XMPP has the jingle extension for audio and video calls: https://en.wikipedia.org/wiki/Jingle_(protocol) https://en.wikipedia.org/wiki/Jingle_(protocol) I have

XMPP has the jingle extension for audio and video calls: https://en.wikipedia.org/wiki/Jingle_(protocol) https://en.wikipedia.org/wiki/Jingle_(protocol) I have successfully used this for voice calls between the chat clients Gajim/Pidgin (I do not remember which) and Google Talk (the now-discontinued XMPP client by Google). I have also done video calls between two Nokia N900 phones, to see if it works. Voice and video via XMPP has worked since approximately 2009 and is just neglected by the companies for business reasons.