Most common CODEC in the US?

[Frank86]

What is the most common CODEC supported by all devices in the US? POTS landlines, cell phones, VoIP providers? In other words, the CODEC that requires no (or less) transcoding?

 

[Evolute IT]

PCMU in the North America. PCMA in Europe.

For high quality, use G729 or G722 which are also very common.

However, don't feel limited by "the most used" one, providers supports the codecs they want to. So, if you are configured in G722 from the provider to the phone, there's no transcoding required on your end.

 

[cobaltit]

G729 is not high quality but G729 is common. But more to the point you have now way of knowing or controlling the codec used on the far side so the only devices you should be concerned about are the extensions on your PBX and then your trunk connection. Everything else is handled by your provider unless you are talking direct SIP.

 

[leejor]

It is usually best to stick with a Codec that is supported by your provider, for internal calls as well. Some people do prefer to use a high quality internal Codec. If this Codec is not supported by your provider, it will require transcoding on external calls. In rare cases, this has caused voice issues to crop up .

Here is a chart with more information than you'll ever want to know about Codecs.
https://en.wikipedia.org/wiki/Comparison_of_audio_coding_formats

 

[eddv123]

You can use you G711 as an internal codec and G729 for external.

G729 is a compressed codec which means it consumes less bandwidth but is a lesser quality codec.

OPUS is another codec you may see in 3CX, it is up and coming and provides many benefits but is not as widely used currently as it is fairly new in principle.