On IMAG and Latency

Product(s)

TriCaster 40

Search Tags

Lag, latency, delay, IMAG, projector, live, frames

PROBLEM DESCRIPTION

In live situations where you are using a projector as part of your production there may be visible latency or delay. Here is a brief discussion on what it is and things to keep in mind when in this scenario.

SOLUTION AND WORKAROUND

“IMAG” is short for “image magnification”. Typically in modern IMAG applications, video cameras supply live imagery to projection systems. Which then magnify  the performers to give  the audience members at large venues a better view.

IMAG is a very tricky task at the best of times, one that calls for excellent planning, and where possible- testing. For those designing an IMAG installation, have not just one, but two inter-related broadcasts to consider- the Audio and the Video streams.

If audio and video travelled at the same speed, wherever you were seated in the audience, the sound and video image from the front of the auditorium would reach your ears and your retinas at precisely the same moment.

This is not the case however. Even in relatively small venues sound reaches those in the rear of the audience noticeably later than those in the front, while the image arrives effectively instantaneously.

So for our purposes in this discussion “latency” refers to the time it takes for the video signal to transit one part of the IMAG path, from camera lens to the final display.

It is desirable to keep video latency to an agreeable minimum- but put away any notions about “zero latency” as being ideal, since this would only result in those nearest the front of the audience enjoying acceptable lip-sync.

It is common for each device in the production pipeline ( even the cameras and monitors) to contribute to the combined total latency. TriCaster’s portion is well within standards for devices of this sort. It is roughly between 1.5 and 2.5 frames.

Here are some things to consider when designing and connecting your system:

• If you use Multiview output from the TriCaster to the projector, match the resolution sent from the TriCaster to the native resolution of the projector.
• Try supplying the projector with analog video.
• Certain projectors provide a ‘low latency mode’ to disable features of the unit that carry a heavy toll in latency.
• Some cameras include features that add extra latency, such as image stabilization. Disable anything of that sort that you can.
• Latency may be slightly lower for progressive sessions.