START = FILEOPEN

FILEOPEN, which is the default value, makes the movie start when the file is opened.

For example, this code

<IMG 
   SRC="../graphics/moonflag.gif" 
   DYNSRC="../graphics/moonflag.mpg" 
   START=FILEOPEN 
   ALT="Astronauts on the moon">

starts the movie as soon as the page is opened: