Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!agate!shelby!bloom-beacon!atrp.mit.edu!pshen
From: pshen@atrp.mit.edu (Paul Shen)
Newsgroups: sci.electronics
Subject: Re: Converting PAL to NTSC on the fly
Message-ID: <12663@bloom-beacon.MIT.EDU>
Date: 14 Jul 89 05:08:26 GMT
References: <15315@pasteur.Berkeley.EDU> <10350003@otter.hpl.hp.com> <2825167777@Lewis.Steinmetz> <918@anise.acc.com>
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lars@salt.acc.com (Lars J Poulsen) writes:

>(2) 50 Hz vs 60 Hz scan rates.
>    This requires the memory to be dual-ported. To reduce the effect of
>    access collisions, you'd probably need to pre-fetch a line-buffer's
>    worth of data on each port.
The simple minded, cheapest solution is three-two pull-down. Then all
you need is off-shelf dual port DRAM.

>(3) Interlace versus non-interlace scan.
>    Broadcast video is usually interlaced to reduce flicker, computer
                                              ^^^^^^^^^^^^^^
Interlace will introduce flicker. The purpose of interlace is to
increase the temporal sampling rate.

>(4) Distortion due to 525-600-625 rate differences. Yes, it looks ugly
>    in broadcast, but you can live with it on home viewing by fiddling with
>    the height and/or horizontal gain.
This can be dealt with by proper sampling rate on the AD and DA
convertor. (This adjusts the spatial rate.)

>Am I the only person with family in Europe that would like to run
>videomovies through the computer ? Will this open up a new vertical
>market for Commodore, Apple or NeXT ?

With the proper design, such a stand alone system can be well below
$1000. I did design one of such system, PAL-to-NTSC and NTSC-to-PAL
convertor. It died in the middle stage of design, because of the
limited market demand.

						Regards,
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| Email:        pshen@atrp.mit.edu                  |       Paul Shen       |
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