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

  • From: Bob Miller <bob@xxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Fri, 17 Dec 2004 15:56:32 -0500

Craig Birkmaier wrote:

>>Imagine with WM10... seven HD like program streams per ATSC OTA multiplex!
>Looks like Terry get's it.
>Oversample in production, Then resample enough to get rid of any 
>remaining entropy and encode at HIGH QUALITY for emission. IF the 
>receiver has high quality samples to work with, upscaling  by 25 -50% 
>is not an issue.
What is the trade off if we just compressed 720P more and pre filtered 
it some so that the bit rate would be the same as a 480P for broadcast 
anyway? You would lose no more in difficult frames than you do with 480P 
but with simpler scenes you would have true 720P. That is let the codec 
do the choosing instead of pre choosing 480P. 

Also by going from 720P to 480P, assuming the same compression, you are 
not saving as many bits in the broadcast as the reduced pixel count 
(408,960/921,600) would imply, 56%. The scenes are still just as 
complicated so with MPEG2 you might save only 25%  and with an advanced 
codec like MPEG4 you would save even less, maybe 15%.

A compromise might also be in reducing from 1280 to 1024 or even 720 by 
720P. Or you could do both, compress 720P down more and also reduce from 
1280 to 1024 or 720 by 720P.

Wouldn't these be better compromises than just going from 720P to 480P 
everything else being equal?

Bob Miller
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