Codec help

[Daryl DeAngelis]

I have started to play around with 3cx. Big question I have right now is how the codec selection happens.

1. Each extension under phone provisioning has a list for codec priority.
2. Each SIP trunk under options has a list for codec priority.
3. Settings -> General -> Codec Priority for Local/Internal Calls
4. Settings -> General -> Codec Priority for External Calls

Which setting makes the decision of what list of codecs to present?

 

[Evolute IT]

I have started to play around with 3cx. Big question I have right now is how the codec selection happens.

1. Each extension under phone provisioning has a list for codec priority.
2. Each SIP trunk under options has a list for codec priority.
3. Settings -> General -> Codec Priority for Local/Internal Calls
4. Settings -> General -> Codec Priority for External Calls

Which setting makes the decision of what list of codecs to present?

Just align codecs everywhere using the same order always (preferably, order them by your provider's codecs list, this way you can prevent transcoding).

For example, I always use : G722, G729,
PCMU, PCMA.

 

[eddv123]

@Frederick Marcoux I would add a couple of points to what you have already said.

The bottom line is there is no right or wrong way of doing this, it depends purely on your setup, how much bandwidth is available and what provider your use.

As said you must align codecs base on what the provider supports - using a 3CX supported provider will ensure that the supported codecs are included from start however I would add some points.

Agreed G711 is normally the general default on everything on 3CX, and at least on the providers we use also (GAMMA/Twilio) it is the same.

However some of these settings may have to be tweaked for calls traversing WAN links/Internet (lossy links) within your own controlled network depending on how much bandwidth is available.

This obviously includes VPN, SBC and STUN setups from site to a hosted 3CX system also. We use VPN mostly: https://www.voipmechanic.com/voip-over-vpn.htm

All you need to be aware of mostly is that G711 a/ulaw using a higher bandwidth consumption where compressed codecs (such as G729 or iLBC) are not as clear as G711 but consume less.

This guide is useful for confirming codec bandwidth figures and codec types:https://www.3cx.com/blog/docs/bandwidth-utilised-for-voip/

The OPUS codec: http://opus-codec.org/ is a newer codec introduced which offers quality calls with less bandwidth consumption, but due to it being newer some devices, providers etc are yet to support it.