Chapter 3 - Setting Defaults
Table
Option | Description |
|
|
Annexes | Annexes are additions to the Video Format when |
| 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 for 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 |
| This annex enables the transmitting encoder to |
| apply a |
| 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, |
| 4CIF, etc. |
|
|
