[asterisk-bugs] [Asterisk 0015407]: Multiple m=video or m=audio lines cause a ip port number mismatch.

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=15407 
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Reported By:                arunpunj
Assigned To:                dvossel
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Project:                    Asterisk
Issue ID:                   15407
Category:                   Channels/chan_sip/General
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     feedback
Asterisk Version:           SVN 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2009-06-26 10:04 CDT
Last Modified:              2009-09-02 12:38 CDT
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Summary:                    Multiple m=video or m=audio lines cause a ip port
number mismatch.
Description: 
Test Setup
-----------

Two Sip terminals capable of generating multiple m=video lines. Say
terminals
T1 and T2. T1 calls T2.

T1 generates following offer to T2 ( some lines and fields edited out for
privacy)

v=0
o=ViPr 1 1 IN IP4 10.55.100.53
s=-
e=NoEmail at NoEmail.com
t=0 0
m=audio 51068 RTP/AVP 9 113 112 111 0 8 15
c=IN IP4 10.55.100.53
a=rtpmap:9 G722/8000
a=rtpmap:113 G7221/32000
a=fmtp:113 bitrate=32000
a=rtpmap:112 G7221/24000
a=fmtp:112 bitrate=24000
a=rtpmap:111 G7221/16000
a=fmtp:111 bitrate=16000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:15 G728/8000
a=sendrecv
m=video 31074 RTP/AVP 109 34 31 32
c=IN IP4 10.55.100.53
a=rtpmap:109 H264/90000
a=fmtp:109 profile-level-id=42801e
a=rtpmap:34 H263/90000
a=fmtp:34 CIF=1 QCIF=1 MaxBR=40000
a=rtpmap:31 H261/90000
a=fmtp:31 CIF=1 QCIF=1 MaxBR=40000
a=rtpmap:32 MPEG/90000
a=sendrecv
m=video 31076 RTP/AVP 109
c=IN IP4 10.55.100.53
a=rtpmap:109 H264/90000
a=fmtp:109 profile-level-id=42801e
a=recvonly

The asterisk forwards the call to T2. However, 2 video offers are replaced
by only 1 video offer. T2 accepts the call with single video offer. And the
call comes up fine, the audio is good but no video is seen. The audio/video
are both to be relayed through asterisk.

Upon investigation it is found that asterisk is relaying video from T2 to
T1 on port 31076 which is the port corresponding to second video stream.

A simple one line change in chan_sip.c fixes the issue.I think same one
line fix is applicable to m=audio and m=text lines as well. I have marked
is as blocking as it blocks the use of our device with asterisk, but
obviously it does not seem to block most people.

I tried to locate if this bug is already reported, if its a duplicate I
apologize for taking your time.


thank you
Arun Punj
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---------------------------------------------------------------------- 
 (0110062) arunpunj (reporter) - 2009-09-02 12:38
 https://issues.asterisk.org/view.php?id=15407#c110062 
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I am afraid I cannot provide you the trace right now. I can provide you the
packet traces in a week or so. Essentially the traces are simple an offer
with 3 m blocks, one audio and two video is converted to an offer with only
2 m blocks, the second video block overrides the first one. Which though a
bug by itself is not so much an issue. The real problem is that it forward
the wrong port number for video to the originator of the call.

You are right this is not the most appropriate fix, just the quickest one
to get me going. Ideally there would be a way to convey more than one
stream info from source side to destination side of a call, but since there
is support only for single audio, single video and single text stream in
the SDP this change is enough.

thanks
Arun 

Issue History 
Date Modified    Username       Field                    Change               
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2009-09-02 12:38 arunpunj       Note Added: 0110062                          
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