BUG: Mpeg4 video format doesn't work for HTML5 video
The mpeg4 setting for ffmpeg_video_codec doesn't work correctly with the HTML5 <video> tag, the needed settings are different. It would make a lot more sense to add another setting with good defaults for html5 video. An example of those settings is here:
http://pitchpublish.com/ffmpeg-commands-for-html5-compatible-videos/
It would also make a lot more sense to not have ffmpeg linked into motion at all and just have the on_motion_detected event receive the raw image input on stdin so that the user can configure ffmpeg or any other encoder with whatever options he chooses.