Tuesday 14 April 2009

Mp3 BPM calculation and iTunes

I recently bought an iPod touch and started running for fitness. I have a large collection of MP3s and I wanted to get the BPM field completed for all of my MP3s so that I can choose audio based on it's tempo.


After a *lot* of googling I ended up with the following working solution:
a) use the freeware Mixmeister BPM calculator to batch analyse all of the files. This took hours to do but it's the core of it all. Note that this tool outputs accurate bpms to 2 decimal places, which need fixing with the following step.
b) round all of the BPMs up/down to the nearest integer. This is a more recent requirement as apparently iTunes 8.1 and above ignore decimal points for BPM so you *have* to get them all to integers. e.g., 123.4 won't work, 123 will work.
I do this by running scripts through Mp3tag as written here: http://forums.mp3tag.de/lofiversion/index.php/t8295.html
c) I use ITLU (iTunes Library Updater) to tell iTunes the new BPM files have changed and it needs to refresh. If you don't do this, iTunes won't update it's understanding of the BPM.