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MathGroup Archive 2005

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Re: Importing part of a WAV file

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60686] Re: Importing part of a WAV file
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sat, 24 Sep 2005 02:55:29 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, U.K.
  • References: <dh0ecg$q3i$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hugh Goyder wrote:
> I have some long sound files in WAV format. Typically files are of length 26
> MB. These files are too long to read in using Import["filename.wav"] and
> anyway I just want portions of the file for Fourier analysis and so I don't
> even want the data in sound file format. How can I read in a fixed number of
> data points from a specified part of the file? To experiment I started with
> generating a short sound file and exporting it as a WAV file. The following
> code does this.
> 
> 
> vals = {f0 -> 1000, tt -> 5, inc -> 1./8192};
> f = 2*Pi*(f0*t - (f0/(2*tt))*t^2) /. vals;
> e = Table[Evaluate[Sin[f]], {t, 0., tt /. vals, inc /. vals}];
> Length[e]
> 
> 
> e1 = ListPlay[e];
> 
> 
> Export["t1.wav", e1]
> 
> 
> 
> Attempts at reading part of the file fail. I can read in the whole file but
> not part of it. In the example below Read does not give any sensible answer.
> Should I be using something other than Record? Is this a case for
> BinaryRead? What is the correct approach? How is the data in WAV files
> organised?
Hi Hugh,

About data organization you may check the following URLs:

http://ccrma.stanford.edu/courses/422/projects/WaveFormat/

http://www.sonicspot.com/guide/wavefiles.html

http://www.tsp.ece.mcgill.ca/MMSP/Documents/AudioFormats/ (this one 
contains also samples of different audio file formats).

Hope this helps,
/J.M.


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