IMAG + Genlock... again

Hello Blackmagic community, I'm a long time lurker, first time poster.

I am working on a project in my organization. Our boardroom is being remodeled. This is a demolition and rebuild. The room hasn't been updated since 1993. We've had AV upgrades over the years, though not as many as you might think. The most recent additions to the space were, 5 Sony EVI-H100S PTZ cameras, a Newtek Tricaster 860 and associated gear to record our board meetings. Those updates were made in 2014.

With this remodel we are replacing all of our production equipment. I'm planning to use a ATEM Constellation for this project. We will be replacing our cameras with 5 new 4K PTZs. I know some might think 4K cameras are overkill for our board meetings but, it will likely be another 10 years before we update this facility again.

In our current setup we do not do any IMAG. In the new design we are planning to have the ability to send camera feeds to our displays in the room. With IMAG, I know dealy is something I should think about. I've seen a lot of posts here and elsewhere online about IMAG and Genlock. There's a lot of information and depending on who you choose to believe, you either can't do IMAG without Genlock or you shouldn't even bother with Genlock because frame sync is good enough.

There are many components in the chain from the output on the back of our PTZ cameras to the video wall and other displays in the room. I know each of those devices are opportunities to introduce delay. I know that a Genlock won't have a huge impact in delay, 1 frame or less but, it still seems like there's some value in using a Genlock if your equipment can support it.

I'm unclear on whether or not a Blackmagic switcher will turn off it's frame syncs if a genlock signal is present. The best I can gather is that it will not disable it's frame syncs but, genlock will still help in reducing some delay.

I just returned from NAB 2024. While I was there, I visited the Blackmagic booth and asked several people many questions to refine my plan for this project. I talked to two different people about the BMD Sync Generator. I spoke to two people because I didn't believe the answer the first person gave me. The second person gave the same answer as the first so I guess I should take their word. Still, I'm confused.

Here's my question
If you have more than six devices you want to Genlock how do you accomplish that with the BMD Sync Generator? The Sync Generator only has 6 outputs and no inputs.

Both Blackmagic employees told me, if I have more than 6 devices to sync, I should just buy another Sync Generator. I don't understand how that could work. If I had 6 cameras synced to one BMD Sync Generator and ATEM and two other cameras synced to a second Generator, how would everything be in sync? Sync Generator 1 knows nothing of Sync Generator 2, the are both operating independently from one another.

Can anyone explain to me how everything can be in sync when not all devices are using the same sync source. I know Genlock is not Timecode but, my brain still says there should only be one device generating the sync signal.

[Gary Adams]

Hello Todd. Genlocking cameras and ATEM switchers can buy you up to a frame of delay through the switcher. The switcher itself only has about 10 lines delay but if the input vertical is not timed correctly, the frame sync must delay until the next vertical causing up to the frame. The trick is timing the camera 10+ lines ahead of the ATEM. With our cameras, there is a line timing which may be set to whatever is needed to accomplish this. It's not necessary to turn frame syncs off as their effect is only used to match vertical timing down to the pixel. If there is no adjustment necessary, there is no delay added. Pretty simple. If 3rd party cameras have such an adjustment, then set them to maybe -12 to make sure you are ahead of the 10 lines. If they don't have an adjustment, there are sync generators (not Blackmagic) that have advance controls. This would require one main sync generator that feeds the ATEM and a second one that locks to the first and is timed -12 lines.

As indicated, the Blackmagic sync generator only has 6 outputs. If you need more than that an analog video distribution amplifier to add more outputs. Using two Blackmagic Sync Generators will not work as you were told. I'm sure it wasn't me that said that. Blackmagic cameras have the ability to lock to return video saving the need for the sync feeds altogether.

Remember, latency occurs in cameras, switchers, displays and most any device that scales or rate converts. The ATEM part only needs to be 10 lines. I hope this helps.

Gary

Not my post but a lot of great information here. Thank you Gary.

Gary,

Thank you for the information. I knew using two Sync Generators couldn't be correct. I guess it's time to educate the guys working in your booth at NAB. A representative at another vendor's booth gave me the answer you gave. Use a sync generator and an analog DA to send the genlock signal to more than 6 devices.

Both PTZ cameras I'm considering (one from Canon and one from Panasonic) offer H Phase adjustment in the Genlock settings. Neither camera manual mentions anything about vertical timing.

If the cameras do not offer a way to adjust the timing, I need to look for a 3rd party sync generator that can allow for that adjustment? And I will need two generators to accomplish the -12 offset / delay?

Does anyone have any recommendations on manufacturer's that offer those features in their products?