The type of codec used for voice encoding and companding, and compression or decompression are available on the IP Media Parameters screen. The codecs on the IP Media Parameters screen are listed in the order of preferred use. A call across a trunk between two systems is set up to use the first common codec listed.
Note:
The codec order must be administered the same for each system of an H.323 trunk connection. The set of codecs listed does not have to be the same, but the order of the listed codecs must.
In the IP Media Parameters screen, define the codecs and packet sizes used by each IP network region. You can also enable or disable silence suppression for each codec in the set. The screen dynamically displays the packet size in milliseconds (ms) for each codec in the set, based on the number of 10 ms frames that you administer for each packet.
Finally, you use this screen to assign the following characteristics to a codec set:
Whether endpoints in the assigned network region can route FAX, modem, TTY, or clear channel calls over IP trunks.
The mode that the system uses to route the FAX, modem, TTY, or clear channel calls.
Whether redundant packets must be added to the transmission for higher reliability and quality.
Note:
For pass-through mode, payload redundancy per RFC2198 is used.
These characteristics must be assigned to the codec set, and the codec set must be assigned to a network region. Only after assigning are the endpoints in that region able to use the capabilities established on this screen.
Caution:
Users might use Super G3 FAX machines and modems. Do not assign these FAX machines to a network region with an IP Codec set that is both modem-enabled and FAX-enabled. Do not enable the codec set for both modem and FAX signaling. If both are enabled, a Super G3 FAX machine incorrectly tries to use the modem transmission instead of the FAX transmission. Therefore, assign modem endpoints to a network region that uses a modem-enabled IP Codec set. Assign the Super G3 FAX machines to a network region that uses a FAX-enabled IP Codec set.
