If you launch the MediaPlayer from a Terminal with the --help option, you’ll discover that you can control a whole bunch of parameters from the command line. You can specify the volume of the audio, the three different display modes, whether or not to loop, etc. The parameters passed from the command line will override any attributes stored in the movie or sound file by MediaPlayer the last time the file was played.
Note that you can even specify the location in the file from which to start playing — something you can’t control when launching a movie or sound by double-clicking in the Tracker. For example, the following command will cause Animation1 to be launched full-screen and to loop endlessly through the first one second of video:

MediaPlayer -loop on -inpoint 0 -outpoint 1000000 -full Animation1

These options may come in especially handy for creating self-running demo scripts!