function [y,fs,wmode,fidx]=readwav(filename,mode,nmax,nskip)
%READWAV Read a .WAV format sound file [Y,FS,WMODE,FIDX]=(FILENAME,MODE,NMAX,NSKIP)
%
% Input Parameters:
%
% FILENAME gives the name of the file (with optional .WAV extension) or alternatively
% can be the FIDX output from a previous call to READWAV
% MODE specifies the following (*=default):
%
% Scaling: 's' Auto scale to make data peak = +-1
% 'r' Raw unscaled data (integer values)
% 'q' Scaled to make 0dBm0 be unity mean square
% 'p' * Scaled to make +-1 equal full scale
% 'o' Scale to bin centre rather than bin edge (e.g. 127 rather than 127.5 for 8 bit values)
% (can be combined with n+p,r,s modes)
% 'n' Scale to negative peak rather than positive peak (e.g. 128.5 rather than 127.5 for 8 bit values)
% (can be combined with o+p,r,s modes)
% Offset: 'y' * Correct for offset in <=8 bit PCM data
% 'z' No offset correction
% File I/O: 'f' Do not close file on exit
% 'd' Look in data directory: voicebox('dir_data')
%
% NMAX maximum number of samples to read (or -1 for unlimited [default])
% NSKIP number of samples to skip from start of file
% (or -1 to continue from previous read when FIDX is given instead of FILENAME [default])
%
% Output Parameters:
%
% Y data matrix of dimension (samples,channels)
% FS sample frequency in Hz
% WMODE mode string needed for WRITEWAV to recreate the data file
% FIDX Information row vector containing the element listed below.
%
% (1) file id
% (2) current position in file
% (3) dataoff byte offset in file to start of data
% (4) nsamp number of samples
% (5) nchan number of channels
% (6) nbyte bytes per data value
% (7) bits number of bits of precision
% (8) code Data format: 1=PCM, 2=ADPCM, 6=A-law, 7=Mu-law
% (9) fs sample frequency
%
% If no output parameters are specified, header information will be printed.
%
% For stereo data, y(:,1) is the left channel and y(:,2) the right
%
% See also WRITEWAV.
% *** Note on scaling ***
% If we want to scale signal values in the range +-1 to an integer in the
% range [-128,127] then we have four plausible choices corresponding to
% scale factors of (a) 127, (b) 127.5, (c) 128 or (d) 128.5 but each choice
% has disadvantages.
% For forward scaling: (c) and (d) cause clipping on inputs of +1.
% For reverse scaling: (a) and (b) can generate output values < -1.
% Any of these scalings can be selected via the mode input: (a) 'o', (b) default, (c) 'on', (d) 'n'
% Copyright (C) Mike Brookes 1998-2003
% Version: $Id: readwav.m,v 1.5 2006/11/06 08:16:02 dmb Exp $
%
% VOICEBOX is a MATLAB toolbox for speech processing.
% Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 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 can obtain a copy of the GNU General Public License from
% ftp://prep.ai.mit.edu/pub/gnu/COPYING-2.0 or by writing to
% Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if nargin<1 error('Usage: [y,fs,wmode,fidx]=READWAV(filename,mode,nmax,nskip)'); end
if nargin<2 mode='p';
else mode = [mode(:).' 'p'];
end
k=find((mode>='p') & (mode<='s'));
mno=all(mode~='o'); % scale to input limits not output limits
sc=mode(k(1));
z=128*all(mode~='z');
info=zeros(1,9);
if ischar(filename)
if any(mode=='d')
filename=fullfile(voicebox('dir_data'),filename);
end
fid=fopen(filename,'rb','l');
if fid == -1
fn=[filename,'.wav'];
fid=fopen(fn,'rb','l');
if fid ~= -1 filename=fn; end
end
if fid == -1 error(sprintf('Can''t open %s for input',filename)); end
info(1)=fid;
else
info=filename;
fid=info(1);
end
if ~info(3)
fseek(fid,8,-1); % read riff chunk
header=fread(fid,4,'uchar');
if header' ~= 'WAVE' fclose(fid); error(sprintf('File does not begin with a WAVE chunck')); end
fmt=0;
data=0;
while ~data % loop until FMT and DATA chuncks both found
header=fread(fid,4,'char');
len=fread(fid,1,'ulong');
if header' == 'fmt ' % ******* found FMT chunk *********
fmt=1;
info(8)=fread(fid,1,'ushort'); % format: 1=PCM, 6=A-law, 7-Mu-law
info(5)=fread(fid,1,'ushort'); % number of channels
fs=fread(fid,1,'ulong'); % sample rate in Hz
info(9)=fs; % sample rate in Hz
rate=fread(fid,1,'ulong'); % average bytes per second (ignore)
align=fread(fid,1,'ushort'); % block alignment in bytes (ignore)
info(7)=fread(fid,1,'ushort'); % bits per sample
fseek(fid,len-16,0); % skip to end of header
if any([1 6 7]==info(8)) info(6)=ceil(info(7)/8);
else info(6)=1; sc='r';
end
elseif header' == 'data' % ******* found DATA chunk *********
if ~fmt fclose(fid); error(sprintf('File %s does not contain a FMT chunck',filename)); end
info(4) = fix(len/(info(6)*info(5)));
info(3)=ftell(fid);
data=1;
else % ******* found unwanted chunk *********
fseek(fid,len,0);
end
end
else
fs=info(9);
end
if nargin<4 nskip=info(2);
elseif nskip<0 nskip=info(2);
end
ksamples=info(4)-nskip;
if nargin>2
if nmax>=0
ksamples=min(nmax,ksamples);
end
elseif ~nargout
ksamples=min(5,ksamples);
end
if ksamples>0
info(2)=nskip+ksamples;
pk=pow2(0.5,8*info(6))*(1+(mno/2-all(mode~='n'))/pow2(0.5,info(7))); % use modes o and n to determine effective peak
fseek(fid,info(3)+info(6)*info(5)*nskip,-1);
nsamples=info(5)*ksamples;
if info(6)<3
if info(6)<2
y=fread(fid,nsamples,'uchar');
if info(8)==1 y=y-z;
elseif info(8)==6
y=pcma2lin(y,213,1);
pk=4032+mno*64;
pkp=pk;
elseif info(8)==7
y=pcmu2lin(y,1);
pk=8031+mno*128;
pkp=pk;
end
else
y=fread(fid,nsamples,'short');
end
else % 3 or 4 byte values
if info(6)<4
y=fread(fid,3*nsamples,'uchar');
y=reshape(y,3,nsamples);
y=([1 256 65536]*y-pow2(fix(pow2(y(3,:),-7)),24)).';
else
y=fread(fid,nsamples,'long');
end
end
if sc ~= 'r'
if sc=='s'
sf=1/max(max(abs(y)),1);
elseif sc=='p'
sf=1/pk;
else
if info(8)==7
sf=2.03761563/pk;
else
sf=2.03033976/pk;
end
end
y=sf*y;
else % mode = 'r' - output raw values
if info(8)==1 y=y*pow2(1,info(7)-8*info(6)); end % shift to get the bits correct
end
if info(5)>1 y = reshape(y,info(5),ksamples).'; end
else
y=[];
end
if all(mode~='f') fclose(fid); end
if nargout>2
wmode=setstr([sc 'z'-z/128]);
if info(8)==1 % PCM modes
if ~mno wmode=[wmode 'o']; end
if any(mode=='n') wmode=[wmode 'n']; end
wmode=[wmode num2str(info(7))];
elseif info(8)==6
wmode = [wmode 'a'];
elseif info(8)==7
wmode = [wmode 'u'];
end
fidx=info;
elseif ~nargout
codes=' '*ones(9,6); codes(1+[1 2 6 7],:)=['PCM ';'ADPCM ';'A-law ';'Mu-law'];
fprintf(1,'\n%d Hz sample rate\n%d channel x %d samples = %.3g seconds\ndata type %d: %d bit %s\n',info([9 5 4]),info(4)/info(9), info([8 7]),char(codes(1+max(0,min(8,info(8))),:)));
end
e-REdING. Biblioteca de la Escuela Superior de Ingenieros de Sevilla.
