Changes between Initial Version and Version 1 of 0.9/Media_Interface_Change

Timestamp:

Jun 9, 2008 2:02:51 PM (17 years ago)

Author:

bennylp

Comment:

--

0.9/Media_Interface_Change

@@ +1 @@
+= Background =
+
+Currently this is how the media channel interacts with SIP call in PJSUA-LIB:
+
+{{{
+pjsua_call_make_call():
+pjsua_call_on_incoming():
+pjsua_call_update():
+pjsua_call_reinvite():
+pjsua_call_on_rx_offer():
+pjsua_call_on_create_offer():
+{
+        pjsua_media_channel_init();
+        pjsua_media_channel_create_sdp();
+}
+
+pjsua_call_on_media_update():
+{
+        pjsua_media_channel_update();
+}
+
+pjsua_call_on_state_changed(DISCONNECTED):
+pjsua_call_on_media_update(HOLD):
+{
+        pjsua_media_channel_deinit();
+}
+}}}
+
+and this is the implementation of media channel functions above:
+
+{{{
+pjsua_media_channel_init()
+{
+        pjmedia_transport_srtp_create();
+}
+
+pjsua_media_channel_create_sdp():
+{
+        pjmedia_endpt_create_sdp();
+        pjmedia_transport_media_create();
+}
+
+pjsua_media_channel_update():
+{
+        pjmedia_transport_media_start();
+        pjmedia_session_create();
+}
+
+pjsua_media_channel_deinit():
+{
+        stop_media_session();
+        pjmedia_transport_media_stop();
+        pjmedia_transport_close(srtp);
+}
+}}}
+
+= Reasons for Fix/Change =
+
+The interface above has some drawbacks:
+
+ 1. The main drawback is it does not distinguish between a new/freshly created call and existing call (which needs updating the media because of re-INVITE/UPDATE), functions such as pjsua_call_on_create_offer() will actually re-initialize the media, hence causing problems such as ticket #525 (crash on UPDATE/re-INVITE).
+ 1. It requires media transports to be re-created during application startup and kept-alive throughout the application lifetime. The drawbacks of this are (as documented by ticket #539):
+   a. it requires STUN and TURN transport to be kept-alive, which means it needs to send periodic keep-alive packets, and this is not good for battery consumption in mobile devices.
+   a. it requires TURN long-term allocation, which will fail if the NAT/mapped public IP address mapping has changed.
+   a. even when TURN is not used it may still fail when normal UDP media transport (i.e. not ICE) is used and the IP address (STUN or not) changes.
+   a. it allocates a lot of resources when the number of max_calls is large. 
+
+
+
+= New Design Specification =
+
+
+
+