H.264 1080p playback: video-audio desync

[Sovereign]

I have some large, high-def Matroska files. They play fine on several friend's computers (Core2 Quad, Core2 Duo) but my Opteron 170 can't seem to handle them. The audio and video come un-synced and it gets worse as the video plays. 720p content plays back fine.

I've tried the following players/codecs:
- VLC "as-is"
- VLC w/ffdshow
- WMP11 x86 w/ffdshow
- WMP11 x86 w/NVIDIA PureVideo
- WMP11 x64 w/ffdshow x64
- WMP11 x64 w/NVIDIA PureVideo
- Media Player Classic (latest stable) w/ffdshow

In every case, the video plays fine, but the audio starts late and slowly falls further behind. There are blotchy spots in the video as well that do not appear on my friend's computers. In no case do I observe CPU usage above 75% (there's more CPU there if the decoder wants it...)

The system in question is...
Opteron 170 stock, x64 mode
4GB DDR500 @ 400
A8N32-SLI Deluxe
150GB Raptor
2x750GB Caviar AAKS (the video files are on one of these)
2x7900GTX SLI
X-Fi XtremeMusic
Windows Vista Ultimate x64
17" 1280x1024 (hopefully being replaced)

I think that's fast enough, isn't it?

[allenpan]

it runs fine on my....
both pc

both @ XP64

Opteron 185 stock
4GB
X1800XT 512MB
2TG
VLC @ D3D

P-D 4G
8GB
GF7950GX2
4TG
VLC @ OGL

both system only use 105mb @ idle or boot up

very clean system, even my old lesser power one runs fine, 1080p video mkv file

[Sovereign]

Not having the whole file FTL!

We transferred the file over the network, and my friend reset his computer in the middle of it. Because Windows had created the folder for the file and had moved on, we assumed the file was "complete" but lo and behold, filesize on his computer: 8.02GB, filesize on my computer: 7.94GB. Somehow this file played back anyway...