Hi,

I did this in a project once and after a lot of searching, this is the best paper I have found on the subject: http://www.owlnet.rice.edu/~elec301/Projects01/beat_sync/beatalgo.html (its Matlab Code)

Here is a small outline of the steps involved in doing this Perl.

1. first convert your mp3 file into a .wav file with the lame encoder (-d option).
2. Using the Win32::Sound module load this .wav file and read the samples.
3. Take a FFT to convert your time signal into frequency domain
4. Optionally, you can use a comb filter (it involves convolving a series of sample signals to determine which signal yields the highest energy) as described in the above paper. Personally, I skipped it

Cheers!
san.

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