我目前正在开发一个具有录音和播放功能的
Android应用程序.我是处理音频的新手,我在编码和格式方面遇到了一些麻烦.
我能够在我的应用程序中录制和播放音频,但在导出时我无法重现音频.我找到的唯一方法是导出我的.pcm文件并使用Audacity进行转换.
这是我记录音频的代码是：
private Thread recordingThread private AudioRecord mRecorder; private boolean isRecording = false; private void startRecording() { mRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC,Constants.RECORDER_SAMPLERATE,Constants.RECORDER_CHANNELS,Constants.RECORDER_AUdio_ENCODING,Constants.BufferElements2Rec * Constants.BytesPerElement); mRecorder.startRecording(); isRecording = true; recordingThread = new Thread(new Runnable() { public void run() { writeAudioDataToFile(); } },"AudioRecorder Thread"); recordingThread.start(); } private void writeAudioDataToFile() { // Write the output audio in byte FileOutputStream os = null; try { os = new FileOutputStream(mFileName); } catch (FileNotFoundException e) { e.printStackTrace(); } while (isRecording) { // gets the voice output from microphone to byte format mRecorder.read(sData,Constants.BufferElements2Rec); try { // // writes the data to file from buffer // // stores the voice buffer byte bData[] = short2byte(sData); os.write(bData,Constants.BufferElements2Rec * Constants.BytesPerElement); } catch (IOException e) { e.printStackTrace(); } } try { os.close(); } catch (IOException e) { e.printStackTrace(); } }
要播放录制的音频,代码为：
private void startPlaying() {
new Thread(new Runnable() {
public void run() {
try {
File file = new File(mFileName);
byte[] audioData = null;
InputStream inputStream = new FileInputStream(mFileName);
audioData = new byte[Constants.BufferElements2Rec];
mPlayer = new AudioTrack(AudioManager.STREAM_MUSIC,AudioFormat.CHANNEL_OUT_MONO,Constants.BufferElements2Rec * Constants.BytesPerElement,AudioTrack.MODE_STREAM);
final float duration = (float) file.length() / Constants.RECORDER_SAMPLERATE / 2;
Log.i(TAG,"PLAYBACK AUdio");
Log.i(TAG,String.valueOf(duration));
mPlayer.setPositionNotificationPeriod(Constants.RECORDER_SAMPLERATE / 10);
mPlayer.setNotificationMarkerPosition(Math.round(duration * Constants.RECORDER_SAMPLERATE));
mPlayer.play();
int i = 0;
while ((i = inputStream.read(audioData)) != -1) {
try {
mPlayer.write(audioData,i);
} catch (Exception e) {
Log.e(TAG,"Exception: " + e.getLocalizedMessage());
}
}
} catch (FileNotFoundException fe) {
Log.e(TAG,"File not found: " + fe.getLocalizedMessage());
} catch (IOException io) {
Log.e(TAG,"IO Exception: " + io.getLocalizedMessage());
}
}
}).start();
}
Constants类中定义的常量是：
public class Constants {
final static public int RECORDER_SAMPLERATE = 44100;
final static public int RECORDER_CHANNELS = AudioFormat.CHANNEL_IN_MONO;
final static public int RECORDER_AUdio_ENCODING = AudioFormat.ENCODING_PCM_16BIT;
final static public int BufferElements2Rec = 1024; // want to play 2048 (2K) since 2 bytes we use only 1024
final static public int BytesPerElement = 2; // 2 bytes in 16bit format
}
如果我按原样导出文件,我将其转换为Audacity并播放.但是,我需要以可以自动播放的格式导出它.
我已经看到了实施Lame的答案,目前正在研究它.我也找到了使用以下方法转换它的答案：
private File rawToWave(final File rawFile,final String filePath) throws IOException {
File waveFile = new File(filePath);
byte[] rawData = new byte[(int) rawFile.length()];
DataInputStream input = null;
try {
input = new DataInputStream(new FileInputStream(rawFile));
input.read(rawData);
} finally {
if (input != null) {
input.close();
}
}
DataOutputStream output = null;
try {
output = new DataOutputStream(new FileOutputStream(waveFile));
// WAVE header
// see http://ccrma.stanford.edu/courses/422/projects/WaveFormat/
writeString(output,"RIFF"); // chunk id
writeInt(output,36 + rawData.length); // chunk size
writeString(output,"WAVE"); // format
writeString(output,"fmt "); // subchunk 1 id
writeInt(output,16); // subchunk 1 size
writeShort(output,(short) 1); // audio format (1 = PCM)
writeShort(output,(short) 1); // number of channels
writeInt(output,Constants.RECORDER_SAMPLERATE); // sample rate
writeInt(output,Constants.RECORDER_SAMPLERATE * 2); // byte rate
writeShort(output,(short) 2); // block align
writeShort(output,(short) 16); // bits per sample
writeString(output,"data"); // subchunk 2 id
writeInt(output,rawData.length); // subchunk 2 size
// Audio data (conversion big endian -> little endian)
short[] shorts = new short[rawData.length / 2];
ByteBuffer.wrap(rawData).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(shorts);
ByteBuffer bytes = ByteBuffer.allocate(shorts.length * 2);
for (short s : shorts) {
bytes.putShort(s);
}
output.write(bytes.array());
} finally {
if (output != null) {
output.close();
}
}
return waveFile;
}
private void writeInt(final DataOutputStream output,final int value) throws IOException {
output.write(value >> 0);
output.write(value >> 8);
output.write(value >> 16);
output.write(value >> 24);
}
private void writeShort(final DataOutputStream output,final short value) throws IOException {
output.write(value >> 0);
output.write(value >> 8);
}
private void writeString(final DataOutputStream output,final String value) throws IOException {
for (int i = 0; i < value.length(); i++) {
output.write(value.charAt(i));
}
}
但是,这在导出时会播放正确的持续时间,但只是白噪声.
我尝试但无法工作的一些答案：
> Android:Creating Wave file using Raw PCM,the wave file does not play
> How to convert PCM raw data to mp3 file?
> converting pcm file to mp3 using liblame in android
任何人都可以指出什么是最好的解决方案？它是真的实施跛脚还是可以更直接的方式完成？如果是这样,为什么代码示例将文件转换为白噪声？
解决方法
你已经掌握了大部分代码.我能看到的唯一问题是将PCM数据写入WAV文件的部分.这应该很简单,因为WAV =元数据PCM(按此顺序).这应该工作：
private void rawToWave(final File rawFile,final File waveFile) throws IOException {
byte[] rawData = new byte[(int) rawFile.length()];
DataInputStream input = null;
try {
input = new DataInputStream(new FileInputStream(rawFile));
input.read(rawData);
} finally {
if (input != null) {
input.close();
}
}
DataOutputStream output = null;
try {
output = new DataOutputStream(new FileOutputStream(waveFile));
// WAVE header
// see http://ccrma.stanford.edu/courses/422/projects/WaveFormat/
writeString(output,44100); // sample rate
writeInt(output,RECORDER_SAMPLERATE * 2); // byte rate
writeShort(output,rawData.length); // subchunk 2 size
// Audio data (conversion big endian -> little endian)
short[] shorts = new short[rawData.length / 2];
ByteBuffer.wrap(rawData).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(shorts);
ByteBuffer bytes = ByteBuffer.allocate(shorts.length * 2);
for (short s : shorts) {
bytes.putShort(s);
}
output.write(fullyReadFileToBytes(rawFile));
} finally {
if (output != null) {
output.close();
}
}
}
byte[] fullyReadFileToBytes(File f) throws IOException {
int size = (int) f.length();
byte bytes[] = new byte[size];
byte tmpBuff[] = new byte[size];
FileInputStream fis= new FileInputStream(f);
try {
int read = fis.read(bytes,size);
if (read < size) {
int remain = size - read;
while (remain > 0) {
read = fis.read(tmpBuff,remain);
System.arraycopy(tmpBuff,bytes,size - remain,read);
remain -= read;
}
}
} catch (IOException e){
throw e;
} finally {
fis.close();
}
return bytes;
}
private void writeInt(final DataOutputStream output,final String value) throws IOException {
for (int i = 0; i < value.length(); i++) {
output.write(value.charAt(i));
}
}
如何使用
它使用起来非常简单.只需将其称为：
File f1 = new File("/sdcard/44100Sampling-16bit-mono-mic.pcm"); // The location of your PCM file
File f2 = new File("/sdcard/44100Sampling-16bit-mono-mic.wav"); // The location where you want your WAV file
try {
rawToWave(f1,f2);
} catch (IOException e) {
e.printStackTrace();
}
这一切是如何运作的
如您所见,WAV标头是WAV和PCM文件格式之间的唯一区别.假设您正在录制16位PCM MONO音频(根据您的代码,您是). rawToWave函数只是巧妙地将标题添加到WAV文件中,以便音乐播放器知道打开文件时会发生什么,然后在标题之后,它只会从最后一位开始写入PCM数据.
酷提示
如果你想改变你的声音音调,或者做一个语音转换器应用程序,你所要做的就是增加/减少writeInt的值(输出,44100); //代码中的采样率减小它将告诉玩家以不同的速率播放它,从而改变输出音高.只是一点额外的’好知道’的事情.
