Chapter 3 - Setting Defaults
3-20
Annexes Annexes are additions to the Video Format wh e n
using H.263 Video Protocol, increasing the quality
of the video display.
Annexes N, P and F are enabled only when you
are in Video Switching mode and the Video
Protocol is set to H.263. The Video Format may be
set to QCIF, CIF, 4CIF, 16CIF, VGA, SVGA, XGA,
or NTSC.
When Video Format is set to Auto, the system
selects the appropriate annexes according to the
endpoint's capabilities. The annexes are required
in the Dual Stream mode, but may also be
selected independently.
•Annex F - Advanced Prediction Mode. This
annex 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 fo r optimal
prediction of the macro block.
•Annex N - Reference Picture Selection Mode.
This annex enables the conference to recover
efficiently after transmission errors have
occurred in the macro blocks, and reported via
a relevant message to the speaker encoder.
•Annex P - Reference Picture Re-sampling.
This annex enables the transmitting encoder to
apply a re-sampling 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, wh ich had a
different source format, such as CIF, QCIF,
4CIF, etc.
Table 3-1: Reservation Defaults - Settings1 Parameters (Continued)
Option Description