[opendtv] Re: Philips ClearLCD technique for motion sharpness
- From: jeroen.stessen@xxxxxxxxxxx
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 20 Jan 2005 17:22:31 +0100
Dear Craig,
> Thanks for this educational post Jeroen!
You're welcome. Somebody has to do it... ;-)
>> So the bottom of the screen is refreshed some 15 ms later than
>> the top, and the pulsing of the backlight must match that delay,
>> in order to sample the transmitivity of the LCD at the moment
>> when it is most stable. It is the only proper way...
> How does this compare to the time difference from top to bottom
> for a scanning CRT. If my calculations are correct it is very close.
Yes, obviously. Every display likes to use as much time as possible
for refresh. So the vertical active scan period will be the frame
period minus the minimum necessary time for vertical "retrace".
Even with LCD that is a few line times, not zero. Very much like CRT.
>> And then there's that issue that the manufacturers just
>> won't specify these panels at more than 60 Hz. Yet.
> Glad you have added "yet," as some of your competitors have
> announced chips that work at these clock rates.
It's not about the "chips", it's about the row and column drivers
and especially the TFT switches on the panel. If you try to drive
them too fast then there will be all sorts of image artefacts.
Worse: these artefacts may show up (or increase) over time.
So it takes more than just faster silicon to increase the speed.
The developments are going the right way, but they can also be used
for making larger screens. Just not for both at the same time...
>>> As for re-writing the ATSC or DVB standards, it is mostly an
>>> editing job, and a rather easy one at that.
>> And in the process you lose compatibility with only a couple
>> of million receivers and displays out there... :-(
> Not at all.
> I am not suggesting that the existing DVB formats be abandoned;
> the marketplace ALREADY supports them.
I thought that you proposed to erase some magic numbers from the
standards in order to allow arbitrary frame rates. I warn against
that because I know that there are LCD panels that will work at
ONLY 60 Hz. Same with PDPs, they are really optimized for only 1
or 2 frame rates. Your own DLP RPTV might even have this feature...
Best,
-- Jeroen
+-------------------------------+----------------------------------------+
| From: Jeroen H. Stessen | E-mail: Jeroen.Stessen@xxxxxxxxxxx |
| Building: SFJ-5.22 Eindhoven | PHILIPS Applied Technologies |
| Phone: ++31.40.2732739 | Visiting & mail address: Glaslaan 2 |
| Mobile: ++31.6.44680021 | NL 5616 LW Eindhoven, the Netherlands |
| Pager: ++31.6.65133818 | Website: http://www.pdsl.philips.com/ |
+-------------------------------+----------------------------------------+
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