[opendtv] Re: Why Europe should choose 720P for HDTV

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 15 Dec 2004 10:46:40 -0500

At 7:49 PM -0500 12/14/04, Tom Barry wrote:
>You really do not like interlace. ;-)

NO. I REALLY DO NOT like interlace...


>And you are somewhat optimistic, and may be surprised.  For instance I
>think I read D-Theater is filtered for interlace and, IIRC, not even
>coded with repeat flags.

This may be true. At the moment the mass market is still interlaced. 
Only those who are going after the HDTV niche can afford to optimize 
their content for HDTV, although there is real progress on the 
coverage of live sports, where it looks like 720P is beginning to 
dominate. This makes it easy to downconvert to SDTV, while retaining 
many of the advantage of progressive acquisition and production 
(particularly the improvements in slo-mo).

>And the blu-ray folks are still trying to use MPEG-2.

MPEG-2 is not the culprit, although the additional tools in AVC will 
produce better results at the same bit rate. The culprit is the 
source. If you filter it for presentation on  an interlaced display, 
you are throwing away information that is useful for progressive 
displays. The key is to start with the highest quality PROGRESSIVE 
source. Form there it is easier to encode (even with MPEG-2) and it 
is easy to produce a properly filtered interlaced output, whether for 
480i or 1080i.

>I agree 4:2:0 is way too sparse. (as is 24 FPS)

Hollywood seems to like 24P; I don't think it is going away.

But Hollywood also understands that that the viewer DOES benefit from 
full color resolution. 4:2:0 is not a bad thing, IF the source is 
progressive, since it is easy to filter (scale) the color difference 
signals in both the H & V axis. But you are throwing away some useful 
color details that CAN be seen. 4:2:2 is an artefact of interlace, 
and is meaningless in the context of progressive formats. 4:4:4 
delivers more color detail - I have seen demonstrations of source 
that was transferred as 4:4:4 and 4:2:0, then encoded using MPEG-2. 
On high end DLP projectors the difference is highly visible, 
especially on computer generated imagery. There are even more benefit 
if we expand the color space beyond the present Rec 709 limits and 
use logarithmic encoding of the uncompressed source to extend the 
color gamut while preserving the "knee and shoulder" characteristics 
of the film source.

>But why screw around?  If they made HD-DVD's with modern codecs they
>could probably use 4:4:4 at 1080p@24.  It is true that 1024x576 RGB
>could look very good but we might as well go the whole way once we can
>afford the bits.

1280 x 720 @ 24P  with 4:4:4 color is MORE THAN ADEQUATE for 99.9% of 
ALL home theater installations. You can make a case for 1920 x 
1080@24P for BIG SCREEN theatrical e-cinema displays, but 2 Mpixel 
resolution is NOT necessary until the screen size exceeds 100 inch 

>Just because we couldn't see it on almost all current displays (1080i or
>   720p fixed) doesn't mean we shouldn't do it.

So we should optimize the source for 0.01% of the market?

I think not.  While we may well be moving in the direction of 
displays that can support 1920 x 1080 @ 60P, there will be little 
visible benefit in delivering 1920 x 1080 source to these displays. 
Scaling 1280 x 720 up to fill these displays will produce virtually 
indistinguishable results, except for the reduction in the number of 
scenes that fall apart because of compression artefacts. The key, as 
I keep stating is the delivery of HIGH QUALITY SAMPLES, not 
necessarily HIGH RESOLUTION samples. What DIgital TV needs is 
consistency in presentation quality. The ability, on rare occasions, 
to sneak a little more resolution through the pipe, is strongly 
outweighed by the presence of compression artefacts when the pipe is 
inadequate for the delivery of those extra details.

>I would happily be willing to wait for my upscaling display on that
>format until I could afford a 4kx2k fixed pixel display.

And what benefit would YOU derive from a 4K x 2K display?

How big would you expect the screen to be, and at what distance would 
you sit to watch it?

(Hint) The 1+ Mpixel DLP theater projectors still produce better 
pictures than any 2 Mpixel projection system I have seen. That being 
said, I have not seen a projector based on the new 2 Mpixel DLP chips.

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