0 votes

Our PBX supports opus with fec enabled offering significant improvement in call quality with packet loss, however I'm unsure if zoiper advertises its opus implementation with sip command: useinbandfec=yes

See here:

Anyone can shed some light on this?

I see its enabled for Windows. Any developer know is this applies to Android as well (zoiper gold)? 


in Android by (230 points)

2 Answers

0 votes


The implementation of Opus in all Zoiper product comes with FEC enabled by default. However Zoiper will never initiate a call with it. But if the server sends an INVITE with FEC, Zoiper will obey and use it. 

by (34.3k points)
edited by

Thanks, it sounds like this whole setup is then incompatible with FreePBX to enable FEC. I really don't think it sends an invite with FEC,,,

Any reason why it doesn't initiate a call with it? From what I've read the decoder on the receiving side will blindly accept weather it has fec enabled or not.

Usually the FEC option can cause loss of quality and delay, as you can see here: http://blogs.asterisk.org/2017/04/12/asterisk-opus-packet-loss-fec/

This will also limit Opus to narrow or medium. Additionally by default most servers come with FEC disabled, so unless the server requests FEC we do not want to force it.

0 votes

So I do see useinbandfec advertised in the SIP INVITE from for both freepbx and Voiper, but it doesn't sound like its using any at all.

I use Network Link Conditioner for mac os, join its wifi sharing and add 10% packet loss both up and down. packet_loss=30 is set in codecs.conf for freepbx, the quality should still be very good based on the OPUS comparison page they have.

Quality is not good. Is voiper's opus compiled with packet_loss >= 10 as well? 

by (230 points)


Any update on this?


As you can see in my previous comment, the FEC will be used only for incoming Invites with FEC enabled. Zoiper will never initiate a call with FEC.

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