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Chapter 4 - Setting Up Conferences
4-64
Annexes In Video Switching conferences set to the H.263
protocol, Annexes can be activated to improve
specific aspects of video display quality.
When the Video Format is set to Auto, the system
selects the appropriate annexes according to the
endpoint's capabilities.
Annexes are required for the Dual Stream mode,
but can also be selected independently.
You can select an the following annexes:
• Annex N - Reference Picture Selection Mode.
It enables the conference to recover efficiently
after transmission errors have occurred in the
macro blocks, and were reported via a relevant
message to the speaker encoder.
• Annex P - Reference Picture Resampling. It
enables the transmitting encoder to apply a
resampling process to the previous decoded
reference picture in order to generate a warped
picture, for use in predicting the current picture.
The main purpose of this annex is to support
the relationship of the current picture to a
previous picture, which had a different source
format, such as CIF, QCIF or 4CIF.
• Annex F - Advanced Prediction Mode.
It enables the transmitting encoder to use four
motion vectors for every macro block (one
motion vector per block). A macro block is a
piece of the picture that contains four blocks.
Without this annex, the transmitting encoder
can only choose one motion vector for optimal
prediction of the macro block.
Table 4-7: Conference Properties Advanced Settings - Media (Continued)
Field/Option Description