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EnTerr
Level 11

RGB 16..235 or 0..255 ?

From RTFM,
"1.3.4 Color" wrote:
  • RGB color values should be between 16 and 235.


Can someone explain the meaning of this? Does it mean should use programmatically RGB(16,16,16) for black and RGB(235,235,235) for white? Or is this video-related only?

I saw someone complaining that Roku outputs "full 0-255", went reading what's wrong with that - so far i found [0, 255] is considered "full swing" (or "PC levels", "extended-range"), whereas [16, 235] is considered "studio swing" (or "TV levels", "legal-range", "narrow-range").
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squirreltown
Level 9

Re: RGB 16..235 or 0..255 ?

I'm pretty sure Roku insists that any graphics for the store are limited to a white value of 235 and black of 16, so no it's not just about video. As a photographer, which means I really care about the way color and density render, I always profile my images & graphics with HDTV (Rec. 709) 16-235, which basically does the same thing as adjusting it manually to those values. The only exception is trying to match a color/density to the Roku interface - like matching an overhang to the background - For some bizarre reason the Roku is outputting with a profile that matches (NTSC 1953) even in hi-def. Now the Roku is not color managed so who knows what going on - to me its just basic Roku, "one of these things is not like the other" . It actually makes a lot of sense, PC monitors are light years ahead of TV's in rendering quality- even mucho $ TV monitors in edit bays. TVs have way too high a contrast for a given brightness level and black 0 & white 255 are colors that don't actually exist in nature, so it would be prudent to use them exceedingly sparingly.
Kinetics Screensavers
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TheEndless
Level 9

Re: RGB 16..235 or 0..255 ?

The legacy Rokus (firmware 3.x) only output 16-235. Starting with the Roku 2 (previous generation), they started outputting full range 0-255 (which has some correlation to the RGB vs. YCbCr arguments). I believe most televisions today can adjust automatically, but there's a small, vocal minority who insist that it results in poorer picture quality, I guess because it forces the television to switch to a mode that isn't native to the source material. As far as I know, Roku still says you should adhere to the 16-235 range to ensure compatibility with all displays.

In my experience, with the same Roku model, on my primary dev monitor, #000000 and #101010 look distinctly different, whereas on my main TV downstairs, they look identical.
My Channels: http://roku.permanence.com - Twitter: @TheEndlessDev
Instant Watch Browser (NetflixIWB), Aquarium Screensaver (AQUARIUM), Clever Clocks Screensaver (CLEVERCLOCKS), iTunes Podcasts (ITPC), My Channels (MYCHANNELS)
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squirreltown
Level 9

Re: RGB 16..235 or 0..255 ?

Endless, have you tried those two colors side by side output by a Roku? Curious what happens on a legacy box as i don't have one. Our brain has a natural "white-balance" function as it were and unless you compare the colors, anything close to white will appear white without something to compare it to. On my TV the 10 10 10 will look distinctively redder than 0 0 0 , My PC monitor is calibrated so it just appears darker, which is what you want.

Edit - Ok I must not have read your message properly at first, your downstairs TV clearly must have some automatic (or not) limiting going on.
Kinetics Screensavers
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TheEndless
Level 9

Re: RGB 16..235 or 0..255 ?

"squirreltown" wrote:
Endless, have you tried those two colors side by side output by a Roku? Curious what happens on a legacy box as i don't have one. Our brain has a natural "white-balance" function as it were and unless you compare the colors, anything close to white will appear white without something to compare it to. On my TV the 10 10 10 will look distinctively redder than 0 0 0 , My PC monitor is calibrated so it just appears darker, which is what you want.

They look indistinguishable on the legacy boxes, regardless of display.
My Channels: http://roku.permanence.com - Twitter: @TheEndlessDev
Instant Watch Browser (NetflixIWB), Aquarium Screensaver (AQUARIUM), Clever Clocks Screensaver (CLEVERCLOCKS), iTunes Podcasts (ITPC), My Channels (MYCHANNELS)
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squirreltown
Level 9

Re: RGB 16..235 or 0..255 ?

They look indistinguishable on the legacy boxes, regardless of display.


That would certainly follow, given what you describe about the output.
Kinetics Screensavers
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EnTerr
Level 11

Re: RGB 16..235 or 0..255 ?

Does anyone know what's the "right way" to convert between the two? I cooked up this formula, assuming linear scaling:

narrow = int(wide * 219/255 + 16.5)
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