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 Post subject: PMS Crystalio II Comb Filter Settings
PostPosted: 21 Feb 2021, 18:19 
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I know not many people have these and they're getting harder and harder to find. However, they are one of the best options for LD processing. The people here who drove me to the madness of video processors have moved on to the next stratosphere of technology and I am happy to watch them try to reach the Sun.

The C2 is still a valid option for LD and still one of the best if you can find one. Part of the reason why is due to the fact that you can adjust the comb filter settings. Very few processors out there allow this. Some TVs will have these adjustments in the Service Menus but that isn't as convenient as a normal menu. Lumagen and the EVAL board are the only two that come to mind.

Anyway, I've read the threads here about the settings and also experimented myself. Some of the info seems unclear as presented and I'd like to share my own personal experience and settings. You don't have to use them and maybe they aren't correct for your system. Use these as a guide and a stepping stone.

There are 4 settings. Each setting is from 0-100 steps. They are:
Luma Gain
Chroma Gain
Luma Coring
Chroma Coring

Previously, I was using settings found here in other posts. While that was helpful it did not get me the results I had hoped for. So I re-read them and also re-read the TI TVP5160 3d Comb Filter Operation Guide and experimented on my own.

Here are my conclusions:

Think of Gain as a balance between 3D and 2D combing. Depending on the setting it defines how fast the filter switches between 3D/2D. But it doesn't just switch between them, it blends them together unless you're at the extreme ends like 1 or 100. In my mind I see it as a see-saw or a fulcrum. At 50 it has an equal bias toward either 3D or 2D and the change is blended so not a drastic change (no artifacts). At 1 it is locked to 3D all the time and at 100 it is locked to 2D. The switch is very visual and artifacts appear on screen. I have mine set somewhere between 25-50 depending on the disc. So a slight bias towards 3D combing.

The Luma Gain register is an 8-bit register that controls the gain (or attenuation) for inter-frame luma difference. Least significant 3 bits specify a fractional gain. Gain can vary from 0 to 31.875 in steps of 0.125. The minimum value of 0 favors 3D comb output, and the maximum value of 31.875 favors 2D comb output.

If the frame differences are large, Km saturates to the upper limit and 2D comb is output. If the frame differences are smaller than the threshold, 3D comb is output. If the frame differences are such that a Km between the upper and lower limits occurs, 2D and 3D comb are mixed proportional to Km. This provides for a smooth transition between 2D and 3D comb outputs.

Coring is a threshold for noise/motion. The way I set it was with the Video Essentials S&W pattern. Playing a loop on the S&W test pattern and looking at the resolution squares on the top of the image I increased the value until the diagonal lines in the 400 square stopped giving me cross color distortion (rainbows). This was at 26 for me.
The Luma Coring register is a 10-bit register that controls the coring level for inter-frame luma difference. A difference smaller than the set value is assumed to be noise, resulting in the pixel to be recognized as 'no motion' or 'still picture', favoring intra-frame (3D) comb output. The minimum value of x000 favors 2D comb output, and the maximum value of x3FF favors 3D comb output.

I set both Luma and Chroma values the same, but I suppose if you really wanted to dial it in you'd have slight variance for Luma and Chroma based on your set up.

Based on the settings found here, which were both gains at 1 and both corings at 26, I was seeing terrible artifacts on fine details and wide shots because the gain was always biased toward 3D combing when it should be falling back to 2D.

I'm no expert and I don't have an X0 or a Lumagen to compare to but damn if the C2 doesn't make LDs look fantastic when set properly. No artifacts, checker boarding or annoyances just a great film-y image.
LD-S2|CLD-D704|CLD-D406|DVL-V888|LX-900U|Crystalio II|Yamaha APD-1|Sony XBR55X810C
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