Grass Valley MRC v.1.2 - Manual (Page 162)

152
Tutorials
Pass-Through Sources
Pass-Through Sources
“Pass-through” is a concept designed with respect to the disembedder/embedder output cards
of NV8500 family routers.
The concept of pass-through was created to allow panel operators to take audio from standard
input cards to hybrid output without an extraordinary amount of effort. It is the disembedder/
embedder output card that performs pass-through.
Each output of a disembedder/embedder card has logic that allows “pass-through” (as well as
null audio). Figure 6-2 illustrates one such output:
Fig. 6-2: Output of Disembedder-Embedder Card
The output path has a disembedder that extracts the audio from the video source and an
embedder. Each audio channel of the embedder receives one of 3 multiplexed inputs:
• An audio channel i from the disembedder.
• Silence.
• An audio signal from the router’s audio matrix.
Each embedder channel has a ‘null’ flag (i.e., the ‘Insert Silence’ flag) set by the logic of
embedded group control. (See
Embedded Group Control on page 151.) If the channel’s null bit
is set, the EGC logic will drop the entire group if all its null bits are set. Otherwise, the channel
carries generated silence.
If the embedder’s audio channel is not null, the audio comes from the disembedder if the
channel’s pass-through bit is set. Otherwise, the audio comes from the router’s audio matrix.
Basic and Extended Pass-Through
Panel operators are given the choice of basic pass-through and extended pass-through:
• Basic. The operator routes an audio source designated as the basic pass-through source to
an output. The actual result (given a correct NV9000-SE Utilities configuration) is that all 16
audio output channels are taken from the video at the output.
• Extended. The operator can route individually up to 16 audio sources configured as
“extended” pass-through sources to the output. The audio outputs represented by those
pass-through sources are taken from the video at the output.
MUX 1
Pass-Through 1
Null 1
Disembedder
Port
Embedder
Port
Silence
Generator
Audio Matrix
SDI In
SDI In SDI In
Group 1
Group 2
Group 3
Group 4
Output
Audio 1
Pass-Through Null Mux Output
0 0 Source from audio matrix
1 0 Disembedder output
x 1 Generated silence
(If null is selected for all
channels of a group,
the group is omitted
from the output.)
Audio 2
Audio 16
• • •
• • •
MUX 2
MUX 16
(from video
matrix)
Null 2
Pass-Through 2
Null 16
Pass-Through 16