Color Space and Bits - AVS Forum
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post #1 of 9 Old 09-18-2013, 08:12 AM - Thread Starter
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I understand Blu-rays are recorded with the YCbCr4:2:0 color space. What about 8-bit, 12-bit, 16-bit, 20-bit, 30-bit, 36-bit, or 48-bit color? What is the native color type in bits on Blu-ray discs?
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post #2 of 9 Old 09-18-2013, 06:58 PM
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Blu-ray video is encoded with 8-bits per color component.


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post #3 of 9 Old 09-19-2013, 05:13 AM - Thread Starter
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Originally Posted by ADU View Post

Blu-ray video is encoded with 8-bits per color component.
Thank you. I prefer to have my TV and player set to perform as little processing as possible. I have HDMI deep color off and color space set to YCbCr4:2:2. I haven't seen a Blu-ray player yet with a 4:2:0 setting. So I leave it on the closest setting.
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post #4 of 9 Old 09-19-2013, 05:29 AM
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Quote:
Originally Posted by Big C View Post

I understand Blu-rays are recorded with the YCbCr4:2:0 color space. What about 8-bit, 12-bit, 16-bit, 20-bit, 30-bit, 36-bit, or 48-bit color? What is the native color type in bits on Blu-ray discs?

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Originally Posted by ADU View Post

Blu-ray video is encoded with 8-bits per color component.

To clarify, Blu-ray is 8-bits per color, which is to say that it is 24bpp (bits per pixel). People often refer to this as 24-bit color. The terminology is thrown around rather loosely which only adds to the confusion. There are also different combinations of red, green, blue, alpha (transparency), etc. that can complicate things.

2/3-bits per R-G-B + alpha = 8/9-bit color = 64 to 256 colors (Amiga, NES, DOS era) lots of weird combinations of channel blending

4/5-bits per R-G-B + alpha = 15/16-bit color (High Color) = 32 or 65 thousand colors (Super Nintendo, Windows 3.1 era) lots of weird combinations of channel blending

8-bits per R-G-B = 24-bit color (True Color) = 2^24 = 16 million colors (DVD, Blu-ray, modern computer and gaming console graphics) add 8-bits for alpha blending and you get "32-bit color".

10-bits per R-G-B = 30-bit color (Deep Color) = 2^30 = 10 billion colors (professional workstations, editing environments)

12-bits per R-G-B = 36-bit color (Deep Color) = 2^36 = 68 billion colors

16-bits per R-G-B = 48-bit color (Deep Color) = 2^48 = 281 trillion colors

What I find most frustrating is that many TVs and monitors sold today are still cheap 6-bit (18-bit color) displays, capable of only 262,000 colors.
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post #5 of 9 Old 09-20-2013, 04:27 AM
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Quote:
Originally Posted by Big C View Post

Thank you. I prefer to have my TV and player set to perform as little processing as possible. I have HDMI deep color off and color space set to YCbCr4:2:2. I haven't seen a Blu-ray player yet with a 4:2:0 setting. So I leave it on the closest setting.

HDMI doesn't even carry 4:2:0, so that won't be an option in the player.

It is hard to know what causes the display to do as little processing as possible. If you want it to do no chroma upsampling then that should be done in the player by using 4:4:4. But displays have been known to do strange things and there is no fixed rule.

Eventually the video must be converted to RGB for display, but if you send RGB to the display it might convert it to YCbCr and then back to RGB again.

Spears & Munsil have an article on choosing a color space; they have patterns you can use to test the results yourself.

-Bill
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post #6 of 9 Old 09-22-2013, 01:17 PM
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Originally Posted by wmcclain View Post


HDMI doesn't even carry 4:2:0, so that won't be an option in the player.

It is hard to know what causes the display to do as little processing as possible. If you want it to do no chroma upsampling then that should be done in the player by using 4:4:4. But displays have been known to do strange things and there is no fixed rule.

Eventually the video must be converted to RGB for display, but if you send RGB to the display it might convert it to YCbCr and then back to RGB again.

Spears & Munsil have an article on choosing a color space; they have patterns you can use to test the results yourself.

-Bill

 

Good points.

 

I wonder why HDMI doesn't support 4:2:0, and how BD players with "direct digital" connections cope with that? I believe all digital broadcast content (OTA/sat/cable) is encoded/transmitted with 4:2:0 chroma subsampling btw.

 

I use RGB with my older CRT, because it doesn't support YCbCr. And use YCbCr 4:4:4 on my Gateway LCD monitor.

 

I think my old Sony HDMI DVD upscaling player had some chroma upsampling issues ("CUE"). Diagonal red lines/edges would sometimes look pretty jagged on that player, for example. Haven't really looked for those sort of issues on my Blu-ray player though.

 

I think your advice is sound though. You should use whatever mode looks best/most accurate on your particular TV/player. Maybe there are some patterns in the AVS 709 tests to check for chroma upsampling errors as well.

 

There may be other differences in the color output of the RGB and YCC modes as well, which could be more noticeable than upsampling errors. Most of the 2011 and 2012 Sony players I tested had bad green push/clipping in their RGB modes before Sony released a firmware update to fix the problem, for example. I found similar problems in the RGB modes on other brands as well. Errors in implementation can occur in either the RGB or YCC modes though, on both player and TV, so using YCC doesn't necessarily guarantee accurate color either.

 

There's a pretty good illustration of the differences between 4:4:4, 4:2:2, and 4:2:0 here btw...

 

http://en.wikipedia.org/wiki/Chroma_subsampling#Sampling_systems_and_ratios


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post #7 of 9 Old 09-22-2013, 02:32 PM
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Quote:
Originally Posted by nathanddrews View Post

To clarify, Blu-ray is 8-bits per color, which is to say that it is 24bpp (bits per pixel). People often refer to this as 24-bit color. The terminology is thrown around rather loosely which only adds to the confusion. There are also different combinations of red, green, blue, alpha (transparency), etc. that can complicate things...

...8-bits per R-G-B = 24-bit color (True Color) = 2^24 = 16 million colors (DVD, Blu-ray, modern computer and gaming console graphics) add 8-bits for alpha blending and you get "32-bit color".
 

 

There are other differences between the 24-bit (8-bits x 3 colors) graphics generally used on PCs, and video as well. Most still imaging applications on computers will use 0-255 "full swing" levels, for example, while consumer video (including Blu-ray) uses 16-235 "studio swing" levels as described here...


http://en.wikipedia.org/wiki/Rec._709#Digital_representation


...And there are some slight differences in the way gamma is encoded/decoded.


Another discussion on why we're able to make due with only 8-bits per color component for video...


http://www.avsforum.com/t/1337403/white-level-and-contrast-display-vs-mastering-and-video-dynamic-range


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post #8 of 9 Old 09-22-2013, 02:49 PM
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Quote:
Originally Posted by ADU View Post
 

 

There are other differences between the 24-bit (8-bits x 3 colors) graphics generally used on PCs, and video as well. Most still imaging applications on computers will use 0-255 "full swing" levels, for example, while consumer video (including Blu-ray) uses 16-235 "studio swing" levels as described here...


http://en.wikipedia.org/wiki/Rec._709#Digital_representation

 

 

I believe xvYCC is designed to recover some of the "head and foot room" in the chroma component of 8-bit YCC video to slightly expand it's possible gamut of colors (on displays/players which support it).


http://en.wikipedia.org/wiki/XvYCC


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post #9 of 9 Old 09-22-2013, 03:18 PM
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Quote:
Originally Posted by wmcclain View Post

HDMI doesn't even carry 4:2:0, so that won't be an option in the player.
HDMI 2.0 adds support for 4:2:0.
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