From 5c1851cbc0e31cc1fee108983b1937212002860c Mon Sep 17 00:00:00 2001
From: Richard Mudgett <rmudgett@digium.com>
Date: Thu, 20 Apr 2017 19:25:10 -0500
Subject: [PATCH] stream: Make ast_stream_topology_create_from_format_cap()
 allow NULL cap.

Change-Id: Ie29760c49c25d7022ba2124698283181a0dd5d08
---
 include/asterisk/stream.h   | 2 +-
 main/channel_internal_api.c | 8 ++------
 main/stream.c               | 6 ++----
 3 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/include/asterisk/stream.h b/include/asterisk/stream.h
index 924bfb65cd..1e07407a9f 100644
--- a/include/asterisk/stream.h
+++ b/include/asterisk/stream.h
@@ -356,7 +356,7 @@ int ast_stream_topology_set_stream(struct ast_stream_topology *topology,
  * creates a topology and separates the media types in format_cap into
  * separate streams.
  *
- * \param caps The format capabilities structure
+ * \param caps The format capabilities structure (NULL creates an empty topology)
  *
  * \retval non-NULL success
  * \retval NULL failure
diff --git a/main/channel_internal_api.c b/main/channel_internal_api.c
index d838ea80cf..7f32b21966 100644
--- a/main/channel_internal_api.c
+++ b/main/channel_internal_api.c
@@ -852,14 +852,10 @@ void ast_channel_nativeformats_set(struct ast_channel *chan,
 		return;
 	}
 
-	if ((!ast_channel_is_multistream(chan)) || !value) {
+	if (!ast_channel_is_multistream(chan) || !value) {
 		struct ast_stream_topology *new_topology;
 
-		if (!value) {
-			new_topology = ast_stream_topology_alloc();
-		} else {
-			new_topology = ast_stream_topology_create_from_format_cap(value);
-		}
+		new_topology = ast_stream_topology_create_from_format_cap(value);
 		ast_channel_internal_set_stream_topology(chan, new_topology);
 	}
 }
diff --git a/main/stream.c b/main/stream.c
index cf2633e1b7..39b6b1b13f 100644
--- a/main/stream.c
+++ b/main/stream.c
@@ -345,11 +345,9 @@ struct ast_stream_topology *ast_stream_topology_create_from_format_cap(
 	struct ast_stream_topology *topology;
 	enum ast_media_type type;
 
-	ast_assert(cap != NULL);
-
 	topology = ast_stream_topology_alloc();
-	if (!topology) {
-		return NULL;
+	if (!topology || !cap || !ast_format_cap_count(cap)) {
+		return topology;
 	}
 
 	for (type = AST_MEDIA_TYPE_UNKNOWN + 1; type < AST_MEDIA_TYPE_END; type++) {