Re: Why interlaced HDTV?

On Tue, 23 Aug 2005 01:05:30 +0100, Kennedy McEwen
<rkm@xxxxxxxxxxxxxxxxxx> wrote:

>progressive display. That isn't the only possible trade-off. As
>described, it is possible to design a progressive display that will
>eliminate motion tearing with interlaced video. That particular
>trade-off results in 50Hz flicker, but no worse than on a conventional
>interlaced CRT.

But conventional 50 Hz CRT flicker is horrible, especially on larger
screens. Hence the number of 100 Hz TVs on the market and all the
artifacts that their frame stores cause.

>However there is a third trade-off which maintains the flicker
>elimination of these screens. Instead of blanking the lines which are
>not present in each field, just repeat the data from the previous field.
>Again, the latency is consistent on all pixels, however the hold time on
>each pixel is now doubled, which is the analogous to a very long
>persistence CRT phosphor. Consequently this time you are trading some
>motion blur to eliminate both flicker and motion tearing.

This is effectively what any good broadcast interlace to progressive
converter would do and as I said, I'd rather it was done by the
broadcaster than a sub £ 5 chip in my TV. The blurring artifacts
within the picture reduce the visable resoloution to, it would appear,
similar to 720p levels. However the adoption of a progressive
broadcast system allows the migration to all progressive production
over time eliminating this problem completely.

>manufacturers agendas than a limitation of interlace per se. You can't
>display progressive images on an interlaced screen though, without
>artefacts or throwing half the information away, which defeats any
>advantage the system has.

But nobodies going to be using an interlaced screen for HD. Even an HD
CRT should be capable of 50 or 100 Hz progressive refresh without
interlace and I'd be very surprised to see an HD CRT set in Dixons etc
in a years time.

Production is already moving to progressive formats and of course film
is natively progressive. Film has been converted to interlaced SD TV
for decades without problems (as far a the interlace goes) and
ironically often looks better on progressive sets due to this than
natively interlaced material.

Progressive production and display is the future. To tie our HD
broadcast standards to the legacy interlace is even more crazy than
tieing DAB to Layer 2.

>I was looking at some 720p a couple of days ago, and wasn't overly
>impressed. Yes, better than 625i, but not dramatically so. When I saw
>1080i a while ago, I was completely bowled over by it. That extra
>horizontal resolution isn't worthless, you know. Equipment was
>different of course, and perhaps my expectations have changed with time,
>but that was my impression viewing both options. As always, YMMV.

Was the 1080i and 720p displayed on a progressive or interlaced
screen? I have to say some of the HD material I've seen has been a bit
of a disappointment but still a worthwhile improvement. One thing I
can say is that in my experience, 720p beats 1080i hands down for what
I would call "normal" TV material.

Rgds
Jonathan

.

Relevant Pages

  • Re: Why interlaced HDTV?
    ... elimination of these screens. ... Again, the latency is consistent on all pixels, however the hold time on each pixel is now doubled, which is the analogous to a very long persistence CRT phosphor. ... The normal interlace display on a CRT, where each pixel is only present for a very short period of the frame time is actually temporally undersampling - which artificially exaggerates the limitations of interlace. ... There is nothing intrinsically superior about a progressive source which has the same overall bandwidth as the alternate interlace system, and generally it has inferior resolution, as demonstrated by the ...
    (uk.tech.digital-tv)
  • Re: Why interlaced HDTV?
    ... A progressive display can be configured to display interlaced material perfectly correctly. ... That particular trade-off results in 50Hz flicker, but no worse than on a conventional interlaced CRT. ... However there is a third trade-off which maintains the flicker elimination of these screens. ... You can display interlaced images on a progressive screen correctly, and I suspect that the reason it isn't done has more to do with manufacturers agendas than a limitation of interlace per se. ...
    (uk.tech.digital-tv)
  • Re: HDV camcorder with 720p
    ... May I also suggest that you download some Sony HDV samples from the Internet ... Interlace is fixed by deinterlacing which in effect means that you try ... -If your main intended display equipment is interlaced (as for example ... limitations of shooting at low frame rates like 24P or even 30P. ...
    (rec.video.desktop)
  • Re: Why interlaced HDTV?
    ... >To display such a signal with the whole picture changing 50 times per second ... which is why interlace has been used by all broadcasters since the ... >Updating only one field's worth of the picture, or half the number of picture ... which is why there is a move to 1080p/720p 50 FRAME ...
    (uk.tech.digital-tv)
  • Re: 1080i or 720p
    ... display causes information to be lost forever. ... I'm talking about any content that has been converted for interlace display or captured with an interlaced camera. ... it was converted to or captured as interlaced and information that a progressive capture would have had is *not* recaptured by de-interlacing. ... A careful reading of that source shows nothing to support your theory that information lost during the capture of or conversion to interlaced format can be recovered by de-interlacers. ...
    (alt.tv.tech.hdtv)