I'm doing some auditing of my music library (using Mutagen/Python), including looking for duplicates. In particular, I am writing a program to look for duplicates and I am using track-length as part of the way I compare two tracks. In the process of doing that, I'm finding some small discrepancies (say 2 seconds) between the track length of the mp3 version versus the m4a version.
Is this "real" (i.e., the different encoding distorts the track length - yikes!) or is this something to do with how the tags are created or how they are read?
If the difference is real and unavoidable, what comparison tolerance should I be setting for equality?