Summary:ASTERISK-25309: [patch] iLBC 20 advertised
Reporter:Alexander Traud (traud)Labels:
Date Opened:2015-08-10 07:49:07Date Closed:2015-08-12 13:38:16
Versions:SVN 13.5.0 Frequency of
causesASTERISK-26221 chan_sip: iLBC does not include correct mode
Environment:Attachments:( 0) asterisk_iLBC_30.patch
Description:Since version 13, chan_sip advertises iLBC 20. However, only iLBC 30 is implemented in the transcoding module of Asterisk. When the callee accepts iLBC 20, this negotiates ilBC 20 (see [RFC 3952|https://tools.ietf.org/html/rfc3952#section-5] section 5) and creates a call without audio.

This was caused because chan_sip queried a property ({{framing}}) included in the capabilities of a channel ({{ast_format_cap}}). However, the framing of a channel (ptime) does not change the iLBC variant. Furthermore, because iLBC 30 is the default variant, and reading the RFC literally – {{a=fmtp:xx mode=30}} is not defined in the RFC – the second part of this patch removes sending of a=fmtp for iLBC in SIP/SDP at all. That way, chan_sip offers iLBC 30 for sure.

This bug was not reproducible in Asterisk 11 or earlier.