[opendtv] Re: Math of oversampling
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 23 Apr 2005 09:44:22 -0400
Bob -
I can't prove it or do the math but I generally feel that with
proper oversampling & scaling you can get away with only about 1/2
the pixels (1/1.414 the dimensions) in your delivery format before
anyone can really notice the difference, at any viewing distance.
So if you started at 1080p and targeted only a display format of
1280x720p then you might want at least 905x509, rounded to some
nearest convenient multiple of 16 that most codecs like.
"Wide PAL" resolution of 1024x576p like Craig sometimes mentions
would almost certainly do it or HD 1/4 rez at 960x544p. A wide
480p rez of 848x480 would probably even come close. See John
Watkinsons article and one of my own favorite most posted links at:
http://www.microsoft.com/whdc/archive/convrg1.mspx#top
- Tom
Bob Miller wrote:
> 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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