Thompson ViBE EM4000, Руководство пользователя

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Appendix A ’Technical Specifications’ — Features
182 ViBE EM4000 — Release 1.10
User Manual — 46073586AB02
Flextream
„ Principle
Flextream, a statistical multiplexing device, has been designed to
increase video compression quality when several encoders share a given
bitrate. The Operator configures each encoder with a minimum and
maximum bitrate and a quality level. The bitrate of each Encoder varies
and is dependent on the complexity of the signal to be encoded (the
complexity being evaluated by each of the encoders), and the quality
level requested.
Each Encoder sends information about video source complexity and the
bitrate required to reach the requested quality level to the bitrate
allocator for each frame. The bitrate allocator allocates each Encoder with
a bitrate which is proportional to the complexity level of the video source.
If the Operator so wishes, the allocator can limit the allocated bitrates to
the values required to reach the set quality levels. In this way, if none of
the Encoders have complex frames, the allocator will only allocate a
portion of the total bitrate and the bandwidth will be filled with stuffing
bytes which can then be replaced by opportunistic data injected on a
downstream multiplexer. Stuffing quantity varies as it depends on the
complexity of the incoming video signals.
„ Flextream Bitrate allocator
The bitrate allocator responsible for collecting the complexity of pictures
to be encoded and for allocating bitrates to each Encoder in a pool can
be located on a site that is remote from the Encoder site or on the same
site. The allocator is built in the 9030/9040 NetProcessor (multiplexer)
device and communicates with the Encoders via the UDP/IP multicast
network. The allocator can manage several pools of Encoders.
A Flextream pool can contain ViBE EM4000 Encoders, ViBE EM2000
Encoders, ViBE EM1000 Encoders, ViBE EM3000 Encoders and ViBE Dual
Pass Encoders (DP ENC, AD ENC, IP ENC).
This feature is a software option. Refer to section ’Local Flextream’ on
page 192 and section ’Remote Flextream’ on page 192.