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[project @ 2006-11-03 18:26:11 by jwe]
author jwe
date Fri, 03 Nov 2006 18:28:37 +0000
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1 @c Copyright (C) 1996, 1997 John W. Eaton
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2 @c Written by Kurt Hornik <Kurt.Hornik@wu-wien.ac.at> on 1996/05/14
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3 @c This is part of the Octave manual.
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4 @c For copying conditions, see the file gpl.texi.
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6 @node Audio Processing
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7 @chapter Audio Processing
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8
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9 Octave provides a few functions for dealing with audio data. An audio
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10 `sample' is a single output value from an A/D converter, i.e., a small
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11 integer number (usually 8 or 16 bits), and audio data is just a series
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12 of such samples. It can be characterized by three parameters: the
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13 sampling rate (measured in samples per second or Hz, e.g. 8000 or
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14 44100), the number of bits per sample (e.g. 8 or 16), and the number of
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15 channels (1 for mono, 2 for stereo, etc.).
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17 There are many different formats for representing such data. Currently,
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18 only the two most popular, @emph{linear encoding} and @emph{mu-law
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19 encoding}, are supported by Octave. There is an excellent FAQ on audio
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20 formats by Guido van Rossum <guido@@cwi.nl> which can be found at any
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21 FAQ ftp site, in particular in the directory
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22 @file{/pub/usenet/news.answers/audio-fmts} of the archive site
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23 @code{rtfm.mit.edu}.
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25 Octave simply treats audio data as vectors of samples (non-mono data are
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26 not supported yet). It is assumed that audio files using linear
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27 encoding have one of the extensions @file{lin} or @file{raw}, and that
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28 files holding data in mu-law encoding end in @file{au}, @file{mu}, or
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29 @file{snd}.
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31 @DOCSTRING(lin2mu)
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33 @DOCSTRING(mu2lin)
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35 @DOCSTRING(loadaudio)
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37 @DOCSTRING(saveaudio)
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39 The following functions for audio I/O require special A/D hardware and
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40 operating system support. It is assumed that audio data in linear
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41 encoding can be played and recorded by reading from and writing to
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42 @file{/dev/dsp}, and that similarly @file{/dev/audio} is used for mu-law
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43 encoding. These file names are system-dependent. Improvements so that
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44 these functions will work without modification on a wide variety of
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45 hardware are welcome.
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47 @DOCSTRING(playaudio)
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49 @DOCSTRING(record)
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51 @DOCSTRING(setaudio)
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