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Old 14th February 2011, 05:36   #1  |  Link
OvejaNegra
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Confused about color correction for playbak

Most of the time when i see a DVD on a TV an then on a pc monitor, i have to adjust the controls in FFDSHOW to get a comfortable gamma / saturation (and sometimes contrast).


As far as i know, the white range on the YV12/MPEG videos is 16 - 236 (not sure rigth now about the accuracy of these numbers). So the output must be scaled to proper 0-255 to get correct black and white.
But the same applys to chroma gamma?Let me explain.

Accordeing to what i have read about adjusting a chroma with vectorscopes, the maximun reccomended saturation is about the 75% of the full range (taking spacial care with the red because is the color that saturates most).

That means that i must increase the saturation a 25% during playback to get the correct colors of the video? Most of the time i increase the saturation a little because i see the videos very palid.


The common gamma for a healthy monitor on windows is 2.20 if i remember correctly.
That means that i must increase the gamma control on FFdshow to 1.20 to get the correct gamma during playback?
On windows 7 if you use the display calibration you will see that the results also apply during video playback, so i assume that the gamma correction stuff is valid for video too.

Of course i have my monitor properly calibrated and showing correct black and white, but must of the time i'm tweaking the videos during playblack so maybe theres more than just levels correction.
(before knowing about the levels correction stuff and all the 16/235 -> 0/255 thing i was thinking that the ffshow decoder was crap). Now i see that the problem is more complicated.

Thanks
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Old 14th February 2011, 13:59   #2  |  Link
yetanotherid
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I wouldn't want to adjust the whole monitor to fix the video, only adjust the video itself.

I do it via the video playback settings in the Nvidia control panel (change it from 16/235 to 0/255). I don't know how you'd do it with other video cards.

Which media player do you use? If it's MPC-HC, as long as you have it set to use the appropriate renderer, under Play/Shaders you can select "16/235 -> 0/255"
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Old 14th February 2011, 14:01   #3  |  Link
Ghitulescu
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What kind of monitor do you have and how it's connected to the card?
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Old 15th February 2011, 06:59   #4  |  Link
OvejaNegra
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i have an asus-nvidia GT 9800, the options that i set in the control panel (the 16/235 to 0/255) and edge enhancement sometimes.
i have a lcd viewsonic display to the (dvi / hdmi i dont remember now) one aopen CRT 17 inch monitor with the hdmi-vga adapter (i think) and one LG CRT 17 inch conected to the VGA output (what a mess
i use MPHC with the EVR set and output to 0/255.
that's all. all my monitors are calibrated to show black and white and im using windows 7 with the display calibration set up.
most if the time i set the saturarion / gamma / etc with FFDSHOW and the color settings on nvidia cp are off.

im happy with my black / white levels on all my monitors but most of the time im unhappy with the saturation and gamma (too palid videos and too dark mid tones).
and yes, i have the asus splendid auto adjust feature off.

PD i know that lcd VS CRT is different (the levels and gamma is different) but it cant be that i dont have a single disc that looks fine without touching the gamma/color settings, i must have something wrong. on the other hand, when i use any kind of auto correction stuff (like asus splendid / cyberlink eagle vision ) the picture looks better to me, and when i play the disc on my normal tv with my DVD player it looks ok (the picture is clear but with good contrast and the saturation is ok).

yetanotherid: you set the options in the nvidia panel and on the player at the same time? i do it too but, maybe we are doing a double correction (the renderer on MPCHC stretchs the levels and the video card do it again).
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Old 15th February 2011, 21:59   #5  |  Link
yetanotherid
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Quote:
Originally Posted by OvejaNegra View Post
yetanotherid: you set the options in the nvidia panel and on the player at the same time? i do it too but, maybe we are doing a double correction (the renderer on MPCHC stretchs the levels and the video card do it again).
I think if you do both you're double dipping. At least on my XP PC it does. If I change the luminance level via the video card while a video is playing there's a noticeable difference, if I also change it again via MPC it gets way too dark. I just let the video card do it because then it's right regardless of the player being used.
I can't speak for what the EVR renderer does as I'm still on XP without much dot $%$#$ net crap installed, so I don't have the EVR renderer. Maybe try a different renderer too.

I'm pretty happy with the way my monitors display video but I've never "calibrated" one in my life. Plus I still run a pair of 22" CRTs so with any luck it'll be another ten years before I've had much experience with LCDs.

It made me think the first time you mentioned it, and it's made me think again now you've mentioned it again.... Windows 7 display calibration? I wonder if that's your problem? I've never used it, being still on XP. Can you disable it or reset it and set up the monitor via it's own adjustments (if LCDs have the same adjustments as CRTs)?

Myself, I just adjusted the colour, contrast and brightness etc on my CRTs until I was comfortable reading text from a couple of feet away and white looked white (not blueish or greenish etc... in fact originally I taped a white A4 piece of paper to the front of the monitor and set out to duplicate it), then being CRTs I spent about another week fiddling until I got them both to look pretty much exactly the same. I changed the setting to 0/255 in the Nvidia Control Panel and that was it. Video looks pretty good.
If anything, I'd say the video looked a little washed out and lacked colour before I changed the NviDia setting, whereas you seem to have the opposite problem.

Sorry I can't be of more help aside from the double dipping thing and maybe thinking you should ignore the Windows Display calibration. I'd maybe reset one of the CRTs, and then without Windows interfering use the CRTs own controls to adjust the monitor with your eyes. Maybe do it with the other monitors off so they don't influence what your eyes are seeing, then when you're happy set the video card to 0/255 and try playing a video. Maybe the monitors aren't set up right "by themselves", then Windows tries to calibrate them, and in the end you've got a bit of a mess? Just a thought....
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