User`s manual

MediaPack
SIP User's Manual 72 Document #: LTRT-65408
5.5.1.3 Coders
From the Coders screen you can configure the first to fifth preferred coders (and their
attributes) for the gateway. The first coder is the highest priority coder and is used by the
gateway whenever possible. If the far end gateway cannot use the coder assigned as the
first coder, the gateway attempts to use the next coder and so forth.
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To configure the gateway’s coders, take these 9 steps:
1. Open the ‘Coders’ screen (Protocol Management menu > Protocol Definition
submenu > Coders option); the ‘Coders’ screen is displayed.
Figure 5-7: Coders Screen
2. From the 'Coder Name' drop-down list, select the coder you want to use. For the full
list of available coders and their corresponding attributes, refer to Table 5-5.
3. From the 'Packetization Time' drop-down list, select the packetization time (in msec)
for the coder you selected. The packetization time determines how many coder
payloads are combined into a single RTP packet.
4. From the 'Rate' drop-down list, select the bit rate (in kbps) for the coder you selected.
5. In the 'Payload Type' field, if the payload type for the coder is dynamic, enter a value
from 0 to 120 (payload types of ‘well-known’ coders cannot be modified).
The payload type identifies the format of the RTP payload.
6. From the 'Silence Suppression' drop-down list, enable or disable the silence
suppression option for the coder you selected.
7. Repeat steps 2 through 6 for the second to fifth coders (optional).
8. Click the Submit button to save your changes.
9. To save the changes so they are available after a power fail, refer to Section 5.10.2 on
page 205.
Notes:
• Each coder can appear only once.
• If not specified, the ptime gets a default value. The ptime specifies
packetization time the gateway expects to receive. The gateway
always uses the ptime requested by the remote side for sending
RTP packets. Only the ptime of the first coder in the list is declared
in INVITE / 200 OK SDP, even if multiple coders are defined.
• If payload type is not specified, a default is used.
• For G.729 it's also possible to select silence suppression without
adaptations
• If coder G.729 is selected and silence suppression disabled, the
gateway includes the string ‘annexb=no’ in the SDP of the relevant
SIP messages. If silence suppression is enabled or set to ‘Enable
w/o Adaptations’, ‘annexb=yes’ is included. An exception to this logic
is when the remote gateway is a Cisco device (IsCiscoSCEMode).