[ILUG] sound files and conversion

[Matthew French]

Declan asked:
> Ideally, I'd like to convert my wav file to a series of x-y points, so
> that I can do some fft to generate a list of x-y points for a 
> spectrum analysis.
>
> Any pointers.

Google for "wav file format"?!?  :)

Seriously, this sounds like my final year University project - which
involved running a WAV file through an FFT.

WAV files are actually dead simple. Take a look at:
http://www.technology.niagarac.on.ca/courses/comp630/WavFileFormat.html

The sound data is stored as amplitude, 1 byte for 8-bit mono, 4 bytes for
16-bit stereo, etc. The only tricky bit is writing an FFT that works. (I
remember squashing bugs for days - all of them silly single character
typos).

Of course, you could do it the easy way and use an FFT library and a sound
file filter library:
# apt-cache search fft
fftw-dev - Library for computing Fast Fourier Transforms
fftw2 - Library for computing Fast Fourier Transforms
grace - An XY plotting tool
libwn-dev - Many numerical and memory management functions
libwn6 - Many numerical and memory management functions
mixviews - Powerful soundfile editor.
octave2.0 - The GNU Octave language for numerical computations (2.0 branch)
octave2.1 - The GNU Octave language for numerical computations (2.1 branch)
paul - Yet another image viewer (displays PNG, TIFF, GIF, JPG, etc.)
python-numeric-ext - Extension modules for Numeric Python
python2.1-numeric-ext - Extension modules for Numeric Python
python2.2-numeric-ext - Extension modules for Numeric Python
sfftw-dev - Library for computing Fast Fourier Transforms
sfftw2 - Library for computing Fast Fourier Transforms
synaesthesia - A program for representing sounds visually

And:
#  apt-cache search audio files library
libsndfile-dev - Library for reading/writing audio files
libsndfile0 - Library for reading/writing audio files

Should be enough to get you started?

HTH,

- Matthew

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