This article describes how issues related to the RTP Packetization interval can be solved in the case of conference calls on VoipNow servers. The recommended solution is to make sure that all parties involved in that call have the packetization interval set to to 20ms during conference calls on VoipNow servers. Otherwise, when channels are bridged, voice breaks, missing or dropped syllables, unexplained clicks or noises may occur.
Overview
Voice breaks, missing or dropped syllables, unexplained clicks or noises are triggered by different values of the the ptime
parameter when channels are bridged. According to the RFC3551 for packetized audio, the default packetization interval must be 20 ms or one frame, whichever is longer, unless required otherwise. However, a receiver should be able to accept packages with a packetization interval between 0 and 200ms.
Good to
...
know
If If autoframing=yes
is set in in sip.conf
within the global section, all calls will try to set the packetization based on the preferences of the remote end point.
...
If one of the parties involved in a call does not provide a a ptime
interval, the recommended value that should be used is 20ms.
Note |
---|
In VoipNow, autoframing autoframing is not enabled in |
Ptime and
...
different devices
The The ptime
parameter for codecs can be set through provisioning by adding a specific value for each codec in the the Device Configuration File #3
:
Code Block |
---|
voice.audioProfile.X.payloadSize="20" |
The value for the payload size is in milliseconds: 10, 20, 30,...80;
Tip |
---|
X X can be replaced by G711Mu, G711A, G722, G7221, and G729AB. |
For example, when setting a a ptime=20
for the G711A codec, the following line should be added to the provisioning template:
Code Block |
---|
voice.audioProfile.G711A.payloadSize="20" |
Aastra 480i
- To set the the
ptime
parameter on a Aastra 480i codec, you need to go to the Advanced Settings->Global SIP->RTP Settings area; - Enter a Customized Codec Preference List which allows you to use the codecs that you prefer for this IP phone.
...
Code Block |
---|
payload=8;ptime=20; payload=0;ptime=20; |
Note |
---|
Please note that that |
Aastra 6751i
- To set the RTP packetization interval on Aastra 6751i, you need to go to the Advanced Settings->Global SIP->Codec Preference List;
- Valid values: 5 to 90, in increments of 5 milliseconds;
- To use this phone registered on a VoipNow server, you need to set the Packetization interval to 20ms;
Grandstream Gxp2020
Web Interface
Go to Advanced Settings -> iLBC frame size and select a framesize of 30ms.
...
Code Block |
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# iLBC Frame Size. 0 - 20ms(default), 1 - 30ms. P97 = 1 |
Yealink T20P
The The ptime
parameter can be set via provisioning templates.
...
Code Block |
---|
[ account ] path=/config/voip/sipAccount0.cfg <yealink t20p configuration parameters> ptime = 20 [ account ] path=/config/voip/sipAccount1.cfg <yealink t20p configuration parameters> ptime = 20 |
Linksys PAP2
Some Linksys devices, such as PAP2 or SPA2102, have the the RTP Packet Size
parameter set to 30ms by default.
In such cases, the the RTP Packet Size
parameter can be changed from the SIP tab of the web interface.
For most users, the 0.030 factory default preset should be replaced with 0.020.
Note |
---|
Please note that the the |
Siemens Speedstream 3610
To set the the RTP packetization
interval on Siemens Speedstream 3610, you need to go to the Voice Setup -> Advanced Setting.
If you are using this device registered on a VoipNow server, please set the RTP Packetization period to 20ms. Valid values: in increments of 10ms.
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