[opendtv] Re: Half Truths - Was More 1080p@60

At 10:03 AM +0100 12/6/07, Jeroen Stessen wrote:

Hello,

Craig wrote:

 Display Oversampling.


I think that on the next CES we are going to show you something
interesting, like temporal up-conversion (50 to 100 fps) on LCD.
That really makes a big impact, especially on pans. 50-60 fps
is so passé, you really want 100-120 fps...  ;-)  Stay tuned.

PS, 90+% of the credit is for our friends at NXP Semiconductors.
They did a great job on HD Natural Motion in the new PNX5100.
  http://www.google.com/search?hl=en&q=PNX5100



Thanks Jeroen!
It is unfortunate that there is so little understanding about the decoupling of acquisition, emission and display, and how to optimize each to deliver the highest quality to the viewer. We placed a great deal of emphasis on this in the 1992 SMPTE/EBU Task Force Report on Digital Image Architecture.
As we have learned with the evolution of computer display systems, there is a great deal that can be done to enhance the presentation of different types of imagery using the image processing capabilities of the display processor. In this, I believe that Philips has been a leader, starting with the Tri-media processors back in the '90s.
Having spent much time working with HDTV acquisition and display systems, we learned early on how to acquire, encode and display imagery to maximum benefit. I fully understand why the 100/120 fps numbers are now emerging - this is the easiest way to deal with the 50/59.94Hz heritage of analog legacy formats, and for the 120 fps crowd, we get an integer multiple of the important 24 fps source library (actually 23.97).
While I am certain that your neww developments will look very good, it is unfortunate that we did not take advantage of the DTV transition to move to a more friendly/useful set of frame rates that are a better match for the human visual system. The task force recommended a family of frame rates with integer relationships; the most important members of this family being 24/36/72 fps. Itis important to note that for bandwidth conservation this family could also support 12 and 18 fps. As you are well aware, the flicker fusion rate for the average human - where we start to see continuous motion - is about 18 fps. But at low frame rates like 18 or 24, we need careful control of the viewing environment to prevent the perception of flicker (i.e. a darkened movie theater). By the time we get to 36 fps we get very good motion continuity, although this is not adequate for rapid motion like sports. For sports, 72 fps would have been a good target, as it provides excellent continuity in rapid motion, better instant replays, and the frame rate is high enough to prevent the perception of flicker even in brightly lit environments - there were good reasons why Europe established 72 fps as the floor for computer display refresh rates!
It is interesting to note that 30 fps has never taken off as an acquisition frame rate. I believe that there are several reasons for this:
1. First, it is not that different from 24 fps, which IS a widely used acquisition frame rate. We have seen a major shift to cameras that can acquire at both 24 and 30 fps, but only 24 fps has seen widespread usage. 

2. 30 fps still has motion discontinuity issues like 24 fps.
If we have a family with 24/36/72 there is better separation between the rates. 36 fps become desirable for application like talking head shows - it could also be used for virtually everything that Hollywood produces, although it is unlikely they will abandon 24 fps.
Underlying all of this, however, is a very important reality. To implement features such as motion compensated frame prediction, which is needed to gain the full benefit of 100/120 fps display, you need high quality samples. It is impossible to do a good job with this if you are starting with samples that have severe compression artifacts including blocking and the sample distortions introduced by excessive quantization. Just look at how most HDTV capable displays deal with legacy interlaced video sources - they make crappy video look soft to hide all of the artifacts of the digitizing and deinterlacing processes needed for progressive displays. And the image pre-processing that takes place during emission encoding removes critical detail that your image processing algorithms need to do a good job.
Alas, it may be another decade before the television industry figures out that they are using the wrong family of frame rates, and that it is MORE IMPORTANT to deliver high quality samples than a high quantity of impaired samples. 

Regards
Craig


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