sync problems when encoding a raw capture

[situationist]

i'm having synch problems with certain captures and i can't figure out why. i'll post as much info as possible to make it easier to diagnose.

here's what i'm doing to capture:

Video:
Pic Video MJPEG codec, quality 20
640x480, 29.976 FPS

Audio: PCM, 44.100 kHz, 172kbps

My hard drive is Fat32, so I use segmented avi's.

Then I use virtual dub to re-encode as follows:

Video:
Divx 3.11 Low Motion
A couple filters to clean it up, etc.

Audio:
MPEG Layer-3, 96kbps, 48,000 Stereo

I've done a bunch of captures like this at about 30 minutes each, with no problem. It's when I try to capture a 60min tv show that I run into problems. The audio ends up out of synch after about 30 minutes on the final encode and I can't figure out why. It seems to get more and more off as it goes too.

When capturing the raw file, I notice that I never drop frames, but when I do, it's like 30 at a time (1.87ghz, 512mb ram, no programs running). Yet when I open the raw files in WMP, the audio is fine.

What gives? I've never had synch problems with DVDs, or even tv shows under 30 minutes. Any help you could offer would be greatly appreciated.

[Fasola_Jan]

Hi :)

Just a wild guess: audio at 48 kHz?

Bye.
Fasola

[theReal]

Just a wild guess: audio at 48 kHz?:confused:
I always capture the audio at 48kHz because my soundcard keeps to this closer than to 44.1kHz and so VDub is dropping much less frames compared to 44.1kHz.


Also a wild guess:
Maybe after 30 min. you are reaching a region of your HD where it's getting slower and so can't keep up with the amount of data anymore?

[Fasola_Jan]

Hi :)

I think situationist capture is:
"Audio: PCM, 44.100 kHz, 172kbps "


Dropped frames because of sound card?
Try this:
http://www-user.rhrk.uni-kl.de/~dittrich/sync/

No need for 48kHz capture :))

Bye.
Fasola

[theReal]

good modification - but unfortunately I need VirtualDub VCR most of the time because of the timer.

Does someone want to join these two mods into one "VirtualDub Sync-VCR"? :D

[situationist]

thanks for the suggestions...

as for the mod, i think you'd be better off making a timer mod for virtual dub.

[theReal]

VirtualDub VCR already is a good timer-mod of VirtualDub.
My problem is that I'd need the audio-sync mod in the same application...