JavaSound:提取一个声道立体声

Question

我有一个立体声波文件，我需要读和播放只选定的频道。实现这一目标的最佳方法是什么？

Answer 1

当您通过AudioInputStream导入wav文件时，使用AudioFileFormat信息将字节转换为PCM。右和左交替的数据。因此，如果行为16位，则每帧将有4个字节.前两个将组装到左侧通道，第二个将组装到右侧通道。(反之亦然-我很难直截了当地记住哪个频道是左还是右)

下面是一个很好的教程，其中包含如何读取一行的示例：http://docs.oracle.com/javase/tutorial/sound/converters.html

可能需要前面的一些教程来帮助澄清。另外，如果您有关于将字节转换为PCM和向后转换的问题，那么已经有几个关于StackOverflow的解释可供参考。应该不难找到他们。

Answer 2

这是一种从多通道直接音频线路(JavaSound)中提取单通道的简单方法。在我的Line6(r)，Helix(r)吉他音效板(8个频道)的尝试，它的工作相当好。我想它适用于任何类型的DataTargetLine。在这种情况下，我们处理基于AudioFormat的16位样本的数据。希望能帮上忙。

    public ArrayList<byte[]> extract16BitsSingleChannels(byte[] audioBuffer, int channels) {

    /* Parameters :
     * 
     * audioBuffer : the buffer that has just been produced by
     * your targetDataLine.read();
     * channels : the number of channels defined in the AudioFormat you 
     * use with the line
     * 
     *  the AudioFormat which I tested :
     *       float sampleRate = 44100; 
     *       int sampleSizeInBits = 16;
     *       int channels = 8;
     *       boolean signed = true;
     *       boolean bigEndian = true;
     */


    /* let's create a container which will receive our "per channel" buffers */

    ArrayList<byte[]> channelsData = new ArrayList<byte[]>();

    /* take care of adjusting the size of the audioBuffer so that 
     * audioBuffer % channels == 0 is true ... because :        
     */

    final int channelLength=audioBuffer.length/channels;

    /* let's create one buffer per channel and place them in the
     * container 
     */

    for (int c=0 ; c < channels ; c++) 

    {
        byte[] channel=new byte[channelLength];
        channelsData.add(channel);
    }

    /* then process bytes from audioBuffer and copy each channels byte 
     * in its dedicated buffer 
     */

    int byteIndex=0; 

    for(int i = 0; i < channelLength; i+=2) //i+=2 for 16 bits=2 Bytes samples
    {
        for (int c=0 ; c < channels ; c++) {
            channelsData.get(c)[i]=audioBuffer[byteIndex];   // 1st Byte
            byteIndex++;
            channelsData.get(c)[i+1]=audioBuffer[byteIndex]; // 2nd Byte
            byteIndex++;
        }

    }

    /* Returns each set of bytes from each channel in its buffer you can use to
       write on whatever Byte streamer you like. */

    return channelsData;   

}