Frequently Asked Questions (FAQs):What codecs do you allow?

VoIP: What codecs do you allow?

For calls sent/recieved via the PSTN network that are forwarded to an extension not using the following facilities:
Huntgroups
Voicemail
IVR
our system supports g729-a, g711-u and g711-a.

For calls between two SIP devices all codecs are supported provided the devices at each end of the call support them.


Bandwidth calculations

The following table shows the relevant bandwidth usage for these codecs.

Codec

Packet Size

Codec Bandwidth

IP Bandwidth
G.711 120 64Kbps 80Kbps
G.729A 10 8Kbps 24Kbps

Notes:

  1. Figures above are for simplex traffic - normal duplex voice traffic will double these figures

  2. The main cause of the extra IP bandwidth usage is IP and UDP headers.

  3. Because a normal conversation includes a lot of silence, which often means no packets are sent at all, the full bandwidth is not used at all times.

 

Mac and Softphones

There are as far as we are aware at the moment, no softphone packages that support the g729-a codec on the MAC