最近在做一个聊天的模块,聊天的模块很简单:
录音-上传-接收-播放
录音
录音部分可以采用MediaRecord和AudioRecord两个类进行录音.但是各有优缺点.
MediaRecord已经封装了很多方法,方便使用.
AudioRecord能获取录音的原生数据,以便对录音二次加工.
在录音过程我采用的是AudioRecord.但是AudioRecord录音数据是PCM格式,数据占用存储空间很大.必须压缩后才能传输.项目中的压缩是项目其他成员写的一个so库进行压缩的,有点不太方便.在网上翻阅了下,其实Android系统内部已经携带有压缩的库文件了.
压缩库
Android自带的有一个Pcm转amr的库:media_jni.so.
但是由于是Android系统内部的库,无法直接使用.根据网上的说明,最终终于弄明白如何使用了.
AmrInputStream
在要使用压缩库的项目中新建包:
com.android.media
在此包中新建AmrInputStream类,代码如下:
public final class AmrInputStream extends InputStream {
static {
System.loadLibrary("media_jni");
}
private final static String TAG = "AmrInputStream";
// frame is 20 msec at 8.000 khz
private final static int SAMPLES_PER_FRAME = 8000 * 20 / 1000;
// pcm input stream
private InputStream mInputStream;
// native handle
private int mGae;
// result amr stream
private byte[] mBuf = new byte[SAMPLES_PER_FRAME * 2];
private int mBufIn = 0;
private int mBufOut = 0;
// helper for bytewise read()
private byte[] mOneByte = new byte[1];
/**
* Create a new AmrInputStream, which converts 16 bit PCM to AMR
* @param inputStream InputStream containing 16 bit PCM.
*/
public AmrInputStream(InputStream inputStream) {
mInputStream = inputStream;
mGae = GsmAmrEncoderNew();
GsmAmrEncoderInitialize(mGae);
}
@Override
public int read() throws IOException {
int rtn = read(mOneByte, 0, 1);
return rtn == 1 ? (0xff & mOneByte[0]) : -1;
}
@Override
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
@Override
public int read(byte[] b, int offset, int length) throws IOException {
if (mGae == 0) throw new IllegalStateException("not open");
// local buffer of amr encoded audio empty
if (mBufOut >= mBufIn) {
// reset the buffer
mBufOut = 0;
mBufIn = 0;
// fetch a 20 msec frame of pcm
for (int i = 0; i < SAMPLES_PER_FRAME * 2; ) {
int n = mInputStream.read(mBuf, i, SAMPLES_PER_FRAME * 2 - i);
if (n == -1) return -1;
i += n;
}
// encode it
mBufIn = GsmAmrEncoderEncode(mGae, mBuf, 0, mBuf, 0);
}
// return encoded audio to user
if (length > mBufIn - mBufOut) length = mBufIn - mBufOut;
System.arraycopy(mBuf, mBufOut, b, offset, length);
mBufOut += length;
return length;
}
@Override
public void close() throws IOException {
try {
if (mInputStream != null) mInputStream.close();
} finally {
mInputStream = null;
try {
if (mGae != 0) GsmAmrEncoderCleanup(mGae);
} finally {
try {
if (mGae != 0) GsmAmrEncoderDelete(mGae);
} finally {
mGae = 0;
}
}
}
}
@Override
protected void finalize() throws Throwable {
if (mGae != 0) {
close();
throw new IllegalStateException("someone forgot to close AmrInputStream");
}
}
//
// AudioRecord JNI interface
//
private static native int GsmAmrEncoderNew();
private static native void GsmAmrEncoderInitialize(int gae);
private static native int GsmAmrEncoderEncode(int gae,
byte[] pcm, int pcmOffset, byte[] amr, int amrOffset) throws IOException;
private static native void GsmAmrEncoderCleanup(int gae);
private static native void GsmAmrEncoderDelete(int gae);
}
AmrEmcoder
只有AmrInputStream类是不够,还需要一个转码的类AmrEncoder,代码如下:
public class AmrEncoder {
public static void pcm2Amr(String pcmPath , String amrPath) {
FileInputStream fis;
try {
fis = new FileInputStream(pcmPath);
pcm2Amr(fis, amrPath);
fis.close();
} catch (FileNotFoundException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void pcm2Amr(InputStream pcmStream, String amrPath) {
try {
AmrInputStream ais = new AmrInputStream(pcmStream);
OutputStream out = new FileOutputStream(amrPath);
byte[] buf = new byte[4096];
int len = -1;
/*
* 下面的AMR的文件头,缺少这几个字节是不行的
*/
out.write(0x23);
out.write(0x21);
out.write(0x41);
out.write(0x4D);
out.write(0x52);
out.write(0x0A);
while((len = ais.read(buf)) >0){
out.write(buf,0,len);
}
out.close();
ais.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
这里有两个方法:
- pcm2Amr(String pcmPath , String amrPath): 将pcm文件转为amr文件
- pcm2Amr(InputStream pcmStream, String amrPath): 将pcm数据流转为amr文件
测试
测试的界面
测试的界面很简单,就一个按钮一个文本显示,布局界面就不再给出,下面是MainActivity代码:
public class MainActivity extends Activity implements OnClickListener{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
private TextView hintView;
private Button startButton;
private void initView() {
startButton = (Button) findViewById(R.id.btn_start);
startButton.setOnClickListener(this);
hintView = (TextView) findViewById(R.id.hint);
}
@Override
public void onClick(View v) {
if (v.getId() == R.id.btn_start) {
transferButtonClicked();
}
}
private void transferButtonClicked(){
showWaitDialog();
startTransfer();
}
private ProgressDialog waitDialog;
private void showWaitDialog(){
waitDialog = new ProgressDialog(this);
waitDialog.setTitle(getResources().getString(R.string.transfer_wait_title));
waitDialog.setMessage(getResources().getString(R.string.transfer_wait_message));
waitDialog.show();
}
private void startTransfer() {
new TransferThread(this, new TransferCallback() {
@Override
public void onSuccess() {
transferSuccess();
}
@Override
public void onFailed() {
}
}).start();
}
private void transferSuccess() {
runOnUiThread(new Runnable() {
@Override
public void run() {
waitDialog.dismiss();
hintView.setText(getResources().getString(R.string.transfer_result));
ToastUtil.showShort(MainActivity.this, R.string.success_hint);
}
});
}
}
转换线程
由于文件转换是耗时操作,所以需要一个转换线程来实现文件转换.
public class TransferThread extends Thread{
private TransferCallback callback;
private Context context;
public TransferThread(Context context, TransferCallback callback){
this.callback = callback;
this.context = context;
}
@Override
public void run() {
transfer();
}
private void transfer(){
String rootPath = Environment.getExternalStorageDirectory().getPath();
String amrPath = rootPath + "/test.amr";
try {
InputStream pcmStream = context.getAssets().open("test.pcm");
AmrEncoder.pcm2Amr(pcmStream, amrPath);
callback.onSuccess();
} catch (IOException e) {
callback.onFailed();
e.printStackTrace();
}
}
public static interface TransferCallback{
void onSuccess();
void onFailed();
}
}
测试结果
经过测试,160KB的test.pcm压缩后的amr文件大小为15KB,且可以正常播放.
本文的项目文件在此:Pcm2Amr
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