Someone with username "parallax" has investigated which videos are blocked by YouTube's content ID system.

He uploaded dozens of copies of a music video, with a different modification of the audio track on each one. From this, he determined that:

- Audio Content ID seems to match against the first 30 seconds of each song.

- In general, a change to speed or pitch of 5% or more made Audio Content ID think it was a different song.

- A speed-up of 5% is similar to what happens when a movie (made at 24 frames per second) is played on PAL TV (at 25 frames per second).

- The matching is very resistant to noise, and didn't fail until the music was almost unlistenable due to the added noise.

Full details of the experiments:
http://www.csh.rit.edu/~parallax/

[Moved from "How to test YouTube's Content ID system" – Tony]

http://www.csh.rit.edu/%7Eparallax/

via http://www.eff.org/deeplinks/2009/04/testing-youtubes-aud