Cisco Model D-PCG1000 PowerKEY CAS Gateway Referências técnicas
Operations Alert Bulletin
Configuring Stat Mux Dejitter Groups
on the DNCS
Configuring Stat Mux Dejitter Groups
on the DNCS
Background
Statistical multiplexing is the process of using a statistical multiplexer (or stat mux)
to combine a number of MPEG programs so that the sum total bit rate of the
included programs does not exceed a programmed limit. This allows system
operators to change the bit rates of channels dynamically according to the
bandwidth requirements of each channel.
The GQAM does not provide statistical multiplexing, but it does process the stat
The GQAM does not provide statistical multiplexing, but it does process the stat
mux data with an algorithm that uses time shifting of information, glue frame (valid
frames with no video data) replacement, and/or frame dropping to reduce the
individual program bit rates, as required by the bandwidth limitations.
This GQAM algorithm can introduce jitter as compared to the input signal, so
This GQAM algorithm can introduce jitter as compared to the input signal, so
dejitter techniques are applied as part of the processing.
A stat mux dejitter group (SMDG) processes the stat mux stream as a group of
A stat mux dejitter group (SMDG) processes the stat mux stream as a group of
programs (as a single unit). In the GQAM, it ensures that the stream realizes the
optimum dejittering. Using SMDGs, the GQAM uses just one buffer dedicated to
one, and only one, transport stream. This produces an output stream closest in
quality to the original.
The SMDG provides the following functions:
The SMDG provides the following functions:
Processes the variable bit rate (VBR) stream as a group of programs
Ensures optimum dejitter by using one buffer that is dedicated to only one
transport stream
Produces an output stream closer to the received jitter
Processes the SMDG as a session, so it can be created and torn down as needed