Chroma delay on Laserdisc?
 

Hello,

Been a long time.

My LD player LD-S2 shifts chroma a bit. In order for 3D filter to work perfectly, this has to be corrected. I'm able to delay chroma using Allen Avionics VAR-256 device. My workflow is to split S-Video into luma and chroma channels, run the chroma channel through Allen Avionics VAR-256 device and then plug luma and chroma channels into Extron YCV 100 to get composite output. This is not a problem.

My problem is to find the optimal delay value. I don't know how to scientifically eye the correct value. Thus, I was curious if I send a few test samples including Snell&Wilcox with various values, will some be able to advise me which delay value should be optimal? Thanks in advance.

Lordsmurf, do you think you can help?

Test capture, then plugin into Avisynth. Eyeball it there, figure out values. To help, you can also offset it.

That's not something I've really dealt with very often. Usually, it;s due to the device embedding the error in a tape. And it can still mostly be fixed, even after tape embedding. The magic of Avisynth.

But how do you do it in AVISynth? Care to send me the script samples?
Also the end result must be Composite video fed into motion adaptive 3D comb filter. That’s why I can’t be correcting in AVISynth. Only eyeballing it. But do let me know the script.

I don't think anyone can give you a working script without a sample of the problem you're asking about. What do you mean by "chroma delay"? Do you mean chroma ghosting from blended-field processing? Chroma ghosting from preceding or following frames? Chroma bleeding or displacement?

avisource
assumetff()
separatefields()
A=Last
B=A.Greyscale()
Overlay(B,A,X=0,Y=-2,Mode="Chroma") # change X or Y or both values
weave()

That's how you do in avisynth for interlaced video

If you want to fix the chroma automagically (not so magic actually, many errors but haven't tried in a long time) try the plugin AutoChromaFix

How do you know the video is interlaced? What if it's telecine? We still don't know what the poster means by "chroma delay".

Sanlyn, I believe it is called bleeding.

The explanation:

This is the example of Y/C delay error: https://mediaarea.net/_/img/QCTools/image60.jpg
This is corrected: https://mediaarea.net/_/img/QCTools/image61.jpg

I am attaching 4 screenshots. Take a look at Snail&Wilcox screen shots one run with 99 nano seconds delay (AvionicsDelay99.PNG) and the other one run without (NoDelay.PNG).
Take a look at the bottom right center where it says 1.5. You can see that the image that was run with chroma delay has full chroma resolution. This is not the case when it was run with no delay. However, I am not certain 99 nano seconds is the optimal value.

themaster1, this script is for correcting delay, right? Not to eyeballing delay, right? I will need to correct delay in hardware and to eyeball it in AVISynth. The reason is, I split luma and chroma, then correct chroma, and then I need to comb them to run through motion adaptive 3D comb filter. The input to the comb filter should have chroma corrected.

2 more screenshots. TestPattern1NotCorrected.jpg and TestPattern2Corrected.jpg.

@sanlyn: I think metaleonid knows enough that it's not a case of simple telecine. So that the assumption I'll go on for now.

@metaleonid: If it truly is a chroma delay, then an Avisynth script to correct it is what you'll do. What themater1 provided will probably work fine. If I'm deciphering it correct, the -2 value is the temporal offset. Probably -2 frames, but read the filter documentation. Or ask themaster1 for clarification.

If it is -2 frames, and you need timecode, then break out the pencil for some basic algebra. The frames are either base25 or base29.97(then rounded), and 2 frames is about 1/12th or 1/15th of seconds (base60). You may be able to find a dummy calculator online, but I prefer the math.

I'm not sure what timebase S&W is using there, assuming base60 standard seconds.

The script i gave you is to fix chroma shift manually (move chroma up ,down, right,left basically) not sure if that was what you were looking for. (you have to eyeball and change X=,Y= values according to your needs)
Autochromafix can do that automatically. Last time i checked it wasn't bad, but not 100% safe and very slow

Unless I'm reading it wrong, he wants temporal offset.
I guess it's time for him to re-explain his needs, as I'm no longer sure either. :hmm:

Hello,

I’d like to fix it but not in the AVISynth. My workflow is:

S-Video out with breakout cable where chroma channel goes through a delay line. Then luma and chroma channels go to Extron VYC-100 which combs them together. Now I get composite signal with the correct sync between luma and chroma. The composite signal is then going to a capture card with motion adaptive 3D comb filter. The motion adaptive 3D comb filter is the reason why I want to fix the delay before analog to digital transfer because for the filter to work properly luma and chroma must be in sync. If I do it in AVISynth, the signal is already incorrectly transferred to digital which is unfixable.

What I want to do is to eyeball he delay and adjust it it.

It's not an issue to fix the chroma shifts after analog>digital convertion especially if you use a lossless codec.
You're working with a good source material (laserdisc) so the shift should be constant throughout, unlike old vhs recordings that i work with sometimes; so it's a piece of cake i'd say.
A 3D comb filter only work on chroma artefacts, it fix cross-colour interference or colour bleeding and don't take Luma into account or it's spacial position relative to chroma.
That's my 2 euro's cents

No, I wasn't able to bring full chroma resolution back. Also I am including 4 more screenshots from Video Standard LD player. There are 2 samples. The player Pioneer CLD-D703 exhibits no delay or very minimal one which is not worth correcting. The player Pioneer Elite LD-S2 exhibits delay such that to the right of red vertical bars there is a tiny black line on the right edge. Please take a look.

i don't see the black line on the right, i need glasses perhaps.

The "black lines" are internal sharpening (edge contrast) from the player. Common trick.

Fair enough. But the black lines on LD-S2 screen shots are only to the right of red bars. On CLD-D703 screen shots it is symmetrical on both sides.

Black is usually paired with white. So black on right, white on left.
But some can be black and black.

You're probably running into the sharpening of the Laserdisc players. Most consumer stuff does that. LD was only consumer, so I'm not at all surprised by it. Whether it's good or bad is debatable.

Sharpening doesn't really have much to do with chroma.

LD is one of the few areas of video where I never dabbled directly, always supported others. I'd been offered players and discs many times in past years, sometimes even for free, but circumstances at the time made me decline. Even now, honestly, I'm not sure if it's something I'd want to mess with. I'd rather give an LD to somebody like you, if ever I wanted one processed.

Ok, but how would you explain that in my 1st screen shots cyan bars on snell and wilcox appeared only when I delayed chroma by 98 ns?

I'm not sure what you mean, nor what I'm looking at. :question:

If you look at the post #8, you will see 4 attachments. Open NoDelay.png and AvionicsDelay99.png. Look at the bottom center-right. You will see the square number 1.5. On NoDelay.png, there is clearly crippled chroma. No color where cyan is supposed to be. But on AvionicsDelay99.png, the chroma is in full resolution, thus the bars are cyan. In other words red bars alternate with cyan bars. But when no delay, cyan bars are shifted such that they overlap with red bars.

Hello, I'd like to resume the thread. After a thorough investigation, I noticed that if I apply chroma delay, the red colors got corrected but the rest of the colors would be shifted in wrong direction. I tried to split chroma into 2 channels (U and V) and noticed that the U channel is in place. While the V channel is the one which needs to be delayed. The question I have is how to achieve it? This needs to be done before I comb chroma and luma and feed it into motion adaptive 3D comb filter. Are there any hardware processors that can delay chroma channels rather than the entire chroma?

If I split the signal into RGB component, delay R and comb into composite, will this work? Please advise.

Perhaps you need to work in RGB such as:

OP, Maybe you should address the root cause of the problem rather than patching the problem, First why are you capturing via S-Video, LD is composite so capture it from the composite output, If there is still a shift maybe it's a defective player or just that particular disc. If it's the player, try to get a different LD player, If it's the disc, see if you can get a copy on DVD or Blu-ray and call it a day.

Hi themaster1,

The thing is that I need to do this in hardware before I comb the signal into composite and feed it to the capture card. Unfortunately AVISynth TComb filter is not nearly as good as hardware motion adaptive 3D comb filter.

Ideally, I could've made a capture twice: one capture with delay and the other one without delay and then comb them with AVISynth splitting chroma into U and V. But given the number of LDs I have it is very time consuming. So the solution is either find a piece of hardware that does it or just get a different LD player (which I am considering).

Here's another question though. Does each of 3 RGB channels carry luma information? If I delay one of the channel, would it screw up the whole picture?

Yes, I'm aware that the signal is composite. However, in order to delay chroma channel, I split the signal into luma and chroma right out of S-Video out and delay chroma.

It turns out that all line of LD-S2 players are like that. I was told about the issue by Anthony Cuozzo who has the same player. But I investigated further and found out that only V channel of chroma is off.

The discs are not defective. My other player Pioneer CLD-D703 doesn't exhibit the delay. However, the other player is noisy (grainy) compared to LD-S2 (which is considered 2nd best player). I am capturing the discs that are not available on DVDs/BDs. If they were, I probably wouldn't even bother.

As far as getting a different player - it maybe an option. But the one I'm seeing on eBay HLD-X0 goes for $3000. Not sure it is worth it. Also not sure if this player exhibits similar problems.

PS. In fact a lot of people in the past have been pointing out that the picture on LD-S2 is soft while less noisy. When I delayed chroma, I get a lot of sharper image.

Grainy doesn't always mean a bad thing, Most of the time it means that you are getting a sharper not washed out picture, If I was in your shoes I would take the grainy source and apply a light DNR filter in post digitally than fiddling with chroma in the analog domain, Big difference.

This is possible too. I'm also trying to investigate if the less noisy but softer picture from LD-S2 is simply the result of chroma channel being not in sync.

BTW, care for screenshots later in the day?

Sure, But a simple video from both players would be preferable.

Hello, here're the test captures from Video Essentials LaserDisc. It has bars and Snell&Wilcox. I used 2 players:
1. LD-S2 with no chroma delay and with chroma delay 99 nanoseconds
2. CLD-D703

Later on I intend to post 2 more samples of the real capture (not the test LaserDisc).

What's your opinion on the sample video clips that I have posted so far?

I have exercised many options up to purchasing S-Video to Component converter and Component to Composite converter. Unfortunately putting them in the workflow significantly degrades quality.

I'm left with 3 options
1. Use just S-Video.
2. Not using LD-S2 at all and stick with CLD-D703
3. Make 2 captures: with delay and without delay and then combine U and V channels in AVISynth.

I didn't see anything wrong with Pioneer CLD-D703 samples, I would use it for capturing using composite out, In my opinion you are looking for a solution to a problem that doesn't exist. You should focus your effort in getting a capture device with the best comb filter, that can make a lot of difference.

The only problem with CLD-D703 is that the footage is noisier (has more grain) than that of LD-S2. But yes, it is a lot sharper and no colors are lost.

I have 2 capture devices with best motion adaptive 3D comb filters - so this part is not an issue.

From the samples I don't see a problem with CLD-D703, The problem you are trying to solve is created by the LD-S2, But this is my personal opinion.

Thanks for the feedback. As you see I seriously do need a second opinion to decide which equipment to use.

PS. By the way as far as motion adaptive comb filter goes, I did previously capture some of the LDs using CLD-D703. I was doing 2 captures simultaneously: one via S-Video (no 3D filter) using https://www.diamondmm.com/product/diamond-ati-theater-hd-750-usb-tv-tuner/ and the other via composite using https://www.diamondmm.com/product/diamond-ati-theater-750-pcie-hd-tv-tuner-card/ (with 3d filter on). Honestly, I didn't notice any difference. The only difference there was during rare moment of static displays. That's it. During motions 3D filter acts like 2D one. That PCIe card has one of the best 3D comb filters BTW.