I can't tell you the number of times I've had some "universal" converter unable to properly convert video files with no audio stream. I spent 3 hours on somebody else's computer a day ago trying to convert a damn video for my PSP, but the PSP kept saying it was unsupported and I only found out at the end that it was because the video file lacked an audio stream. Not just PSP, but I run into this a lot. Too many things choke if there's no audio stream. Is there some easy way to insert a blank audio stream into a video file? MP4 or AVI containers are preferable as those are often dealt with either in the middle or as the end product of video work.