[Freeswitch-users] Inbound 1-way audio issue using GSM codec

[Peter P GMX]

Hello Maxim,

can you reach another internal device except the GSM one in order to see
whether it's GSM codec specific?

However I can see that you're using local IPs (10.x.x.x) so I expect
that they are natted. This often causes one way audio when the external
rtp-ip is not set. Please try to set a
    <param name="ext-rtp-ip" value="stun:stun.freeswitch.org"/>
entry to internal.xml and external.xml in your SIP profiles and see if
it works. Use stun at least for the internal profile (FQDN and external
IP most probably will not work)

Best regards
Peter

Maxim Karp schrieb:
> Hello,
>
> I am using a GSM based endpoint connected to freeswitch that makes calls to
> the PSTN via a SIP gateway (SBC).  The SBC uses PCMU between itself and
> freeswitch.
>
> When I make an outgoing call from a GSM based device via freewsitch to the
> PSTN via the SBC, everything works fine and audio works in both directions
> for both end points.  I looked at the console logs and they do indicate that
> I am using GSM.
>
> Console output when I dial and before answer on the GSM device:
>
> v=0
> o=- 74 0 IN IP4 10.229.0.58
> s=session
> c=IN IP4 10.229.0.58
> b=CT:17
> t=0 0
> m=audio 59806 RTP/AVP 8 0 3 97 101
> k=base64:P6l1kBQy3canYTWZkxccjAVtTWO9g/N5L4gxLtX0UnM
> a=rtpmap:8 PCMA/8000
> a=rtpmap:0 PCMU/8000
> a=rtpmap:3 GSM/8000
> a=rtpmap:97 RED/8000
> a=rtpmap:101 telephone-event/8000
> a=fmtp:101 0-16
> a=encryption:optional
>
> Console output once it rings and after I answer on the PSTN side:
>
> v=0
> o=FreeSWITCH 1227887572 1227887573 IN IP4 10.229.0.10
> s=FreeSWITCH
> c=IN IP4 10.229.0.10
> t=0 0
> a=sendrecv
> m=audio 30896 RTP/AVP 3 101 13
> a=rtpmap:3 GSM/8000
> a=rtpmap:101 telephone-event/8000
> a=fmtp:101 0-16
> a=rtpmap:13 CN/8000
> a=ptime:20
>
> When I receive a call from the SIP gateway, the endpoint making the call
> (not on freeswitch) can't hear me speaking from the GSM device connected to
> freeswitch.  I can hear everything fine on the GSM device.
>
> Here is the console output for the call info coming in from the PSTN.
>
> v=0
> o=FreeSWITCH 1227902084 1227902085 IN IP4 38.113.164.132
> s=FreeSWITCH
> c=IN IP4 38.113.164.132
> t=0 0
> a=sendrecv
> m=audio 16724 RTP/AVP 0 101 13
> a=rtpmap:0 PCMU/8000
> a=rtpmap:101 telephone-event/8000
> a=fmtp:101 0-16
> a=rtpmap:13 CN/8000
> a=ptime:20
>
> Here is how I have vars.xml configured:
>
> <X-PRE-PROCESS cmd="set" data="global_codec_prefs=GSM"/>
> <X-PRE-PROCESS cmd="set" data="outbound_codec_prefs=PCMU,PCMA,GSM"/>
>
>
> When I prioritize GSM on the outbound codec prefs I get static on the PSTN
> side. 
>
> <X-PRE-PROCESS cmd="set" data="outbound_codec_prefs=GSM,PCMU,PCMA "/>
>
> Any ideas?
>
> Maxim.
>
>
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