I am using ffmpeg 2.0.1 and python2.7. When I save an animation using the (default) ffmpeg backend I do not get an error but the video comes out all garbled.

This is due to setting the bounding_box=tight option in matplotlibrc (see comments below).

Running the script with --verbose-debug I do get an ffmpeg error:

Invalid buffer size, packet size 2440992 < expected frame_size 3780000944.4kbits/s
Error while decoding stream #0:0: Invalid argument

The full log is here https://gist.github.com/6787110

At the very least we should document this issue, and maybe throw a warning/exception to save people time when they run into this. Pull request #2493 includes a version of this.