[asterisk-bugs] [JIRA] (ASTERISK-27351) iLBC Codec Mismatch

[Alexander Traud (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-27351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=252879#comment-252879 ] 

Alexander Traud commented on ASTERISK-27351:
--------------------------------------------

Mhm. Works here guys. Please, do not play around with the packetization because that is independent to the mode in iLBC.

Could you please test ‘my’ [open-source Opus Codec module|https://github.com/traud/asterisk-opus]? It [contains a fix|https://github.com/traud/asterisk-opus/commit/2c091bae6b7c12628a01b641672d452755fcda38] for iLBC 30. I doubt that fix is included in the closed-source module from Digium -- although I mentioned what to do in ASTERISK-25353.

If that open-source module works, does iLBC work if you transcode to G.711, too?
bq. Asterisk does not take into account format parameters with regards to whether or not things should be translated. So if two codecs are the same, but with different format parameters translation will not occur.

Well, that is not correct. A codec module can honor both the (incoming†) packetization and format parameters. Furthermore, if the formats are incompatible and the codec module cannot transcode, it could reject the format. However, I am not aware of a codec module with that requirement.

† There is a specific issue, but not a general issue with outgoing packetization, see ASTERISK-25579.

> iLBC Codec Mismatch
> -------------------
>
>                 Key: ASTERISK-27351
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-27351
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Codecs/codec_ilbc, Formats/format_ilbc
>    Affects Versions: 15.0.0, 16.0.0
>         Environment: x64 CentOS
>            Reporter: Luke Escude
>            Assignee: Unassigned
>            Severity: Minor
>              Labels: pjsip
>         Attachments: one-way-20-20-ast20.pcap, one-way-matched-30-30-ast20.pcap, pjsip.conf.txt, two-way-30-30-ast20.pcap, two-way-mismatched-20-30-ast20.pcap
>
>
> Asterisk, when set to use iLBC, has 2 issues:
> 1. The INVITE SDP from Asterisk always contains 20ms frame size, regardless if ilbc is set in asterisk as ilbc:30 or ilbc:20
> 2. Asterisk always sends 30ms frames regardless of what was negotiated/set in pjsip.conf
> Attached are 4 packet captures:
> [^one-way-matched-30-30-ast20.pcap] is a one-way audio example where Asterisk is configured to use ilbc:30, but offers 20 in the SDP, and the phone uses 20.
> [^two-way-mismatched-20-30-ast20.pcap] is a two-way audio example where Asterisk is configured to use ilbc:30, but offers 20 in the SDP, and the phone uses 30 (therefore, 2-way audio).
> [^two-way-30-30-ast20.pcap] is a two-way audio example where Asterisk is configured to use ilbc:30, but offers 20 in the SDP, and the phone uses 30, (therefore, 2-way audio)
> [^one-way-20-20-ast20.pcap] is a one-way audio example where Asterisk is configured to use ilbc:20, offers 20 in the SDP, and phone is configured to use 20 (but it's still one-way audio because Asterisk is actually sending 30).
> Let me know if you need me to do more testing, it's 100% repeatable. 



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