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Posted by Richard Crowley on 01/12/06 17:53
"Jeff_BTFP" wrote ...
> I just bought a Sony SEG-2550a Video Switcher (a relic, I know) and am
> having problems with it. When I hook up an external source (I tried
> with both a Camera and a commercial grade DVD deck) the picture jitters
> a million which ways, and looks very unstable. All of the internal
> video sources (color backgrounds and the like that generate inside the
> actual unit) all work fine.
>
> My Question: Do all of the sources on this switcher (or any real Video
> Switcher for that matter) NEED to be synched to run decent video
> through it?
Yes. Those type of "traditional" video switchers REQURE all the
inputs to be precicely timed ("Gen-locked") to a single sync standard.
If the 2550 is anything like my SEG-2000, it has both an internal
sync ("Black-burst") generator (and several outputs on the back panel)
AND the ability to "gen-lock" the SEG (and its internal sync generator)
itself to another external source.
I frequently run my industrial cameras (Sony DXC-3000) from the
built-in sync generator. I sometimes even use the NTSC output
from a computer to feed INto the Gen-lock input on the switcher so
that I can cut/dissolve/wipe between live camera and the computer
image. I even made up a special cable so I can feed the computer
video into the input on the switcher which allows me to superimpose
titles over live camera video (titles generated using PowerPoint and
white letters on black background).
> When I say decent, I mean using the Mix or Wipe modes from
> 1 source to another and not feeling like im in the twilight zone.
Yes, you are describing exactly what happens when you use a
synchronous switcher with non-synchronous inputs.
> I upgraded (however slightly) from a Sima FX-9 video mixer
> that wouldn't allow me to do straight cuts because the sources
> weren't synched.
The Sony SEG isn't even in the same class as anything from Sima,
but for your purposes, you need a different kind of switcher.
> I really only need that mixing feature on the new switcher.
There are several more consumer-oriented switchers that will
do that. For example I really like my old Panasonic WJ-AVE5
for simple two-input, casual production with consumer cameras.
You didn't say how many inputs you need? But for two inputs,
the Panny is cool. Another unit recommended by someone on
this newsgroup is the Alta Pyxis E which is a heavy-duty,
industrial version of the consumer asynchronous switchers.
I just bought one on Ebay for $50 but haven't had a chance to
try it yet.
> Should I be able to run video that isn't Genlocked through the
> board and still get a decent picture when mixing, or did I screw
> up and now need to go buy some TBC's??
You need to either buy some frame synchronizers, or get one
of the switchers which have built-in frame-sync on all the inputs.
Getting an asynchronous switcher may be cheaper than buying
a bunch of frame synchronizers. Note that the frame sync units
must themselves be capable of genlock, and that you must tune
("time") each of them for horizontal sync, and for subcarrier
phase. This can even be done by "eye" for non-critical use, but
doing it properly requires a waveform monitor and a vector-
scope. It also requires that each of the inputs be capable of
generating a color-bars test signal (or that you can feed a color-
bars signal into the input of each frame-sync).
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