Videos are NOT stored in RGB - YUV vs RGB and Digital Color Explained

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A common misconception is that digital video is processed and stored as RGB data. At first glance, this might sound reasonable - after all, the input on the camera sensor is RGBG, and your display is RGB. However, this is not the case! Videos are typically stored as YUV (or technically YCbCr in the digital realm).
Why? Well, in this video, we explore digital colour and how we encode and represent images and videos on computers. To answer the why question briefly then: efficiency and legacy. YUV and YCbCr are a form of separating the luma and chroma (the brightness and colour) signal to be able to gain efficiency by lowering the quality on the colour component. It also goes back to colour TV working by adding a colour to an existing black-and-white grayscale image.
=== Timestamps ===
00:00 - Introduction
00:21 - RGB vs YUV
01:45 - How YUV Works
04:03 - The UV Plane
06:05 - Similarity to Analog Component Video
07:23 - Why Is This More Efficient? (Chroma Subsampling)
13:04 - Does Subsampling Matter?
15:20 - Why Would We Do This?
17:18 - Conclusion
=== Helpful resources/more information ===
en.wikipedia.org/wiki/YUV
www.pcmag.com/encyclopedia/te...
/ eli5_rgb_vs_yuv
en.wikipedia.org/wiki/YCbCr
en.wikipedia.org/wiki/YPbPr
Fun fact: Red/Blue used by YCbCr/YUV are not the only colour planes. DSC (display stream compression) used for high refresh rate monitors over DisplayPort uses YCoCg uses green(/pink) and orange(/blue) for its two planes!
You can also totally notice chroma subsampling in the credits at the outro of ‪@LinusTechTips‬ videos, as they typically use coloured text on a coloured background!
=== Thanks for Watching! ===
I hope you enjoyed this video and learned something new! If you found this useful and want to see more videos like it in the future, leave a comment and consider subscribing!
You can use this video under a CC-BY-SA license. I used a lot of helpful images from WikiMedia throughout this video. They should all be credited at the corresponding points - unfortunately, descriptions are limited to 5000 characters and so I can't list them out individually here.
=== Shoutouts ===
Shoutout to Andy Roberts, Felipe Clark, Paul Janes and Mohammad Ansari from AMD Markham who answered my questions about display technologies and how stuff works. This video was filmed before my term there, but I learned a lot from them.
Also a small shoutout to Dixon Huang, Lucas Choi, and Mrugank Upadhyay who had to endure me lecture/rant about topics like this (and have me point out every time they left a display running in YUV 4:2:0 mode when testing FreeSync...)
=== Clarifications and Corrections ===
- I use YUV and YCbCr almost interchangeably in this video. I am aware they are technically different/distinct things, but my point is comparing these luminance/chrominance schemes to RGB, and they are all similar enough for that purpose.
- Why are all the text fields in the video a different typeface/colour? I edit in multiple passes, and work on multiple videos concurrently. Kdenlive defaults to using the last used settings which differ for each video and I don't change it since it's good enough. Hey, still faster than using Cinelerra...
- Color? Colour? Argue it in the comments. It doesn't matter but I'm sure I'll hear how I'm wrong from both sides.
Thanks for watching! I hope this video helped you out!
Produced by Tony Tascioglu
tonytascioglu.com

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7 июл 2024

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Комментарии : 14

@carekbean 7 месяцев назад

Thanks. Had to watch this twice with starting and stopping to read the little comments... But after years of YUV mystifying me, I finally understand it. Great tutorial

@TonyTascioglu 6 месяцев назад

Thanks! Glad I could help demystify this a bit!

@ArunKumar-zd4ue 2 месяца назад

Thank you !! GReat video

@BurningDrake39 Месяц назад

I feel like I can lecture people about this now, thx

@anzhel3268 3 месяца назад

thanks, cool video!

@Thomas_Shelby_295 10 месяцев назад

Please tell me whether I use RGB or yuv color format for watching content on phone? ❤

@TonyTascioglu 9 месяцев назад

If you're watching on RU-vid, the video is 8 bit YUV420, which is then converted to RGB for the phone screen. If you plug your phone into a TV, it depends. HDMI supports either scheme (but you should probably force it to use RGB)

@MePeterNicholls 3 месяца назад

4K colour space Rec. 2020 has a really wide RGB gamut too HENCE why it really is a huge upgrade

@KirsGM 11 месяцев назад

The thing that is bugging me out, is that even if in theory, we are not suposed to notice 422 from 444, on my TV (an LG C9) the difference is pretty evident. 422 is definitely a bit blurrier, and 444 have razor sharp edges and retains more fine detail in textures. I'm starting to think that maybe I'm too sensitive to color?¿

@TonyTascioglu 11 месяцев назад

For general text or graphics? I find it very noticeable as well - particularly coloured text on a background graphic. If there's a difference when watching movies or something however, that might come down to how the TV handles processing with different inputs. There are a couple other things with TVs: - Make sure your colour range is set to limited/full depending on how your TV works. Full uses 0-255 for representing each channel, but most TVs expect limited range 16-235. - If overscan is kicking in, it also makes everything very blurry since it scales (usually bilinear) the input

@NielsGx Год назад

If you have a 4K 4:2:0 video from a DSLR, and re-encode at 1080p 4:4:4, would you have more informations than reencoding at 1080p 4:2:0 ? Well nothing would beat the original 4K obviously

@TonyTascioglu 11 месяцев назад

Hm. In theory, yes, you should be able to then have 1080p luma and full 1080p chroma vs 1080p luma and 540p chroma. That being said, I have not looked into how FFMPEG/etc actually handle the chroma channels. I know that they do use different scaling algorithms for luma and chroma by default when transcoding, but if it'll work as you mentioned, I'm not sure.

@shaanlama3610 6 месяцев назад

YUV vs RGB wich best?

@TonyTascioglu 6 месяцев назад

Depends what you're trying to do and what your priorities are. As shown in the video, on PC displays, full 24 or 30 bit RGB would be the "best" video quality, but with terrible efficiency and be very wasteful. On the other hand, if your goal is compressing video down to manageable bitrates with something simple enough that it can be mostly decoded in hw, YUV420. In terms of workloads, videos and JPEG photographs are typically in YUV. Mostly for efficiency and due to legacy/backwards compatibility reasons. PNG (graphics) are stored in RGB, as they are often used for graphics or charts for web use, where you want something lossless. This is actually an ongoing discussion, as we need to decide whether to use YUV or RGB for new image formats such as JXL and AVIF. Photography tends to use YUV with lossy compression, but PC and web graphics tends to use RGB with lossless compression. AVIF for example, has a lossless mode, but, since it uses AV1 video I frames (simplifying a fair bit here), it converts an input image in RGB to YUV. This process however isn't lossless, and you can see color artifacts around edges of certain objects. TLDR - which is best depends on what you're doing, and what your goals are.