Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!att!alberta!calgary!ctycal!ingoldsb
From: ingoldsb@ctycal.COM (Terry Ingoldsby)
Newsgroups: sci.electronics
Subject: Re: NTSC-PAL (in)compatibility
Summary: Chroma and Luminance aren't separated
Message-ID: <367@ctycal.UUCP>
Date: 23 Jun 89 19:03:19 GMT
References: <124@nisca.ircc.ohio-state.edu> <566@axis.fr>
Organization: The City of Calgary, Ab
Lines: 34

In article <566@axis.fr>, philip@axis.fr (Philip Peake) writes:
> > I would like some adivce/references about compatibility/incompatibility
> > between the NTSC and PAL color TV systems. I have several questions like:
....> 
> The main difference between PAL and SECAM is how the colour info is coded
> (the sub-carrier frequencies are different, and the means of indicating
> the current phase of the colour info is different) - the line frequencey
> is the same though (not true for NTSC).
> 
....> 
> I would be interested if anyone could explain why the difference in
> coding between the two systems - I would have just put the colour info
> directly onto the tape ona parallel track - this would give compatability
> between the two systems.
> 
First of all, unless I'm very mistaken ordinary VCR's do not separate the
chrominance and luminance info when they store it on the tape.  It is all
stored together.  Somebody please correct me if I'm wrong about this
(no flames, just corrections please :^).  As for putting the chroma on a
parallel track, do you mean a parallel helical track or a linear track?
If the former, then you are going to complicate the head design considerably,
if the latter then
  1) You will have a hard time getting enough bandwidth out of a linear track
     to store chroma info
  2) It will be a *devil* of a job keeping chroma and luminance synchronized
     to the necessary accuracy.  (You don't notice if the audio is 5 msec
     off, but you would sure notice if the chroma was 5 msec out)



-- 
  Terry Ingoldsby                       ctycal!ingoldsb@calgary.UUCP
  Land Information Systems                           or
  The City of Calgary         ...{alberta,ubc-cs,utai}!calgary!ctycal!ingoldsb