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Author Topic: SDI Genclock/Ref?  (Read 5691 times)

Tom Williams

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SDI Genclock/Ref?
« on: March 10, 2011, 03:08:44 am »

Hi Guys,

You will have to excuse my ignorance on this matter as I have been flung into a pit of SDI equipment that seems like it has no bottom.

The crux of the question is this

I have to buy, borrow or steal a SDI scaler that has the capability to be externally Genclocked, now I have genclock outs via Camera cotrol units and some DA's but I also have a Ref out on the vision mixer I/O unit. Are these the same thing?

Thanks for any advise you can give.
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Kevin Hoober

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Re: SDI Genclock/Ref?
« Reply #1 on: March 10, 2011, 09:51:09 pm »

Tom,
I'm really an audio guy...but dabble in video engineering--I'll try to shed some light.  I'll consult the book in the morning to make sure I don't lead you too far astray :-)

Here we go:

SDI (SD) typically uses BlackBurst as a sync source (or to Genlock).  This is the same sync signal that analog video used for ages.  There are other names for the same signal, such as Black and Burst (a accurate description of the signal), Bi-level sync, Color Black, or just Reference.

BlackBurst is distributed w/ analog video DAs (don't use SDI DAs)

Many devices have loop-thru BNC connections for Sync inputs so that you can daisy chain the sync signal from one device to another.

You probably have an external reference source that the entire system is synced to.  My preference is to run dedicated lines back to a DA (that gets it's source from the reference source) instead of daisy chaining devices.  I figure less bad happens if a cable goes bad or if a device fails.

The short answer to your question is that they are all likely the same signal.  Your Ross Vision can accept more than just BlackBurst as a sync source (for instance Tri-level sync), hence the ambiguity of it's naming.

Kevin H.

PS nice switcher :-)
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Tom Williams

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Re: SDI Genclock/Ref?
« Reply #2 on: March 11, 2011, 03:01:29 am »

Thanks very much Kev!

I had a feeling they were going to be similar. This unit will be used for a once a year OB so it has been shoe horned into the system, I will probably clock (or should that be ref :o) direct out of the mixer.

Thanks

P.S How did you know I was using a Ross?
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Brad Weber

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Re: SDI Genclock/Ref?
« Reply #3 on: March 11, 2011, 08:02:12 am »

What are the CCUs and are you sure the Genlock out is a sync signal they create and not just a loop through of an input?

Ideally you would have a master clock for the entire system and often that is a dedicated device that can provide the various timing sources needed by all the audio and video equipment in the system.  In your case, if you don't have a master clock then using the mixer/switcher as the clock source probably makes sense.  There may be a switch or setting on the CCUs that has to be set to get them to sync to an external source.
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Kevin Hoober

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Re: SDI Genclock/Ref?
« Reply #4 on: March 11, 2011, 08:40:10 am »

P.S How did you know I was using a Ross?

You mentioned the Vision Frame--Just installed a Vision @ work :-)

Kevin H.
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Mike Fariss

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Re: SDI Genclock/Ref?
« Reply #5 on: March 17, 2011, 10:12:07 pm »

...I have genclock outs via Camera cotrol units and some DA's but I also have a Ref out on the vision mixer I/O unit. Are these the same thing?

Thanks for any advise you can give.

In other parts of the world the term “Vision Mixer” is used to describe what we call a “Switcher” in the states. 

If the switcher is an older Ross Synergy, the ref input needs to be SDI.  It is the only box that I have used that dose not use an analog ref signal.

The OP says that there is Gen Lock available form the CCUs and some DAs.  CCUs do not generate ref, but have loop outs form their referance inputs.  DAs only give you copies of what is going in, so unless there is a ref source somewhere in the system you do not have gen lock.

The Ross Vision and Synergy switchers do not have internal reference generators, you will need an external ref source with these.  The Ross Crossover has reference outputs that can be used as your master ref source.  In either case, take your master ref signal and use DAs to feed all of your gear.  Like Kevin said, you can daisy chain using loop throughs, but if one cable goes bad, everything downstream form that one cable will loose gen lock.
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Kevin Hoober

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Re: SDI Genclock/Ref?
« Reply #6 on: March 18, 2011, 02:27:24 pm »

In other parts of the world the term “Vision Mixer” is used to describe what we call a “Switcher” in the states.
If the switcher is an older Ross Synergy, the ref input needs to be SDI.  It is the only box that I have used that does not use an analog ref signal.

Mike,
Thanks for that great info--that explains why my old Synergy was referenced to SDI Black, instead of BlackBurst, like the rest of the system!

Kevin H.
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ProSoundWeb Community

Re: SDI Genclock/Ref?
« Reply #6 on: March 18, 2011, 02:27:24 pm »


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