diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
index 9af572daf2..21a5fda8ac 100644
--- a/libavformat/rtsp.c
+++ b/libavformat/rtsp.c
@@ -606,7 +606,7 @@ static void rtsp_parse_transport(RTSPHeader *reply, const char *p)
             p++;
         get_word_sep(profile, sizeof(profile), "/;,", &p);
         lower_transport[0] = '\0';
-        if (*p == '/') {
+        if (*p == '/') { /* rtp/avp/<protocol> */
             p++;
             get_word_sep(lower_transport, sizeof(lower_transport),
                          ";,", &p);