[opendtv] Re: De-interlacing with HQV high quality video processing
- From: Jeroen Stessen <jeroen.stessen@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 10 Oct 2005 09:48:09 +0200
Hello,
Olivier Houot:
> I thought it was perfectly acceptable to run a LED, for example, at
> twice its rated current, provided it is switched on at a duty rate of
> 50%, which averages out to the rated current. Wouldn't that solve your
> problem of reduced light ouput power ?
If it is a passive matrix, or other measures have been taken for
improving the motion portrayal by reducing the on-time, then we may
assume that the display is already running at the highest possible
peak current. There will be no margin for blanking half the lines.
The ALiS solution is cleverer: it defines between which pair of
electrodes the plasma is discharged. And then the size of the
discharge is large enough to create just enough overlap between
the lines. It is the perfect interlaced flat-panel display (if
there exists such a thing in the mind of some people, hehe).
> So it seems the universal HDTV display should be exactly 1080 lines
> vertically, no more, no less, as this is the only way to avoid scaling
> of interlaced signal.
a. You seem to be forgetting 480i and 576i signals...
b. As others have already indicated, there is still a good case for
a modest amount of overscan. FHP's choice of 1024i lines seems to
have been a good one. But all other displays are now 1080p.
Displaying only 1024 out of 1080 lines gives a very nice amount (5.5%)
of overscan. This also applies for up-scaling from 720 to 1080 lines
(a factor 1.50x) and then discarding 56 lines again. No problemo.
> 720p, being progressive, can easily be scaled to 1920x1080, and
> displayed as either interlaced or progressive, depending on display
> capability. In that regard, the 1024 lines resolution of the ALIS
> seems to be a particularly bad choice, considering the specificity
> of that technology.
FHP has been under some pressure to make 1080 lines, because "the
rules" require that HD displays have 1080 lines, not just 1024 lines.
And everyone else seems to have gone to 720p, 768p, 1080p, so 1024
lines is exceptional. But personally I find 1024 a very good choice.
It's worse if you have a display with 1080 lines and then find out
that the top and bottom lines in the source contain artefacts and
then you have to do a tiny amount of scaling to get rid of them.
Scaler (polyphase) artefacts can become very visible in such case.
> However it would not be possible to take advantage of a x2 oversampling
> display without compromising interlace. According to some recent news,
> this may become a significant drawback in a not so distant future
What are you saying ? That you can't have a 2160i display, or that
you can't properly display 1080i sources on 2160p displays ?
(That would be a bit of overkill, given that 720p and 1080i sources
should contain only approx. 280 cycles per height of information.
Even for 1080p sources it would be a royally oversampled display.)
Best,
-- Jeroen
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