Create technical/6.1. Conference Protocol

technical/6.1.-Conference-Protocol.md

+# Conference protocol
+
+This document aims to describe evolutions we will do for managing conferences (audio/video). The goal is to improve the current implementation which simply merge SIP calls together and provide a grid view, to a view where participants are listed, can be muted independantly, or the video layout changed (to show only one participant)
+
+## Definitions
+
++ Host: Is the user which mix the audio/video streams for the others
++ Participant: Every user in the conference, even the host
+
+## Disclaimer
+
+This document only describes the first steps for now. This means the identification of participants and position in the video mixer sent to all participants.
+
+## Improve on layouts
+
+Actually, Jami only provides the possibility to show a grid view of the users. We want to be able to only show one member of the conference (the one which shares its screen for example)
+
+### Possible layouts
+
++ GRID: Every member is shown with the same height/width
++ ONE_BIG_WITH_SMALL: One member is zoomed and the other preview are shown
++ ONE_BIG: One member take the full screen rendered
+
+### New API
+
+Two new methods are available to manage the conference Layout in CallManager:
+
+```cpp
+/**
+ * Change the conference layout
+ * @param confId
+ * @param layout    0 = matrix, 1 = one big, others in small, 2 = one in big
+ */
+void setConferenceLayout(const std::string& confId, int layout);
+
+/**
+ * Change the active participant (used in layout != matrix)
+ * @param confId
+ * @param participantId    If participantId not found, the local video will be shown
+ */
+void setActiveParticipant(const std::string& confId, const std::string& participantId);
+```
+
+### Implementation
+
+The implementation is pretty straight forward. Everything is managed by `conference.cpp` (to link participant to sources) and `video_mixer.cpp` (to render the wanted layout).
+
+
+## Syncing Conferences Informations
+
+Note: Actually, the word participant is used for callId mixed in a conference. This can lead at first to some problems for the API and must be fixed in the furture
+
+The goal is to notify all participants the metadatas of the rendered video. This means what participant is in the conference and where the video is located.
+
+### Layout Info
+
+The Layout is stored as a VectorMapStringString with the following format:
+
+```
+Layout = {
+    "participant0": {
+         "x":"0", "y":"0", "w": "0", "h": "0"
+    },
+    "participant1": {
+         "x":"0", "y":"0", "w": "0", "h": "0"
+    }
+    (...)
+}
+```
+
+### New API
+
+A new method (in CallManager) and a new signal to respectively get current conference infos and updates are available:
+
+```cpp
+VectorMapStringString getConferenceInfos(const std::string& confId);
+
+void onConferenceInfosUpdated(const std::string& confId, const VectorMapStringString& infos);
+```
+
+### Implementation
+
+The `Conference` Object (which only exists if we mix calls, this means that we are the master) manages the informations for the whole conference, based on the LayoutInfos of each `Call` objects. The getConferenceInfos will retrieve infos directly from this object.
+
+So, every `Call` object now have a LayoutInfo and if updated, ask the `Conference` object to updates its infos.
+
+The master of a conference sends its infos via the SIP channel as a message with the following MIME type:
+`application/confInfo+json`
+
+So, if a call receives some confInfo, we know that this call is a member of a conference.
+
+## Future
+
++ Multiple master management
++ Separate streams to allow more controls?
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