[opendtv] Re: Why Europe should choose 720P for HDTV
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 11 Dec 2004 10:40:34 -0500
Craig Birkmaier wrote:
> So here's John's commentary, which I hope will promote so "new"
> discussions on a very "old" subject.
>
Craig -
I may reply more to this later but please say whether you meant to say
"NO new discussions" or "SOME new discussions" on a very old subject? ;-)
- Tom
> Donald Koelemanhas just learned that we moved OpenDTV to Freelists,
> and has re-upped with the list. He asked me to post the following
> provocative message while I am setting up his account.
>
> As many are aware, the Europeans are now growing interested in
> HDTV...again. As Alan Roberts has pointed out, there has been
> considerable debate in Europe whether they should move forward with
> 1080i or 720P. The following piece delivers what I believe to be
> convincing arguments for 720P from industry guru John Watkinson, from
> whom I have learned nearly everything I know about digital television
> and sampling theory (please no comments from the peanut gallery about
> the depth of my knowledge on these subjects ;-)
>
> So here's John's commentary, which I hope will promote so "new"
> discussions on a very "old" subject.
>
> Regards
> Craig
>
> P.S. and welcome back Donald!
>
>
>>From Dave Sparks' The Prompt!!! A discussion piece by longtime progressive
> scan advocate John Watkinson.
>
> Cheers,
>
> Donald
>
> .....as does the 'Prompt!' 'HD in Europe' debate with this latest
> contribution from a somewhat irked John Watkinson - author, lecturer and
> digital guru. John writes:-
>
> "Let us be quite clear that interlace is a primitive lossy compression
> technique that allows a TV signal with an inadequate frame rate to give an
> imperfect illusion that the picture rate is twice as high. All lossy
> compression systems produce artefacts and in the case of interlace these
> are quite serious. They include a substantial amount of residual frame rate
> flicker as well as serious loss of resolution in the case of even very slow
> subject motion. Unfortunately the loss of resolution is accompanied by
> serious vertical aliasing.
>
> "Thus you either have to categorise PAL as having 600ish lines of static
> resolution and a picture rate of 25Hz, giving very poor motion capability,
> or it has a picture rate of 50Hz and the resolution is halved.
>
> "Static resolution is an outmoded and discredited metric of TV picture
> quality. A bit like quoting how well the handbrake performs on an F1 car.
> In all real TV programme material dynamic resolution gives a metric that
> better represents perceived quality.
>
> "I don't care for Mike Tooms' simplistic view of high definition.
> Resolution is not the only parameter. What about the artefacts?
>
> "When an interlaced picture is watched by a tracking eye, at a very low
> vertical speed the lines in successive fields are superimposed on the
> retina, leaving a subsampled image that is riddled with aliasing. Thus to
> say that 720p doesn't have much more resolution than 625i is to be utterly
> ill-informed. On real TV material, the dynamic resolution of 720p is about
> three times that of 625i. In addition 720p doesn't flicker or alias. You
> can tell an interlaced TV from a progressive TV several hundred feet away
> because of the difference in flicker.
>
> "Those who understand interlace know that it works better with a small
> number of lines and a high field rate. This is why NTSC works so well. A
> corollory of this is that interlaced high definition is an oxymoron.
>
> "It's well known that you shouldn't concatenate compression schemes, so it
> must be sub-optimal to put interlaced pictures into MPEG. You need a higher
> bit rate with interlace, but you still get the interlace artefacts.
>
> "Those who understand imaging will also know that the resolution of a
> display is always less than the number of lines it contains because of
> aperture effects. Thus a display with 1024 physical lines will be perfectly
> matched to a 720p transmission by use of an interpolator. Interlace
> complicates the design of interpolators.
>
> "Consequently as far as I am concerned, the logical choice for future TV
> broadcasts is 720p and this has been understood for several years now. The
> continued existence of a debate on the subject simply illustrates the depth
> of ignorance or the strength of vested interests, both of which I find
> exceedingly tedious.
>
> "If we accept that the HD viewer is supposed to sit closer, doesn't that
> put more of the picture in peripheral vision, where the tolerance of
> flicker is lower? Is this not an argument for increased frame rate? Surely
> 1080p is not the way to improve 720p. Far better to retain 720p but
> increase the frame rate to 72 or 75Hz.
>
> "Having seen such a system working I can vouch for the performance, freedom
> from artefacts and general realism.
>
> "Note that with a higher frame rate, temporal coding, which is where the
> power of MPEG resides, becomes more efficient. Thus in an MPEG delivery
> environment it is a myth that high frame rates cause difficulty."
>
> I have a feeling John's comments may provoke some interesting reaction. And
> you have all of the holiday season to compose your thoughts! (Next
> 'Prompt!' - 07 January 2005.)
>
>
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