Losing audio sync during AVI Capture - ATI AIW

[manub]

I'm almost new into capture, and I liked to capture (not sure if to DivX or DVD yet) TV shows broadcasted by Cable TV. I read lordsmurf guide (thank you very much, lord, keep up the good work), and I set my ATI MMC for an AVI Capture, using Huffyhuv at 640x480 and PCM Native 48KHz 16 bit Stereo Audio. When I start capturing, it shows me a warning for wrong tipe of video standard selected (I select NTSC - PAL-M, to have 640x480 and a proper 4:3 resolution, even if I live in Italy - PAL-B standard). But that's not a problem, I think, as little captures work properly - very smooth and good quality. When I start to capture long videos, however, I notice that the displayed "Frames Recorded", instead of going on 25 by 25 (at the beginning they go like this: 10-35-60-95-110-135 and so on), sometimes lose a frame (135-160-194-209-244...) even with no frame dropped. It goes on and on (about a loss every 20 minutes). When it stops to capture and I playback captured video, audio is initially sync with video, but it loses sync going forward on .AVI file, making it really bad. I notice that there's a little "slowing" on video, immediately followed by correct video, but the audio goes on, so this makes desync. What can be wrong ? In last capture I've also got 3 frames dropped in a specific point of the show, but no other on a total of 170000 (and audio desync begin before this point).

Here's my PC specs related to this:

AMD Athlon XP 2400+
MoBo Asus A7V8X
ATI AIW 8500DV
Sound Blaster Audigy 2 Platinum eX
Western Digital ATA100 80GB HD
Windows XP Professional SP1

Catalyst 3.9, last drivers for SB (don't remember version but I've updated 2-3 days ago) and ATI MMC 8.8.

Thanks for your answers !

post-added: I read questions about ATI issues on sticky topic. I've got a new XP installation about a month ago so no old drivers installed. Need to use VirtualDUB to do AVI capture ? Is the thing I mentioned before on post about not-25 progression important to this ?

[Tommyknocker]

Now run your AVI file through Virtual Dub and scan for bad frames.

[manub]

Deleted it as it happened a while ago (I know, perhaps not a good idea but I did it). Now I'm trying to do something with VirtualDUB... any hope to handle it well ?

[manub]

now I'm trying to capture with VirtualDub (on another computer), after 30 mins of capture at 25fps I've dropped 2 frames and got a VT adjust on audio of -41ms. I will finish the capture and not delete the AVI file to see if it's good. Why do you think of this frame dropping ? Can I solve them ? I think my computer is tuned ... perhaps frame dropped due to bad source (cable TV broadcasting from MPEG2 files not so good - old shows). And, at least ... it's possible to scan an AVI file for bad frames with VirtualDUB ? How ?

Sorry for the questions but I'm really new into this ...

post-added: after 50 mins of capture, dropped frame are 4 with a VT Adjust of -80ms. I think the problem is the same as ATI MMC: gradually audio goes forward video and capture program can't handle it. When VirtualDUB finds audio out of sync, it try to resync but drops frames (this is what I'm thinking - perhaps it's really wrong as I am a newbie). But CPU usage is really low - about 25%. Any suggestions ? I'm capturing to my OS drive as I haven't got space con the other HD.

[Tommyknocker]

now I'm trying to capture with VirtualDub (on another computer), after 30 mins of capture at 25fps I've dropped 2 frames and got a VT adjust on audio of -41ms. I will finish the capture and not delete the AVI file to see if it's good. Why do you think of this frame dropping ? Can I solve them ? I think my computer is tuned ... perhaps frame dropped due to bad source (cable TV broadcasting from MPEG2 files not so good - old shows). And, at least ... it's possible to scan an AVI file for bad frames with VirtualDUB ? How ?

Sorry for the questions but I'm really new into this ...

Click here for guide to scan for bad frames.

Click here for extensive guide to tuning Virtual Dub.

Also, your frame dropping problem really is not that severe. You may want to view your final product and judge for yourself. Also, were you doing anything else on your system while you were capturing?

[manub]

I'm scanning now for bad frames ... watched it (only a little bit in various points) and it's synced. However I wonder how VirtualDUB doesn't adjust audio on the fly, but it does only at some point dropping frames. I'm thinking of an issue with Creative Audio Manager loaded in the Systray ... after this I'll reboot and try a new capture with all TSRs terminated. I did nothing with my system while capturing. I'll keep you updated. Thanks for your help.

[Tommyknocker]

There is also an audio function where you can lock the video to audio as well.

[manub]

I notice that function but it works only in compatibility mode (no compression of course). And I'm using Huffyuv. I scanned my file following the guide you told me about and it found no bad frames. Now I'm trying to recapture it, I'm at about 20 mins and no frame drop but also no VT Adjust. I'm wondering why average frame rate is 24.99901 and not 25.0000 - perhaps this little error goes bigger second by second and affect audio-video sync ? This time I'll finish the capture and let you know.

post - added: got 2 frames dropped at about 25-26 min and VT adjust gradually goes to -41ms. It seems that's a source problem, as it seems the same point as the previous capture dropped, but I'm suspicious about that average frame rate. Is it normal ? I'll let capture end then scan for bad frames ... if I found none and audio synced, I think I'll keep the capture and use it for conversion. Any ideas about this ? and, as time goes on (and dropped frames get high, about 2 every 20 mins), average frame rate gets near to 25 fps (now with 4 frames dropped is about 24.99975)

[manub]

I've scanned my captured files and no bad frames found. I've watched it (not entirely), also seeking from random points, and no desync found. I think that's a good capture - now I'm converting it into DivX. However, I wonder about that 9 frames dropped on a total of 172000 - of course a little percentage, but I hope to drop no frames in the future. Is a capture like the mine "good" ? Hope also to hear from lordsmurf, he's a master of ATI AIW and I'd like to know what he thinks about this.

[lordsmurf]

I only have sync errors if I deinterlace with MMC, and it's minimal and I'd have to look for it.

Otherwise, never an error with sync.