Re: [photo-3d] Re: Digital Video 3D

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

----- Original Message -----
From: <mramstad@xxxxxxxxxx>
To: <photo-3d@xxxxxxxxxxxxxxx>
Sent: Tuesday, March 13, 2001 11:13 PM
Subject: [photo-3d] Re: Digital Video 3D


> John, I had assumed that the advantage of genlocking was
> that the two video signals would not be up to a half
> frame displaced in time.  Is this not important in your
> work?  Also, when you view the video in the field, are you
> viewing in stereo using two separate displays?  Thanks
> for sharing your expertise!

The main purpose of genlocking is to keep two or more video images
synchronized. Precisely (to the pixel, not just the field or frame).  When
shooting a broadcast television show, for example, several cameras are
usually used.  The output of these cameras is selected on a switcher.   Each
camera is set for "External Sync".  They all receive a common sync signal
sent from the switcher to all of them (this is called "House Sync").  None
of them operate on their own internal sync signal.  Therefore, they are
"genlocked" together.  If they weren't, the images would fight each other:
the pictures would tear and colors would drift aimlessly, across the screen.
This would occur if they were only a microsecond off.  It is so critical,
that video engineers in the studio are careful to keep cable lengths the
same (or compensate electronically if they are not).

Back in the days when only analog mixers and switchers existed, it was not
possible to genlock amateur cameras, unless they were internally modified.
Today, we can use sophisticated digital switchers (still not cheap, I can't
afford one) or certain software (also usually pricey) to synchronize almost
any camera.  However, any temporal differences that occurred during the
original videotaping will be passed along.  These will be seen in stereo
images as z-axis changes when there are certain types of action on the
screen (especially diagonal motion).

JR


 

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/