The mp4 file generated from the moviewriter.py example does not appear to work in the browser. I have tested on Firefox 49.0.2 and Chromium 53.0.2785.143. My OS is Ubuntu 16.04, and my matplotlib version is 1.5.3.

Firefox complains that the movie is corrupt, while Chromium gives the message MediaEvent: PIPELINE_ERROR demuxer: no supported streams.

I have found a mailing list thread mentioning this issue, but I'm not sure how the proposed solution:

anim.save('file.mp4', extra_args=['-pix_fmt', 'yuv420p']))

fits into the moviewriter.py example, since the this example uses the saving( ... ) context manager, which does not accept the extra_args argument.

Can this be fixed from matplotlib? or is this a browser / ffmpeg issue?