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<p class="MsoNormal">We are, unfortunately, locked into an old version of Asterisk, and modelling this on a current version may be difficult, but we noticed that when the response to a native bridge re-invite changed the codecs, Asterisk didn’t seem to react,
even though the resulting codecs were incompatible with the other side.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">On looking through the code (rtp.c / rtp_engine.c), it looks like the basic RTP native bridge loop has a structure like this (and this has survived several reworks between 1.6.1 and 11, although I have yet to find the equivalent code in
trunk):<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><<<<<o:p> </o:p></p>
<p class="MsoNormal">If codecs or addresses have changed<o:p></o:p></p>
<p class="MsoNormal" style="text-indent:9.0pt">Do actions (which may trigger new re-invites)<o:p></o:p></p>
<p class="MsoNormal" style="text-indent:9.0pt">Set old codecs and addresses to current ones.<o:p></o:p></p>
<p class="MsoNormal">endif<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Wait for some frames and digest them, possibly breaking out of the loop, but I’m not interested in that case.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Unconditionally set old codecs and addresses to current ones.<o:p></o:p></p>
<p class="MsoNormal">>>>><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">To me this seems me to make it very difficult for a codec change to actually be detected, as when you unroll the loop, the unconditional set precedes the test for changes!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Am I reading the code correctly? If so, could someone explain why it is doing this?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-family:"Lucida Sans Unicode","sans-serif"">--
</span><span style="font-family:"Arial","sans-serif""><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lucida Sans Unicode","sans-serif"">David Woolley</span><span style="font-family:"Arial","sans-serif""><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lucida Sans Unicode","sans-serif"">BTS Holdings Plc</span><span style="font-family:"Arial","sans-serif""><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Lucida Sans Unicode","sans-serif"">Tel: +44 (0)20 8401 9000 Fax: +44 (0)20 8401 9100</span><span style="font-family:"Arial","sans-serif""><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial","sans-serif""><a href="http://www.bts.co.uk/"><span style="font-family:"Lucida Sans Unicode","sans-serif";color:blue">http://www.bts.co.uk</span></a></span><span style="font-family:"Lucida Sans Unicode","sans-serif"">
</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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BTS Holdings PLC - Registered office: BTS House, Manor Road, Wallington, SM6 0DD - Registered in England: 1517630<BR>
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