Posted by Bill Vermillion on 01/03/06 00:05

In article <9v7jr1dfk8irva1s907edn6ucq7bf828fs@4ax.com>,
Roy L. Fuchs <roylfuchs@urfargingicehole.org> wrote:
>On Mon, 02 Jan 2006 17:45:01 GMT, bv@wjv.com (Bill Vermillion) Gave
>us:
>
>>but CAA is
>>actually a series of CAV that change every few revolutions.
>
>
> If one could not obtain a perfect frame still, it was not CAV.

> It is one frame per revolution.

CAV means 'constant angular velocity' - which means the number of
degrees of rotation for a given time unit remains constant.

The orignal CAV disk did have one frame per revoltion. But with
CAA - there would be several frame with the same angular
accelleration then a lower angle for many frames, and then another
lowering of the angle.

IOW it was made of many many bands of video with the same angular
velocity. This meant you could get the same amount of time as the
original CLV but without the adjacent frame interference.

CLV uses a constantly changing disk speed, while CAA uses many
segments of differing disk speeds all grouped together.

And I can get a perfect still frame on one of my players :-)

It's a Pioneer 8000 - industrial unit - which actually buffers the
frames to give perfect still - that's why those units originally
cost so much. But I think those may have been the only ones -
except perhaps the Sony 2000 and Sony 3000 industrial players.

The latter were pretty amazing as you'd never lose a picture when
you were seeking a disk if it was recorded properly. Those were
rugged beasts - designed to be used in such places at military
tanks.

THe best description of CAA is probably from Bob Niland's original
FAQ - now maintained by others - but Bob and I corresponded in the
early 1990s.

Here's the segment on CAA

========================================
5.6 What is CAA then?

CAA stands for Constant Angular Acceleration.

To be exact, the discs that nowadays are entitled CLV, are actually
CAA discs. In CAA the disc speed is not slowed down constantly, but it
is kept constant for some time and then rapidly slowed down. The point
in this system is to keep the horizontal sync signals aligned on
adjacent disc tracks to keep crosstalk to a minimum. In Blaine Youngs
(blam1@oz.net) words:

"CLV: This format is dead. The name is still used for simplicity's
sake, but 3M is the only manufacturer which uses it. In 1982/3, there
was a shift to CAA. This is the only format used today. (Again, except
for 3M which incorporates a minor variant on CLV to eliminate
crosstalk). Regardless of which format is used (CLV or CAA) it is
still required to have crosstalk rejection code built into the
mastering software to prevent master crosstalk. Technidisc does not
use such software and as a result, most of their CLV stuff looks like
crap.

CAA also offers something else, 5 different encoding routines. This
will allow for variable playback times, depending on the program. What
happens is that the initial CAV pattern at the beginning of the disc
is altered (lengthened or shortened as necessary) and the track pitch
is modified. The 5 formats are CAA45, CAA55, CAA60, CAA65 and CAA70.
CAA45 has been used only once, that I know of. Any disc side running
less than 55:05 uses CAA55 encoding. All other discs are CAA60. There
are 2 known occurances of CAA65 and there has never been a CAA70 disc
released in the US."

From now on, CLV and CAA discs are just called CLV for simplicity, and
because that's what's written on the disc sleeves.

========================================

And I first started working the laser disks when I was part of team
writing what turned out to be the worlds first electronics parts
catalog using Sony 1000 players [with a format incompatible with
the Pioneer until the A model from Sony], and IBM PCs using
DOS 2.0. That was October 1983. I made so much money during that
time frame I stopped being a recording engineer and moved into
computers full-time.

The local video production company used to make a lot of training
LDs for both military and commercial, and had one of the few units
in the South that could handle frame and chapter encoding.

If they finished the tape and had it shipped by freight by 5PM
then 3M would get check disk shipped back from Minneapolis by
5PM the next day - so we could check disks in about 36 hours from
shipping the tape.

Things surely have gotten better and a hell of a lot cheaper since
those days.

Bill
--
Bill Vermillion - bv @ wjv . com

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