udp: Clarify the comment about binding the multicast address

Signed-off-by: Martin Storsjö <martin@martin.st>

1 files changed, 3 insertions, 1 deletions

diff --git a/libavformat/udp.c b/libavformat/udp.c
index 12de48cc4e..e91b95cde4 100644
--- a/libavformat/udp.c
+++ b/libavformat/udp.c
@@ -380,7 +380,9 @@ static int udp_open(URLContext *h, const char *uri, int flags)
             goto fail;
     }
 
-    /* if multicast, try the multicast address bind first */
+    /* If multicast, try binding the multicast address first, to avoid
+     * receiving UDP packets from other sources aimed at the same UDP
+     * port. This fails on windows. */
     if (s->is_multicast && (h->flags & AVIO_FLAG_READ)) {
         bind_ret = bind(udp_fd,(struct sockaddr *)&s->dest_addr, len);
     }