[opendtv] Re: Dell's new LCD display - was Re: Motorola Introduces...

  • From: Jeroen Stessen <jeroen.stessen@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 11 Jan 2006 10:50:57 +0100

Colin Wright wrote: 
> A 50Hz country question about the new Dell LCD screen and in fact most 
> pixel array displays (PDPs, etc) for home theatre or even notebook PCs - 

> they all have a single nominal 60 Hz vertical rate - only !!!

It is true that many LCD monitors accept 60 Hz frame rate only. And even 
if they accept 75 Hz (because that is "more ergonomic"), it is possible 
that an internal scaler equipped with a frame memory converts that back 
to 60 Hz by dropping every 5th frame. Sometimes in the Lab we override 
the EDID data and use Powerstrip to operate an LCD at 50 Hz anyway, and 
usually that works, but you might see 25 Hz flicker from the inversion 
process, or non-uniformity from the pixel charging process. That is why 
manufacturers like to stay away from 50 Hz and design / optimize a panel 
for 60 Hz only. "Graphics standards are 60 Hz." Yeah right. 

Note that we have always been able to run our VIDEO displays (LCD and PDP) 

on 50 Hz, and sometimes even 48 Hz (for you guys). For plasma we have to 
make sure that the brightest sub-fields repeat at 100 Hz, or else the 
50 Hz frame flicker would be intolerable. That problem is less severe at 
60 Hz, so then the drive scheme can be optimized for other properties. 

We have the technology ("Natural Motion") to convert to 60 Hz, 72 Hz, 75 
90 Hz, 100 Hz, 120 Hz, take your pick, and we might apply that to 
the frame flicker. It is even available in software-only form for running 
on a Pentium-4 PC, under the trade name of "TriMension" (in WinDVD 

> So is this the reason occasional picture stutter might be seen when 
> 25 and 50 frame per second video - or what mechanism/process removes 
> and does this make these type of displays absolutely OK for critical 
> evaluation of material that may involve temporal artifacts (particularly 
> trying to play out of a hi-grade PC GPU)?
> Maybe Jeroen or others can offer an answer.

I would recommend that you do not buy a display that is optimized only for 

60 Hz graphics if your application is video. Flat panel TVs for 50 Hz 
countries should be able to receive 50 Hz on the VGA / DVI / HDMI inputs. 
But we have seen some exceptions, so you should try it before buying. 
(It's amazing what a fool with a frame memory can do to a video signal...) 

-- Jeroen

| From:     Jeroen H. Stessen   | E-mail:  Jeroen.Stessen@xxxxxxxxxxx |
| Building: SFJ-5.22 Eindhoven  | Deptmt.: Philips Applied Technologies |
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