I have a wav format mono audio file and I have a second file which contains a small clip from that file (so the second file is a much smaller wav file). All I need to know is the approximate start points of the clip within the larger audio file (the clip may be repeated --I would like the byte position of each occurrence.) I'm looking for particular sounds in a speach file

My natural thought was to do a regexp in Perl. I'm running activestate Perl 5.8 on Windows, so I know I have to use binmode to deal with binary files. Some trial and error revealed that to do anything with a regexp with a binary search I have to escape all of the interesting characters in the clip I'm searching for. Here's some code just to try to get the basic concept working:

#!/usr/bin/perl -w
use strict;

my $wordsound = 'balks.wav';
my $lettersound = 'a.wav';
my $letter;

open (WORDSOUND, $wordsound) or die "can't open $wordsound: $!";
binmode (WORDSOUND);
open (LETTERSOUND, $lettersound) or die "can't open $lettersound: $!";
binmode (LETTERSOUND);

#actual data starts on byte 4097
seek (LETTERSOUND, 4097,0);
#100 bytes ought to be OK for identifying the clip
my $error = read (LETTERSOUND, $letter, 100);

my $word = <WORDSOUND>;

#escape all potentially nasty characters with \'s 
#I'm not sure if I'm escaping everything I need to (?)
$letter =~ s/(\\|\||\(|\)|\[|\{|\^|\$|\*|\+|\?|\.)/\\$&/gsm;

$word =~ /$letter/gms;

print pos($word);

[download]

All I get is
"Use of uninitialized value in print at parsesound.pl line 25, <WORDSOUND> line 1."

If anyone has ever looked for a binary string within a binary file and has any code, that'd be great. I would have thought it would be a pretty routine thing, but googling didn't yield much. I didn't see it in the Perl Monks search either. Hmmmm.

For a nice place to live in Portland, OR

In reply to searching for a binary string in a binary file by rochlin

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