[opendtv] Re: Sparkle

From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
Date: Sun, 4 Dec 2016 01:25:00 +0000

Craig Birkmaier wrote:

Wow! The folks at Dolby are going to have to rethink everything now...

Well, inform yourself first, Craig. I've said this many times. Before arguing,
education.

Here are two sources. One that explains what is happening now, and one that
explains what has been tested and the results.

http://www.expertreviews.co.uk/tvs-entertainment/1404660/dolby-vision-vs-hdr-10-whats-the-difference

Quoting:

"Most of the differences between the competing standards arise around colour
bit depth and brightness. Dolby Vision films are mastered in up to 12-bit
colour, whereas HDR 10 is mastered for 10-bit colour, hence the name. Films are
colour graded specifically for Dolby Vision and studios have to provide
artistic approval of Dolby's mastering.

"The difference that 12 bit makes is that Dolby Vision has 4,096 possible RGB
values versus the 1,024 values for HDR 10 meaning greater granularity of colour
production. A 10-bit colour depth amounts to over 1bn colours, whereas 12-bit
opens it up to over 68bn colours. Needless to say, both offer a far wider
colour gamut than non-HDR sets of today, which make do with just 256 RGB values
for 16m colours. All Dolby Vision branded TVs will support the 12-bit colour
depth required."

That seems pretty clear to me. You'll see the same explained in other sources.
Find me a source that says otherwise, before going any further.

Then this is a comparison of multiple standards, including ones which use log
coding and floating point, even for Y Cb Cr (what they call LogLuv used by
TIFF):

http://www.anyhere.com/gward/hdrenc/hdr_encodings.html

You will note that there is indeed a LogLuv 24 standard, perceptually
compressed, that comes very close to 5 orders of magnitude in dynamic range.
But, according to this paper,

"Although the LogLuv format has been adopted by a number of computer graphics
researchers, and its incorporation in Leffler's TIFF library means that a
number of programs can read it even if they don't know they can, it has not
found the widespread use we had hoped. Part of this is people's reluctance to
deviate from their familiar RGB color space. Even something as simple as a 3´3
matrix to convert to and from the library's CIE XYZ interface is confounding to
many programmers. Another issue is simply awareness - unless one has key
industry partners, it is difficult to get word out on a new format, no matter
what its benefits might be. The follow-up article, written for the ACM Journal
of Graphics Tools (vol. 3, no. 1), "LogLuv encoding for full-gamut,
high-dynamic range images," was an effort to stem these difficulties. We are
still hopeful that this format will find wider use, as we have found it to work
extremely well for HDR image encoding, ourselves. There is no more appropriate
format for the archival storage of color images, at least until evolution
provides an upgrade to human vision."

Who knew?

Evidently, not you. But you'll never use that as an excuse to inform yourself
first, right Craig? This is the problem with your way of arguing. If you know
otherwise, do not tell me that you know. Prove it. Show me that the standards
people are talking about today, for HDR, are different from what the first post
described.

I've caught you to many times spouting factual errors without justification. If
I'm wrong, prove it. At the very least, going about proving things will teach
you all sorts of new stuff. And it may also save you from a huge amount of
pointless arguing.

Bert

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