Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cbmvax!thomas
From: thomas@cbmvax.UUCP (Linda Thomas - QA)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Interlace and Multiscan Moniters
Message-ID: <7718@cbmvax.UUCP>
Date: 21 Aug 89 13:14:38 GMT
References: <654@rhea.trl.oz>
Reply-To: thomas@cbmvax.UUCP (Linda Thomas - QA)
Organization: Commodore Technology, West Chester, PA
Lines: 32

In article <654@rhea.trl.oz> aduncan@rhea.trl.oz (Allan Duncan) writes:
> From article by mikela@tekig3.LEN.TEK.COM (Mike Larson):
> > I recently connected my A1000 to an Intec multiscan moniter (this moniter
>  
> > This multiscan performed flawlessly when the Amiga was displaying a
> > non-interlaced screen.
> > An interlaced screen, however, showed an incredible amount of flicker, much
> > worse than my 1080.  Upon closer inspection of the CRT I realized that
> > the odd and even frames were being SUPERIMPOSED on each other rather
> > than being displaced by half of a scan line.
> 
> If the scan-lines were over the corresponding ones from the previous
> field, you would not expect to get worse flicker, rather you have an
> approximation of non-interlace.  If, however, there was a substantial
> vertical offset between the odd and even fields, severe flicker would
> appear.  If you had been feeding composite sync to the monitor (as used
> by the 1080) there could have been interaction with the complicated
> vertical sync region (designed for cheap valve sync circuits when I was
> but a lad).  All I can offer is that the unit is iffy, OR it has
> significantly brighter output.  Flicker is strongly brightness
> dependant.
> 

Some multi-sync monitors don't know how to interpret an interlaced signal. They
don't know which frame (or field, I always get the two mixed up) is even and
which is odd.  What happens is that the scan lines may not get drawn in the
same place from frame to frame (it's odd once, then even).  This does cause
an incredible amount of flicker and often makes text nearly illegible.

-- 
Linda Thomas, Commodore Amiga Test Engineering
UUCP  ...{allegra,rutgers}!cbmvax!thomas