Hello folks, for a customer of us we are trying to make asterisk and windows RTC library work together, but without success. We *need* to use gsm codec, so in the "peer" section we have disallow=all allow=gsm the sip signaling is ok, and when sniffing we got this session description: INVITE from windows RTC: v=0. o=- 0 0 IN IP4 172.31.9.130. s=session. c=IN IP4 172.31.9.130. b=CT:1000. t=0 0. m=audio 4632 RTP/AVP 97 111 112 6 0 8 4 5 3 101. k=base64:ftJemQZ2pTDV5gzzqxG6ps5Ol5qiOt2qbP9L9Or5JQg. a=rtpmap:97 red/8000. a=rtpmap:111 SIREN/16000. a=fmtp:111 bitrate=16000. a=rtpmap:112 G7221/16000. a=fmtp:112 bitrate=24000. a=rtpmap:6 DVI4/16000. a=rtpmap:0 PCMU/8000. a=rtpmap:8 PCMA/8000. a=rtpmap:4 G723/8000. a=rtpmap:5 DVI4/8000. a=rtpmap:3 GSM/8000. a=rtpmap:101 telephone-event/8000. a=fmtp:101 0-16. a=encryption:optional. a=direction:active. OK from asterisk 1.6 PBX: v=0. o=PBX 1705093286 1705093286 IN IP4 172.31.9.251. s=PBX. c=IN IP4 172.31.9.251. t=0 0. m=audio 14962 RTP/AVP 3 101. a=rtpmap:3 GSM/8000. a=rtpmap:101 telephone-event/8000. a=fmtp:101 0-16. a=silenceSupp:off - - - -. a=ptime:20. a=sendrecv. so, the rtp session should be GSM. But the audio does not work. In asterisk logs I see 'Got Siren7 offer at 24000 bps but only 32000 bps supported'. any hint? anyone with the same issue? unfortunately GSM is mandatory for us (we could not use alaw/ulaw, that seems working). thanks so much stefano