Merge branch 'develop' of github.com:matrix-org/synapse into registration-api-changes

docs/specification.rst

@@ -1182,16 +1182,16 @@ This event is sent by the caller when they wish to establish a call.
     - ``type`` : "string" - The type of session description, in this case 'offer'
     - ``sdp`` : "string" - The SDP text of the session description
 
-``m.call.candidate``
+``m.call.candidates``
 This event is sent by callers after sending an invite and by the callee after answering.
-Its purpose is to give the other party an additional ICE candidate to try using to
+Its purpose is to give the other party additional ICE candidates to try using to
 communicate.
 
   Required keys:
     - ``call_id`` : "string" - The ID of the call this event relates to
     - ``version`` : "integer" - The version of the VoIP specification this messages
                                 adheres to. his specification is version 0.
-    - ``candidate`` : "candidate object" - Object describing the candidate.
+    - ``candidates`` : "array of candidate objects" - Array of object describing the candidates.
 
 ``Candidate Object``
 
@@ -1249,7 +1249,33 @@ Or a rejected call:
                  <------- m.call.hangup
 
 Calls are negotiated according to the WebRTC specification.
- 
+
+
+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.
+
+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
+setup for use on a call should be transferred and used for the call that
+replaces it.
  
 Profiles
 ========