I want to convert an .mp4 file to an .asf file, but I need to keep the size of the file below 150 mb (the server I need to upload the file to can only take files under 150 mb). Basically I want to recontain the .mp4 in an .asf file. The code I'm using currently is ffmpeg input.mp4 -c copy output.asf The command runs, however when I try to play the file on windows media player (I'm on windows xp) I get an error message saying "Windows media player has encountered a problem while playing the file." Anyone have any idea why this is happening? And what other ways I can accomplish this task?