Frequently Asked Question

Supported Codecs

G722 Wideband HD 48-64 kb/s, Highest Quality (Not supported by many backbone carriers)
G711 A-Law (PCMA) (Universal) 64kb/s, High Quality (Recommended, Most common for AU/NZ/EU)
G711 u-Law (PCMU) (U.S.A.) 64kb/s, Good Quality, fallback codec if you can't successfully use A-law
G729 Compressed 8 kb/s, Medium Quality, a last resort fallback codec if nothing else works

* The Codec specified kb/s speeds above are one way and exclude network overheads


Typical Bandwidth Requirements Including Network Overheads

* A G711 call will use about 90 kb/s each way (90up/90dwn)
* A G729 call will use as much as 32 kb/s on average each way (32up/32dwn)


General Notes

G711 provides uncompressed high quality voice, but uses a lot of bandwidth.
G729 is compressed so that it uses less bandwidth at the cost of some audio quality, though it is still more than good enough for most calls.

If you're interested in the technical as to why G711 A-Law is recommended by most, see http://www.voip-sip-sdk.com/p_214-g711-alaw-codec-voip.html