利用libmp3lame实现在Android上录音MP3文件示例

之前项目需要实现MP3的录音，于是使用上了Lame这个库。这次做一个demo，使用AndroidStudio+Cmake+NDK进行开发。利用Android SDK提供的AndroidRecorder进行录音，得到PCM数据，并使用jni调用Lame这个C库将PCM数据转换为MP3文件。并使用MediaPlayer对录音的MP3文件进行播放。另外此次的按键是仿微信的语音按键，按下录音，松开结束，若中途上滑松开即取消

效果如下：

项目地址: LameMp3ForAndroid_jb51.rar

一、主要类的介绍

• Mp3Recorder―― 是负责调用AudioRecorder进行录音的类
• SimpleLame――是负责将MP3Recorder录制出的PCM数据转换成MP3文件
• DataEncodeThread――是负责执行PCM转MP3的线程
• LameMp3Manager――是对Mp3Recorder的多一次封装，增加了取消后删除之前录制的数据的逻辑
• MediaPlayerUtil――是对系统的MediaPlayer进行简单的封装，使其只需要三步就可以播放音频文件
• MediaRecorderButton ――是一个仿微信录音按键的控件，按下录制，松开结束，录制时上滑则取消录制

二、录制的流程

1. Mp3Recorder调用startRecording()开始录制并初始化DataEncoderThread线程，并定期将录制的PCM数据，传入DataEncoderThread中。
2. 在DataEncoderThread里，SimpleLame将Mp3Recorder传入的PCM数据转换成MP3格式并写入文件，其中SimpleLame通过jni对Lame库进行调用
3. Mp3Recorder调用stopRecording()停止录制，并通知DataEncoderThread线程录制结束，DataEncoderThread将剩余的数据转换完毕。

三、主要的实现代码

Mp3Recorder

public class Mp3Recorder {
static {
System.loadLibrary("lamemp3");
}
//默认采样率
private static final int DEFAULT_SAMPLING_RATE = 44100;
//转换周期，录音每满160帧，进行一次转换
private static final int FRAME_COUNT = 160;
//输出MP3的码率
private static final int BIT_RATE = 32;
//根据资料假定的最大值。 实测时有时超过此值。
private static final int MAX_VOLUME = 2000;
private AudioRecord audioRecord = null;
private int bufferSize;
private File mp3File;
private int mVolume;
private short[] mPCMBuffer;
private FileOutputStream os = null;
private DataEncodeThread encodeThread;
private int samplingRate;
private int channelConfig;
private PCMFormat audioFormat;
private boolean isRecording = false;
private ExecutorService executor = Executors.newFixedThreadPool(1);
private OnFinishListener finishListener;
public interface OnFinishListener {
void onFinish(String mp3SavePath);
}
public Mp3Recorder(int samplingRate, int channelConfig, PCMFormat audioFormat) {
this.samplingRate = samplingRate;
this.channelConfig = channelConfig;
this.audioFormat = audioFormat;
}
public Mp3Recorder() {
this(DEFAULT_SAMPLING_RATE, AudioFormat.CHANNEL_IN_MONO, PCMFormat.PCM_16BIT);
}
public void startRecording(File mp3Save) throws IOException {
if (isRecording) return;
this.mp3File = mp3Save;
if (audioRecord == null) {
initAudioRecorder();
}
audioRecord.startRecording();
Runnable runnable = new Runnable() {
@Override
public void run() {
isRecording = true;
//循环的从AudioRecord获取录音的PCM数据
while (isRecording) {
int readSize = audioRecord.read(mPCMBuffer, 0, bufferSize);
if (readSize > 0) {
//待转换的PCM数据放到转换线程中
encodeThread.addChangeBuffer(mPCMBuffer,readSize);
calculateRealVolume(mPCMBuffer, readSize);
}
}
// 录音完毕，释放AudioRecord的资源
try {
audioRecord.stop();
audioRecord.release();
audioRecord = null;
// 录音完毕，通知转换线程停止，并等待直到其转换完毕
Message msg = Message.obtain(encodeThread.getHandler(), DataEncodeThread.PROCESS_STOP);
msg.sendToTarget();
encodeThread.join();
//转换完毕后回调监听
if(finishListener != null) finishListener.onFinish(mp3File.getPath());
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
if (os != null) {
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
};
executor.execute(runnable);
}
public void stopRecording() throws IOException {
isRecording = false;
}
//计算音量大小
private void calculateRealVolume(short[] buffer, int readSize) {
double sum = 0;
for (int i = 0; i < readSize; i++) {
sum += buffer[i] * buffer[i];
}
if (readSize > 0) {
double amplitude = sum / readSize;
mVolume = (int) Math.sqrt(amplitude);
}
}
public int getVolume(){
if (mVolume >= MAX_VOLUME) {
return MAX_VOLUME;
}
return mVolume;
}
public int getMaxVolume(){
return MAX_VOLUME;
}
public void setFinishListener(OnFinishListener listener){
this.finishListener = listener;
}
private void initAudioRecorder() throws IOException {
int bytesPerFrame = audioFormat.getBytesPerFrame();
//计算缓冲区的大小，使其是设置周期帧数的整数倍，方便循环
int frameSize = AudioRecord.getMinBufferSize(samplingRate, channelConfig, audioFormat.getAudioFormat()) / bytesPerFrame;
if (frameSize % FRAME_COUNT != 0) {
frameSize = frameSize + (FRAME_COUNT - frameSize % FRAME_COUNT);
}
bufferSize = frameSize * bytesPerFrame;
audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, samplingRate, channelConfig, audioFormat.getAudioFormat(), bufferSize);
mPCMBuffer = new short[bufferSize];
SimpleLame.init(samplingRate, 1, samplingRate, BIT_RATE);
os = new FileOutputStream(mp3File);
// 创建转码的线程
encodeThread = new DataEncodeThread(os, bufferSize);
encodeThread.start();
//给AudioRecord设置刷新监听，待录音帧数每次达到FRAME_COUNT，就通知转换线程转换一次数据
audioRecord.setRecordPositionUpdateListener(encodeThread, encodeThread.getHandler());
audioRecord.setPositionNotificationPeriod(FRAME_COUNT);
}
}

DataEncodeThread

public class DataEncodeThread extends Thread implements AudioRecord.OnRecordPositionUpdateListener {
public static final int PROCESS_STOP = 1;
private StopHandler handler;
private byte[] mp3Buffer;
//用于存取待转换的PCM数据
private List<ChangeBuffer> mChangeBuffers = Collections.synchronizedList(new LinkedList<ChangeBuffer>());
private FileOutputStream os;
private CountDownLatch handlerInitLatch = new CountDownLatch(1);
private static class StopHandler extends Handler {
WeakReference<DataEncodeThread> encodeThread;
public StopHandler(DataEncodeThread encodeThread) {
this.encodeThread = new WeakReference<>(encodeThread);
}
@Override
public void handleMessage(Message msg) {
if (msg.what == PROCESS_STOP) {
DataEncodeThread threadRef = encodeThread.get();
//录音停止后，将剩余的PCM数据转换完毕
for (;threadRef.processData() > 0;);
removeCallbacksAndMessages(null);
threadRef.flushAndRelease();
getLooper().quit();
}
super.handleMessage(msg);
}
}
public DataEncodeThread(FileOutputStream os, int bufferSize) {
this.os = os;
mp3Buffer = new byte[(int) (7200 + (bufferSize * 2 * 1.25))];
}
@Override
public void run() {
Looper.prepare();
handler = new StopHandler(this);
handlerInitLatch.countDown();
Looper.loop();
}
public Handler getHandler() {
try {
handlerInitLatch.await();
} catch (InterruptedException e) {
e.printStackTrace();
Log.e(TAG, "Error when waiting handle to init");
}
return handler;
}
@Override
public void onMarkerReached(AudioRecord recorder) {
// Do nothing
}
@Override
public void onPeriodicNotification(AudioRecord recorder) {
//由AudioRecord进行回调，满足帧数，通知数据转换
processData();
}
//从缓存区ChangeBuffers里获取待转换的PCM数据，转换为MP3数据,并写入文件
private int processData() {
if(mChangeBuffers != null && mChangeBuffers.size() > 0) {
ChangeBuffer changeBuffer = mChangeBuffers.remove(0);
short[] buffer = changeBuffer.getData();
int readSize = changeBuffer.getReadSize();
Log.d(TAG, "Read size: " + readSize);
if (readSize > 0) {
int encodedSize = SimpleLame.encode(buffer, buffer, readSize, mp3Buffer);
if (encodedSize < 0) {
Log.e(TAG, "Lame encoded size: " + encodedSize);
}
try {
os.write(mp3Buffer, 0, encodedSize);
} catch (IOException e) {
e.printStackTrace();
Log.e(TAG, "Unable to write to file");
}
return readSize;
}
}
return 0;
}
private void flushAndRelease() {
final int flushResult = SimpleLame.flush(mp3Buffer);
if (flushResult > 0) {
try {
os.write(mp3Buffer, 0, flushResult);
} catch (final IOException e) {
e.printStackTrace();
}
}
}
public void addChangeBuffer(short[] rawData, int readSize){
mChangeBuffers.add(new ChangeBuffer(rawData, readSize));
}
private class ChangeBuffer{
private short[] rawData;
private int readSize;
public ChangeBuffer(short[] rawData, int readSize){
this.rawData = rawData.clone();
this.readSize = readSize;
}
public short[] getData(){
return rawData;
}
public int getReadSize(){
return readSize;
}
}
}

SimpleLame 主要的逻辑是通过jni调用Lame库

public class SimpleLame {
public native static void close();
public native static int encode(short[] buffer_l, short[] buffer_r, int samples, byte[] mp3buf);
public native static int flush(byte[] mp3buf);
public native static void init(int inSampleRate, int outChannel, int outSampleRate, int outBitrate, int quality);
public static void init(int inSampleRate, int outChannel, int outSampleRate, int outBitrate) {
init(inSampleRate, outChannel, outSampleRate, outBitrate, 7);
}
}

#include <cwchar>
#include "SimpleLame.h"
#include "lamemp3/lame.h"
static lame_global_flags *glf = NULL;
void Java_com_clam314_lame_SimpleLame_close(JNIEnv *env, jclass type){
lame_close(glf);
glf = NULL;
}
jint Java_com_clam314_lame_SimpleLame_encode(JNIEnv *env, jclass type, jshortArray buffer_l_,
jshortArray buffer_r_, jint samples, jbyteArray mp3buf_) {
jshort *buffer_l = env->GetShortArrayElements(buffer_l_, NULL);
jshort *buffer_r = env->GetShortArrayElements(buffer_r_, NULL);
jbyte *mp3buf = env->GetByteArrayElements(mp3buf_, NULL);
const jsize mp3buf_size = env->GetArrayLength(mp3buf_);
int result =lame_encode_buffer(glf, buffer_l, buffer_r, samples, (u_char*)mp3buf, mp3buf_size);
env->ReleaseShortArrayElements(buffer_l_, buffer_l, 0);
env->ReleaseShortArrayElements(buffer_r_, buffer_r, 0);
env->ReleaseByteArrayElements(mp3buf_, mp3buf, 0);
return result;
}
jint Java_com_clam314_lame_SimpleLame_flush(JNIEnv *env, jclass type, jbyteArray mp3buf_) {
jbyte *mp3buf = env->GetByteArrayElements(mp3buf_, NULL);
const jsize mp3buf_size = env->GetArrayLength(mp3buf_);
int result = lame_encode_flush(glf, (u_char*)mp3buf, mp3buf_size);
env->ReleaseByteArrayElements(mp3buf_, mp3buf, 0);
return result;
}
void Java_com_clam314_lame_SimpleLame_init__IIIII(JNIEnv *env, jclass type, jint inSampleRate, jint outChannel,
jint outSampleRate, jint outBitrate, jint quality) {
if(glf != NULL){
lame_close(glf);
glf = NULL;
}
glf = lame_init();
lame_set_in_samplerate(glf, inSampleRate);
lame_set_num_channels(glf, outChannel);
lame_set_out_samplerate(glf, outSampleRate);
lame_set_brate(glf, outBitrate);
lame_set_quality(glf, quality);
lame_init_params(glf);
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。

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