What is better to use for SIP calls from a browser?

Question

Asterisk

Actually, the choice is rather between sipml5 and jssip. For browsers that don't support WebRTC, webrtc4all is planned to be used (again, only Windows is supported). But ideally, I would like to choose a set of libraries (or rather one) that could work via WebRTC, if it is supported, and work via flash, if it is not.
We also come up with an option with our own intermediate proxy server and SIP implementation, to which we will simply send Ajax requests, but again, I would like to use some kind of ready-made library.
The PBX is powered by Asterisk.

Answer 1

In order to file sipml5, two logical servers are needed:
1) Statefull SIP proxy, which supports SIP over Websocket and SIP over UDP/TCP.
2) Media server, which transcodes audio, if for example there is only g.729 codec.
There is a ready-made Web Call Server , but it is paid. But there is a function to automatically switch to Flash, if there is no support for WebRTC.