Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!oliveb!tymix!tardis!jms
From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga
Subject: Re: Converting PAL to NTSC on the fly
Summary: The Video Toaster does not use RGB.
Message-ID: <417@tardis.Tymnet.COM>
Date: 13 Jul 89 01:04:15 GMT
References: <15315@pasteur.Berkeley.EDU> <10350003@otter.hpl.hp.com> <2825167777@Lewis.Steinmetz> <918@anise.acc.com>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: McDonnell Douglas Field Service Co, San Jose CA
Lines: 32

[I forced this followup back to comp.sys.amiga because of the Toaster]

In article <918@anise.acc.com> lars@salt.acc.com (Lars J Poulsen) writes:
<Certainly the conversion requires buffering through a digital
<framestore. I believe that the cost of fast enough RAM used to be the
<driving cost factor. You probably need 24 bitplanes and about 600 x 800
<resolution. <This still leaves some problems:
<(1) 525 lines versus 625 lines.
<(2) 50 Hz vs 60 Hz scan rates.
<(3) Interlace versus non-interlace scan.
<(4) Distortion due to 525-600-625 rate differences. Yes, it looks ugly

You assumed two steps that you forgot to mention:
  1) Convert PAL video from analog chroma/luma into digital RGB
  2) Convert digital RGB to NTSC analog chroma/luma
There are a lot of frame buffers that to the latter, but very few American
ones that can do the former.

I bring this up because I talked to New Tek's Tim Jennison about that.
I asked, "since you are already converting NTSC to RGB in RAM, couldn't
you store into RAM at PAL rates and read at NTSC rates?"  He said, "we
don't store RGB in RAM.  That's what makes the Toaster affordable."
Apparently the signal is kept in chroma/luma form.

Also, he mentioned that the signals coming out of home VCRs do not have
the strict timing that the Toaster requires.  There's supposed to be a
low-cost time base corrector in the works.
-- 
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com
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