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March 26, 2021
PRECISE TRIGGERING
No matter how perfectly synchronized two
clocks may be, it doesn’t do much good if you can’t start playback at
the same time. To illustrate by example, let’s walk through a typical dark ride system that requires synchronized
on-board audio and off-board audio. If the on-board audio starts playi
ng 300ms late, it’s going to be off
consistently for 300ms the entire time. There are several common factors that make this a challenging problem to
contend with.
PLAYBACK LATENCY
First, most AV playback equipment is not capable of triggering consistently upon command. This is especially true
for PC-
based hardware running operating systems that are often busy running unpredictable tasks. Let’s say you
send a command to play audio and playback begins about 100ms after the command is issued. Repeat this same
process, and next time it might take 200ms. It is simply impossible to ensure synchronization between two (or
more) devices when playback reaction time is not consistent.
Network L Inconsistent Playback Device
NETWORK LATENCY
Specialized AV
playback equipment can greatly improve this situation by offering consistent reaction time. Let’s say
that this equipment guarantees that playback will begin exactly 100ms after a command is received. The idea is
that you send the same command to two different devices and they both start after exactly 100ms. Viola! They
are synchronized! The catch is that those commands must be received by both devices at exactly the same time
for this concept to work. This is quite challenging, especially via wireless networks where packet latency can
sometimes exceed 300ms.
Network L Consistent Playback Device
