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

For the 'real life' benefits of 1080i just read the AV Science Forum. 
The 1080i stations (all but Fox & ABC/Disney) seem to be generally rated 
as having a better picture. www.avsforum.com , but the site is down 
today and I can't provide links to the recent topics.

I'm not sure I'm able to provide any really convincing theoretical 
arguments, though I'll mention one thing.  See the paper on Craig's site 
on "An Increase of Vertical Resolution in Progressive Scanned Moving 
Images", at http://opendtv.org/Progressive.html .

This paper talks about how our eyes can gather more detail from an image 
by tracking motion, considering multiple adjacent frames at a time.  I 
believe we can also do this for interlaced images.  So, either way, we 
pick up a bit more detail than the number of lines or pixels might suggest.

Depending upon whether an image is moving (say) vertically at multiples 
of 0, .5, 1, 1.5, etc. lines / frame we may or may not be able glean 
extra detail from the series of video images since the pixels on 
adjacent frames may just more or less line up the those on the current 
frame, helping nothing.  And images move in 2 dimensions, not just 
vertically so it gets a bit more complicated. But one possible advantage 
of interlace is that for the case of (close to) zero vertical motion we 
get the maximum amount of enhancement from this process.  Compare this 
to progressive where the optimum values are .5, 1.5, etc.

Now I believe zero motion is not only the most commonly occurring value 
but also the one where it is easiest for our eyes to track (non) motion 
and thus see more detail.   This should give a small benefit to 
interlace, since it the worst case for progressive.   I'm really only 
saying that interlaced still pictures have more resolution than moving 
pictures, which everyone knows.  But it is still an advantage that can 
be used and seems to work well.  The whole thing is a bit more 
complicated than that but it's the best I can explain it.

I realize there are a number of compensating MPEG-2 and other drawbacks 
and a couple of popular studies that suggest interlace is a very bad 
thing.  I'm sure many will now point them out again so I guess I don't 
have to.

- Tom



Terry Harvey wrote:

> Tom,
> 
> Please elaborate what you mean by 'theoretical' and 'real life' benefits? 
> Is not your statement non sequitur considering the earlier discussions in 
> this thread?
> 
> Terry Harvey
> 
> 
> 
>>Not withstanding, I've since started to see both the theoretical and
>>obvious real life benefits of interlace and have changed my mind a bit
>>about that issue.  I'm not so sure that each successive frame should
>>represent samples from the same location, which is what 'progressive' is
>>all about.
>>
>>- Tom
> 
> 
> 
>  
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