Video overlay box

B

Bill

Guest
Hello,

At my church we've just purshased a video overlay box to overlay song words
from a computer onto a video signal which carries live video during a church
service. however currently the setup is a little AV switcher to switch
between a couple of cameras.
However the overlayed computer signal starts to scroll when the AV switcher
is switched and then stops after it's done a complete scroll. sometimes the
scrolling is different. AFAIK this is caused by the different video signals
from the cameras not being in sync.
What would be an easy fix for this without having to purchase a video mixer
or is a video mixer the only solution since it syncs all the video signals
together.


This is the overlay box we are using:
http://www.citysouthelectronics.com.au/ccpt370.html

thanks,

Bill
 
"Bill"
At my church we've just purshased a video overlay box to overlay song
words from a computer onto a video signal which carries live video during
a church service. however currently the setup is a little AV switcher to
switch between a couple of cameras.
However the overlayed computer signal starts to scroll when the AV
switcher is switched and then stops after it's done a complete scroll.
sometimes the scrolling is different. AFAIK this is caused by the
different video signals from the cameras not being in sync.
Click to expand...

** Correct.


What would be an easy fix for this without having to purchase a video
mixer or is a video mixer the only solution since it syncs all the video
signals together.
Click to expand...

** You need to synch the two cameras together - some cameras have
provision for external synch.

A video mixer would likely provide such a synch signal.




.............. Phil
 
Bill wrote:
Hello,

At my church we've just purshased a video overlay box to overlay song
words from a computer onto a video signal which carries live video
during a church service. however currently the setup is a little AV
switcher to switch between a couple of cameras.
However the overlayed computer signal starts to scroll when the AV
switcher is switched and then stops after it's done a complete
scroll. sometimes the scrolling is different. AFAIK this is caused by
the different video signals from the cameras not being in sync.
What would be an easy fix for this without having to purchase a video
mixer or is a video mixer the only solution since it syncs all the
video signals together.


This is the overlay box we are using:
http://www.citysouthelectronics.com.au/ccpt370.html
Click to expand...
Depending on what kind of cameras you have, you may be able to supply a
master sync signal from the video mixer to the camera, or use the composite
output of one camera to feed the sync inputs of the other cameras. However,
most non-pro cameras don't have the option for external sync.

Any device, whether it is a switcher or mixer, needs the inputs to be in
sync. You can get video switchers that have individual time base
correctors/frame sychronisers on each video input, but the one's I've seen
are designed for SDI and cost a small fortune.

Another cheaper option may be a downstream time base corrector that you'd
put between the output of the switcher and the overlay box.

I'd suggest you give these guys a call - they probably have something that
will help you:
http://www.questronix.com.au/

Russ.
 
"Bill" <someone@microsoft.com> wrote in message
news:coeub3$1ada$1@otis.netspace.net.au...
Hello,

At my church we've just purshased a video overlay box to overlay song
words
from a computer onto a video signal which carries live video during a
church
service. however currently the setup is a little AV switcher to switch
between a couple of cameras.
However the overlayed computer signal starts to scroll when the AV
switcher
is switched and then stops after it's done a complete scroll. sometimes
the
scrolling is different. AFAIK this is caused by the different video
signals
from the cameras not being in sync.
What would be an easy fix for this without having to purchase a video
mixer
or is a video mixer the only solution since it syncs all the video signals
together.
Click to expand...
Not too sure, but rather than going a to b, have a null in the middle so
rather than a roll you get a frame or two of black screen by switching a to
null to b?

Just a random thought...

Mike
 
"Mikegw"

Not too sure, but rather than going a to b, have a null in the middle so
rather than a roll you get a frame or two of black screen by switching a
to
null to b?

Just a random thought...
Click to expand...

** How *very* Quantum Mechanical of you ......

Heisenberg would be impressed.




............ Phil
 
"Phil Allison" <philallison@tpg.com.au> wrote in message
news:312s3cF35s53pU1@uni-berlin.de...
"Mikegw"


Not too sure, but rather than going a to b, have a null in the middle so
rather than a roll you get a frame or two of black screen by switching a
to
null to b?

Just a random thought...



** How *very* Quantum Mechanical of you ......

Heisenberg would be impressed.


He would have to find me first.
Click to expand...

I recon you know more on this than me. would this work or am I wasting
electrons??

Mike
 
"Mikegw"
"Phil Allison"


Not too sure, but rather than going a to b, have a null in the middle
so
rather than a roll you get a frame or two of black screen by switching
a
to
null to b?

Just a random thought...


** How *very* Quantum Mechanical of you ......

Heisenberg would be impressed.


He would have to find me first.

I recon you know more on this than me. would this work or am I wasting
electrons??
Click to expand...

** The overlay box: http://www.citysouthelectronics.com.au/ccpt370.html
takes the camera's video signal in, locks onto it and configures the PC
video data to suit exactly - but not instantly. When the video signal
changes phase as a new camera is switched in - the PC has to do a
reconfig to suit again.

What possible help to this would a black out be ???

The other posts here have the options that work.



.............. Phil
 
Mikegw wrote:
"Phil Allison" <philallison@tpg.com.au> wrote in message
news:312s3cF35s53pU1@uni-berlin.de...

"Mikegw"


Not too sure, but rather than going a to b, have a null in the
middle so rather than a roll you get a frame or two of black screen
by switching a to
null to b?

Just a random thought...



** How *very* Quantum Mechanical of you ......

Heisenberg would be impressed.


He would have to find me first.

I recon you know more on this than me. would this work or am I wasting
electrons??
Click to expand...
It kinda sounds half convincing, but unfortunatelty, just because a frame is
black, doesn't mean it hasn't got sync, colour burst, front/back porch and
all the rest that goes into a video frame. A "black" frame just means is
that during the picture information part of the signal, the video level is
down at the black level. So switiching to an unused input (with no signal at
all) before the desired input would actually make things worse. In the
absence of a proper video signal, the overlay box would probably get angry
as it would have nothing to sync to and stop outputting. Or explode.

Video signals are pretty simple waveforms (thankfully for me) if you do a
little Googling it only takes probably 15 minutes to understand how they
work (OK, maybe 5 more to get your head around the idea of fields). Any info
you find on NTSC is very similar to PAL, but for slightly different voltages
and a thing called "pedestal" that NTSC has.

Russ.
 
On Mon, 29 Nov 2004 21:40:34 +1100, "Bill" <someone@microsoft.com>
wrote:

Hello,

At my church we've just purshased a video overlay box to overlay song words
from a computer onto a video signal which carries live video during a church
service. however currently the setup is a little AV switcher to switch
between a couple of cameras.
However the overlayed computer signal starts to scroll when the AV switcher
is switched and then stops after it's done a complete scroll. sometimes the
scrolling is different. AFAIK this is caused by the different video signals
from the cameras not being in sync.
What would be an easy fix for this without having to purchase a video mixer
or is a video mixer the only solution since it syncs all the video signals
together.


This is the overlay box we are using:
http://www.citysouthelectronics.com.au/ccpt370.html

thanks,

Bill

about the only cheap and nasty ways out of this would be to adjust the
Click to expand...
vertical hold on the TV sets/monitors (assuming they even have a
vertical hold adjustment these days) to an extreme so as to get the
scrolling over with as quickly as possible - or make up a blanking
circuit that kills the video content for a couple of seconds to a
blank screen (but not the sync) when the source is changed to give the
picture time to lock unseen. making up one of those video effects
kits that have been in EA or SC over recent years that allow a " fade
to from black" options etc might be a more elegant way to achieve this
- and cover up the unwanted scrolling.

I hear that in WES news (flyer that has new items not yet in the main
catalogue) that there was an audio video mixing desk for about $800.

However if you have your video signal is going into the overlay box (
I would imagine it would have to in order to be able to sync itself to
the video content) then the rolling is probably an internal matter of
the overlay box having to re-lock itself into the suddenly changing
input signal to it. Possibly momentarily dropping the power to the
overlay box (to reset it) while signals are being changed may possibly
help ? its a real long shot - but it may help ?


I hear that in WES news (flyer that has new items not yet in the main
catalogue) that there was an audio video mixing desk for about $800.

I would make sure it isnt going to make problems for the video overlay
unit though. (dont know if it will)
 
"Bill" <someone@microsoft.com> wrote in message
news:coeub3$1ada$1@otis.netspace.net.au...
Hello,

At my church we've just purshased a video overlay box to overlay song
words from a computer
Click to expand...
may have been the wrong way to go.

may have been better to use a 4 input video capture card , so the PC gets
the camera of your choice,
writes the overlay on, and then outputs your video.

That way the output never changes its sync, and the display doesnt scrolling
doesnt happen.

The problem is the overlay machine is a time base corrector, it prevents the
sync on the input any large % of a frame per frame. when the signal is off
sync, it outputs junk that you see as scroll.
 
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