I've been having problems getting MPEG Streamclip, what used to be my best trimming program, to open mp4s. It tosses up an error window saying it's not a recognized file format. I checked the Quicktime components, I do indeed have mpeg4 in there (along with mpeg2, for what it's worth). So why won't it open? Is it just a case of a few bad files, or is the program itself?
It doesn't seem to like mkvs much either, but then again, nothing I've tried seems to, even Avidemux. =/
I have sitting on my comp at the moment: MPEG Streamclip (regular release, and YouTube-compatible beta), Avidemux2, VLC, and for putting it all together, iMovie HD.
Oh how I miss VirtualDub.