Any idea why YCbCr 4:4:4 only works at 61hz+ on Vizio M651?

Talk about overclocking displays at a higher refresh rate. This includes homebrew, 165Hz, QNIX, Catleap, Overlord Tempest, SEIKI displays, certain HDTVs, and other overclockable displays.
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trey31
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Any idea why YCbCr 4:4:4 only works at 61hz+ on Vizio M651?

Post by trey31 » 23 Mar 2014, 09:58

I checked compatibility with with belle-nuit test and when I lower the refresh rate to match 59.94 for watching video, the test no longer passes. There is blurring and single pixel doubling/shading, which I assume is due to the signal no longer being 4:4:4. I suppose it could be due to the panel turning on some of the internal processing (this is a TV by the way) that isn't on above 60hz, and that it is 4:4:4 but its being blurred. But that doesn't line up with Input being named PC, Game mode being On and all Internal processing set to off, including Smooth Motion and Film Mode (which is 3:2 pulldown rather than a 23.976 mode, I believe), Sharpness at 0, and calibrated. Even with everything off, refresh rates at 60.00 or lower are either not encoded correctly or are being scaled/blurred somehow, while 61hz to 109hz are not.

Any ideas of why this is happening, or suggestions about how I can fix this for watching video?

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Re: Any idea why YCbCr 4:4:4 only works at 61hz+ on Vizio M6

Post by Chief Blur Buster » 26 Mar 2014, 11:21

trey31 wrote:Any ideas of why this is happening, or suggestions about how I can fix this for watching video?
This can be from logic that automatically switches the same HDMI input from PC scaling mode to HDTV scaling mode, or vice versa, which can be quite annoying.

If your Windows taskbar is being cropped, try adjusting the overscan settings / zoom / stretch settings. This usually fixes everything immediately. Try finding a setting named "Aspect", "Zoom", "Stretch", or "Scaling", and toggling through all the options. See if that works.

Another thing to try is to use a different Timings mode -- a Custom Resolution but still using 60Hz. Create a custom 60Hz mode using a "Timings" setting of something else other than "Auto", by using large blanking intervals, or "Reduced" blanking intervals, to get away from ATSC standard timings (e.g. avoid 1125 Vertical Total during 1080i/1080p). The use of a custom 60Hz using either NVIDIA Custom Resolution or ToastyX, might actually trick things back into PC scaling mode rather than HDTV scaling mode.

TV's often do some annoying things, so you have to find workarounds for that.
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trey31
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Re: Any idea why YCbCr 4:4:4 only works at 61hz+ on Vizio M6

Post by trey31 » 26 Mar 2014, 15:03

Chief Blur Buster wrote:This can be from logic that automatically switches the same HDMI input from PC scaling mode to HDTV scaling mode, or vice versa, which can be quite annoying.

Another thing to try is to use a different Timings mode -- a Custom Resolution but still using 60Hz. Create a custom 60Hz mode using a "Timings" setting of something else other than "Auto", by using large blanking intervals, or "Reduced" blanking intervals, to get away from ATSC standard timings (e.g. avoid 1125 Vertical Total during 1080i/1080p). The use of a custom 60Hz using either NVIDIA Custom Resolution or ToastyX, might actually trick things back into PC scaling mode rather than HDTV scaling mode.

TV's often do some annoying things, so you have to find workarounds for that.
You, sir, are awesome!

So I made a new custom resolution in NCP for 1080p at 59.94hz with 2420 x 2160 total pixels just to see what would happen, and sure enough after I saved it nothing was being scaled or blurred. I already had a 1080p @59 mode in the NVIDIA panel under "Ultra HD, HD, SD" section and another 1080p @60 mode under "PC" section. Now with the new resolution at 60 (59.94hz) under "Custom" section, anytime I choose any of the 1080p @59 or @60 modes, it refreshes the screen and when it comes back on it is always set at the "Custom" 1080p @60 resolution with the massive blanking intervals. Which is fine considering pixel clarity/uniformity is now available at 59.94hz which is what I wanted.

Also the TV only has Normal and Stretch in "game" mode so that wasn't a problem.

After checking, the default @23 and @24 settings in NVIDIA panel still shows the blurring, but I don't care about that because the TV itself has a great 3:2 pulldown option and I hate using a mouse at 24hz.

But to be honest the "blurred" pixels look an awful lot like the 4:4:4 vs 4:2:0 macro comparison photos that are on some other sites. I wonder if it isn't NVIDIA that sees the default timings over HDMI as a TV and compresses the color space before the information is sent?

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Re: Any idea why YCbCr 4:4:4 only works at 61hz+ on Vizio M6

Post by Chief Blur Buster » 26 Mar 2014, 20:27

trey31 wrote:You, sir, are awesome!
trey31 wrote:...to be honest the "blurred" pixels look an awful lot like the 4:4:4 vs 4:2:0 macro comparison photos that are on some other sites. I wonder if it isn't NVIDIA that sees the default timings over HDMI as a TV and compresses the color space before the information is sent?
Glad that my tip actually got you somewhere!

Yes, sometimes a chroma loss occurs when you output a HDTV video mode, I find that behavior fairly annoying when there's no way to override this easily.
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Re: Any idea why YCbCr 4:4:4 only works at 61hz+ on Vizio M6

Post by trey31 » 26 Mar 2014, 22:25

Chief Blur Buster wrote:Yes, sometimes a chroma loss occurs when you output a HDTV video mode, I find that behavior fairly annoying when there's no way to override this easily.
So just for kicks I did the same custom resolution trick with 23.976 to see if it fixed the issue with that too, and wouldn't ya know it... 4:4:4 chroma at 24hz now too.

I did all of this in NCP, but I'll do custom timings with CRU at some point and report back on that as well. Making them appear as a native resolutions but not with "TV" timings should definitely work with that method as well. Plus this way they won't get lost with every driver update.

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