[asterisk-bugs] [JIRA] (ASTERISK-23262) Audio degredation with codec_dahdi and ChanSpy'ing

[Sean Bright (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-23262?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=215255#comment-215255 ] 

Sean Bright commented on ASTERISK-23262:
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The {{SIP/from-internal-user/1}} packets are G729 from a transcoder card in another machine, so I assume 20ms, but I will confirm.  {{SIP/from-external-user/1}} is pass-through from upstream, so I will check there as well.
                
> Audio degredation with codec_dahdi and ChanSpy'ing
> --------------------------------------------------
>
>                 Key: ASTERISK-23262
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-23262
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Codecs/codec_dahdi
>    Affects Versions: SVN
>         Environment: Linux pbx-host 3.5.0-45-generic #68~precise1-Ubuntu SMP Wed Dec 4 16:18:46 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> Dell PowerEdge R620
>            Reporter: Sean Bright
>            Assignee: Sean Bright
>         Attachments: 0001-wip-codec_dahdi-Add-configurable-synchronous-mode.patch, irc.txt, rattle.sln
>
>
> The server has 2 TCE400P cards and I'm using the latest wctc4xxp driver from the DAHDI-Linux git repository (master branch).
> There are 3 channels involved in this scenario:
> * {{SIP/from-internal-user/1}}
> * {{SIP/from-external-user/1}}
> * {{SIP/from-spying-user/1}}
> The native format for all 3 of these channels is G729.
> {{SIP/from-internal-user/1}} enters dialplan and goes immediately into {{MusicOnHold}}.  The {{MusicOnHold}} class consists of only .g729 files, so no encoders/decoders are used at this point.
> {{SIP/from-external-user/1}} enters dialplan, and hit these three apps/functions in this order:
> * {{MixMonitor(<somefile>.sln,...)}}
> * {{VOLUME(RX)=2}}
> * {{Bridge(SIP/from-internal-user/1,...)}}
> Now, the third channel channel, {{SIP/from-spying-user/1}}, enters dialplan and goes into {{ChanSpy}}:
> * {{ChanSpy(SIP/from-internal-user/1,...)}}
> At this point, both {{SIP/from-internal-user/1}} and {{SIP/from-external-user/1}} begin to hear distortion/delay and are unable to understand each other.  There is also distortion/delay observed by {{SIP/from-spying-user/1}}.
> Spying on {{SIP/from-external-user/1}} does not cause the audio degredation.  Also, based on a suggestion by Josh Colp, removing the call to {{VOLUME(RX)=2}} appears to resolve the problem as well.

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