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.) > > > ---------------------------------------------------------------------- > You can UNSUBSCRIBE from the OpenDTV list in two ways: > > - Using the UNSUBSCRIBE command in your user configuration settings at > FreeLists.org > > - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word > unsubscribe in the subject line. > > ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.