If you have a wav file (in what format?) you can convert it using the sox program.

– Raw linear, signed 16 bit, mono, 8000 Hz (.slin)

    sox file.wav -t raw -r 8000 -c 1 -w -s file.slin

– Raw mu-law, mono, 8000 Hz (.mulaw or .u)

    sox file.wav -t raw -r 8000 -c 1 -b 8 -U file.mulaw

– Raw A-law, mono, 8000 Hz (.alaw or .A)

    sox file.wav -t raw -r 8000 -c 1 -b 8 -A file.alaw

– Raw GSM, mono, 8000 Hz (.gsm)

    sox file.wav -t raw -r 8000 -c 1 -b 8 -g file.gsm
    (not all versions of sox support this conversion)

– SUN/SGI audio/basic file, mono 8000 Hz (.au) containing:

    - Signed linear
        sox file.wav -r 8000 -c 1 -w -s file.au
    - alaw
        sox file.wav -r 8000 -c 1 -b 8 -A file.au
    - mulaw
        sox file.wav -r 8000 -c 1 -b 8 -U file.au

In addition basic format “conversion” if needed:

– WAV into RAW (tested with an A-law, mono, 8000 Hz riff wavefile)

    sox file.wav file.raw

The SUN/SGI formats have the advantage of being easily playable in a Web browser and it also preserves the format information.

The output format should always be mono, 8 kHz as that is required for telephony.

Converting into WAV files

If you have a mono 8kHz raw data file you can convert it into wave file by using sox

– Raw A-law, mono, 8000 Hz (.alaw or .A)

    sox -t raw -r 8000 -A -b 8 -c 1 file.alaw file.wav

– mulaw, mono 8000 Hz (.mulaw)

    sox -t raw -r 8000 -U -b 8 -c 1 file.mulaw test.wav