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Appendix d: performance considerations, Testing, one two, Imag and latency – NewTek TriCaster TC1 (2 RU) User Manual

Page 325: D.2.1, Relativity and the speed of light, D.2.2, Latency and your audience

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APPENDIX D:

PERFORMANCE CONSIDERATIONS

In this section, we’ll consider the most common questions

you may have (and of course

we’ll provide the answer, too). Answers are

intentionally brief

perhaps just a

reminder of one or two steps required to perform some operation. For this reason,

we’ll also point you to explanatory information elsewhere in this manual whenever

that would be useful.

D.1

TESTING, ONE TWO …

Professionals simply do not leap into new environments blindly. They prepare, plan, plan some more, and
then

most importantly

they test. This allows them to tackle the really tough jobs with confidence.

D.2

IMAG AND LATENCY

What’s IMAG? It’s a

compression of the expre

ssion “I

mage MAG

nification.” Typically in modern IMAG

applications, video cameras supply live imagery to projection systems, magnifying speakers and performers
so that audience members further back in large ven

ues can still see what’s going on.

IMAG is a very tricky task at the best of times, one that calls for excellent planning, and where possible,
testing. Those designing an IMAG installation have, not just one, but

two

inter-related broadcasts to consider

in the form of the audio and video streams.

D.2.1

RELATIVITY AND THE SPEED OF LIGHT

Wouldn’t it be nice if audio and video travelled from their respective broadcast devices at the same speed?

Then, wherever you were seated in the audience, the sound from hypothetically perfect speakers and the
video image from huge video displays co-located at the front of the auditorium would reach your ears and
your retinas at precisely the same moment!

This is not the case, however. Sound travels quite slowly

so slow, in fact, that even in relatively small venues

it reaches those in the rear of the audience noticeably later than those in the front.

In loose terms, for a mid-size auditorium 600 feet long, it takes around a half-second for the audio to reach
those in the back. For this reason, audio engineers often po

sition speakers throughout the ‘house’, then

introduce carefully considered delays by electronic means

to ensure ‘late sound’ from front speakers does

not arrive after sound from the nearest speaker to those further back.

Light, on the other hand, travels so much faster that for all intents transmission can be considered
instantaneous in the same setting. So a person in the rear will see the image on a screen at the front long
before sound from a

co-located

speaker arrives.

If transmission of the video signal from the camera lens right through to the projection screen were

instantaneous (it’s not, mind you), we’d likely need to

find

a way to delay it. Viewed in this light, a certain

amount of latency is actu

ally “A Good Thing!”