[opendtv] Re: BBC Demonstrates HDTV Broadcasts over SD Channels

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Tue, 21 Jun 2005 08:09:11 -0400

At 7:33 AM -0400 6/21/05, Tom Barry wrote:
>At a viewing distance below about 2 screen widths some people
>might want to consider 1080p as it becomes affordable.

This has already happened. There is only one caveat:

This viewing distance is not practical for lean back entertainment 
viewing except at the extremes (iMax etc). In viewing preference 
tests, average consumers did not choose to sit 3.3 picture heights 
from an entertainment display until the screen size was 117" inch 

If you doubt this, look at how many people sit in the first few rows 
of a theater (unless the screening is sold out).

At viewing distances below 2 picture heights we are talking about a 
"lean forward" viewing experience such as that which is common for 
computing applications. And as one would expect, this is the market 
where people are buying and using displays with roughly 1080P 

Unless you have room for a 100" diagonal screen in your home, and the 
requisite 13-14 foot viewing distance (~3.3 picture heights), you 
really do not need 1080P display resolution.

>And at a
>viewing distance above 3 screen widths 480p might be enough for many.
>But 720p is probably just perfect in between. ;-)

When you add the capability to resample 720P up to 1080P for the 
small percentage of homes that will have very large home theater 
installations, it become crystal clear that encoding 1080 for 
emission - either i or P-  is a waste of transmission bandwidth. 
Several companies have introduced sophisticated image processing 
chips to do this - they include de-interlacing capabilities, and in 
some cases motion compensated frame rate conversions that improve the 
presentation of 24P material.


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