[opendtv] Re: Sparkle
- From: Craig Birkmaier <brewmastercraig@xxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 02 Dec 2016 07:18:40 -0500
On Dec 1, 2016, at 10:43 PM, Manfredi, Albert E
<albert.e.manfredi@xxxxxxxxxx> wrote:
Good for you, Craig. But it proves nothing. I will explain below what it
takes to claim you have an HDR display. You stated that smartphones and
tablets are available with HDR displays. All you have to do is support your
claim. Or just say ooops, my bad. Should be simple enough.
Ooops, my bad...
There, does that make you feel better Bert?
The reality is that displays are moving beyond the old 8 bit definition of
luminance and color optimized for CRT displays. Do they meet the new
definitions of what an LCD or OLED HDR display should offer?
NO.
Did every NTSC display fully support the capabilities of NTSC? Does every HD
display fully support the capabilities of HD (pick a definition as there are
several)?
We are in a transitional period. There are several existing/proposed standards
for HDR; and several for WCG. There are many sets being sold today as HDR
capable that do not meet all of these specs. All one needs to do is look at LCD
and an OLED displays that claim to offer HDR side by side to understand that
there will be a range of products offering varying levels of performance. And
then there is the minor matter that it may not matter based on the viewing
conditions where the display is installed.
I wrote:
What you are missing is that there is a continuum between
today's 8 bit luminance representations and the specifications
that Mark was citing for HDR.
Except that there are specific definitions at play now. This first, very
recent article, only tells half the story, but it's a start.
Yup. And there are specific products being sold that claim to offer HDR that
are very different.
http://www.digitaltrends.com/home-theater/hdr-for-tvs-explained/
It states that SDR displays, at their brightest, provide 300 to 500 nits.
Compare that to the displays of smartphones and tablets, to see if they are
meaningfully better. It also states:
A meaningless definition. There are SDR displays for outdoor use that have more
than 8500 nits of brightness.
Clearly modern mobile devices have displays with HD or better pixel
resolutions. Some support improved color gamuts; some offer more than 500 nits
brightness. You cannot say what a display is today based on definitions. What
you can say is that displays now have the ability to conform to multiple
standards.
"In April, the UHD Alliance - an inter-industry group made up of companies
like Samsung, LG, Sony, Panasonic, Dolby, and many others - announced the
Ultra HD Premium certification for UHD Blu-ray players. This benchmark sets
some baseline goals for HDR, like the ability to display up to 1,000 nits of
brightness and feature a minimum of 10-bit color depth. Both HDR10 and Dolby
Vision meet the standards set by the certification, but how they go about it
varies greatly between the two."
Sounds like a bunch of technophiles arguing about the future. Oh wait!
That's what's happening. Maybe I'll come up with a spec for HDR.
They should also have provided an idea of the dimmest possible content, but
at least you have the 1000 nits parameter to work with. The wider color gamut
might be associated, but you can have WCG without HDR, in principle. Getting
the super bright output from your small hand held devices is a much harder
nut to crack.
But that nut is being cracked. The nits requirement is related to the display
technology, and is heavily influenced by the amount of ambient light where the
display is used. Here's one clue that may help Bert over this misunderstanding:
Why is the peak brightness for OLED based HDR only 500 nits, while for LCD it
is more than 1000?
I guess it is not related to the actual screen brightness or the requirements
of the human visual system. If 0 to 500 nits is good enough for HDR on an OLED
display, why do we need twice as much peak brightness for LCD?
Explain this Bert?
This article is better. It quantifies the range of brightness needed for HDR:
https://pro.sony.com/bbsccms/assets/files/cat/hdr/latest/MK20109V1_1_HDR.pdf
It says that SDR covers a range of nits of 3 orders of magnitude, whereas HDR
provides 5 orders of magnitude. So, something like 0.3 to 300 nits is SDR. To
qualify as HDR, you would need to be able to display a range 0.01 to 1000
nits, for example, or 0.005 to 500 nits. This is what I'm talking about. Now
you have the information needed to prove whether smartphone and tablet
displays can achieve this range, rather than just barely meet the same specs
as SDR displays.
The Sony article is informative in that it places all of this in the context of
what the human visual system can perceive under various ambient conditions. The
nits requirements above are related to delivering HDR with various display
technologies under various ambient conditions.
There is no single point stand here Bert; there is a continuum that is related
to source, emission coding, and display.
What is abundantly clear is that you need at least 10 bit luminance to deliver
the dynamic range needed for HDR. The FACT that this visual information can be
displayed at varying light levels based on the display technology is what you
should be focused on.
A mobile device that is capable of displaying 10 bit luminance and color - I'm
talking about the internal processing paths and standards supported by the
device, not the display - can deliver an improved viewing experience. The
quality of that experience will depend on the display technology, the
calibration of that display, and the ambient lighting conditions.
The same is true for any TV.
I wrote:
I would note that there is little difference between "real" HDR image
acquisition and the three exposure technique used in many smartphone
cameras - both acquire the HDR information.
This is what convinces me you have yet to understand what HDR display is.
Funny thing is, I have never noticed any confusion on dynamic range when it
comes to audio.
I'm not talking about HDR display Bert. I'm talking about capturing an image
then optimizing it for any display. Take another look at that Sony article
Bert. It does an excellent job of explaining (with pictures too!) how we
process images captured with High Dynamic Range, then map them into limited
representations for emission. As I said, there is little difference between
what a video camera and a smartphone camera do in the real world. In both cases
we can acquire more dynamic range than a device with an 8 bit display can
deliver. In both cases a human or an algorithm determine how the higher dynamic
range data is mapped into a more limited "display space."
In principle, if you play the little game of taking three images on an SDR
camera, IN PRINCIPLE (I repeat), you can process the images to send to HDR
displays. But that is **not** what these hand held appliances are doing. The
fact that you don't see the difference is truly weird, because the processing
these devices *are doing* is exactly the opposite of what it takes to send
images to HDR displays.
Correct. It is more closely related to what a processing system that starts
with HDR data does with this data in order to display it on a display with 8
bit luminance.
Let me repeat this: HDR mode in a smartphone camera is used to capture high
dynamic range in a *scene*, and then compress that high dynamic range so it
can better be displayed on an SDR display. The bright parts are dimmed, the
dim parts are brightened. There is no way you can pretend this is HDR display.
Yup. Just like EVERYTHING we watch on our fancy HDTVs Bert. You are showing
your ignorance of how imaging systems are used to create an optimal product for
use across a range of displays with varying capabilities.
This is a very complex subject with MANY, MANY variables. You cannot neatly fit
this into a box and say "this is what it takes to be HDR."
Clearly display technology has evolved and improved. And it will keep
improving. What is really in play here is how do we deliver better quality
images with HDR and WCG. And how do we do this in a manner that is compatible
with billions of screens with varying capabilities.
Regards
Craig
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