Hi, We are trying to figure out playback of our WebM videos in Firefox. Looking at the native video player by going directly to a video url we have some strange behavior. We have found that the browser seems to download the entire video before beginning playback. When the video finally does download and playback, we find that often the playhead will be placed at the end of the video. If the playhead is not at the end of the video, you can't just click play, you have to click a position in the "timeline" to get the video to begin playing. Ideally, the behavior would be that the video beings playback as it starts to download from the beginning of the file. We are encoding the videos with FFMPEG using libvorbis and libvpx. We server our content from Amazon Cloudfront, but can also test from a lighttpd server (same behavior). Please let me know if you would like more information and thank you for your help! Here are a bunch of our videos to look at: http://cdn.computerscience1.net/2013/spring/lectures/1/lecture1-240p.webm http://cdn.computerscience1.net/2013/spring/lectures/1/lecture1-360p.webm http://cdn.computerscience1.net/2013/spring/lectures/1/lecture1-720p.webm http://cdn.computerscience1.net/2013/spring/lectures/1/lecture1-1080p.webm