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I'm currently using FreePBX which has GUI settings to set Jitter Buffer for SIP, but not PJSIP.

We have around 90 remote extensions using PJSIP and i would like to enable the Jitter Buffer for all as we are seeing a few issues.

I've read that i should make use of a predial hook instead of extending the context for each extension.

Would placing the following in the predial hook do the job?

exten => outbound_jitterbuf,1,NoOp()
same => n,Set(JITTERBUFFER(adaptive)=default)
same => n,Return()
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Yes, it would. However, only on the B-leg in your example. You'd need to think carefully on if you want the JB on the A/B-leg of the call or both and apply it accordingly.

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  • We're looking to do the same for all B-leg calls. We have handsets out in the field using WiFi / 3G / LTE and this would help our call quality immensely... Any way to set it for all B-Leg calls regardless of incoming / outgoing / destination / source? – Kevin Parker Jan 7 '19 at 23:36
  • Hi @KevinParker, most likely it isn't a good idea to do what you suggested since the JB exists on the handsets as well and should be handled there. Also, if latencies increase too much you will have cross-talk and echo cancellation polution thus reducing the perceived quality. Run a lot of tests and make small careful changes. – grandnasty Jan 10 '19 at 15:27
  • Well you're right about the jitter buffer on the receive side of the WiFi handset, but there is no receive jitter buffer on the PBX side of things. So when there is any delay in receiving packets from the handsets, there is a noticeable separation in the audio... Adding even a 25-50ms buffer would probably do wonders for the call quality. – Kevin Parker Jan 11 '19 at 16:23

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