VHS dot crawl with RGB and S-Video

[Hajker]

I noticed some noise on the image when capturing VHS. It looks like dot crawl but not quite?

It happens when:
-Capturing random tapes to MiniDV via firewire and shielded s-video.
-DVD player - to VHS - back to DVD combo capture. All by using a thick, shielded SCART RGB cable, i've opened it.

I can get a better image after filtering, but just would be cool to know why this happens..


The sample is captured via that scart cable. As you can hear, there's no buzzing sound that unshielded scart cables have.

[dellsam34]

That looks about normal for VHS quality especially if the recording VCR is a low end budget VCR using a low grade blank tape.

[Hajker]

What do you mean it's low end? The vcr has almost the same quality as a NV-FS1000, at least i didn't notice much of a difference between them. And the crawling happens on lots of tapes.

I don't mean the noise, which obviously is there on anything analog, but look in the cyan color. There's a similar artifact to dot crawling, just blurrier.

[Sharc]

With a bit of post processing:

[Hajker]

Yeah it looks decent with filtering, but it takes quite a while to render stuff.. The problem is with the plugins not utilizing system resources much :/

[dellsam34]

What do you mean it's low end? The vcr has almost the same quality as a NV-FS1000, at least i didn't notice much of a difference between them. And the crawling happens on lots of tapes.

I don't think you understood my post. Do you know the original recording VCR is not a low end?
If you are recording this yourself try S-Video, there is no RGB in VHS, Either composite or Y-C (S-Video). If using SCART you are most likely recording from composite.

[Hajker]

This sample is recorded and captured from the same VCR (Panasonic DVD player with shielded scart > Panasonic NV-FS88 with shielded scart > dvd-vcr combo for capturing, with shielded scart input from the NV-FS88). Same dots are visible when capturing with Sony MiniDV camcorder using a shielded S-Video cable as source. I tested 2 s-video cables. The cheaper one i cut open, and it was wired up properly, and for the second one you can open up the metal cap and see it's wired up properly as well. But no matter if i use a proper s-video or proper scart cables, there's that dot crawl in some colors, but most colors are fine.

[dellsam34]

Neither DV nor DVD are lossless sources, they have their own problems, If you want to test your VCR recording capability you are going to have to supply it with a clean digital source, such as a media player or a computer with an analog S-Video output, Alternatively you can use a HDMI to S-Video converter to use with any digital device.

But I'm confident that you are at the limit of what VHS is capable of, any extra efforts are going to be in the diminishing returns domain.

About SCART: Keep in mind SCART is always defaults to CVBS (composite), to force into Y-C you have to make sure both the source and destination devices are manually set to Y-C in their control menus, Otherwise composite only.

[Hajker]

I don't know if a 1% loss of quality can introduce dot crawl. 6000kbps video with just a still image looks basically the same as a .png i think.

And the scart doesn't default to composite on the dvd player. It's either RGB, or blank screen on other settings.

But after all that, I just checked the test pattern again, and paused it. And i noticed that the dot crawls are engraved in the tape, as they freeze in place when paused. Don't know how that is even possible. Complete mystery.

[mammo1789]

About SCART: Keep in mind SCART is always defaults to CVBS (composite), to force into Y-C you have to make sure both the source and destination devices are manually set to Y-C in their control menus, Otherwise composite only.

Scart is carrying RGB, Svideo, YPbPr, Composite, and can even go to 1080p so no it doesn't default on composite it depends on the source and the end machine or TV

[dellsam34]

@mammo, For a VCR, it is only Y-C or CVBS and if you don't select Y-C it will default to CVBS, it's from personal experience not from google search, at least the VCR's and sat receivers I owned.

@Hajker, If your DVD is ouputting RGB, there is no way in hell your VCR can accept that signal, VCRs video processing unit takes only Y-C or CVBS, no other signal will be recognized or displayed.

[Hajker]

https://files.videohelp.com/u/304501/Title_1.mkv This capture is with the following setup: 1-DVD Player -> 2-VCR -> 3-DVD/VCR Combo. The "2-VCR" does accept RGB, as there are no dot crawls in this capture. But, as I recorded from the "1-DVD player" on to a tape on "2-VCR", the dots showed up and were engraved on the tape. Just wondering why this happens.

[dellsam34]

Again, VCR's don't accept RGB signal, you can argue all you want. Component out can output 4 signals, CVBS, Y-C, YPbPr, RGB, By having a component cable connected to the 3 red-green-blue RCA connectors doesn't mean you have RGB out, Even the menu in the sample you posted says RGB no output. Read up on how these things work instead of arguing and confusing yourself even further.

[dellsam34]

Here is how that menu works, See the screenshot below, When you select the top option you are sending composite out, the second option is S-Video, the third option is not supported by a VCR, Hope this clears up the confusion you have:


[Attachment 74191 - Click to enlarge]

[Hajker]

You mean recording to the tape doesn't accept scart-rgb? That makes sense then, although I've read that the tape seperates luma and chroma, which should've got rid of dot crawling.

[Hajker]

Because the dvd player is literally connected to the NV-FS88 via scart, and then sent from NV-FS88 to a combo vcr which captured it. And that RGB option is the only one which sends a signal.

[dellsam34]

You mean recording to the tape doesn't accept scart-rgb? That makes sense then, although I've read that the tape seperates luma and chroma, which should've got rid of dot crawling.

No, the entire VCR video processing has no option to accept RGB, It has only two pins, one is called Luma or Y, the other is called chroma or C.

Because the dvd player is literally connected to the NV-FS88 via scart, and then sent from NV-FS88 to a combo vcr which captured it. And that RGB option is the only one which sends a signal.

That is incorrect, RGB option is the only one not sending any video per your own video sample, Read up on how 21 pin SCART works, because you clearly have no clue how SCART works.

[Hajker]

if i understood you correctly, you're saying the sample video is fake?
you can see it looks clear, stable, and better than a composite video would look. i can't test composite currently, as i don't have the wires.
and you can see if i set it to anything other than RGB, the video goes blank.

i feel like we're not on the same track somehow..

[Skiller]

When RGB is fed through Scart, pin 20 is still used to carry a standard Composite signal along with it.
It is required for it's sync pulses (there are none in the actual RGB lines) and it is also a silent(!) fall back if the receiving device does not handle RGB.


If you connect a DVD-player with RGB enabled in the settings via Scart to a VCR, the RGB signals are dropped with most decks (there are a few exceptions) and only the Composite signal is routed through. In such case it does not make a difference whether you have the DVD-player set to output RGB or Video (Composite) – you get Composite either way.

[Hajker]

Does it look like composite, honestly? I don't understand, what format is it then? Certainly doesn't look like composite to me.

What I understand is that when recording to tape, it drops RGB and only does composite or y-c, but dellsam34 said that is incorrect... I'm confused.

[Sharc]

Does it look like composite, honestly? ... I'm confused.

Yes. Your sample in post#1 looks like composite. You clearly see the dotcrawl (and rainbows) which is typical for Composite video with poor luma/chroma separation (poor separating filter). Your DVD recorder has most probably a setting for switching a 3D comb filter (or similar naming) ON which will widely eliminate the luma/chroma crosstalk of the composite signal (if you can't use S-video throughout your setup).

[dellsam34]

if i understood you correctly, you're saying the sample video is fake?
you can see it looks clear, stable, and better than a composite video would look. i can't test composite currently, as i don't have the wires.
and you can see if i set it to anything other than RGB, the video goes blank.

i feel like we're not on the same track somehow..

You're still confused, let me try to get through your thick wall of confusion:

SCART is a multi signal cable, it has 21 pins, Some of them are inputs, others are outputs. SCART can carry composite, S-Video, and component (RGB or YPbPr), In the menu I posted above for your DVD model:
1- If you select Video, you get composite signal in the SCART cable, the VCR senses composite and records it.
2- If you select S-Video, you get S-Video signal in the SCART cable, the VCR senses S-Video and records it.
3- If you choose RGB, the VCR will fall back to composite and records it, because it cannot record any type of component tri-signal, Even your DVD recorder senses the VCR cannot accept it and disables it.

If you are still confused, I'm afraid that you will never get it. It is what it is sometimes. But just take our word for it, choose option #2.

[Hajker]

1- If you select Video, you get composite signal in the SCART cable, the VCR senses composite and records it.

I know SCART is able to do many signals, but you cannot select "Video" on the dvd player. As you could see the screen went black, and there was a picture only when selecting RGB.

I recorded the same pattern as in sample #1, but didn't put it through TAPE, and passed it through from VCR to vcr/dvd combo, and there were no dot crawls. Why? Only explanation is that rgb or y-c is not supported only when recording to tape, but you said that's incorrect. That's why i don't understand what you're trying to say.

[dellsam34]

I said incorrect to the RGB output being recorded or even accepted by the VCR and I still stand corrected. Not really sure what you did in that video but I know it wasn't RGB. But as I said before, to be able to select a pin in the SCART every device in the chain has to be set to that pin, Meaning, if you select S-Video at the source device, every device down stream has to be set manually to S-Video for this to work.

[Hajker]

So the vcr doesn't accept scart rgb signal but is only able to pass it through? Then i'm sorry for not understanding that sooner.

[Skiller]

So the vcr doesn't accept scart rgb signal but is only able to pass it through?

Yes, but only few VCRs even have the ability to do RGB passthrough (read the manual). Most VCRs simply do not have the required pins for RGB wired to anything at all. It goes nowhere and instead the accompanying Composite signal is used for both passthrough and recording to tape as usual.

[Hajker]

Oh okay. And so the S-Video also works in composite, as it also has dot crawl? Pretty sad you can't get y-c out of the tapes properly..

[lollo]

And so the S-Video also works in composite, as it also has dot crawl?

No

Pretty sad you can't get y-c out of the tapes properly

No

[dellsam34]

So the vcr doesn't accept scart rgb signal but is only able to pass it through? Then i'm sorry for not understanding that sooner.

No, VCRs cannot record nor passthrough RGB, they have only two pins, RGB has 3 pins, Jesus Christ, I'm out.

[Hajker]

No

"No" as in - s-video works in Y-C or something even different?

No, VCRs cannot record nor passthrough RGB, they have only two pins, RGB has 3 pins, Jesus Christ, I'm out.

Alright I admit I am a magician and used my secret powers to do it.

I know how that screen looks with composite on a crt. Everything's moving around. When i switch to scart on the same crt, the image was just as stable as in the 2nd capture.
I will not believe a single word you're saying, if you say the second capture is in composite, brother.