Group calls Group calls powered by Matrix.
Shipped version: 0.5.9~ynh1
Demo: https://call.element.io/
Maybe an useless question, but does it contain it’s own Matrix server or will it use the one already on the system if there is one ?
According to the documentation :
By default, the app expects you to have a Matrix homeserver (such as Synapse) installed locally and running on port 8008. If you wish to use a homeserver on a different URL or one that is hosted on a different server, you can add a config file as above, and include the homeserver URL that you’d like to use.
Element Call requires a homeserver with registration enabled without any 3pid or token requirements, if you want it to be used by unregistered users. Furthermore, it is not recommended to use it with an existing homeserver where user accounts have joined normal rooms, as it may not be able to handle those yet and it may behave unreliably.
Therefore, to use a self-hosted homeserver, this is recommended to be a new server where any user account created has not joined any normal rooms anywhere in the Matrix federated network. The homeserver used can be setup to disable federation, so as to prevent spam registrations (if you keep registrations open) and to ensure Element Call continues to work in case any user decides to log in to their Element Call account using the standard Element app and joins normal rooms that Element Call cannot handle.
If I understand correctly, to contact people already on Matrix, it is not useful at all, but it can be to contact people not on it, like any visioconference app ?
To be honest I haven’t tried yet the app and I don’t know if and how is it working. But I am pretty sure that some fine tuning will be needed.
From what I understand of the install script, it only installs Element-call, so it can break an existing Matrix server, and will break if no Matrix server is installed 
(But I am not really fluent in scripting)
Element-call is expected to be merged to Element. so this package is more a project preview.