Best software for trimming from videos without recompressing? (ie Avidemux)

[Iced Coffee]

I've got a large number of videos in a few formats, mainly VC1/WMV3 and MPEG-4 Pt2 ASP. What I'd like to do is simply chop a number of big 5-10 minute chunks out of them, without recompressing. Obviously to do this I need to cut solely on I frames, but that's not a concern.

To do this, I've been using AVIdemux, which does a perfectly good job... when it works. Which is about 1/3 of the time. The rest of the time, the video displays as a garbled mess of purple and green, or it'll display the first 20 minutes of a video and not the rest, or a variety of other bugs and display issues.

MPEG Streamclip can work too, but not on these files. Premiere cuts them perfectly, but doesn't allow a same-as-source/non-recompressed export.

So what tool shoul dI use for this job?

[poisondeathray]

WMV => asfbin

MPEG4-ASP => virtualdub