[opendtv] Math of oversampling

  • From: Bob Miller <bob@xxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Fri, 22 Apr 2005 11:44:15 -0400

If a broadcaster uses a 1080p camera and broadcast as 480P and on the 
reception end it is upconverted to 720P or stays 480P I understand that 
because of oversampling both the 720P or 480P image would be better than 
otherwise would be expected. What I would like to do is quantify this 
value. How would you compare a straight thru 720P broadcast to one such 
as that above. Would the 1080P>480P>720P route be 75% of the quality of 
the 720P>720P>720P route? Would 1080P>480P>480P be 110% of 480P>480P>480P?

I also have been made to understand that the bit cost of a 480i 
broadcast, say X, would not be 2X that of a 480P signal. More like 1.4X 
but with the extra juice added by the 1080P acquisition maybe more like 
1.5 or 1.6X.

What I am trying to do is find a balance between bit cost, quantity of 
programs delivered, quality of programs delivered and the reality of 
both the installed analog TV set world and the HDTV set world.

As has been discussed here many of the HDTV sets sold so far are 42" or 
less and on those sets a good 480P signal would be more than adequate. 
Add to the equation the public's, not early adopters, aversion to paying 
a lot more for added PQ value.

Seeking a sweet spot, a spot where you don't pay a lot more for a better 
PQ bit wise yet get more programming with little loss for HDTV set 
owners and a gain for analog TV set owners.

Such a sweet spot could last for years.

If you add MPEG4 and COFDM to the equation it becomes even better.

What I am really looking for is a continuation of the discussion on 
oversampling and what it could mean in the real world with some kind of 
quantification if possible.

Bob Miller


 
 
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