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View Full Version : Capturing from bad source on a TV Tuner card?


GrofLuigi
20th December 2002, 02:27
Hi all,

This is a problem I often encounter when I capture from bad sources. My system is otherwise fine optimized (as much as it can get, but I think I've done a pretty good job) and there are absolutely no problems while capturing. But when an old VHS comes in, there are zillions of dropped frames - sometimes up to half of the total frames. I have tried three VCR's with same symptoms. If I press stop during capturing and the input switches to VCR's tuner, dropped frames stop. Also, there are no drops on good tapes.

I should mention that I have tried most of the recommended drivers and applications mentioned in this and other forums (btwincap and other drivers, VirtualDub_Sync, IuVCR, VirtualVCR, AviIO and many others, more or less exotic :)

I guess this is what happens: when it receives bad/weak signal, the card cannot distinguish the sync sygnals and the boundaries of the frames. So the solution comes by itself: to have a capturing application or driver which does not depend on the timing of the card, but on it's own timing for frame boundaries, something like a software TBC or kind of framebuffer. I am sure someone will say that this is technically impossible and that it doesn't work that way, but that's how progress is achieved. I think that no such thing exists so far for this low-end cards, but there are many people who can not afford something better.

So, if somebody can point me to an application that can combat dropped frames I would be most grateful. Or this could be an idea for developers to include in their applications... who knows?

Anyway, any comments and suggestions are wellcome.

My computer's specs:

- Athlon 1,2G
- VIA KT133A
- SoundBlaster128 (now many would open their mouth to shout, but I assure everybody that I don't have the well known problems with this particular MoBo and SoundCard) :)
- Pinnacle PCTV Rave
- Maxtor 40G ATA100 7200 RPM
- Riva TNT2 M64Pro
...and other things not so important

- Windows XP SP1 (really tuned up with very few services running on startup and of course NTFS)
- RivaTuner
- Pinnacle Performance Enhancer (to raise the latency of the Pinnacle Card - often not used and I can't really tell the difference)
- PowerStrip (to lower the latency of the Riva Card - often not used and I can't really tell the difference) :)))
...and other things not so important

Uhhh... now I realize how long a post this became... So I'd better stop here. :)

Greetings
GL

Ookami
20th December 2002, 12:21
Love your style of posting. Every info we need is there. :)

No "Help!!!!!!!! dropped frames" posting...

In my experience only VirtualDub sync is better with bad sources than other programs. As you've already tried it...

Also, be sure to read the FAQ and follow the links in it. Many good advices are in there. Altough this is a problem and without a hardware TBC I doubt that you'll have much luck (you can get it better, but if that's still good enough is another question).

You could also fiddle with the VCR settings. For instance in some cases I get better results when I turn the TBC and picture improvement off (who knows why, but still...).

Good luck.

Cheers,

Mijo.

^^-+I4004+-^^
22nd December 2002, 14:47
>I guess this is what happens: when it receives bad/weak signal, the card cannot distinguish the sync sygnals and the boundaries of the frames.

i discussed that issue on the
http://forum.doom9.org/showthread.php?s=&threadid=40231
and i have the same feeling as you (i only got a lil bit
further on describing it..) ie. sync signals can't be distinguished...

TBC?(soft or hard)
well it's interesting idea,that soft solution,BUT
bt8x8 has some means of doing that without help
,utilising it's "UltraLock" principle.......

TBC also (as bt device on it's own) has some limitations:
obviously,if you have that much noise,then how will
even TBC find sync signals and put that frame to memory ?

also i think i have heard some pro's teling that with enough noise
in video TBC fails too (no surprise to me...)
and some examples of people failing to capture poor VHS'
with very decent S-VHS machines that incorporated TBC's....
( interestingly enough bt8x8 failed on different spots than ADVC100 + such S-VHS machine ,and generally tended to produce less frame drops than ADVC... )

cheers

Ivo

ps.also,my tests on wdm platform tended to show that it's less prone
to frame drops than vfw (win98) system
but i usually get a/v sync issues with wdm and poorer sound (SBPCI128 has
poorer sound on with w2k drivers...)
so i'm doing it on win98 and only if there are too many drops i go for
win2k....(and do smaller segments,as after 20-30' there's no lipsync
with wdm anymore..)