Screenshots not generated for odd-sized videos

I recently re-transcoded one of my test videos with dimensions 570x321, and found that it had no thumbnails. Further investigation revealed that ffmpeg was throwing a "Frame size must be a multiple of 2" error when asked to generate the screenshots.

The problem appears to be fixed by commenting out this line in _op_video_ffmpeg_create_png:
$params[] = '-s ' . $info['width'] . 'x' . $info['height'];
However, I don't know whether this change could cause other problems, since I haven't done any real testing.