GSM codec with IAX softphone (?)

Can’t I use GSM codec with an IAX softphone ? (ZoIPer)

When I try to call a sip trunk (or sip phone), I get: Bearer capability not available

I looks like that only alaw and ulaw works. (can’t get iLBC 30,iLBC20 and Speex to work either)

(I need a codec with lowest possible bandwidth and IAX softphone. Which one is that?)

Zoiper Biz will do G.729

On ZoIPer website is written: Available codecs - GSM, ulaw, alaw, speex, ilbc (for the free edition).

GSM works with SIP :smile: but NOT with IAX :unamused:

Is it supposed to be like that ?