Nevion SPG-AVA-DMUX - Manual (Page 4)

SPG-AVA-DMUX Rev. C
nevion.com | 4
1
Product overview
Figure 1: Simplified block diagram of the SPG-AVA-DMUX card
1.1 The core functionality
The SPG-AVA-DMUX takes an SDI input signal and uses this as a frequency reference to
generate an analog sync signal, either Black burst or Tri-level. The sync signal is also
available in digital SDI form on two BNC outputs, and these signals can then be fed to DACs
or distribution amplifiers. Alternatively, the signal on these BNC outputs can be taken directly
from the reclocked input.
A full frame synchronizer and de-glitcher handles interruptions on the input and ensures that
the signal to the frequency generating logic is kept stable. If the input should disappear, the
SPG-AVA-DMUX will still generate Black burst or Tri-level signal with the same frequency.
The frequency generating logic has two modes: One that will react instantly to input frequency
changes and try to follow it (slave mode), and one that will average out frequency variations
over a long time (master mode). If cascading several SPG-AVA-DMUX units, the first could
be put in master mode to average out frequency variations, while the down-stream units
should be put in slave mode to follow the frequency generated by the master as tightly as
possible.
1.2 Secondary functionality
1.2.1 Audio sync output
At the same time as producing the video sync signal, the SPG-AVA-DMUX also generates
an audio reference signal based on the same input frequency. This can be either AES11 or
Word clock, both intended to synchronize external audio equipment, and thereby prevent
unintentional and unnecessary use of sample rate converters. The audio sync output will still
be generated if the input signal is lost.
1.2.2 Linear time code output
Linear Time Code (LTC) is de-embedded and available on a separate output. Since this is
de-embedded from the input and not generated, the output will be missing if the input signal
disappears.
1.2.3 Input change-over with fallback to internal generators
The SPG-AVA-DMUX comes with an electrical SDI input and an additional (optional) optical
input. Sophisticated input selection logic can switch between the physical input when signals
are available, and/or switch to internal video generators in the event that no physical input is
present.