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Unofficial VirtualDub Support Forums > Newbie Questions > Large File Problem

Posted by: Slargos Aug 8 2004, 11:36 PM

I set Vdub to stop capturing after 7200s or 2 hours.

Went fine until 1h 12m at which it stopped capturing. Filesize at this time was 9,63.

Is there an upper limit for filesize, and do I have to compress it more while capturing/only capture 1h at a time?

Posted by: fccHandler Aug 9 2004, 03:11 AM

I doubt it's a file size problem, instead it sounds very much like the infamous 71 minute bug. The following is copied from Avery Lee's site:

QUOTE

Why does my video capture stop at 1 hour, 11 minutes, but I still get audio?

This is a bug in many video capture drivers. The exact limit is actually 2^32 microseconds, or 1 hour, 11 minutes, 34 seconds. Many TV tuner devices are susceptable to this bug, as are the miro/Pinnacle DCxx devices; you may be able to fix the problem simply by upgrading to the latest capture drivers. There are two incarnations of this problem. In the non-fatal version, video frames are still sent to the application, but the timestamp on the video stream starts over from zero. VirtualDub will correct for this problem automatically, allowing you to capture beyond 71 minutes. The other possibility is that the driver stops sending data altogether. VirtualDub will notify you if this occurs, but will not be able to capture past 71 minutes in this case.

Vanilla capture devices based on the Conexant/Brooktree BT848/878 reference drivers are usually either immune to the problem or have the non-fatal form of it. I'm told that the bug in Pinnacle's DC30(+) drivers still exists but is nonfatal as of the 1.41a drivers. As of this writing, the bug in the DC10/10+/20/20+ drivers is fatal and cannot be worked around.

There are apparently a few drivers that are even susceptable to half this limit (35 min.) due to using signed 32-bit arithmetic. VirtualDub does not yet detect or attempt to bypass the 35 minute limit that results.

I encountered the 71 minute bug more than once on my old PC, using an ATI All-In-Wonder 128. I later discovered that changing my capture frame rate from 29.971 to 29.9697 cured it for good, but I'm not sure why. You'll just have to experiment. As Avery points out, the nature of the problem (and its solution, if any) are very dependant on your specific capture card and drivers.