Capturing with S-Video. There are dots in a grid.

[SyncroScales]

Hi.

I have captured Hi8 tapes from a camcorder with S-video connections. I noticed there are dots or o's or 0's in a grid like pattern. I think this is called dot crawl and rainbow artifacts? It can also be seen when the camera starts up after pressing record and the screen is blue.

How can I eliminate this?

It seems to be when there was lower light in the room. The static/non-moving objects usually don't appear to have these o's or dots. But the moving person or objects do(es).

Could it also be that it was recorded in 60i not 30p? Is the problem interlacing isn't great with moving objects or people? But the camera was stationary.

I'm using a 3 foot (30 cm) monster cable to capture. It is thick, gold plated.

Do you need a screen shot?

[jagabo]

A short sample video would be best. Try capturing via composite rather than s-video. Any different?

[pandy]

Probably common problem with http://en.wikipedia.org/wiki/Comb_filter

If You are interested in not practical theory then check

http://www.intersil.com/data/an/an9644.pdf

Practical perhaps this:
http://home.earthlink.net/~tacosalad/video/dotcrawl.html

But perhaps jagabo approach is more correct (sample).

[JVRaines]

There should be no comb filtering or dot crawl if your connection is S-video all the way. What capture device are you using and what is the codec (format) of the resulting computer file?

[SyncroScales]

Hi8FootageExport01 -

I tried to show the circles. They show up in the footage. It looks like Dot Crawl. I would need footage or pictures of comb filter to understand that.

It seems that the footage I watched with the problem was when the lighting was not good by the camera. It is dark near the camera and has light where it was pointing (on a person). In another clip where there is more lighting and similar stuff, there are no issues. Same camera.

The DotCrawl.vdf only works in VirtualDub. Do programs sold in stores or online have these kinds of filters? So far I cannot find any and don't know if they would be good.

The codec was mpeg2. When I first transferred my Hi8 tapes I uses a Pinnacle Dazzle 150b capture device. I plan to get another and re-do the captures.

Edit: I looked at some DVD captures that I used S-Video with. They also had the problem. And when there was movement.

[jagabo]

I believe the blue screen from a camcorder is often generated from a chip that produces composite video. Then s-video is produced from that without a comb filter (or a very cheap one) so you get lots of dot crawl artifacts -- it's just the blue menu screen of the camcorder so the picture doesn't have to be great.

The signal on the tape is stored as separate luma and chroma so it shouldn't show any dot crawl artifacts when piped via s-video. But on some camcorders the s-video output is an add-on to the basic model that only outputs composite video. Rather than redesigning the entire camcorder to output the separate luma/chroma stored on the tape they add a cheap circuit to convert composite video to s-video. That cheap converter leaves dot crawl artifacts.

This is somewhat analogous to laserdiscs where the signal is stored as composite video. Most laserdisc players with s-video outputs had a crappy composite to s-video converter. The s-video output was worse than the composite output for most people (the comb filter in most TVs was better than that in laserdisc player).

Here's an example of a composite signal captured on an s-video connection with no comb filter:



Notice how there are dot crawl artifacts anywhere there is color (not in the greyscale areas). That is because the chroma signal was not separated from the luma. The more saturated the color the more severe the dot crawl artifacts. After a 2d comb filter the large areas of color are cleaned up:



Dot crawl artifacts still appear at the borders of different colors. A 3d comb filter can eliminate those in static portions of the video. But not in moving parts of the video. After CheckMate() in AviSynth:



I don't know about dot crawl filters in commercial video editors. But one thing you can do to reduce dot crawl is to downscale the image to half width, then upscale back to full width. That blurs away a lot of the dot crawl. For sharp sources that blurs the picture unacceptably. But with VHS and other consumer based sources it's not so bad because the picture isn't very sharp to begin with.

[kissvid]

I saw your post and read it real fast on my way out. I think I had something similar to what you are going through. If you have the analog cable plugged in at the same time with the s-video cable this will cause it. Just unplug the yellow analog cord. You can only have 1 input plugged in at a time. It worked for me when I did it. Hope this helps you.

Marc

[Brad]

@SyncroScales: refer to post #2, which you never answered.

@Jagabo: He did say the issue is present in playback, not just the blue screen. The blue screen image isn't very helpful as a check, for the reason you described.

I'm personally going to guess Poor Y/C Decoding (S-Video crosstalk) resulting in checkerboarding, like in this thread.

[usually_quiet]

Yes, using one connection should be sufficient and better. Unfortunately the OP believes that using both the camera's S-Video and composite connections at the same time when capturing from S-Video produces a better picture, no matter what anyone says. https://forum.videohelp.com/threads/368918-Is-it-possible-to-capture-with-2-inputs-And-...-better-signal

[jagabo]

Here are some other dot crawl removal filters in AviSynth:

https://forum.videohelp.com/threads/368836-Avisynth-Filters-Help-Needed-%28DVD-MPEG2-Ar...=1#post2361526
https://forum.videohelp.com/threads/368611-Edge-noise-when-TBC-is-active?p=2359187&view...=1#post2359187

[SyncroScales]

I don't know about dot crawl filters in commercial video editors. But one thing you can do to reduce dot crawl is to downscale the image to half width, then upscale back to full width. That blurs away a lot of the dot crawl. For sharp sources that blurs the picture unacceptably. But with VHS and other consumer based sources it's not so bad because the picture isn't very sharp to begin with.

So capture at half size and then re-export at full size? Or capture full size, downscale to half width, then upscale to full width? Is it only the width or the height too?

jagabo I'll try with composite.

kissvid and usually_quiet: This dot-crawl was during capture. So only 1 input at a time. The other post was when I viewed it on my TV through the camcorder with composite and S-Video connected.

Since my camcorder probably has the S-Video add-on, this explains the problems in this and the other post.

vaporeon800: Poor Y/C Decoding (S-Video crosstalk) - Is there any way to tell which cables are good quality? When the cables are too close to the camera and capture device - is that part of the problem? When I captured I had everything close together on a small table. About 60cm/2ft from the computer tower.

When I used a DVD player with S-Video to capture a DVD I noticed the dot-crawl. At this point it's probably the cable that is a problem. My question is: Could using a DVD player or copying DVD's with a S-Video cable create certain issues such as this? (Obviously I can see the dot-crawl.). Would digital to analog be a problem? Or is that a whole different set of links?