User guide

Operating the Multiplexer using nCompass Control
Table 4.4 Suggested Bit rates for Various Programme Types (Mbps)
Resolution
(pixels)
Sport News Film General
704 x 576 6.0 - 8.0 4.0 - 6.0 3.0 - 5.0 5.0 - 7.0
352 x 576 3.0 - 6.0 2.0 - 3.0 1.5 - 2.5 2.5 - 3.5
352 x 288 2.0 - 3.0 1.5 - 2.5 1.0 - 2.0 1.5 - 3.0
An example of a bit rate allocation is given in Table 4.5. The Operator can monitor
the quality on each channel and adjust the bit rate allocation.
Table 4.5 Typical Bit rate Allocations
Encoder Resolution
(pixels)
Programme
Type
Allocated Bit
rate (Mbps)
1 704 x 576 Sport Channel 6.0
2 352 x 576 Sport Channel 4.0
3 352 x 576 News Channel 3.0
4 352 x 576 Film Channel 2.0
TOTAL:
15.0
The more Encoders there are in a group, the more potential there is to reduce the
group bit rate, although this may have to be modified in the light of any
remultiplexing further downstream.
4.5.5.3 Weighting Factor
A weighting factor can be assigned to each Encoder in a group to create a bias to
that channel. In the example above, Encoder 1 can be given priority thus ensuring
higher picture quality in the event of a conflict. If no bias is required, the weighting
factor should be set to the same value.
Table 4.6 Example of Weighting Factor Allocation
Encoder Resolution
(pixels)
Target Picture
Quality
Average Bit rate
(Mbps)
1 704 x 576 95 6.0
2 352 x 576 80 4.0
3 352 x 576 80 3.0
4 352 x 576 80 2.0
TOTAL:
15.0
2/1553-FGC 101 1014 Uen B
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