void errorOperator() {
}
}
}