[Freeswitch-users] Early media + T38 in SDP = Codec negotiation error

Brian West brian at freeswitch.org
Sat Aug 19 20:24:40 UTC 2017 

We do not support this!

On Thu, Aug 17, 2017 at 3:18 AM Tristan Dean <tristan at mocha.net.nz> wrote:

> Hi animal_alpha
>
> This sounds very much like a problem I had when we upgraded from 1.4 to
> 1.6.
> In our case, the carrier was sending the initial INVITE messages with 2
> m-lines. One with audio, one with image. Both had non-zero port numbers. In
> my testing, it seemed to be that having 2 m-lines with different port
> numbers upset FreeSWITCH's SDP parsing.
>
> If I set bypass_media=true and FreeSWITCH could step out of media path,
> the call could connect normally, but this wasn't an option for us as we
> needed to transcode. I can't recall if proxy_media=true worked (I.E.
> FreeSWITCH just proxies RTP and doesn't transcode). Our application
> required transcoding anyway.
>
> In the end I made a rather ugly work-around, but I'm sure there are nicer
> ways to manage this.
> I found that FreeSWITCH 1.6 could parse the SDP correctly if I rewrote the
> port for the m-line containing image.
>
> Since we were using mod_xml_curl for the dialplan, this was quite easy.
> Effectively I have a bit of perl script  parsing the SDP lines from
> 'variable_switch_r_sdp'.
>
> if ($line =~  /^m\=image\s+(\d+)\s+udptl\s+(.*)$/) {
>                         $line = "m=image 0 udptl $2";
>                         $rewrite_reqd = 1;
>                         }
> $line = "$line\r\n";
>
> You can insert the rewritten SDP with
> <![CDATA[switch_r_sdp=$rewritten_sdp]]>
> This worked around the problem and didn't interfere with T.38 revinites
> from fax machines.
>
> All this being said, I am not certain that my approach would work as if I
> understand you correctly, your problem is with the SDP attached to the 18X
> message. Hopefully this might inspire some other ideas if nothing else.
>
> I am very interested to hear other's thoughts on this. I feel I'm probably
> missing something and there is a cleaner way of managing these SDPs.
>
> Many thanks,
>
> Tristan
>
> -----Original Message-----
> From: FreeSWITCH-users [mailto:
> freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of animal_alpha
> Sent: Wednesday, 16 August 2017 5:57 PM
> To: freeswitch-users at lists.freeswitch.org
> Subject: [Freeswitch-users] Early media + T38 in SDP = Codec negotiation
> error
>
> Hello everybody. Have some problem with fs.
> I've got codec negotiation error when i try use early_media and sdp has T38
>
> pre_answer()
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [PCMA:8:8000:20:64000:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4504 Audio Codec
> Compare [PCMA:8:8000:20:64000:1] ++++ is saved as a match
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [PCMA:8:8000:20:64000:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [PCMA:8:8000:20:64000:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [PCMA:8:8000:20:64000:1]/[G722:9:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [PCMU:0:8000:20:64000:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [PCMU:0:8000:20:64000:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4504 Audio Codec
> Compare [PCMU:0:8000:20:64000:1] ++++ is saved as a match
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [PCMU:0:8000:20:64000:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [PCMU:0:8000:20:64000:1]/[G722:9:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:101:8000:20:0:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:101:8000:20:0:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:101:8000:20:0:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:101:8000:20:0:1]/[G722:9:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [iLBC:97:8000:30:0:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [iLBC:97:8000:30:0:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [iLBC:97:8000:30:0:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [iLBC:97:8000:30:0:1]/[G722:9:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [iLBC:98:8000:30:0:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [iLBC:98:8000:30:0:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [iLBC:98:8000:30:0:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [iLBC:98:8000:30:0:1]/[G722:9:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [gsm:3:8000:20:13200:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [gsm:3:8000:20:13200:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [gsm:3:8000:20:13200:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [gsm:3:8000:20:13200:1]/[G722:9:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [speex:99:8000:20:0:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [speex:99:8000:20:0:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [speex:99:8000:20:0:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [speex:99:8000:20:0:1]/[G722:9:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:18:8000:20:8000:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:18:8000:20:8000:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:18:8000:20:8000:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4504 Audio Codec
> Compare [G729:18:8000:20:8000:1] ++++ is saved as a match
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:18:8000:20:8000:1]/[G722:9:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:100:8000:20:0:1]/[PCMA:8:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:100:8000:20:0:1]/[PCMU:0:8000:20:64000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:100:8000:20:0:1]/[G729:18:8000:20:8000:1]
> 2017-08-16 08:50:36.337346 [DEBUG] switch_core_media.c:4449 Audio Codec
> Compare [G729:100:8000:20:0:1]/[G722:9:8000:20:64000:1]
>
> 2017-08-16 08:25:36.105410 [DEBUG] switch_core_media.c:4365 Set
> telephone-event payload to 96 at 8000
> 2017-08-16 08:25:36.105410 [DEBUG] switch_core_media.c:3061 Set Codec
> sofia/external/4995196123 at 10.34.111.140:5061 PCMA/8000 20 ms 160 samples
> 64000 bits 1 channels
> 2017-08-16 08:25:36.105410 [DEBUG] switch_core_codec.c:111
> sofia/external/4995196123 at 10.34.111.140:5061 Original read codec set to
> PCMA:8
> 2017-08-16 08:25:36.105410 [DEBUG] switch_core_media.c:4708 Set
> telephone-event payload to 96 at 8000
> 2017-08-16 08:25:36.105410 [DEBUG] switch_core_media.c:4767
> sofia/external/123 at 10.34.111.140:5061 Set 2833 dtmf send payload to 96
> recv payload to 96
> 2017-08-16 08:25:36.105410 [DEBUG] switch_core_media.c:4028
> sofia/external/123 at 10.34.111.140:5061 T38 REFUSE on request
> 2017-08-16 08:25:36.105410 [ERR] mod_sofia.c:2343 CODEC NEGOTIATION ERROR.
> SDP:
> v=0
> o=- 1502861170 1502861170 IN IP4 10.34.111.143
> s=-
> c=IN IP4 10.34.84.100
> t=0 0
> m=audio 53628 RTP/AVP 8 0 101 97 98 3 99 18 100 96
> a=rtpmap:8 PCMA/8000
> a=rtpmap:0 PCMU/8000
> a=rtpmap:101 G729/8000
> a=fmtp:101 annexb=yes
> a=rtpmap:97 iLBC/8000
> a=fmtp:97 mode=20
> a=rtpmap:98 iLBC/8000
> a=fmtp:98 mode=30
> a=rtpmap:3 gsm/8000
> a=rtpmap:99 speex/8000
> a=fmtp:99 mode=3;vbr=off
> a=rtpmap:18 G729/8000
> a=fmtp:18 annexb=no
> a=rtpmap:100 G729/8000
> a=fmtp:100 annexb=no
> a=rtpmap:96 telephone-event/8000
> a=fmtp:96 0-15
> m=image 41690 udptl t38
> a=T38FaxRateManagement:transferredTCF
> a=T38FaxUdpEC:t38UDPRedundancy
>
> my codecs:
>   <X-PRE-PROCESS cmd="set" data="global_codec_prefs=PCMA,PCMU,G729,G722"/>
>   <X-PRE-PROCESS cmd="set"
> data="outbound_codec_prefs=PCMA,PCMU,G729,G722"/>
>
> Solution: dont use early media (use execute_on_answer=record_session
> instead of application=record_session in my case)
>
> Does not help: t38 ignore, late negotiation=false,
>
>
>
> --
> View this message in context:
> http://freeswitch-users.2379917.n2.nabble.com/Early-media-T38-in-SDP-Codec-negotiation-error-tp7596350.html
> Sent from the freeswitch-users mailing list archive at Nabble.com.
>
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-- 

*Brian West*
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