RGB vs YcBcr 4:4:4 over HDMI NVIDIA and AMD (Chroma Subsampling)
I often have questions by people about quality issues connecting their computers to their new 4K (2160p) UHD LCD TV at 60hz about flickering screen, color changes and dark and bright scenes incorrectly showing. There are multiple reasons for this, but first you need to understand the basic.
RGB is the way your graphic card talks to your monitor. Your PC monitor is normally supposed to handle all color gamut you can imagine. So normally, people don’t really have trouble between their graphic cards and their PC monitors. The problems arise when you want to sit in front of your TV and plug your computer to it and most of the time, it’s in another location.
One thing to understand is a TV is not a monitor and is mostly made for entertainment (movies, TV shows and gaming). PC Monitors have more functions and are also made for working station(Word/Excel/Powerpoints), Photoshoping and more. Graphic cards have different ways to talk to your 4K TV so you can enjoy a Windows desktop on the big screen. HDMI 2.0 link is what you will try to get setup.
HDMI 2.0 can carry color space in RGB (uncompressed) or YcBcr(compressed) from the card to the TVs. Your graphic card will by default set the color range to a limited(16-235) color space and it means you will have less deep black and fewer whiter areas, resulting in missing color mixes and reproduction that will be off, especially while watching movies. You can easily go into the NVDIA or AMD panel and change from “Limited” to “Full range”(0-255) and you will immediately see the difference. Even the cheap 4K UHD TVs can handle Full range.
What is YcBcr? YcBcr is just a way to compress data over the HDMI channel and to understand 4;4:4, 4:2:2, 4:2:0 you should watch this video. If you don’t want to watch the video, 4:4:4 is the best you can get to output details using YcBcr. It can be in 8bit, 10bit and 12bit and as you can guess, the more bit you have, the greater dynamic range you will get(you need content that was recorded in 12bit to enjoy it).
Now, the most important thing you need to consider is the maximum length and the type of HDMI cable you want to consider buying. There are so many wrong description for cables on Amazon and Ebay to promote that you end up buying cables that won’t have enough bandwidth resulting in a flickering screen. It’s important to understand this one thing: the maximum length that I am recommending for Full Range RGB or YcBcr 4:4:4 is 20ft/6 meters. No more! It is short if your TV is in another location, but this is the best you can do without an expensive repeater. Also, make sure you to buy a CERTIFIED HDMI PREMIUM HDMI cable. If the logo is not the one you are seeing in this article, DO NOT BUY. The logo means that the cable has been tested and will work for you. Monoprice is selling a 20ft it for $15.
Now you have all information to get the best picture out of your computer to your 4K UHD TV at 60hz. Remember, RGB Full Range will do just well. Make sure you change from “Limited” to “Full Range”.