The REAL aspect ratio of 601? (fwd)

[Moderator recvideoprofessional]

---------- Forwarded message ----------
Date: Thu, 31 Jan 2002 17:04:06 +0200
From: Toke Lahti <to...@iki.fi>
To: rec-video-p...@moderators.isc.org
Newsgroups: rec.video.professional, alt.tv.broadcasting, alt.tv.tech.misc,
alt.video.equipment.broadcast, alt.video.digital-tv,
alt.video.avid_editors, alt.video.dvd.tech
Subject: The REAL aspect ratio of 601?

I'm doing some resolution conversions in ongoing production.
I've tried to find info about real aspect ratios and resolutions.
So far I have understood that itu-rRec601 resolution is not 4:3.
In 625-line systems only 702 pixels of those 720 represents image.
That 702*576-image is 4:3. I think its same with ntsc: 710*484
is 4:3 picture from 13.5 MHz sampling rate.
Now why every software and hardware (at least premiere, commotion,
targa and after effects) is talking about 1.0667 pixel aspect ratio
referring to 720*576 picture. If 702*576 is the real 4:3, then
720*576 pictures pixel aspect ratio should be 1.094.
Now who's calculating wrong?
Sorry if this is FAQ question, I haven't been reading these groups and
I'm in a big hurry. Can anybody point links to FAQs or other documents
or evidence about this matter?

thanks in advance,
toke
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