Frame Rate Adjustments

[edsmith77]

To Any,

I am converting many old VHS tapes to VCD/SVCD depending on the original quality. Anyway, being relatively new, and doing lots of experimenting I found that with my ATI Rage Fury Pro capture card I was getting some macrovision scan lines in my captures. Ignoring that for a moment, I was able to capture at just about any frame rate, resolution without frame loss or anyother side effects. However, those little green scan lines got the better of me and I ran a program to block the Macrovision (which I got from ATI). Well to make a long story short, I can now only capture at 352x240 and not lose audio sych. If I go higher to say 480x480 it captures just fine except within 30 seconds the audio and video are out of sync QUITE NOTICEABLY. All of this is before going to tempgenc for rendering into vcd/svcd. Yet during capture all appears to be just fine. Could this be a setting problem that I have not gotten the input and output rates correctly matched.? Or why do I not have the problem at the lower resoultion that I have at the higher resolution.
Should I have set the input (source) as NTSC film but the output (capture) as NTSC???

Can you help??

Thanks,
Ed

[Poplar]

You didn't tell us what software you are using to capture. If VirtualDub didn't work all right, maybe you should try AVI_IO.

Are video and audio out of synch in raw AVIs you captured also? Or they are only out of synch after TMPG conversion? Did you encode video and audio separately? If not, do it separately.

If it still doesn't work, perhaps you should try capturing video and audio separately, and line them up correctly later. That should be the last resort. I havn't tried it yet. It shouldn't be very hard, except time-consuming. Fiddling with NTSC Film or Video Templates won't help you.

[edsmith77]

Poplar,
Yes, I think it is the raw avi that is out of sync. But this only exists at the higher capture resolutions. For example, I can capture at std vcd parameters. During the capture with vdub everyting appears normal. Now using playback with vdub and at the std vcd parms the audio and video remain insync. However, repeat the capture at say 480x480 (other parms remain the same), now the video and audio are out of sync within 10-15 seconds. In either case, there is minimal frame loss (<5) and at no time does the CPU usage go above 30-40%. The biggest clue during capture that the audio sync is not going well is watching the VT parameter in the audio section of vdub. After about 5 seconds the VT parameter will start to increase in ever increasing amounts. Verification on playback confirms the out of sync problems. However, when VT stays at 0 or some small constant number, no audio sync problems (as is with the lower resolution captures). Most generally, the number increases positively. However, on some captures the number goes negative. This I presume is the relationship to the video stream. For positive numbers I have noticed that the video is ahead of the audio and vice versa for negative numbers.

I have not tried to capture separate video and audio streams. Basically, I do not know how to or have not figured out how to. But, logically, I do not understand how by capturing them separately and then remuxing them together later will solve the problem. Also, separate captures would seem to require playing the source twice, once to capture the video and again to capture the audio or can this be done at the same time.

Or in another tack, maybe it is with the frame rates. If the source is at 23 and the output is at 29, then wouldn't something go out of sync. Like the audio.??? Do not know. Just exploriing all possibilities.

Any help or clues are greatly appreciated.

Ed

[Poplar]

1. Perhaps you'll be luckier with AVI_IO, as reported by some users.

2. Did you check Drop frame to keep Synch option in VDub?

3. Around 5 percent is big time frame drop to me. 10-30 every 100,000 frames is OK, which is 0.01-0.03 percent. Even 0.1 percent is OK. 5 percent? I don't know.

4. Capture video and audio separately works like this:
a) first you capture video in high resolution with no audio. It will help reduce frame drop.
b) then you capture again with VERY LOW res video and high-quality audio.
c) align audio and video correctly based on a certain reference frame(the first frame in title sequence, e.g.)
It may work in some cases, although I have yet to test it.

5. No matter what your source is, VCR always plays it 29.97 fps interlaced and your card capture it 29.97 fps or 60 fields per second. However, if you used NTSC Film Template and you forgot to adjust audio, you are gonna get synch problem.

[edsmith77]

Poplar,
Thanks for the good advice. I will try the separate capture route but I am somewhat hesitant about the remux issue and getting the two streams to start at exactly the same point.
With respect to the <5 statement. That is not % but actual frame count. Thus, 5 over 1900 is a very small amount of loss.
Lastly, I do not think I mistakenly used the Film Template when I wanted the non-Film template. But, hey, I've made dumber mistakes before. I will recheck to be sure.
This is just a very perplexing problem. Can not seem to correlate to any set of parameters or conditions other than at 352x240 no sync problems. Higher resolution than that creates huge sync problems.

Ed.