[matplotlib-devel] Saving animations

[Tony Yu <ts...@gm...>]

I've been using the animations subpackage since it was introduced, but I
only recently tried to save an animation using the `save` method.
Unfortnately, I get a RuntimeError whenever I try to use it:

...
  File
"/Users/Tony/python/devel/mpl/lib/matplotlib/backends/backend_agg.py", line
4
52, in print_raw
    renderer._renderer.write_rgba(filename_or_obj)
RuntimeError: Error writing to file


This can be reproduced with any animation example, e.g.
simple_anim.py<http://matplotlib.sourceforge.net/examples/animation/simple_anim.html>,
by
replacing `plt.show()` with `ani.save('simple_anim.avi')`. The actual error
is from a shell call to ffmpeg, which roughly boils down to:

#~~~~
    import subprocess
    import matplotlib.pyplot as plt

    fig, ax = plt.subplots()
    ax.plot([0, 1])
    command = ['ffmpeg', '-f', 'rawvideo', '-vcodec', 'rawvideo',
               '-s', '800x600', '-pix_fmt', 'rgba', '-r', '5.0',
               '-i', 'pipe:', '-vcodec', 'mpeg4', '-y', 'test.avi']
    proc= subprocess.Popen(command, shell=False, stdout=subprocess.PIPE,
                           stderr=subprocess.STDOUT, stdin=subprocess.PIPE)
    fileobj = proc.stdin
    fig.savefig(fileobj, format='rgba', dpi=100)
#~~~~

(I just copied the ffmpeg command from an example run, so the option values
may vary on other systems.) The error here is the same, and, unfortunately,
not very informative. Is this saving functionality platform dependent? (I'm
on osx.)

Thanks,
-Tony