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

[Jared Hull (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-27351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=246201#comment-246201 ] 

Jared Hull commented on ASTERISK-27351:
---------------------------------------

Since Opus is fixed at 20ms frame sizes, when we use 30ms iLBC there is audio in both directions but it is very distorted. When we use 20ms frame sizes, Asterisk doesn't comply and calls from Opus have no audio. The RTP packetisation link that Kevin posted suggests that Asterisk's min and max iLBC frame sizes are 30ms. So it seems that it is not possible to transcode between iLBC and Opus until iLBC can have a frame size of 20ms.

This issue report is the result of our bad configuration and broken dreams; I think we are going to stop using iLBC so this issue ma be closed as far as I am concerned.

> 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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