Cisco GoQAM, Installation And Operation Manual

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Input/Output Process
4004834 Rev D 7
Input/Output Process
This section describes how the GoQAMs modulate, encrypt, and transmit the signals
they receive from external sources.
Input/Output Diagram (RF Version)
The following diagram illustrates the stages of the input/output (I/O) process for
the RF GoQAM.
Note:
The stage numbers correspond with the following table.
Input/Output Stage/Description Table
The following table describes the stages of the I/O process of the RF GoQAM. The
numbers correspond to the above I/O diagram.
Stage Description
1 A pair of transport streams (a clear version and a third-party encrypted
version of the same stream) are input to the modulator.
2 The digital I/O board timestamps the MPEG packets in each stream, then
filters and routes them according to their PID values.
3 The digital I/O board selects the packets to pass from both the clear and
third-party encrypted streams.
4 PowerKEY encryption is added to selected clear packets and PID values are
remapped.
5 The clear and encrypted streams are synchronized.
6 An overlay output stream is created by muxing (multiplexing) the clear, S-A
encrypted, and third-party encrypted packets.
7 The output stream is modulated at 64 QAM or 256 QAM.