4:2:0 content on a 4:4:4 display - blurry? - AVS Forum
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post #1 of 8 Old 10-25-2013, 08:00 AM - Thread Starter
 
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I own Samsung LN40B550K LCD HDTV from 2009 that fortunately supports PC Mode, which uses 4:4:4 chroma subsampling when in HDMI -> HDMI mode with working audio. The problem I ran into is that 4:4:4 only works when using a refresh rate of 60Hz. When I switch to 24Hz to watch 24p content, my TV goes into 4:2:2 24Hz mode, which provides the sharpest image for 4:2:0 content. If I remain in 60Hz 4:4:4 mode while playing 24p content, the image is somewhat blurrier and there is more judder, unless I use Smooth Motion in madVR. Is it normal to have blurrier image when playing 4:2:0 content on a 4:4:4 screen? I take it the TV converts 4:2:0 content to 4:4:4 which reduces image quality, right? Is there a way to fix it? I use my power-gaming rig with MPC-HC, madVR (high quality upscaling & downscaling settings), and LAV Video Decoder with nVidia CUVID decoding and acceleration, which provide me with great image quality.

The reason why I don't want to just switch to 24Hz 4:2:2 mode for 24p content is because it needs a completely separate calibration that would mess up my 60hz 4:4:4 calibration. I calibrated 4:4:4 60Hz to D65, but when switching to 24hz 4:2:2 - my contrast, gamma, and RGB are completely off. There does not seem to be a way to calibrate my TV for each refresh rate/chroma subsampling. I would have to re-calibrate many factory settings each time I want to watch a movie and then do it again to play games. That is crazy... I tried using other profiles (like Standard instead of Movie) but they lock me out of several important calibration options..

So, is there a way to play 4:2:0 content on a 4:4:4 screen without making it blurry? LAV Video Decoder can output in 4:2:0, 4:2:2, 4:4:4, RGB, 8-16bit formats. but choosing any of them makes little to no difference.

Any advice will be greatly appreciated! Thank you!
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post #2 of 8 Old 10-25-2013, 07:31 PM
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#1 -- HDMI as it exists today does NOT support 4:2:0 so no products support 4:2:0

4:2:0 is what is used on Blu-ray discs, but every Blu-ray disc player upconverts to 4:2:2 or 4:4:4 (both are YCbCr formats).

#2 4:4:4 indicates NO chroma subsampling (or color decimation to say the same thing a different way)

When you convert RGB to YCbCr without chroma subsampling, you get YCbCr 4:4:4

There is no benefit to using 4:4:4 instead of 4:2:2... there is far more color information in 4:4:4 (and RGB) than human vision can detect. You could argue that 4:2:0 carries all the color information necessary for good human vision acuity, but I don't buy that. I think 4:2:0 is taking away a bit too much data. Upconverting 4:2:0 to 4:2:2 does not add more information, it merely makes the information from the 4:2:0 format take up more space/bandwidth -- and makes the Blu-ray data compatible with HDMI as it exists today.

If you are getting good images with 24p YCbCr 4:2:2 that's often the very best signal to send to the TV since the TV will process the data in that format without an extra conversions. After processing the YCbCr is converted (in the TV) to RGB for final display as an image. But sending RGB to the display is usually worse than sending YCbCr 4:2:2 because the TV will convert the RGB input to YCbCr for processing in the TV, then convert back to RGB for display... that's an extra conversion step and each conversion step causes a slight quality loss.

60p should never be more blurry than 24p in the TV... motion judder problems YES, you will see those from 24p sources like most Blu-ray movies. But if the processing in your computer isn't up to par, that processing could make images look worse.

Computer video is a miasma of despair when you are trying to use a computer as a high quality video source. There are no truly accurate video subsystems. A highly respected consumer video advocate worked with a leading computer video subsystem manufacturer for a LONG time (like 6 months) to help them make a video board that was accurate. Everyone was happy with the result, the board went on the market, things were looking good. Then a firmware update was needed for the board and following the firmware update, the boards were no longer accurate. So all that work was for nothing. They couldn't maintain the accuracy of the board even when they knew they didn't want the firmware update messing with accuracy of the images.

You can trust your disc player to be more accurate than your computer.
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post #3 of 8 Old 10-25-2013, 11:56 PM
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Your issue is the PC is probably re-sizing your desktop to compensate for overscan.

Make sure you've got all scaling turned off in the PC and turned off in the TV. Make sure you have pixel for pixel mapping, ect..

The fact that you have this issue is correlated with setting the Pixel format to YCC 4:4:4, but the actual cause of the issue is a different setting.

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post #4 of 8 Old 10-26-2013, 10:35 AM
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Quote:
Originally Posted by Doug Blackburn View Post

When you convert RGB to YCbCr without chroma subsampling, you get YCbCr 4:4:4

There is no benefit to using 4:4:4 instead of 4:2:2... there is far more color information in 4:4:4 (and RGB) than human vision can detect. You could argue that 4:2:0 carries all the color information necessary for good human vision acuity, but I don't buy that. I think 4:2:0 is taking away a bit too much data. Upconverting 4:2:0 to 4:2:2 does not add more information, it merely makes the information from the 4:2:0 format take up more space/bandwidth -- and makes the Blu-ray data compatible with HDMI as it exists today.

If you are getting good images with 24p YCbCr 4:2:2 that's often the very best signal to send to the TV since the TV will process the data in that format without an extra conversions. After processing the YCbCr is converted (in the TV) to RGB for final display as an image. But sending RGB to the display is usually worse than sending YCbCr 4:2:2 because the TV will convert the RGB input to YCbCr for processing in the TV, then convert back to RGB for display... that's an extra conversion step and each conversion step causes a slight quality loss.

Is there a reason why video game consoles like the Xbox 360 and PS3 don't offer a YCbCr 4:2:2 option? Also, do most TVs handle YCbCr 4:2:2 differently than YCbCr 4:4:4? Is there a reason you recommend the former over that latter?
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post #5 of 8 Old 10-26-2013, 11:39 AM - Thread Starter
 
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Quote:
Originally Posted by sotti View Post

Your issue is the PC is probably re-sizing your desktop to compensate for overscan.

Make sure you've got all scaling turned off in the PC and turned off in the TV. Make sure you have pixel for pixel mapping, ect..

The fact that you have this issue is correlated with setting the Pixel format to YCC 4:4:4, but the actual cause of the issue is a different setting.

I believe that PC Mode allow the PC to send RGB signal directly to TV, without processing on TV's end.

All scaling is 100% off in both TV and PC. PC Mode makes text and games extremely nice (like a regular 1080p PC monitor) and crisp with 4:4:4 @ 60Hz, but movies are a bit blurrier than with 4:2:2 @ 24Hz.

4:2:2 @ 24Hz is the other way around - crisper for movies, but horrible for desktop use due to blurry/odd-looking text, regardless of scaling. This is the case for all media players, formats, codecs, etc.

I take it that 4:2:2 is crisper than 4:4:4 for Blu-Ray material because that material was designed to be played on a 4:2:2 screen @ 24Hz.

And I have an Intel 3770K running at 4.4Ghz, ASUS Sabertooth Z77 motherboard, 8Gb 2133Mhz RAM, GeForce GTX 680 2Gb VRAM, 256Gb Samsung 830 SSD - all stable 24/7. My system can handle any player/codec/shader/scaling at 1080p without any problems.
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post #6 of 8 Old 10-26-2013, 02:43 PM
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on my plasma mostly on bright screens the abl washes the image out and blurs things so it does not look crisp and clean.Also the source is all different clarity levels.One camera at a football game is crystal clear and another camera will be blurrier.sitting at a distance some SD stuff can look HD,and HD can look blurry..Source quality is all over the place.
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post #7 of 8 Old 10-26-2013, 06:46 PM
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Quote:
Originally Posted by MonarchX View Post

I believe that PC Mode allow the PC to send RGB signal directly to TV, without processing on TV's end.

All scaling is 100% off in both TV and PC. PC Mode makes text and games extremely nice (like a regular 1080p PC monitor) and crisp with 4:4:4 @ 60Hz, but movies are a bit blurrier than with 4:2:2 @ 24Hz.

4:2:2 @ 24Hz is the other way around - crisper for movies, but horrible for desktop use due to blurry/odd-looking text, regardless of scaling. This is the case for all media players, formats, codecs, etc.

I take it that 4:2:2 is crisper than 4:4:4 for Blu-Ray material because that material was designed to be played on a 4:2:2 screen @ 24Hz.

And I have an Intel 3770K running at 4.4Ghz, ASUS Sabertooth Z77 motherboard, 8Gb 2133Mhz RAM, GeForce GTX 680 2Gb VRAM, 256Gb Samsung 830 SSD - all stable 24/7. My system can handle any player/codec/shader/scaling at 1080p without any problems.

There SHOULD be zero difference between RGB and YCbCr 4:2:2 and YCbCr 4:4:4. If the conversions are all done correctly, there would be vanishingly small (and invisible) differences. In the real world, conversions aren't always done correctly. That's why we tell people to always check RGB and YCbCr to see if there's a difference. YCbCr 4:2:2 is the most "efficient" option because it sends the same images (that should be identical in appearance) as RGB and YCbCr 4:4:4 but less data has to be transferred and handled. More than likely the TV is going to process video in YCbCr 4:2:2 mode so anything else you send is going to need another conversion. You can (usually) tell if the TV will convert incoming RGB to YCbCr for processing in the TV if the Color and Tint controls do NOT disappear (or get grayed-out) when you put the TV in RGB mode. If the TV is leaving the incoming RGB in RGB mode and NOT doing a conversion to YCbCr, the color and tint controls will not be available as there's no easy way to raise saturation or change tint when you work in RGB mode.

How stable your HTPC is has exactly zero to do wit how accurate it's video subsystem is (the NVidia GeForce bit). And if by some miracle, you were able to get it accurate, the first time you do a firmware update it will be inaccurate again. The as I've mentioned before, the experts have been through this, and a major video board manufacturer couldn't even keep their accurate board accurate after the first firmware update KNOWING they had to be careful with it not to upset the accuracy it took then 6 months to achieve. You are not going to do better than they could/did and it is irrefutable that computer video is a miasma of despair when it comes to trying to make it accurate. Using RGB is not even helpful though it does solve some problems, it doesn't get rid of everything, by a long shot. And using RGB may look worse than YCbCr on some video displays -- or it may look the same, you can't assume either, you have to evaluate both and see which looks better. But looking better still doesn't correlate to being more accurate.
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post #8 of 8 Old 06-05-2014, 10:23 PM
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An update on 4:2:0 over HDMI... HDMI 1.4 (or possibly 1.4a) will support 4:2:0 at resolutions of 3840x2160 at 50 or 60 frames per second because HDMI currently doesn't have the bandwidth to support the transfer of more video data that would be required for 4:2:2 or 4:4:4 or RGB versions of those high-frame rate UHD formats. You can still get 4:2:2 at 3840x2160 at 24, 25 or 30 frames per second.
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