[opendtv] Re: De-interlacing with HQV high quality video processing
- From: Richard Hollandsworth <holl_ands@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 7 Oct 2005 17:50:39 -0700 (PDT)
My Hitachi is a 1024 x 1024 ALIS Plasma Ii.e. 1 Mpixel).
It throws away a few lines on the top and bottom (in CRT-speak you call it
"overscan"), so the
scan conversion from 1920x1080i to display only involves throwing away pixels
along each line. Rescaling for 720p will of course lose some
resolution....theoretically....
Two years ago there wasn't anything on the market for under $8K that came
anywhere close
to the PQ for eitehr 720p or 1080i, other than the Sony ALIS panel.
Today you can buy the 42" Hitachi ALIS panel for $2700, including ATSC and HDMI,
which is half what I paid nearly two years ago without.
Most of the time the source material is the limit, not the panel, whether it is
HD-Lite overcompression (e.g. CBS-HD and anything on D*) or older no-rez
cameras,
or trans-coding losses or chosing to go the way of 1280x720p (0.9 Mpixel) for a
more frequent update rate.
Stepping up to a "true" 1360 x 1080i/p (2.1 Mpixel) HD display may make you
warm and fuzzy inside,
but until the distribution system upgrades to true HD, you're only seeing half
the picture.
Right now HDNET, inHD and PBS-HD are the only ones that even come
close....followed by perhaps DSC-HD.
None of the networks even come close to HD PQ.....just slight improvements over
lo-rez DVD.
==============================================================
Olivier Houot <olho_avatar_i@xxxxxxxxxx> wrote:
Jeroen wrote :
> For emissive displays it is relatively easier to just blank
> half of the lines and thus obtain an interlaced raster. It does
> not necessarily degrade the efficiency, but it will degrade the
> peak light output power by 50% (i.e. less "sparkle").
>
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 ?
> Right, and there is the bigger catch: (vertical) scaling can
> ONLY be done on de-interlaced signals. So in practice de-
> interlacing is always necessary. And then you might as well
> send it to a progressive display. Unless you have a display
> that performs better in interlaced mode (CRT, ALiS), then at
> the end you would convert the signal back to interlaced again.
>
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. 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.
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
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