Convert PCM raw bytes to WAV bytes

1
votes

I am listening to live phone calls and am able to get the raw PCM bytes. I also able to listen to these bytes through java's audio api. These all works on an applet.

Now I want to be able to convert the raw PCM bytes of the phone call to WAV bytes so I could write it directly to a ServletOutputStream. This would allow browsers to actually listen to the phone calls.

Does anybody have any idea how I would be able to convert, on the fly, some raw PCM bytes[] to WAV bytes[]?

The examples I've seen all pertain to converting a file to another file.

java pcm to wav

How can I write a WAV file from byte array in java?

Thank you.

2
javahtml5-audiowavpcmtranscoding
The two links you provide look like valid solutions in that they create the WAVE header that lacks to your raw data. – maxime.bochon
@maxime.bochon: yes they are. The problem though is those solutions do pertain to 'files' and not raw 'bytes[]'. In my case, I don't have the length of the data which is required by the wave header as compared to how those solutions suggest. Again, I only have PCM bytes of an actual phone all and for how long that phone call would last, I don't know. Is there any way to actually stream an infinite wave file to a browser? Thank you. – Miki
That's actually what worried me when I read "be able to convert, on the fly"... I never read about a streaming mode in the WAVE header. Moreover WAVE files have a limit in length if I remember well. You problem is more in the application layer than in the formating layer. Here is a topic related to yours. – maxime.bochon
PCM and WAV are basically the same thing, the only difference is that the wav file has a header. Now, a header needs the audio length to be created properly. Hence, I don't see much of a possibility to create a wav "on the fly". – lCapp
@lCapp: That is true which is why I've given up on this feature. I will have to find another solution to make the feature work. Probably use WebRTC trancoders to get this done with. Thanks! :) – Miki

2 Answers

1
votes

I was also stuck in quite same situation, here's how I figured things out.

public static boolean getWavFile(String filePath, InputStream audioStream) throws IOException {

    boolean result = false;
    try {

        byte[] decodedData = IOUtils.toByteArray(audioStream);

        System.out.println(">>Decoded Data" + Arrays.toString(decodedData));
        File outFile = new File(filePath);
        AudioFormat format = new AudioFormat(8000, 16, 1, true, false);
        AudioSystem.write(new AudioInputStream(new ByteArrayInputStream(
                decodedData), format, decodedData.length), AudioFileFormat.Type.WAVE, outFile);
        result = true;
        return result;
    } catch (IOException ex) {
        System.out.println("<<getWavFile - impl" + ex);
        return result;

    }
}
1
votes

It is been a while but I think this might help someone. Here is my solution - I am writing bytes back to the any output stream (In my case it is servletoutputstream). First, I write WAV header(44 bytes) to output stream and write the pcm bytes (You need to convert pcm data to byte array). I used audio tag in html and specified src tag as my api url and it worked perfectly fine.

public void streamCloudObject(OutputStream stream, InputStream pcmData) throws IOException {

    stream.write(WAVHeader.build(44100,5242880));
    //byte_chunk_size is stream buffer size, I have it as 1MB, so at a time you are streaming 1MB of bytes
    byte[] outBytes = new byte[BYTE_CHUNK_SIZE];

    while(true) {   
        int r = pcmData.read(outBytes);
        if(r == -1)
            break;      
        stream.write(outBytes,0,r); 

    }

}


public class WAVHeader {

private static final int CHUNK_SIZE = 36;
private static final int BIT_RATE_16 = 16;
private static final int MONO = 1;
private static final int HEADER_SIZE = 44;

//inputStreamLength - I send the pcm filesize here and I get it from s3.
public static byte[] build(int sampleRate,int inputStreamLength) {

    byte[] header = new byte[HEADER_SIZE];
    int srate = resp.getSampleRate();
    int channel = MONO;
    int format = BIT_RATE_16;
    long dataLength = inputStreamLength;

    long totalDataLen = dataLength + CHUNK_SIZE;
    long bitrate = srate * channel * format;

    header[0] = 'R'; 
    header[1] = 'I';
    header[2] = 'F';
    header[3] = 'F';
    header[4] = (byte) (totalDataLen & 0xff);
    header[5] = (byte) ((totalDataLen >> 8) & 0xff);
    header[6] = (byte) ((totalDataLen >> 16) & 0xff);
    header[7] = (byte) ((totalDataLen >> 24) & 0xff);
    header[8] = 'W';
    header[9] = 'A';
    header[10] = 'V';
    header[11] = 'E';
    header[12] = 'f'; 
    header[13] = 'm';
    header[14] = 't';
    header[15] = ' ';
    header[16] = (byte) format; 
    header[17] = 0;
    header[18] = 0;
    header[19] = 0;
    header[20] = 1; 
    header[21] = 0;
    header[22] = (byte) channel; 
    header[23] = 0;
    header[24] = (byte) (srate & 0xff);
    header[25] = (byte) ((srate >> 8) & 0xff);
    header[26] = (byte) ((srate >> 16) & 0xff);
    header[27] = (byte) ((srate >> 24) & 0xff);
    header[28] = (byte) ((bitrate / 8) & 0xff);
    header[29] = (byte) (((bitrate / 8) >> 8) & 0xff);
    header[30] = (byte) (((bitrate / 8) >> 16) & 0xff);
    header[31] = (byte) (((bitrate / 8) >> 24) & 0xff);
    header[32] = (byte) ((channel * format) / 8); 
    header[33] = 0;
    header[34] = 16; 
    header[35] = 0;
    header[36] = 'd';
    header[37] = 'a';
    header[38] = 't';
    header[39] = 'a';
    header[40] = (byte) (dataLength  & 0xff);
    header[41] = (byte) ((dataLength >> 8) & 0xff);
    header[42] = (byte) ((dataLength >> 16) & 0xff);
    header[43] = (byte) ((dataLength >> 24) & 0xff);
    return header;
}
}