Hi Charaf,
I haven't used the Softphone much, as WebRTC is so easy to setup and comes in as default with modern browsers.
From an audio quality perspective the Codec will have an important part, you should aim for the OPUS codec, which incidentally is the default on WebRTC, and will provide optimum audio (https://www.opus-codec.org/comparison/) between users and Edge.
I appreciate it's only part of the question, but hope it can help.
Kind regards,
Jean-Christophe
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Jean-Christophe Poyelle
Foehn Ltd.
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