How-To Example Code
FFmpeg
FFmpeg is a very powerful tool, we use it primarily to create thumbnails of our Video files, usually directly from FLV but in the case of a Distribution of Linux that has a lack of codec support we use it to create thumbnails of AVI / MPEG videos (sometimes other formats as well).
To create a single 120 by 80 pixel thumbnail of a video frame at the 1 minute and 23 second mark of your video, use the following code.
/path/to/ffmpeg -i '".$video_file."' -f image2 -vcodec mjpeg -s 120x80 -ss 00:01:23 -t 0.001 '".$thumb_filename."'