Blackmagic Forum

Hi,

Currently at an awards show in London running all the vision from a ATEM production studio. I have 4 macs running 1080i and two cameras running 1080i over hd-sdi. These is all feed to two HD projectors, the data elements look great....however there is a 2 frame drop on the live camera relay to screen. We have put a delay on the PA system via the audio desk, and it's ok not great. Anyone else using the switchers in this way? Should it really be used for live events?

Any thoughts welcomed!

Yes. We use an ATEM 2M/E for live use weekly. The biggest source of delay for us was the projectors themselves. We were operating in 1080i but our projectors had a native resolution of 1280x800. When I switched everything to 720p the delay virtually dissapeared. If you use an SDI router, try routing a camera directly to one projector and have your switcher send the same camera signal to the other projector. When we did this the delay was only 1 frame delayed through the switcher.

While playback input sends may be delayed to align video, it is NEVER acceptable to delay loudspeaker outputs to compensate for video. Loudspeaker delays are used to time align multiple sources such that they arrive to the listener at the same time, this is very important for system intelligibility. By improper use of delay you run the risk of a time offset on stage, as little as 50ms can render many people unable to speak. Also sound travels through air MUCH SLOWER then light, so in a large space you will never be able to sync over the whole space.

Completely agree with Tim. Never delay live audio. You can delay the audio for a record feed or for satellite (overflow) rooms, or for the web, but not for the live audio in the room. Just live with the tiny bit of video delay.

Incidentally, every video input on a ATEM unit is delayed by one frame. If you use a DVE in the video mix, that will delay it another frame. It is very possible that your projector or any converter boxes might delay yet another frame. It is the nature of video devices, when regenerating sync, and is something all video professionals have had to deal with for ages.

Agreed, we sometimes will have to delay a playback audio feed to compensate for frame loss from playback computer to the projectors. Delaying the live audio is not the greatest idea, but in my world 2 frames of live latency is actually really not that bad. In the VGA world it was often much worse. Can I ask what cameras everyone uses? We have experimented with a lot of different models for latency issues and have found that the following cameras have the least amount of latency:

Panasonic HMC 150
Panasonic HMC 40
Sony EX8

The Sony is nice because it has HD-SDI out and you don't need a converter, plus you can swap lenses on it.

BMD gear tends to get used fairly intensely in the Church and worship scene. Specifically in live environments, so yes, live events are on the list of things you can use them. But like others said in this thread, frame delay is something you'll have to live with as there's no real way of getting around it.