NAME
Audio::Analyzer
SYNOPSIS
use Audio::Analyzer;
$source = \*FILEHANDLE;
$source = 'input.pcm';
$analyzer = Audio::Analyzer->new(file => $source);
while(defined($readings = $analyzer->next)) {
my $done = $analyzer->progress;
print "$done% completed\n";
}
#useful information
$freqs = $analyzer->freqs; #returns array referenceDESCRIPTION
This module makes it easy to analyze music files with the Fast Fourier Transform and sync the output of the FFT in time for visual representation.
PLUG
See http://musicwatcher.sf.net/ for programs that use this module.
REFERENCE
- $analyzer = Audio::Analyzer->new(%opts)
-
Create a new instance of Audio::Analyzer ready to analyze a file as specified by %opts. The options available are:
- file
-
A required option; must be either a string which is a filename or a reference to an already open filehandle.
- dft_size
-
The size of the number of samples taken per channel for each iteration of next. Default of 1024.
- sample_rate
-
How many samples per second are in the PCM file. Default of 44100.
- bits_per_sample
-
How many bits per sample in the PCM; must be 16. Default of 16.
- channels
-
How many channels of audio is in the PCM; Default 2.
- fps
-
How many frames per second are going to be used for audio/visual sync. Overrides seek_step. No default.
- seek_step
-
How far to move forward every iteration. Overridden by fps. Default is not to do additional seeking which will not create audio/visual synchronized output.
- scaler
-
Use another scaler class besides the default Audio::Analyzer::ACurve; pass in either a string of the name of the class that will be scaling or undef to perform no scaling at all. See below for information on writting your own scaler classes. The currently available scalers are:
- Audio::Analyzer::ACurve
-
A scaling system that maps the output of the Fourier Transform onto an approximation of the human perception of volume for 20-10,000 hz. This makes the most sense of the output of the Fourier Transform if you want to do visual representations of what you are hearing.
- Audio::Analyzer::AutoScaler
-
A scaling system which tracks the peak level and forces all numbers to be between 0 and 1, with 1 being a magnitude of the peak level.
- $channels = $analyzer->next;
-
Iterate once and return the output of the Fourier Transform after scaling. An array ref is returned which has each channel's worth of information in it, as another array ref; the values of the second ref are the magnitude of each frequency.
- $combined = $analyzer->combine($channels);
-
Combine together 2 or more channels of readings into a single array ref. The returned ref contains the RMS of each of the channel specific readings.
- $freqs = $analyzer->freqs;
-
Return an array reference of the frequency numbers that we analyze. This array ref is the same size as the output of $analyzer->next and serves to enumerate each position of that array.
- $completed = $analyzer->progress;
-
Return a number between 0 and 99 that represents in percent how far along in the file we have processed.
SCALER CLASSES
The scaler classes are simple. The scaler will be created through new and a reference to the analyzer object is provided as an argument. The scaler class must return a blessed instance of itself.
To perform scaling, Audio::Analyzer will periodically invoke the scale method of the scaler class. This method must take an array reference which represents the data returned by the FFT for one channel. The scaler modifies the data inside the array reference and does not return any value.
Your scaler class should also force all output to be between 0 and 1.
AUTHOR
This module was created and documented by Tyler Riddle <triddle@gmail.com>. Many thanks to Andrew Rodland who contributed greatly to getting as far as we got.
BUGS
Please report any bugs or feature requests to bug-audio-analyzer@rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Audio::Analyzer. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
Known Bugs
No known bugs at this time.
Copyright 2007 Tyler Riddle, all rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.