gbs-c incorrect aspect ratio

[mrchief]

using 1080p preset, one of two presets tv supports via HDMI, and 720p is messed up with scaling. But i get stretched image compared to my TV scaler. Tried to use scaling settings, but it maxes out (cannot correct more) and still is not perfect 4:3.

PAL PS2.

[NoAffinity]

Im not sure infollow the question but here's the basics as far as gbs-c processing:

1) 1080 P is a 4:3 image imposed on a 16:9 canvas (will have pillar boxes)
2) 720p is the only true 16:9 image

If you have a "direct" or similar aspect setting on your tv, this will pass through the image as it is output by gbs-c, and you can expect the above. The 720p profile is good for scaling 16:9 480p signals.

[mrchief]

Made some catpures. Discovered that GBSC crushes blacks. RGB ranges are matched. PS2 native captures is from component and RGB scart is for GBSC, i dont have PS2 component cables, my capture card has custom ones.

https://imgur.com/a/2ypPkEb

And aspect ratio thing, on TV looks Ok, bus image is shifted to the left. Probably LCD monitor had its own thing, even it was automatically set to 16:9. need doublecheck.

[mrchief]

ok, black crush was just color correction issue needed brightness +13, could be needed more. But shouldn't default setting be in tune with input signal? Will try to increase contrast to match brightness of direct capture. Very bizarre.
emulated sega captures (ps2) for comparison:
https://imgur.com/a/34BrqbP

[mrchief]

left - GBSC, PS2 PAL, RGB - HDMI (1080p preset, brightness gain +13). Right - direct component. Artifacts from compressed screenshot.

and scaling is incorrect.

[NoAffinity]

Do you have your gbs-c set to auto gain? You're supposed to set it to auto gain while in a lure white screen, leave it there for a minute or so, then leave gbs- set to auto gain. Aside from that, I've never seen perfect colors from gbs-c. It is, after all a budget scaler running a custom firmware which is no longer an active project. Output from different gbs units will vary as well.

[mrchief]

Do you have your gbs-c set to auto gain? You're supposed to set it to auto gain while in a lure white screen, leave it there for a minute or so, then leave gbs- set to auto gain. Aside from that, I've never seen perfect colors from gbs-c. It is, after all a budget scaler running a custom firmware which is no longer an active project. Output from different gbs units will vary as well.

Yeah, with auto gain, using "240p test suite" with sega emualation, and it does very quick. Colors inaccuracy could be a hardware oversight with capacitors, etc. But its a global thing with GBSC, could be programmed wrong. Someone should do a capture from stock GBS8200.

Checked .pdf manuals found scaling calculations.
VSCALE = 1024 * (Input V.active / Output V.active)
HSCALE = 1024 * (Input H.active / Output H.active)

So if i wanted integer 2x scale with overscan (768x576) targeting 1440x1080 (4:3 frame), i would need to use scale value of 512 for V and H scale, if i calculated correctly. 1080p preset values makes no sense, or my calculations are wrong.

Sad reality of open source, people who did nothing profits from it.

very close color accuracy to OSSC, 5725 has potential.
https://www.youtube.com/watch?v=tIsAeTEaZQA

[mrchief]

starting to figure out registers
0xFF, // s3_16
0x3, // s3_17
0x20, // s3_18

So, vscale value of 1023 in the registers equals input resolution of 1918,125, hscale value of 512 equals resolution of 540, if calculations used 1920x1080.

so input resolution is 1918,125x540, but how.

Pal resolution, 720x576 (3:2) > 768x576 (4:3)

[mrchief]

Hello,
couldn't figure out video scaling, so i made adjustments by eye to good enough.

trying to figure out colors. Starting from ADC. Voltage for RGB lines in scart specification should be 0.7V? So we calculate gain control: (0.7Vpp/1Vpp)*255(FF)= 178.5 [HEX] B2 or B3, but registers are 7B ( 0x7B, // s5_9, 0x7B, // s5_A, 0x7B, // s5_B) - calculates roughly to 0.4824V (in GBSC code and 1080p preset), this could explain dimmer image?. offset says to use 64, and it is, hex: 40.

Also in ADC there are hardcoded offset in GBSC code to mitigate hardware errors? from debug console after calibration, ADC offset [HEX]: R:40, G:43, R:40, this could explain tint?

GBS-C is pretty good, reduces input lag significantly, games are much more fun to play. Problem is scaling issues and colors (seems - correct, but lacking in color punch).

Edit:
Double checked the graph, i think my calculations were wrong, because I ignore the blue line. So values should be 0.5Vpp is 00H and 1Vpp is FFH, so calculated 0.7Vpp hex value is 66H. Problem is, i don't know how to test it, since i have a premade gbs-c and i dont want to mess it up.

current gain value: 123 (7BH), new value: 102 (66H). Comment in gbsc firmware says: // gain is actually range, increasing it dims the image.

[NoAffinity]

I don't proclaim to know the technicalities to your level @mrchief, or even half of what youre talking abour, but i've been an enthusiastic tester for past iterations of the custom firmware, and long-time user. Do you anticipate releasing a firmware update with your improvements?

[mrchief]

https://safenote.co/r/68ac8adf1c87f5@00831259 - expires in 14days, dont know where else to upload without account

i dont use github

changed value in gain registers (S5_9, S5_A, S5_B) in all in all presets:7BH to 66H. offset registers are fine - 40H

changed gain registers in gbsc code from 7BH to 66H, except in ADC calibration, i hope this will make colors pop like it shoud.
GBS::ADC_RGCTRL::write(0x66);
GBS::ADC_GGCTRL::write(0x66);
GBS::ADC_BGCTRL::write(0x66);

Changed offset value GBS::ADC_GOFCTRL::write(0x42); from 42H to 40H

I have no experience doing this. Trying to understand it by reading technical files and GBSC code.

Not sure if we need to disable auto gain and ADC calibration, since it uses 7BH register values.

[NoAffinity]

Very nice! I had a chance to test this build last night, briefly. It is immediately noticeable that the colors are sharper and more vibrant, and the image is overall much brighter). I want to say that the scaling is sharper too, but it was a brief test, I'll see if I can carve out some time this weekend to produce some side by side comparisons of rama final fw vs this build.

[NoAffinity]

Did some quick screen captures from a couple different systems. The differences are very minimal, to my eyes, but my opinion is that mrchief's fw provides slightly improved colors and a slight improvement to sharpness.

In all comparisons below, mrchief's fw is on the left, rama's is on the right.

What do you think?

Spoiler