640x480 video capture problems (lines on the screen)

[Layzie310]

I just started trying out capturing at 640x480 with my Hauppauge WinTV-GO and AVI_IO. My 320x240 captures come in nice with no artifacts in the video but at 640x480 I get these lines that pop up every second or two where ever there is some movement on the screen. I'm running a Duron at 750MHz, in Windows XP, 128MB ram, Geforce2 GTS. So, what's causing it? Is my system just too slow to capture at 640x480 without these artifacts in the video or is it something else?

Here's an example of my problem

 

[nemesismk2]

The picture isn't working

 

[LethalWolfe]

What kind of hard drives do you have? Are you trying to capture full resolution video (little/no compression) at 640*480 and 30 FPS?

Lethal

 

[oLLie]

The lines you are talking about are interlacing. There is never any interlacing at 320x240 because of the way that 640x480 is set up to double certain lines sometimes. You can try going to doom9.org and reading up on interlacing or go to deinterlace.sourceforge.net and try to use dscaler.

 

[rbV5]

There is never any interlacing at 320x240 because of the way that 640x480 is set up to double certain lines sometimes.

Yes, thats it.

NTSC interlaced video is 1 full frame(480 lines) comprised of 2 "fields" broadcast every 1/60th of a second apart (30fps 60hz) Each "field" is comprised of every other scan line(240 lines), 1 field of the odd scan lines, 1 field of the even scan lines.

so:

When you capture at 320 X 240 resolution, you are actually capturing 1 field only at 30 fps.
When you are capturing at 720 or 640 X 480, you are capturing both fields.
Because the computer displays both fields at once rather than every 1/60th of a second, you will see artifacts with the full 480 line captures during periods of motion(looks like a combing effect) unless you deinterlace the video. You don't get interlacing artifacts with 240 line captures, because the computer simply is displaying the single field. The trade off is the 240 line captures will look more jerky during periods of motion, you can really see this during pans.

You can process your 480 line captures using virtualdub, and a deinterlace filter, which can use a number of techniques to eliminate or reduce the interlacing artifacts.

 

[Layzie310]

Here's the video again

I don't think it's an interlacing problem (but then again, I'm no expert so set me straight if I'm wrong).

 

[BeefJurky]

You're right. It doesn't look exactly like interlacing, however since you said it doesn't happen in 320x240 I wouldn't rule that out. Maybe it's just a bad source and you can't notice it in 320?

 

[LethalWolfe]

I played the video clip using the Playa and I noticed interlacing, but I'm assuming the random horizontal lines flashing across the screen was what caught your attention, right? Have you tried recaptureing the footage at 640*480? If so, do you still get the same problem?

Can you post some the same clip, but capture at 320*240 res?

To me it looks like some sort of noise in the signal. Have you tried capuring other things at that res? Do you get similar results? What if you capture at 640*480 but drop it down to like 25FPS instead of 30/29.97?


Lethal

 

[Layzie310]

No matter what I capture, what framerate I use, or what compression I use (MJPEG or Huffyuv), I get those lines when capturing at 640x480. With 320x240 I get a perfect picture (but 320x240 is not the greatest resolution in the world and I can tell the two apart).

 

[rbV5]

There are interlacing artifacts (you can see them easily by pausing the video), but those horizontal lines are something else. It strains your system much more to cap at 480 lines, have you tried capturing with no sound? Your cpu should be fast enough, but your transfer sate may not be. Are you dropping frames? Have you tried virtualdub to capture? What settings are you using?