[Freeswitch-users] SDP with double m=audio lines and with the same port

Michael Jerris mike at jerris.com
Tue May 31 19:16:55 MSD 2016


If you don't use some other engine to handle webrtc, then if you are calling something that is registered to you over websockets it will automatically enable media_webrtc for you.  Otherwise you'll need some external way of knowing if the endpoint is webrtc or not so you can apply the settings properly.


> On May 30, 2016, at 9:14 AM, Ján Füri <furi at vmtele.com> wrote:
> 
> Hello, 
> 
> My freeswitch's INVITE sdp offers two m=audio lines. (RTP/SAVP and RTP/AVP). 
> That's OK, because I want it so ;)
> 
> But both use the same audio port number. 
> Is that possible to change this behavior ? To use different audio port numbers for each m=audio line ...
> Please check my example below. In SDP from my freeswitch, both m-lines have m=audio 22284.
> 
> The reason, why I want to change this is WebRTC and RTPengine. RTPengine changes this INVITEs to RTP/SAVPF.
> And the changed RTP/SAVPF is then not acceptable for chrome browsers. Firefox works well (so far).
> I already reported this to the RTPengine but they say the problem is with INVITE from freeswitch because the m-audio lines use the same port.
> 
> My example :
> incoming calls -> Media Server (freeswitch) -> Kamailio (sip and websocket proxy) -> WebRTP and SIP clients 
> 
> I have found a feature media_webrtc=true so I could avoid using rtpengine for webrtc clients (that would be really awesome), but then classic sip clients are offered only with RTP/SAVPF and most sip phones do not know RTP/SAVPF so the calls are rejected :(
> 
> 
> INVITE SDP from freeswitch: 
> 
> v=0.
> o=SBC 1464589775 1464589776 IN IP4 <freeswitch-public-ip>.
> s=SBC.
> c=IN IP4 <freeswitch-public-ip>.
> t=0 0.
> m=audio 22284 RTP/SAVP 8 0 9 3 18.
> a=rtpmap:8 PCMA/8000.
> a=rtpmap:0 PCMU/8000.
> a=rtpmap:9 G722/8000.
> a=rtpmap:3 GSM/8000.
> a=rtpmap:18 G729/8000.
> a=rtcp:22285 IN IP4 <freeswitch-public-ip>.
> a=crypto:1 AEAD_AES_256_GCM_8 inline:Q/O+iUzZ9AZLcrADA7w/XcpkmuW6yArr1vsaWc0coTyWUIRLX2qfCA7XDAs.
> a=crypto:2 AEAD_AES_128_GCM_8 inline:mBb/SmBuSQNSm8lC5giUfZMCv0ZYINvsQiX2sw.
> a=crypto:3 AES_CM_256_HMAC_SHA1_80 inline:ahOTNSsdmHLIOBqvUyGyNjd+gDfAE/+jA6w7XwzGWxBMjtzf5akXNvM/OGy0jQ.
> a=crypto:4 AES_CM_192_HMAC_SHA1_80 inline:k7002pXV/SUT7JHhZTYaMV5keUTp1EP57M4rcNZnAoZZzsceTXA.
> a=crypto:5 AES_CM_128_HMAC_SHA1_80 inline:bHcV4E/OnzMkNeaFplPWt4RELILYZeGlifnJNlRV.
> a=crypto:6 AES_CM_256_HMAC_SHA1_32 inline:zJkowU1tc5rQR5BPpg2m3eE97ZqXLFFJc1Agh89XuZynPFMrXhO266+eMZCd2A.
> a=crypto:7 AES_CM_192_HMAC_SHA1_32 inline:2DwGI3UAPsLFBS5sJBsc+pzEsITQwDHCvB0u7pK/XEE3G8swsrw.
> a=crypto:8 AES_CM_128_HMAC_SHA1_32 inline:Jen6Gm56Z+4RTRmfpXTpSpoG5bduyythl1j21a15.
> a=crypto:9 AES_CM_128_NULL_AUTH inline:Nn83liGQY7eY8LGs9qz/7EoPiHOpRgwY8H7Ts/b5.
> a=ptime:20.
> m=audio 22284 RTP/AVP 8 0 9 3 18.
> a=rtpmap:8 PCMA/8000.
> a=rtpmap:0 PCMU/8000.
> a=rtpmap:9 G722/8000.
> a=rtpmap:3 GSM/8000.
> a=rtpmap:18 G729/8000.
> a=rtcp:22285 IN IP4 <freeswitch-public-ip>.
> a=ptime:20.
> 
> 
> 
> 
> INVITE SDP from RTPengine :
> 
> v=0
> o=SBC 1464589775 1464589776 IN IP4 212.232.17.66
> s=SBC
> c=IN IP4 <rtpengine-public-ip>
> t=0 0
> m=audio 31836 RTP/SAVPF 8 0 9 3 18
> a=rtpmap:8 PCMA/8000
> a=rtpmap:0 PCMU/8000
> a=rtpmap:9 G722/8000
> a=rtpmap:3 GSM/8000
> a=rtpmap:18 G729/8000
> a=ptime:20
> a=sendrecv
> a=rtcp:31837
> a=setup:actpass
> a=fingerprint:sha-1 11:76:2D:2A:F7:0D:5A:23:9D:F6:0C:E7:4C:DF:1E:CB:BF:5D:76:4F
> a=ice-ufrag:NauDcjVU
> a=ice-pwd:AiHk6LF4tE0GElyFMWtLeod1wH
> a=candidate:cE0FGbXWIfwj6OGD 1 UDP 2130706431 <rtpengine-public-ip> 31836 typ host
> a=candidate:cE0FGbXWIfwj6OGD 2 UDP 2130706430 <rtpengine-public-ip> 31837 typ host
> m=audio 31866 RTP/SAVPF 8 0 9 3 18
> a=rtpmap:8 PCMA/8000
> a=rtpmap:0 PCMU/8000
> a=rtpmap:9 G722/8000
> a=rtpmap:3 GSM/8000
> a=rtpmap:18 G729/8000
> a=ptime:20
> a=sendrecv
> a=rtcp:31867
> a=setup:actpass
> a=fingerprint:sha-1 11:76:2D:2A:F7:0D:5A:23:9D:F6:0C:E7:4C:DF:1E:CB:BF:5D:76:4F
> a=ice-ufrag:YxCyPhQV
> a=ice-pwd:2vYt8YaMhIp2DSLPeYOKDqqBX0
> a=candidate:cE0FGbXWIfwj6OGD 1 UDP 2130706431 <rtpengine-public-ip> 31866 typ host
> a=candidate:cE0FGbXWIfwj6OGD 2 UDP 2130706430 <rtpengine-public-ip> 31867 typ host
> 

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