[asterisk-bugs] [JIRA] (ASTERISK-25309) [patch] iLBC 20 advertised

[Kevin Harwell (JIRA)]

     [ https://issues.asterisk.org/jira/browse/ASTERISK-25309?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kevin Harwell updated ASTERISK-25309:
-------------------------------------

    Target Release Version/s: 13.6.0

> [patch] iLBC 20 advertised
> --------------------------
>
>                 Key: ASTERISK-25309
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-25309
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_sip/CodecHandling
>    Affects Versions: SVN, 13.5.0
>            Reporter: Alexander Traud
>      Target Release: 13.6.0
>
>         Attachments: asterisk_iLBC_30.patch
>
>
> 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.



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