Nevion SDI-TD-MUX-4 - Manual (Page 8)

SDI-TD-MUX-4 / SDI-TD-DMUX-4 Rev. N
nevion.com | 8
The SDI-TD-DMUX-4 board receives any combination of four 270 Mbps time division
multiplexed SD-SDI or DVB-ASI signals embedded in the 1.485 Mbps HD signal according to
SMPTE 346M-2000. If the customer has purchased an optional pin diode module for optical
input (in which case the module will identify itself as an SDI-TD-DMUX-4-R), there will be an
option available to select either input manually, or to select between them automatically.
All outputs can be either 270 Mbps SD-SDI or DVB-ASI (188 or 204 word packets). Channel
swapping (“shuffler”) is available either from DIP-switches or remotely via the standard
Multicon GYDA interface. Shuffling is available in both modules, in case the two modules are
on different control networks, or only one of the modules is even connected to the control
network. I cases where fewer than four SD signal are transported, the shuffling feature can
also be used to duplicate channels on the outputs, potentially saving a distribution amplifier.
The SD-SDI clocks for each recovered SD channel will be regenerated based on a frequently
received SCR counter (Stream Clock Reference
– refer to the SMPTE 346M-2000 standard).
This ensures a stable, low-jitter output.
There are four signal generators available on the board. Each can be set to color bar 525,
color bar 625, black 525 or black 625 from Multicon GYDA. Since the SDI-TD-DMUX-4 does
not have a local clock reference input, a valid SD signal must be present in the HD stream
from the SDI-TD-MUX-4 (i.e. at least one SD signal must be connected to one of the SDI-TD-
MUX-4 SD inputs) in order to guarantee that the output signals from the test signal
generators in the SDI-TD-DMUX-4 are compliant with the SD clock requirements. The
module will still generate an output based on the video signal that was lost, but without a
clock reference there’s no guarantee that equipment down the signal chain will be able to
lock (or remain locked) to that output.
By default, there is no fallback for missing SD streams. If fallback is set to black or color bar,
the video format (SD-SDI, 525 vs. 625 lines) will be selected automatically based on the
signal that was lost. If the lost signal was DVB-ASI, no fallback will be available, regardless
of the setting.
The board measures the RSSI (Received Signal Strength Indicator) from the optical input.
Normally, the readout (in the Multicon GYDA GUI) shows the signal strength within ±1-2 dB.
However, the measurement is NOT calibrated and the readout should be used as an
indication only. Also, while the readout is fairly linear within a range from -15 dBm to -30
dBm, outside this range the meter w
ill just “bottom out” at -15dBm or -30dBm. If that occurs,
disregard the actual readout but know that the signal is either strong enough with good
margins or too weak to be detectable.