Codec Question

I’m trying to align my FPBX, endpoints, and gateways with Codec settings. Since everything is on the same LAN, I’m aiming for highest quality to lowest quality. Based on my limited knowledge and research, this is what I have put together - do you have any thoughts or recommendations?

In Order of preference and as supported by device:


A couple of things to be aware of, if you aren’t already:

  1. Any call that transits the PSTN is limited to PSTN (G.711) quality. Using a non-PSTN CODEC at your end will just result in transcoding, which may reduce quality.

  2. If you are using UDP a CODEC list that long may cause SIP messages and responses to exceed the network MTU, depending upon how many Record-Route and Via headers there are. UDP can’t be fragmented.

Also, double-check the MOS values for ILBC and G.726. I’m not sure they are in the right order in your list (and I’m too lazy to check it myself :slight_smile: ).

[ EDIT ]

Just remembered: ILBC and G.726 each has multiple bit rates. To rank by MOS you need to specify the bit rate.

There is no value in having a list of eight codecs. I suggest G.722 and G.711u. Allow Opus if you use a browser (webrtc).

G.711a is not used in North America. There is no point in adding those others. Does your LAN have a link slower than 100Kbps? (Probably not) Your devices will never negotiate codecs low on the list unless you force them.

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