I have to make a video that will need to be watched on different operating systems. Is there a "universal" video codec that can be played on Windows, OS X and Linux without requiring additional plugins or player other than those that comes on a default clean install of each of those systems? Compression is not an issue, I'm merely looking for compatibility (e.g. for audio, I would use WAV as a universal codec).
Note : I must assume that the video will be distributed in countries where software patents are enforced, and therefore can't rely on the user to install non-free codecs on Linux.