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## Copyright (C) 1999 Paul Kienzle
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
## -*- texinfo -*-
## @deftypefn {Function File} {[@var{x},@var{fs},@var{sampleformat}] =} auload (@var{filename})
##
## Reads an audio waveform from a file given by the string @var{filename}.
## Returns the audio samples in data, one column per channel, one row per
## time slice. Also returns the sample rate and stored format (one of ulaw,
## alaw, char, short, long, float, double). The sample value will be
## normalized to the range [-1,1] regardless of the stored format.
##
## @example
## [x, fs] = auload(file_in_loadpath("sample.wav"));
## auplot(x,fs);
## @end example
##
## Note that translating the asymmetric range [-2^n,2^n-1] into the
## symmetric range [-1,1] requires a DC offset of 2/2^n. The inverse
## process used by ausave requires a DC offset of -2/2^n, so loading and
## saving a file will not change the contents. Other applications may
## compensate for the asymmetry in a different way (including previous
## versions of auload/ausave) so you may find small differences in
## calculated DC offsets for the same file.
## @end deftypefn
## 2001-09-04 Paul Kienzle <pkienzle@users.sf.net>
## * skip unknown blocks in WAVE format.
## 2001-09-05 Paul Kienzle <pkienzle@users.sf.net>
## * remove debugging stuff from AIFF format.
## * use data length if it is given rather than reading to the end of file.
## 2001-12-11 Paul Kienzle <pkienzle@users.sf.net>
## * use closed interval [-1,1] rather than open interval [-1,1) internally
function [data, rate, sampleformat] = auload(path)
if (nargin != 1)
usage("[x, fs, sampleformat] = auload('filename.ext')");
end
data = []; # if error then read nothing
rate = 8000;
sampleformat = 'ulaw';
ext = rindex(path, '.');
if (ext == 0)
usage('x = auload(filename.ext)');
end
ext = tolower(substr(path, ext+1, length(path)-ext));
[file, msg] = fopen(path, 'rb');
if (file == -1)
error([ msg, ": ", path]);
end
msg = sprintf('Invalid audio header: %s', path);
## Microsoft .wav format
if strcmp(ext,'wav')
## Header format obtained from sox/wav.c
## April 15, 1992
## Copyright 1992 Rick Richardson
## Copyright 1991 Lance Norskog And Sundry Contributors
## This source code is freely redistributable and may be used for
## any purpose. This copyright notice must be maintained.
## Lance Norskog And Sundry Contributors are not responsible for
## the consequences of using this software.
## check the file magic header bytes
arch = 'ieee-le';
str = setstr(fread(file, 4, 'char')');
if !strcmp(str, 'RIFF')
error(msg);
end
len = fread(file, 1, 'long', 0, arch);
str = setstr(fread(file, 4, 'char')');
if !strcmp(str, 'WAVE')
error(msg);
end
## skip to the "fmt " section, ignoring everything else
while (1)
if feof(file)
error(msg);
end
str = setstr(fread(file, 4, 'char')');
len = fread(file, 1, 'long', 0, arch);
if strcmp(str, 'fmt ')
break;
end
fseek(file, len, SEEK_CUR);
end
## read the "fmt " section
formatid = fread(file, 1, 'short', 0, arch);
channels = fread(file, 1, 'short', 0, arch);
rate = fread(file, 1, 'long', 0, arch);
fread(file, 1, 'long', 0, arch);
fread(file, 1, 'short', 0, arch);
bits = fread(file, 1, 'short', 0, arch);
fseek(file, len-16, SEEK_CUR);
## skip to the "data" section, ignoring everything else
while (1)
if feof(file)
error(msg);
end
str = setstr(fread(file, 4, 'char')');
len = fread(file, 1, 'long', 0, arch);
if strcmp(str, 'data')
break;
end
fseek(file, len, SEEK_CUR);
end
if (formatid == 1)
if bits == 8
sampleformat = 'uchar';
precision = 'uchar';
samples = len;
elseif bits == 16
sampleformat = 'short';
precision = 'short';
samples = len/2;
elseif bits == 32
sampleformat = 'long';
precision = 'long';
samples = len/4;
else
error(msg);
endif
elseif (formatid == 3)
if bits == 32
sampleformat = 'float';
precision = 'float';
samples = len/4;
elseif bits == 64
sampleformat = 'double';
precision = 'double';
samples = len/8;
else
error(msg);
endif
elseif (formatid == 6 && bits == 8)
sampleformat = 'alaw';
precision = 'uchar';
samples = len;
elseif (formatid == 7 && bits == 8)
sampleformat = 'ulaw';
precision = 'uchar';
samples = len;
else
error(msg);
return;
endif
## Sun .au format
elseif strcmp(ext, 'au')
## Header format obtained from sox/au.c
## September 25, 1991
## Copyright 1991 Guido van Rossum And Sundry Contributors
## This source code is freely redistributable and may be used for
## any purpose. This copyright notice must be maintained.
## Guido van Rossum And Sundry Contributors are not responsible for
## the consequences of using this software.
str = setstr(fread(file, 4, 'char')');
magic=' ds.';
invmagic='ds. ';
magic(1) = setstr(0);
invmagic(1) = setstr(0);
if strcmp(str, 'dns.') || strcmp(str, magic)
arch = 'ieee-le';
elseif strcmp(str, '.snd') || strcmp(str, invmagic)
arch = 'ieee-be';
else
error(msg);
end
header = fread(file, 1, 'long', 0, 'ieee-be');
len = fread(file, 1, 'long', 0, 'ieee-be');
formatid = fread(file, 1, 'long', 0, 'ieee-be');
rate = fread(file, 1, 'long', 0, 'ieee-be');
channels = fread(file, 1, 'long', 0, 'ieee-be');
fseek(file, header-24, SEEK_CUR); % skip file comment
## interpret the sample format
if formatid == 1
sampleformat = 'ulaw';
precision = 'uchar';
bits = 12;
samples = len;
elseif formatid == 2
sampleformat = 'uchar';
precision = 'uchar';
bits = 8;
samples = len;
elseif formatid == 3
sampleformat = 'short';
precision = 'short';
bits = 16;
samples = len/2;
elseif formatid == 5
sampleformat = 'long';
precision = 'long';
bits = 32;
samples = len/4;
elseif formatid == 6
sampleformat = 'float';
precision = 'float';
bits = 32;
samples = len/4;
elseif formatid == 7
sampleformat = 'double';
precision = 'double';
bits = 64;
samples = len/8;
else
error(msg);
end
## Apple/SGI .aiff format
elseif strcmp(ext,'aiff')
## Header format obtained from sox/aiff.c
## September 25, 1991
## Copyright 1991 Guido van Rossum And Sundry Contributors
## This source code is freely redistributable and may be used for
## any purpose. This copyright notice must be maintained.
## Guido van Rossum And Sundry Contributors are not responsible for
## the consequences of using this software.
##
## IEEE 80-bit float I/O taken from
## ftp://ftp.mathworks.com/pub/contrib/signal/osprey.tar
## David K. Mellinger
## dave@mbari.org
## +1-831-775-1805
## fax -1620
## Monterey Bay Aquarium Research Institute
## 7700 Sandholdt Road
## check the file magic header bytes
arch = 'ieee-be';
str = setstr(fread(file, 4, 'char')');
if !strcmp(str, 'FORM')
error(msg);
end
len = fread(file, 1, 'long', 0, arch);
str = setstr(fread(file, 4, 'char')');
if !strcmp(str, 'AIFF')
error(msg);
end
## skip to the "COMM" section, ignoring everything else
while (1)
if feof(file)
error(msg);
end
str = setstr(fread(file, 4, 'char')');
len = fread(file, 1, 'long', 0, arch);
if strcmp(str, 'COMM')
break;
end
fseek(file, len, SEEK_CUR);
end
## read the "COMM" section
channels = fread(file, 1, 'short', 0, arch);
frames = fread(file, 1, 'long', 0, arch);
bits = fread(file, 1, 'short', 0, arch);
exp = fread(file, 1, 'ushort', 0, arch); % read a 10-byte float
mant = fread(file, 2, 'ulong', 0, arch);
mant = mant(1) / 2^31 + mant(2) / 2^63;
if (exp >= 32768), mant = -mant; exp = exp - 32768; end
exp = exp - 16383;
rate = mant * 2^exp;
fseek(file, len-18, SEEK_CUR);
## skip to the "SSND" section, ignoring everything else
while (1)
if feof(file)
error(msg);
end
str = setstr(fread(file, 4, 'char')');
len = fread(file, 1, 'long', 0, arch);
if strcmp(str, 'SSND')
break;
end
fseek(file, len, SEEK_CUR);
end
offset = fread(file, 1, 'long', 0, arch);
fread(file, 1, 'long', 0, arch);
fseek(file, offset, SEEK_CUR);
if bits == 8
precision = 'uchar';
sampleformat = 'uchar';
samples = len - 8;
elseif bits == 16
precision = 'short';
sampleformat = 'short';
samples = (len - 8)/2;
elseif bits == 32
precision = 'long';
sampleformat = 'long';
samples = (len - 8)/4;
else
error(msg);
endif
## file extension unknown
else
error('auload(filename.ext) understands .wav .au and .aiff only');
end
## suck in all the samples
if (samples <= 0) samples = Inf; end
data = fread(file, samples, precision, 0, arch);
fclose(file);
## convert samples into range [-1, 1)
if strcmp(sampleformat, 'alaw')
alaw = [ \
-5504, -5248, -6016, -5760, -4480, -4224, -4992, -4736, \
-7552, -7296, -8064, -7808, -6528, -6272, -7040, -6784, \
-2752, -2624, -3008, -2880, -2240, -2112, -2496, -2368, \
-3776, -3648, -4032, -3904, -3264, -3136, -3520, -3392, \
-22016, -20992, -24064, -23040, -17920, -16896, -19968, -18944, \
-30208, -29184, -32256, -31232, -26112, -25088, -28160, -27136, \
-11008, -10496, -12032, -11520, -8960, -8448, -9984, -9472, \
-15104, -14592, -16128, -15616, -13056, -12544, -14080, -13568, \
-344, -328, -376, -360, -280, -264, -312, -296, \
-472, -456, -504, -488, -408, -392, -440, -424, \
-88, -72, -120, -104, -24, -8, -56, -40, \
-216, -200, -248, -232, -152, -136, -184, -168, \
-1376, -1312, -1504, -1440, -1120, -1056, -1248, -1184, \
-1888, -1824, -2016, -1952, -1632, -1568, -1760, -1696, \
-688, -656, -752, -720, -560, -528, -624, -592, \
-944, -912, -1008, -976, -816, -784, -880, -848 ];
alaw = ([ alaw,-alaw]+0.5)/32767.5;
data = alaw(data+1);
elseif strcmp(sampleformat, 'ulaw')
data = mu2lin(data, 0);
elseif strcmp(sampleformat, 'uchar')
## [ 0, 255 ] -> [ -1, 1 ]
data = data/127.5 - 1;
elseif strcmp(sampleformat, 'short')
## [ -32768, 32767 ] -> [ -1, 1 ]
data = (data+0.5)/32767.5;
elseif strcmp(sampleformat, 'long')
## [ -2^31, 2^31-1 ] -> [ -1, 1 ]
data = (data+0.5)/(2^31-0.5);
end
data = reshape(data, channels, length(data)/channels)';
endfunction
%!demo
%! [x, fs] = auload(file_in_loadpath("sample.wav"));
%! auplot(x,fs);