Conversion of Audio Format

Question

I am having trouble in converting the audio format of a WAV file.

I am recording sound from my microphone and the sound is recorded in the following format: PCM_SIGNED 44100.0 Hz, 16 bit, mono, 2 bytes/frame

I want to convert the above format to, ULAW 8000.0 Hz, 8 bit, mono, 1 bytes/frame

I am using the following code,

InputStream is = request.getInputStream(); 
            AudioInputStream ais = AudioSystem.getAudioInputStream(is);
            AudioFormat oldFormat = ais.getFormat();
            AudioFormat newFormat = new AudioFormat(AudioFormat.Encoding.ULAW, 8000, 8, 1, 1, 8000, false) ;
AudioInputStream lowResAIS = AudioSystem.getAudioInputStream(newFormat, ais); //Getting the below Exception on this line

And I am getting the following error,

java.lang.IllegalArgumentException: Unsupported conversion: ULAW 8000.0 Hz, 8 bit, mono, 1 bytes/frame, from PCM_SIGNED 44100.0 Hz, 16 bit, mono, 2 bytes/frame, little-endian

Can someone please help me solve this problem!!!

Thanks a ton!!!

Gamboa

Answer 1

Did you take a look at the documentation?

Throws: IllegalArgumentException - if the conversion is not supported #see #getTargetEncodings(AudioFormat)

Not every system will have sufficient codecs installed to transform to the specific format you've asked for. You've assumed yours does, but it's throwing the exception because it can't transform to that format.

You can use getTargetEncodings to check the suitability of a given format programatically, without relying on an exception, and then can take appropriate action if you desired output format isn't available (e.g. fall back to another one, present the user with feedback that this is impossible, etc.).

Ivoryivorywhite

Hey Andrzej! Thanks for the reply. I have partially gone through the documentation. I used the getTargetEncodings() method in the following way code Encoding[] encArr = AudioSystem.getTargetEncodings(oldFormat); for(int i=0;i<encArr.length;i++){ System.out.println(i + "-->"+encArr[i]); } code And i got the following output: 0-->PCM_SIGNED 1-->PCM_UNSIGNED 2-->ALAW 3-->ULAW, What do you have to say about this? Thanks!! – Gamboa

Since I am getting the above output, my system has the codecs to transform to a ULAW format, I am guessing. What could be the other reason for the exception? Any idea? – Gamboa

It might not support some other aspect of the conversion, such as the sample rate or number of bits. I'm not totally up on this, but the fact that you are "downsampling" raises a flag for me. (going from 44100 to 8000). That's usually tricky, as data info with frequencies between 4000 and 22050 Hz will alias unless you filter them out of the data. So my guess is that is not a standard supported conversion. But I bet you could convert to ULAW with 44100 Hz given your output. (My best guess.) – Mandalay

Answer 2

This class may help you. I found it here:

package uk.co.mmscomputing.sound;

import java.io.*;

public class CompressInputStream extends FilterInputStream{

  /*
    Convert mono PCM byte stream into A-Law u-Law byte stream

    static AudioFormat alawformat= new AudioFormat(AudioFormat.Encoding.ALAW,8000,8,1,1,8000,false);
    static AudioFormat ulawformat= new AudioFormat(AudioFormat.Encoding.ULAW,8000,8,1,1,8000,false);

    PCM 8000.0 Hz, 16 bit, mono, SIGNED, little-endian
    static AudioFormat pcmformat = new AudioFormat(8000,16,1,true,false);

  */

  static private Compressor alawcompressor=new ALawCompressor();
  static private Compressor ulawcompressor=new uLawCompressor();

  private Compressor compressor=null;

  public CompressInputStream(InputStream in, boolean useALaw)throws IOException{
    super(in);
    compressor=(useALaw)?alawcompressor:ulawcompressor; 
  }

  public int read()throws IOException{
    throw new IOException(getClass().getName()+".read() :\n\tDo not support simple read().");
  }

  public int read(byte[] b)throws IOException{
    return read(b,0,b.length);
  }

  public int read(byte[] b, int off, int len)throws IOException{
    int     i,sample;
    byte[]  inb;

    inb=new byte[len<<1];          // get 16bit PCM data
    len=in.read(inb);
    if(len==-1){return -1;};

    i=0;
    while(i<len){
      sample   = (inb[i++]&0x00FF);
      sample  |= (inb[i++]<<8);
      b[off++]=(byte)compressor.compress((short)sample);
    }
    return len>>1;
  }
}

abstract class Compressor{
  protected abstract int compress(short sample);    
}

/*
    Mathematical Tools in Signal Processing with C++ and Java Simulations
        by  Willi-Hans Steeb
            International School for Scientific Computing
*/

class ALawCompressor extends Compressor{

  static final int cClip = 32635;

  static final int[] ALawCompressTable ={
    1,1,2,2,3,3,3,3,
    4,4,4,4,4,4,4,4,
    5,5,5,5,5,5,5,5,
    5,5,5,5,5,5,5,5,
    6,6,6,6,6,6,6,6,
    6,6,6,6,6,6,6,6,
    6,6,6,6,6,6,6,6,
    6,6,6,6,6,6,6,6,
    7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7
  };

  protected int compress(short sample){
    int sign;
    int exponent;
    int mantissa;
    int compressedByte;

    sign = ((~sample) >> 8) & 0x80;
    if(sign==0){ sample *= -1;}
    if(sample > cClip){ sample = cClip; }
    if(sample >= 256){
      exponent = ALawCompressTable[(sample >> 8) & 0x007F];
      mantissa = (sample >> (exponent + 3) ) & 0x0F;
      compressedByte = 0x007F & ((exponent << 4) | mantissa);
    }else{
      compressedByte = 0x007F & (sample >> 4);
    }
    compressedByte ^= (sign ^ 0x55);
    return compressedByte;
  }
}

class uLawCompressor extends Compressor{

  static final int cClip = 32635;
  static final int cBias = 0x84;

  int[] uLawCompressTable ={
    0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
    4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
    5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
    5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
    6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
    6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
    6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
    6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
  };

  protected int compress(short sample){
    int sign;
    int exponent;
    int mantissa;
    int compressedByte;

    sign = (sample >> 8) & 0x80;
    if(sign!=0){ sample *= -1;}
    if(sample > cClip){ sample = cClip; }
    sample += cBias;

    exponent = uLawCompressTable[(sample >> 7) & 0x00FF];
    mantissa = (sample >> (exponent + 3)) & 0x0F;
    compressedByte = ~(sign | (exponent << 4) | mantissa);
    return compressedByte&0x000000FF;
  }
}

Bedell

What does that do? Will it help me with the following error? line with format PCM_SIGNED 44100.0 Hz, 16 bit, mono, 2 bytes/frame, little-endian not supported – Wallraff

I have not used it, but it claims to convert "mono PCM byte stream into A-Law u-Law byte stream." That looks like what you are trying to do. It appears that this conversion is not supported directly in Java, you have to do your own compression (as this class does). – Bedell

Turns out my error was because I couldn't use a data line that was already being used (so the error is misleading). Using the Beads sound library solved all my problems (beadsproject.net). – Wallraff

This may not have answered the OP, but this was useful to me for something related. – Vanhook