Algorithm behind swarm downloads?

I'm curious what's happening under the hood with swarm downloads in the context of piecing together files that have different bitrates. Does swarming only use files that have matching bitrates, or is a least common denominator algorithm for bit rates used thereby throwing away data for files recorded at a higher bit rate. Its an intriguing concept and im curious how you solved the problem.

Thanks,
-j

[Taliban]

Files are only used for swarming if they have the same name and the same size.

[Dividend]

Hashes are soon to be added, which runs a file thru an algorithm and punches out a short sequence of numbers and letters. Only identical files can have the same hash, and therefore swarming is made simple, using only files with the same hash. Hashing is also independant of file name, but unfortunately altering the ID3 & Metadata tags will change the hash.