From 6c3e70d2721554827d14d27ff07e892976ffcd24 Mon Sep 17 00:00:00 2001 From: Kegan Dougal Date: Wed, 30 Sep 2015 17:32:44 +0100 Subject: [PATCH] Start fleshing out voip module --- specification/1-client_server_api.rst | 2 + specification/modules/voip_events.rst | 84 ++++++++++++++++++--------- 2 files changed, 59 insertions(+), 27 deletions(-) diff --git a/specification/1-client_server_api.rst b/specification/1-client_server_api.rst index 7d8d57e4..db88bbd6 100644 --- a/specification/1-client_server_api.rst +++ b/specification/1-client_server_api.rst @@ -427,6 +427,8 @@ the complete dataset is provided in "chunk". Events ------ +.. _sect:events: + Overview ~~~~~~~~ diff --git a/specification/modules/voip_events.rst b/specification/modules/voip_events.rst index 33998cd9..f1b8ae05 100644 --- a/specification/modules/voip_events.rst +++ b/specification/modules/voip_events.rst @@ -1,17 +1,18 @@ Voice over IP -------------- -Matrix can also be used to set up VoIP calls. This is part of the core -specification, although is at a relatively early stage. Voice (and video) over -Matrix is built on the WebRTC 1.0 standard. Call events are sent to a room, like -any other event. This means that clients must only send call events to rooms -with exactly two participants as currently the WebRTC standard is based around -two-party communication. +============= -{{voip_events}} +This module outlines how two users in a room can set up a Voice over IP (VoIP) +call to each other. Voice and video calls are built upon the WebRTC 1.0 standard. +Call signalling is achieved by sending `message events`_ to the room. As a result, +this means that clients MUST only send call events to rooms with exactly two +participants as currently the WebRTC standard is based around two-party +communication. + +.. _message events: `sect:events`_ Message Exchange -~~~~~~~~~~~~~~~~ -A call is set up with messages exchanged as follows: +---------------- +A call is set up with message events exchanged as follows: :: @@ -38,28 +39,57 @@ Or a rejected call: Calls are negotiated according to the WebRTC specification. +Events +------ + +{{voip_events}} + +Client behaviour +---------------- Glare ~~~~~ -This specification aims to address the problem of two users calling each other -at roughly the same time and their invites crossing on the wire. It is a far -better experience for the users if their calls are connected if it is clear -that their intention is to set up a call with one another. In Matrix, calls are -to rooms rather than users (even if those rooms may only contain one other user) -so we consider calls which are to the same room. The rules for dealing with such -a situation are as follows: - - - If an invite to a room is received whilst the client is preparing to send an - invite to the same room, the client should cancel its outgoing call and - instead automatically accept the incoming call on behalf of the user. - - If an invite to a room is received after the client has sent an invite to - the same room and is waiting for a response, the client should perform a - lexicographical comparison of the call IDs of the two calls and use the - lesser of the two calls, aborting the greater. If the incoming call is the - lesser, the client should accept this call on behalf of the user. + +"Glare" is a problem which occurs when two users call each other at roughly the +same time. This results in the call failing to set up as there already is an +incoming/outgoing call. A glare resolution algorithm can be used to determine +which call to hangup and which call to answer. If both clients implement the +same algorithm then they will both select the same call and the call will be +successfully connected. + + +As calls are "placed" to rooms rather than users, the glare resolution algorithm +outlined below is only considered for calls which are to the same room. The +algorithm is as follows: + + - If an invite to a room is received whilst the client is **preparing to send** + an invite to the same room: + + * the client should cancel its outgoing call and instead + automatically accept the incoming call on behalf of the user. + + - If an invite to a room is received **after the client has sent** an invite to + the same room and is waiting for a response: + + * the client should perform a lexicographical comparison of the call IDs of + the two calls and use the **lesser** of the two calls, aborting the + greater. If the incoming call is the lesser, the client should accept + this call on behalf of the user. + The call setup should appear seamless to the user as if they had simply placed -a call and the other party had accepted. Thusly, any media stream that had been +a call and the other party had accepted. This means any media stream that had been setup for use on a call should be transferred and used for the call that replaces it. +Server behaviour +---------------- + +TURN Servers +~~~~~~~~~~~~ + +Security considerations +----------------------- + + +