[Freeswitch-dev] sofia_glue - sdp with m=image 0

Wolfgang Pichler wpichler at yosd.at
Thu Mar 21 18:03:12 MSK 2013

Hi all,

i have encountered a strange behaviour - and i think i have found a
possible problem within sofia_glue

Following scenario:

Carrier sends INVITE with T38 Offer -> Freeswitch does forward offer ->
asterisk does forward offer -> ATA

In this scenario it happend to me - that the T38 Offer (with corrent
m=image and port in sdp) got forwarded by freeswitch to asterisk, asterisk
did forwarded without the T38 Offer (don't know why) - so also without the
m=image sdp part - the ATA did answered correctly (without m=image part) ->
asterisk did created a new sdp with m=image 0, without T38 parts - and
returned this to freeswitch.

Freeswitch did hangup the call - because sofia_glue did extracted the port
0 as audio port - and this is not a legal port...

Sending port 0 is according to rfc legal - so freeswitch should ignore it
in this case.

the question is - if both values are given - which one is the value we need
? I think the audio port is the port which is of higher priority.

So the workflow should be:
 - Try to extract audio port from m=audio part.
 - If you got it - and it is a valid port then go on
 - else try to extract audio port from m=image part...

The function in question is sofia_glue_tech_proxy_remote_addr - in

Is it generaly a good idea to use the m=image part as audio port ? Why is
there no direct image port member in the pvt structure as with the video
port ?

Hope someone can help here...

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