GRASS VALLEY 8920MUX -, Instruction Manual, Page: 41 / 50

8920MUX Instruction Manual 41
Functional Description
Functional Description
The 8920MUX inserts up to two 20- or 24-bit AES/EBU audio streams (2
channels per stream). The audio is collected into a group of up to 2 AES
streams (four channels total). The audio group can be assigned one of four
group IDs (G1, G2, G3, or G4) and can be inserted into the Ancillary Data
of the SD stream. In Auto mode the group can be inserted with the first
available group ID if one is not already present. If a group with the same
ID is present in the stream, the new group cannot be inserted unless the
replace or delete function is used.
Refer to the block diagram in Figure 19 while reading the following func-
tional description.
Figure 19. 8920MUX Block Diagram
Input Equalizing Amplifier
The equalizing amplifier lowers the impedance of the termination as fre-
quency increases. The differential input improves the performance of the
8920MUX in the presence of common mode hum and noise.
Network Interface CPU
Audio
In 2
Audio
In 1
AES Input
Stereo 1
AES Input
Stereo 2
27 Mhz,
64 aFS,
128 aFS
Phase
Lock
Loop
Amplifier
& Equalizer
Serial
Digital
Video
Input
Clock
Regen.
Serial to
Parallel
Converter
Parallel
to Serial
Converter
Serial Digital & Audio
Output Driver
Serial
Digital
Outputs
LED
Display
User
Setup
Switch
Logic
Rotary
Switch
DIP
Switches
FPGA
Group
Control
Logic
MUX
CPU Interface
EDH
24-b
Fault
Comm
Conf
Pwr
525 Mode
2ND
625 Mode
AS1 present
AS2 present
Audio G1
Audio G2
Audio G3
Audio G4
Insert G1
Insert G2
Insert G3
Insert G4
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