[Freeswitch-users] Strange effect with delay_echo against VAD

[Stanislav Sinyagin]

the problem is solved with
<param name="suppress-cng" value="true"/>
in the SIP profile, so that FreeSWITCH stops offering CN in SDP.
Still it will be interesting to know what caused this problem.




On Sat, Mar 28, 2015 at 1:13 AM, Stanislav Sinyagin <ssinyagin at gmail.com> wrote:
> I got a strange effect, and help in understanding it would be appreciated.
>
> My FreeSWITCH server registers at an ITSP, and forwards incoming calls
> to "echo" or "delay_echo" applications, immediately after answering.
>
> The ITSP uses VAD and comfort noise when it sends audio to my server.
>
> If the call is sent to "echo" application, the calling party hears the
> echo, and also it hears comfort noise.
>
> If the call is sent to "delay_echo", with any delay (I tried 200 to
> 1000ms), the calling party hears only a loud noise.
> Here's a recording on the calling side (my voice in the left ear)
> http://www.k-open.com/s/0202eb6bfa655e47974325574ac47c7b.wav
>
> Also if the call is sent to an IVR, and delay_echo is executed as an
> IVR action, the caller hears the echo as expected.
>
> The call is happening in PCMA.
>
> I've got also packet captures, will share them on request, as they
> contain some confidential information.