bridge_simple: Added support for streams

This patch is the first cut at adding stream support to the bridging framework.
Changes were made to the framework that allows mapping of stream topologies to
a bridge's supported media types.

The first channel to enter a bridge initially defines the media types for a
bridge (i.e. a one to one mapping is created between the bridge and the first
channel). Subsequently added channels merge their media types into the bridge's
adding to it when necessary. This allows channels with different sized
topologies to map correctly to each other according to media type. The bridge
drops any frame that does not have a matching index into a given write stream.

For now though, bridge_simple will align its two channels according to size or
first to join. Once both channels join the bridge the one with the most streams
will indicate to the other channel to update its streams to be the same as that
of the other. If both channels have the same number of streams then the first
channel to join is chosen as the stream base.

A topology change source was also added to a channel when a stream toplogy
change request is made. This allows subsystems to know whether or not they
initiated a change request. Thus avoiding potential recursive situations.

ASTERISK-26966 #close

Change-Id: I1eb5987921dd80c3cdcf52accc136393ca2d4163

1 files changed, 37 insertions, 1 deletions

diff --git a/bridges/bridge_simple.c b/bridges/bridge_simple.c
index 35544f84f..47f41cbb3 100644
--- a/bridges/bridge_simple.c
+++ b/bridges/bridge_simple.c
@@ -42,6 +42,10 @@
 #include "asterisk/bridge.h"
 #include "asterisk/bridge_technology.h"
 #include "asterisk/frame.h"
+#include "asterisk/stream.h"
+
+static void simple_bridge_stream_topology_changed(struct ast_bridge *bridge,
+		struct ast_bridge_channel *bridge_channel);
 
 static int simple_bridge_join(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
 {
@@ -56,7 +60,13 @@ static int simple_bridge_join(struct ast_bridge *bridge, struct ast_bridge_chann
 		return 0;
 	}
 
-	return ast_channel_make_compatible(c0, c1);
+	if (ast_channel_make_compatible(c0, c1)) {
+		return -1;
+	}
+
+	/* Align stream topologies */
+	simple_bridge_stream_topology_changed(bridge, NULL);
+	return 0;
 }
 
 static int simple_bridge_write(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel, struct ast_frame *frame)
@@ -70,8 +80,34 @@ static struct ast_bridge_technology simple_bridge = {
 	.preference = AST_BRIDGE_PREFERENCE_BASE_1TO1MIX,
 	.join = simple_bridge_join,
 	.write = simple_bridge_write,
+	.stream_topology_changed = simple_bridge_stream_topology_changed,
 };
 
+static void simple_bridge_stream_topology_changed(struct ast_bridge *bridge,
+		struct ast_bridge_channel *bridge_channel)
+{
+	struct ast_channel *c0 = AST_LIST_FIRST(&bridge->channels)->chan;
+	struct ast_channel *c1 = AST_LIST_LAST(&bridge->channels)->chan;
+	struct ast_stream_topology *t0 = ast_channel_get_stream_topology(c0);
+	struct ast_stream_topology *t1 = ast_channel_get_stream_topology(c1);
+
+	/*
+	 * The bridge_channel should only be NULL after both channels join
+	 * the bridge and their topologies are being aligned.
+	 */
+	if (bridge_channel && ast_channel_get_stream_topology_change_source(
+		    bridge_channel->chan) == &simple_bridge) {
+		return;
+	}
+
+	/* Align topologies according to size or first channel to join */
+	if (ast_stream_topology_get_count(t0) < ast_stream_topology_get_count(t1)) {
+		ast_channel_request_stream_topology_change(c0, t1, &simple_bridge);
+	} else {
+		ast_channel_request_stream_topology_change(c1, t0, &simple_bridge);
+	}
+}
+
 static int unload_module(void)
 {
 	ast_bridge_technology_unregister(&simple_bridge);