VIDEOHUB and REFERENCE INPUT

Reference input on Videohub is used for what ????

The reference input on a video router is usually used to control the timing when a route switch should happen. So if you change the input source assigned to a particular output on the video router/hub, when this switch actually happens would follow the frame timing of the reference input.

The precise timing of the switch generally follows the SMPTE RP 168 standard which specifies that the switch should happen in the video blanking interval so that it does not affect the visible part of the video signal.

So the benefit of the reference input, is that if the various video input signals going into the router are also locked to the same reference timing, then the input-to-output route change would typically happen at a frame boundary. If instead the different video inputs to the router each have their own timing (so they are not genlocked to the same reference), then the reference input to the router doesn't help very much because the change in the route assignment will probably end up happening somewhere in the middle of a video frame anyway.

With independent video sources that do not share a common reference, if you still want the video route changes to cleanly happen at a frame boundary, then you typically need something like the approach followed by the VideoHub CleanSwitch. That model has frame synchronizers on all of the inputs that adds a bit of delay to match up the frame boundaries of the different video signals (the ATEM switchers do this as well, which is why they can be used with video sources that are not genlocked).

The internal frame synchronization approach adds up to a frame of latency to the video signals going through the video router though, which can be a problem for some applications. So if you need to avoid this additional latency, and you need the changes in video routes to match a common frame boundary timing, then you would need lock all of the video sources to a common reference and feed a reference signal into the video router/hub as well.

Dave : Thanx for reply .. I know everything what U wroted ..
I have videoHub 40x40 .. All sources and destination have no refence .. So every gears have own timing .. I have reference generator (used for Wordclock sources) and it have video reference too .. So Im thinking, if I get any advantage , when I connect reference to Videohub and maybe to Atem Constelation .. DO U think , it will be good for something ?

No, if each of the input sources into the video hub have their own timing, then there isn't much benefit to supplying a reference signal. Any route changes on the hub would follow the timing of the provided reference input, but since this timing won't match the timing of any of the video sources, the changes will still likely end up happening in the middle of a frame, so you won't get clean switches.

Dave : yes .. i think it too .. thanx ..

Syncronization seems not easy to grasp...

How a clock made for 1080 (BMD sync generator) can be used on 12G VIDEOHUB ?

Syncronization seems not easy to grasp...

How a clock made for 1080 (BMD sync generator) can be used on 12G VIDEOHUB ?

Sync is about frame rate not resolution. The connector is the same but it’s a different signal required. Black Burst is just composite/analog 480i black signal (black) with a yellow bit (burst) hiding in the blanking interval to adjust color phase.

Tri level has a positive and negative sync pulse +/- 300mv, no color conponent, and unlike burst ,the signal doesn’t rasterize. Plug burst into a composite monitor and you get black, do the same with TLS and it’s just a mess.

With analog video, perfect sync was mandatory, line for line, pixel for pixel. With blackmagic gear it doesn’t matter so much if you can afford the delay. With most other broadcast gear sync is still a part of daily life.

Good Luck