I have an SIP provider that allows me to have incoming calls on a local landline number.
I have tested this number on my server at home, the call ends up on an IVR that is playing some WAV files, and the quality is pretty good.
Then I have tested the number on a server at a client’s place, and the quality is just terrible.
I noticed the audio is bad (robot-style, cut, …) only at the beginning of the WAV file (first two seconds). After the (about) first two seconds (once the WAV file is loaded ?), the quality is good.
It seems not a bandwidth problem (?), because the bandwidth at home and at the client’s place are exactly the same in upload (DL: 5.08 Mbps, UL: 0.46 Mbps).
At the client’s place there is also PSTN/FXO, so I also tested my IVR through PSTN, on the same server, and the quality is good. So the quality is bad only with SIP.
As it is no bandwith problem, and doesn’t seem to be a problem with my server (because through FXO audio is good), what can be the problem ?
I am running out of ideas, thank you for any help!