[opendtv] Re: Some results - 1080p @ 60 is Next?

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Fri, 18 May 2007 10:29:01 -0400

At 1:26 PM -0400 5/17/07, Manfredi, Albert E wrote:
Exactly. In spite of all the previous rhetoric, people do go for image
quality, all else equal. All of the previous overly-positive comments
about how HDTV was a non-starter have been proven wrong. The same could
happen between 1080p and 720p, I'll reserve judgment on that.

There was never any doubt about the need for improved image quality. The issues have always been:

1. How to get there.

AND

2. How much is sufficient.

Most of the world recognized the fact that a SIGNIFICANT increase in quality was possible WITHOUT the need to move directly to HDTV. This recognition has played out via the success of DVD and DTV systems across Europe.

These folks also recognize that HDTV is NOT NEEDED for every application.

Even here in the U.S., where HDTV was the Trojan Horse ridden by the broadcasters to protect their valuable NTSC franchise, it was recognized that the DTV system should support a range of quality levels.

It is worth noting that the only thing that seems to be on the wane is INTERLACE.

The REAL push behind 1080@60P is based in the shortcoming of 1080@30-i, which should NEVER HAVE BEEN ADOPTED AS AN HDTV FORMAT.

There is NOTHING wrong with a DTV system that uses 1080P for low temporal rate programming and 720P for high temporal rate programming. BOTH DELIVER VERY HIGH QUALITY, and from my personal experience 720@60P consistently delivers higher quality than 1080@30i for high action content.

The mere existence of 1080@60P equipment, especially consumer displays is NOT a justification for the emission of a bandwidth hogging format that needs a significantly higher bit budget to deliver images with the same quality as 720@60P.

You seem hung up on the numerology, rather than the logical arguments about the bandwidth needed to maintain a relatively constant level of quality in a bandwidth constrained channel.

 > I think you are basically wrong, at least with respect to
 average screen sizes. 720P is more than adequate for 98% of
 all of the consumer displays sold, and can actually deliver
 BETTER image quality to the really big screens in bandwidth
 constrained applications...like DTV.

The point is, Craig, that these simplistic models are fairly easily
disproven. So I don't put a lot of faith in them.

So disprove what has been written about the relationship between screen size and viewing distance. I'm waiting...


Here's a quantitative example. My 26" widescreen set has a picture
height of 12.8". So since I sit at roughly 10' from the set, you would
tell me that I won't be able to tell the difference between an NTSC
program and HDTV.

I would never tell you that!  To the best of my knowledge I never have.

NTSC is a very crude compression system that can easily be degraded by both the modulation system and downstream distribution systems (i.e. cable). NTSC has very limited color bandwidth and suffers from the use of interlace. It is degraded by multipath, noise and downstream processing that further degrades the image.

What i would tell you - and have told you MANY TIMES - is that you would not be able to tell the difference between one of the HDTV formats shown natively on your 26" display and a properly encoded 480P source viewed on the same display at the viewing distance you have specified. In fact, you could cut that 10 feet in half and still not see the difference. In fact, if the 480P source were downsampled from an HDTV source and encoded at the same bit rate as the HDTV emission, it would probably look significantly BETTER.


(Assume 330 pixel res for NTSC. That says that the angle between
"pixels" at 10 picture height viewing distance is 1.04 arcminutes, which
you say is much better than most people can see.)

But that's so obviously wrong. I can distinguish between HDTV and SDTV,
at the 10' viewing distance, but it's not all that dramatic. But it is
really, really easy to see that NTSC images are soft compared to either
of the DTT modes. Even those NTSC programs that have been upconverted by
the broadcaster and transmitted as SDTV, such as BBC News from PBS.
Whether I watch NTSC upconverted by a broadcaster, or tuned in at my set
as NTSC, the difference between that and SDTV or HDTV is not even
subtle. And I have a really hard time getting interested in anything on
an analog TV set anymore. It looks awful always.

I'm glad you have worked through the flaws in your argument. Here's one more to think through...

As Tom Barry has pointed out, even a good digital network feed can be made to look as bad, or worse, than NTSC with a little "effort." The pre-filtered 2-3 Mbps sub-channel that carries the CW network on our ABC affiliate looks worse than any clean NTSC off-air signal and worse than any analog cable channel we receive.

It's time you started to take into consideration all of the "knobs" that a broadcasters can use to control the quality of what is delivered via their DTV multiplex. THE NUMBERS ARE MEANINGLESS, unless you know what they have done to the source to make it fit any given bit budget.


 There was never much question about delivering HDTV

You and many others used to question the "need." We were told often and
in no uncertain terms that 480p is all anyone would need for TV
programs. There was no money to be made in HDTV.

I never said any such thing. I did say that 480P (actually 1024 x 576P) would deliver quality comparable to HDTV on displays up to 40 inch diagonal. I still stand by that statement. I never had any problem with including HDTV formats, OTHER THAN 1080@xxxxxx

INTERLACE HAS NO PLACE IN A DIGITAL COMPRESSION BASED DTV SYSTEM.


All I'm saying is, some folk are fixin' to repeat that mistake with the
new 720p vs 1080p debate. There's no reason to get stuck on inflexible
positions in these arguments dealing with sensory perception.

Yes, some people are hung up on bigger numbers. They have no understanding about the inter-relationships between acquisition, emission and display.

1080@60P does have a place. It's on really big screens in special venues used for the presentation of high temporal content programming. Venues where you can deliver 40-50 Mbps streams or higher without a problem.

At NAB there were several presentations of 3D HD, using content that was shot during the NBA All-Star game. This content was displayed LIVE in several theaters during NBA week in Vegas, earlier this year. The NBA is quite excited about the prospect of using theaters across the country to expand their PAYING audience. They noted in their presentations at NAB that most NBA venues are sold out most of the time. Providing an enhanced experience in a special venue, where they could charge a healthy admission price is a very real application for the NBA, and I suspect for many other sports. I can even see this stuff making it's way into sports bars. But it is not an application for DTV.

You keep talking about the Bell Curve.

Perhaps you should listen to yourself.

Regards
Craig




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