Originally posted by biboun OK, then it's codec related or your computer has limited cpu power to read such files ( full HD files are preatty heavy to read).
It could also be a bitpack problem as the software you use to repackage the file doesn't reencode but jst rearranges the way file is written.
rgds
Believe me when I say the problem I describe isn't related to cpu ability. I work in a video production facility that handles HD video in all shapes, sizes and flavours. The machines used are more than adequate for the smooth handling of any kind of HD video. We use Premiere Pro CS5 mainly for editing (being PC based) and it is a pain Pro doesn't support MJPEG compression (it did years ago), though sometimes it can be coaxed to work with that codec but in a very buggy way. Just to rub salt in the wound, try sticking the avi in CS5's Media Encoder and it actually breaks the original file! Never seen that before.
To be honest I'm not entirely sure what causes the problem, I've installed Morgan's MJPEG codec to see if that cures it but to no effect; there is something quirky how the audio is packed and the ability of different softwares to decode it. Still, no biggie as there are decent workarounds as mentioned.
Mac users are unlikely to see (hear) this problem I expect, due to the environment they will be using the files in. PC users however, have much more scope for unexpected weirdness due to the open source nature of a lot of stuff they will be using. But that's a cross us multi-media PC types have to bare unfortunately!