REC.709 vs sRGB

[mnm-a]

The HDTV Standard, ITU-R BT.709, defines an RGB encoding and a Y'CbCr encoding.
In accordance with the standard BT.709 Y'CbCr and RGB have black = 16 and white =235

Rec. ITU-R BT.709-5 https://www.itu.int/rec/R-REC-BT.709-5-200204-S/en

Digital representation
Coded signal R, G, B, or Y, CB, CR
Quantization levels(
– Black level R, G, B, Y 16
– Achromatic CB, CR 128
– Nominal peak
– R, G, B, Y 235
– CB, CR 16 and 240
Quantization level assignment(3) 8- bit coding
– Video data
– Timing references(2)
6.12
Filter characteristics(4)
– R, G, B, Y 1 through 254
– CB, CR 0 and 255

------
But here (https://books.google.com.ua/books?id=6dgWB3-rChYC&pg=PA16&lpg=PA16&dq=sRGB+range+16+235&source=bl&ots=1KAjEGJxZ2&sig=raDau0hSC_GATXuvO8ADggqKNlA&hl=ru&sa=X&ved=0CF4Q6AEwB2oVChMIyYPdkJSdyAIVxP1yCh0NSgTq#v=onepage&q=sRGB%20range%2016%20235&f=false) author of book Keith Jack "Video A Handbook for the Digital Engineer" says that the range of sRGB (standartRGB) is 0-255 (in 8bits)
sRGB (standartRGB) values have a normalized range of 0-1, with 8-bit digital sRGB values having a range of 0-255 for black-white.
And bllack is 0 , white is 255

I do not understand this contradiction. Why ITU-R BT.709-5 standard defines black-white for RGB 16-235 but book says that black-white for RGB is 0-255 ?

And one more question.

The HDTV Standard ITU-R BT.709 defines an RGB encoding (and Y'CbCr). YouTube, Vimeo, broadcast HDTV, Blu-ray, and most camcorders and digital cameras use Rec.709 Y'CbCr.

In what cases is the R’G’B’ encoding used (in accordance with the standard BT.709) ?
What are the most common use cases for the R’G’B’ encoding (in accordance with the standard BT.709) ?

Explain, please.

[foxyshadis]

BT.709 isn't sRGB, it defines what's known as Studio RGB with headroom for analog peaks and valleys, and you should never touch it unless you're mastering for over-the-air broadcast.

[mnm-a]

BT.709 isn't sRGB, it defines what's known as Studio RGB with headroom for analog peaks and valleys, and you should never touch it unless you're mastering for over-the-air broadcast.
There are
- standartRGB = sRGB =computer RGB (different names for one and the same ?)
and
- StudioRGB

`standartRGB = sRGB` is RGB with black at 0 and white at 255.
`Studio RGB` is RGB with black at 16 and white at 235.

Do you mean that BT.709 defines `Studio RGB`, which is RGB with black at 16 and white at 235.
Do I understand correctly ?

[mnm-a]

Studio R'G'B' (16-235)
Is this space specific only for program SonyVegas ?
Which standard defines this space?
I can not find a a definition for this color space.

[huhn]

sRGB isn't BT 709 RGB it has the same gamut but a different gamma/ transfer function.

bt 709 RGB is very bad for encoding so it isn't really used.

a computer desktop like windows always works in full range RGB the GPU thinks the input image is full range RGB.

[mnm-a]

sRGB isn't BT 709 RGB it has the same gamut but a different gamma/ transfer function.
bt 709 RGB is very bad for encoding so it isn't really used.

Interestingly.
foxyshadis says that BT.709 RGB encoding is StudioRGB (if I understood him correctly)
You say that there is `bt 709 RGB encoding` .. And it is something separate .. not StudioRGB ..

Is there any information about the `bt 709 RGB` encoding ?

[Asmodian]

Interestingly.
foxyshadis says that BT.709 RGB encoding is StudioRGB (if I understood him correctly)
You say that there is `bt 709 RGB encoding` .. And it is something separate .. not StudioRGB ..

Is there any information about the `bt 709 RGB` encoding ?

It is basically a hack, using the limited range and gamma function of BT.709 with RGB instead of YCbCr.

Besides the range the difference between it and sRGB is the length and slope of the liner section near black in the gamma curve.

[huhn]

Interestingly.
foxyshadis says that BT.709 RGB encoding is StudioRGB (if I understood him correctly)
You say that there is `bt 709 RGB encoding` .. And it is something separate .. not StudioRGB ..

Is there any information about the `bt 709 RGB` encoding ?

yes:
https://en.wikipedia.org/wiki/Rec._709

"Rec. 709 defines an encoding and a Y’CBCR encoding"

sRGB:
https://en.wikipedia.org/wiki/SRGB

foxyshadis said "bt 709 isn't sRGB" this is 100 % correct.

so don't mix sRGB and BT 709 R’G’B’.

[mnm-a]

It is basically a hack, using the limited range and gamma function of BT.709 with RGB instead of YCbCr.
But the "hack" is defined by the standard REC.709.
Besides the range the difference between it and sRGB is the length and slope of the liner section near black in the gamma curve.
From where is this information? Can you give a source? Or is it our own observations?

Do you agree that `BT.709 RGB` is not `StudioRGB` ?

[mnm-a]

yes:
https://en.wikipedia.org/wiki/Rec._709
"Rec. 709 defines an RGB encoding and a Y’CBCR encoding".
I know (virtually) the person who wrote this.
He is based on data of standard that I quoted above.

foxyshadis said "bt 709 isn't sRGB" this is 100 % correct.
so don't mix sRGB and BT 709 R’G’B’.
But he says that `BT.709 R’G’B’` is StudioRGB (not sRGB).. Is this true?
p.s.
Interestingly, in what cases is used the :) mysterious `BT.709 R’G’B’` encoding ?

[huhn]

I know (virtually) the person who wrote this.
He is based on data of standard that I quoted above.


But he says that `BT.709 R’G’B’` is StudioRGB (not sRGB).. Is this true?
i don't know. i know what sRGB is and what BT 709 RGB /limited or full range. studio RGB could be a name for bt 709 with limited range RGB.
Interestingly, in what cases is used the :) mysterious `BT.709 R’G’B’` encoding ?

mastering i guess. maybe the master before it is transformed to YVbCr and sub sampled to 4:2:0. i don't think it's used anymore. DCI P3 has a bigger gamut already.

[foxyshadis]

StudioRGB is Sony Vegas's and Adobe Premiere's name for BT.709 RGB, that's why it's "known as" StudioRGB. I don't know what exactly you're looking for, it's an unofficial name, but it's a well-known one because those software packages are so popular. It seems like your question has been answered several times over already.

[Warperus]

I really doubt Sony Creative Software invented this studio levels thing.
I blame microsoft with their video for windows :)
https://msdn.microsoft.com/en-us/library/windows/desktop/dd206750(v=vs.85).aspx

[raffriff42]

Or maybe it was the original publisher of Vegas before Sony, Sonic Foundry
http://wayback.archive.org/web/20000620190705/http://www.sonicfoundry.com/Products/NewShowProduct.asp?PID=280

EDIT... but after perusing the old manual (http://pdf.textfiles.com/manuals/STARINMANUALS/Sony%20Creative%20Software/Manuals/Archive/Vegas%20Pro%201.0.pdf) where video took a definite back seat to audio, I wouldn't be surprised if Sonic Foundry used Microsoft's code and terminology here.

EDIT... after perusing some old VFW docs, I could not find any reference to encoding levels. They did mention Rec601 (then known as CCIR-601), which defined the 16-235 standard back in 1982 (https://en.wikipedia.org/wiki/Rec._601), ten years before VfW (https://en.wikipedia.org/wiki/Video_for_Windows) came on line.

Here's an interesting quote I stumbled across, from John McGowan's AVI Overview, a very early video website (when Realmedia and H.261 were "the new wave" (www.jmcgowan.com/avicodecs.html#XMPG)), which gives a clue to the original use of studio levelsCCIR-601 (http://www.jmcgowan.com/avigloss.html#CCIR601)
This is now "Recommendation ITU-R BT.601-5, Studio encoding
parameters of digital television for standard 4:3 and wide screen
16:9 aspect ratios". This is a standard for high quality
uncompressed digital video used in studios and video production.
CCIR-601 digital video is frequently stored on D1 digital video
tapes.

EDIT... perusing ITU-R BT.601-7 (https://www.itu.int/rec/R-REC-BT.601/en) (Annex 1 Part 2, "Encoding parameter values for the 4:4:4 member of the family") there is mention of 16-235 R, G, and B ("if used"). I think this is probably the original "Studio RGB," although somebody else (not the ITU) probably came up with that name. BTW the 601 standard allowed for 10-bit quantization right from the very beginning, so saying "16-235" is a simplification, but we all know what is meant. Again however, as foxyshadis has said (post #2), don't use limited-range RGB without good reason. Rule of thumb, YUV is limited-range, RGB is full-range.

[mnm-a]

I thank you all for your answers! Many thanks !!
This question is important for me from a theoretical point of view. I am doing translation ..
And I have found something else ..

"The Filmmaker’s Guide to Digital Imaging" by Blain Brown
It is important to remember that when it comes to video, what constitutes “pure black” is not always the same. In 8-bit video, pure black is not zero, it is 16, although that is still 0%.
It is the same at the top end: “pure white” is not 255, it is 235, and again, this is 100% white. Anything under 16 is called super black and anything over 235 is superwhite.
This is called studio-swing; when the full range from 0 to 255 is used, this is called full range or extended range.

"The Filmmaker’s Guide to Digital Imaging" by Blain Brown
Rec.709 also incorporates what are called legal levels; also known as studio swing or video range. Range or swing in this context really means
excursion, as in how the signal level travels between reference black and reference white. In 8-bit video, the minimum code value is 0 and the maximum is 255.
You would think that 0 represents pure black and 255 represents pure white.
In legal levels, video range or studio-swing, however, black is placed at code value 16 and reference white is at 235 (64-940 in 10 bit).
Code values from 0-16 and from 236-255 are reserved as footroom and headroom.
When this system is not used and the video signal uses all code values from 0-255 (0-1023 in 10 bit) it is called full swing or extended range.



"Digital Video and HD: Algorithms and Interfaces" by Charles A. Poynton

http://i.imgur.com/MM7JWPF.png

http://i.imgur.com/o7WeL04.png

http://i.imgur.com/CU6TBmX.png

http://i.imgur.com/1onKGQZ.png

http://i.imgur.com/fvxBjhl.png

[huhn]

what is the question?

this is just about full range and limited range and there alternative names.

[mnm-a]

what is the question?
this is just about full range and limited range and there alternative names.

It was not a question. It simply sources that are confirms (if I'm not mistaken) what was said above about "StudioRGB"
Prefix "Studio" is `16-235 range`

[huhn]

this is not a joke from AMD:
https://pcmonitors.info/wp-content/uploads/2012/10/AMD-Color-Pixel-Format.png

[raffriff42]

nVidia does this too (http://nvidia.custhelp.com/ci/fattach/get/251942/0/filename/NVTechNotes_0041_v02.pdf) - this is because digital TVs expect 16-235, PC monitors expect 0-255,
but the user can select manually if needed (for example if the driver misreads the monitor type).

https://www.dropbox.com/s/dtt251ljlysh1m5/rgb-levels%20nvid-tech-2.png?raw=1 (http://nvidia.custhelp.com/ci/fattach/get/251942/0/filename/NVTechNotes_0041_v02.pdf)

[feisty2]

Colorspaces that YUV vids are derived from are called "studio RGB", like RGB colorspaces with 601/709/2020 primaries and 709/2020 gamma and stuff..
sRGB is just some widely used RGB colorspace that happens to share the same primaries with bt709

[huhn]

nVidia does this too (http://nvidia.custhelp.com/ci/fattach/get/251942/0/filename/NVTechNotes_0041_v02.pdf) - this is because digital TVs expect 16-235, PC monitors expect 0-255,
but the user can select manually if needed (for example if the driver misreads the monitor type).

https://dl.dropboxusercontent.com/u/108089426/Screenshots/rgb-levels%20nvid-tech-2.png (http://nvidia.custhelp.com/ci/fattach/get/251942/0/filename/NVTechNotes_0041_v02.pdf)

they don't use studio in the name and it was possible to use both before driver 346.

[mnm-a]

ITU-R BT.709, defines an RGB encoding and a Y'CbCr encoding. In accordance with the standard BT.709 Y'CbCr and RGB have black = 16 and white =235

Rec. ITU-R BT.709-5 https://www.itu.int/rec/R-REC-BT.709-5-200204-S/en

Digital representation
Coded signal R, G, B, or Y, CB, CR
Quantization levels(
– Black level R, G, B, Y 16
– Achromatic CB, CR 128
– Nominal peak
– R, G, B, Y 235
– CB, CR 16 and 240
--------------

My question is about REC.601 and R’G’B’ encoding.

I know that REC.601 defines Y’CBCR encoding
Does Rec.601 define an R’G’B’ encoding ?
If `yes` then how does define Rec.601 an R’G’B’ encoding ? I mean nominal range and reference black/white.
Explain, please.

[hello_hello]

https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion
https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.709_conversion

16-235 and 16-240 still apply.
https://en.wikipedia.org/wiki/Rec._601#Signal_format

Edit: Damn..... I completely answered the wrong question...... I've deleted the irrelevant stuff that followed. I'm not sure about the RGB question.

[foxyshadis]

BT.601 Table 4 row 8 give R, G, B, and Y all the same 16-235 range, but doesn't spend any more time on the limited RGB version. It might only exist to make the old analog formula continue to work out correctly.

[Balling]

sRGB is a transfer function which is the just a normal invert to decode, while BT.709 transfer encoding and decoding are different to compensate for dim surround. sRGB has nothing to do with range. sRGB can be limited range, when you set limited RGB in nvidia, e.g. since sRGB is the default for any R'G'B' unless it is tagged.