Most of the players do not support MPEG-4 encode, you are advise to use h264 videos.
By default, videos will play at the beginning and play through till the end, however you can customize that through the URL.
MP4 pseudo streaming's "start" and "end" are in seconds unit. For example, you could use the URL: http://example.com/something.mp4?start=12.34&end=55.66 (12.34, 55.66 in seconds)
FLV pseudo streaming's "start" is in bytes unit (no "end" for FLV pseudo streaming). For example: http://example.com/something.flv?start=1200