From: utzoo!decvax!decwrl!turtleva!ken
Newsgroups: net.video
Title: Re: Video compatibility problems
Article-I.D.: turtleva.187
Posted: Fri Apr 29 23:06:24 1983
Received: Mon May  2 02:58:14 1983
References: uwvax.844 turtleva.186


OOPS!  I made some embarassing errors in my last rather verbose article
about whether NTSC video recorders are compatible with PAL or SECAM.
THEY ARE NOT!  I have had some experience with video, but not
necessarily with video tape recorders.  After consultation with a
friend in the video production business, I was chastised for even
thinking that the only relevant thing about a video signal's ability to
be recorded is its bandwidth.  It turns out that the rotating motion of
the VCR's head is synchronized with the field rate (50 vs. 60 Hz), and
requires substantial modifications to switch from NTSC to PAL.  One
field is recorded with each diagonal swipe of the head across the
tape.  Some professional VTR's such as Ampex's line can be changed from
one video standard to another simply by changing a few boards, but home
units are designed more for low cost than for flexible generality.

There was also a typo:  SECAM is radically different from NTSC, not
PAL, as asserted in my original article.  PAL and SECAM are similar in
one way, and PAL and NTSC are similar in others, but NTSC and SECAM
have twice the dissimilarities.
				Ken Turkowski
			{ucbvax,decvax}!decwrl!turtlevax!ken