[FFmpeg-devel,v1] avformat/sdp, rtsp: add rtcp attribute to sdp file

diff --git a/libavformat/rtpproto.c b/libavformat/rtpproto.c
index 1f0a82ac7e..81a39cc3de 100644
--- a/libavformat/rtpproto.c
+++ b/libavformat/rtpproto.c
@@ -524,6 +524,17 @@  int ff_rtp_get_local_rtp_port(URLContext *h)
     return ff_udp_get_local_port(s->rtp_hd);
 }
 
+/**
+ * Return the remote rtcp port used by the RTP connection
+ * @param h media file context
+ * @return the remote port number
+ */
+int ff_rtp_get_remote_rtcp_port(URLContext *h)
+{
+    RTPContext *s = h->priv_data;
+    return s->rtcp_port;
+}
+
 /**
  * Return the local rtcp port used by the RTP connection
  * @param h media file context
diff --git a/libavformat/rtpproto.h b/libavformat/rtpproto.h
index 131aac5f3c..d42327ea5c 100644
--- a/libavformat/rtpproto.h
+++ b/libavformat/rtpproto.h
@@ -27,4 +27,6 @@  int ff_rtp_set_remote_url(URLContext *h, const char *uri);
 
 int ff_rtp_get_local_rtp_port(URLContext *h);
 
+int ff_rtp_get_remote_rtcp_port(URLContext *h);
+
 #endif /* AVFORMAT_RTPPROTO_H */
diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
index cd6fc32a29..c892f21142 100644
--- a/libavformat/rtsp.c
+++ b/libavformat/rtsp.c
@@ -577,6 +577,10 @@  static void sdp_parse_line(AVFormatContext *s, SDPParseState *s1,
             if (s1->seen_fmtp) {
                 parse_fmtp(s, rt, payload_type, s1->delayed_fmtp);
             }
+        } else if (av_strstart(p, "rtcp:", &p) && s->nb_streams > 0) {
+            rtsp_st = rt->rtsp_streams[rt->nb_rtsp_streams - 1];
+            get_word(buf1, sizeof(buf1), &p);
+            rtsp_st->rtcp_port = strtol(buf1, NULL, 10);
         } else if (av_strstart(p, "fmtp:", &p) ||
                    av_strstart(p, "framesize:", &p)) {
             // let dynamic protocol handlers have a stab at the line.
@@ -2367,6 +2371,7 @@  static int sdp_read_header(AVFormatContext *s)
 
         if (!(rt->rtsp_flags & RTSP_FLAG_CUSTOM_IO)) {
             AVDictionary *opts = map_to_opts(rt);
+            int rtcp_port = rtsp_st->rtcp_port;
 
             err = getnameinfo((struct sockaddr*) &rtsp_st->sdp_ip,
                               sizeof(rtsp_st->sdp_ip),
@@ -2377,10 +2382,13 @@  static int sdp_read_header(AVFormatContext *s)
                 av_dict_free(&opts);
                 goto fail;
             }
+
+            if (rtcp_port <= 0)
+                rtcp_port = rtsp_st->sdp_port + 1;
             ff_url_join(url, sizeof(url), "rtp", NULL,
                         namebuf, rtsp_st->sdp_port,
-                        "?localport=%d&ttl=%d&connect=%d&write_to_source=%d",
-                        rtsp_st->sdp_port, rtsp_st->sdp_ttl,
+                        "?localport=%d&localrtcpport=%d&ttl=%d&connect=%d&write_to_source=%d",
+                        rtsp_st->sdp_port, rtcp_port, rtsp_st->sdp_ttl,
                         rt->rtsp_flags & RTSP_FLAG_FILTER_SRC ? 1 : 0,
                         rt->rtsp_flags & RTSP_FLAG_RTCP_TO_SOURCE ? 1 : 0);
 
diff --git a/libavformat/rtsp.h b/libavformat/rtsp.h
index 54a9a30c16..15747fe6d1 100644
--- a/libavformat/rtsp.h
+++ b/libavformat/rtsp.h
@@ -448,6 +448,7 @@  typedef struct RTSPStream {
     /** The following are used only in SDP, not RTSP */
     //@{
     int sdp_port;             /**< port (from SDP content) */
+    int rtcp_port;            /**< rtcp port (from SDP content) */
     struct sockaddr_storage sdp_ip; /**< IP address (from SDP content) */
     int nb_include_source_addrs; /**< Number of source-specific multicast include source IP addresses (from SDP content) */
     struct RTSPSource **include_source_addrs; /**< Source-specific multicast include source IP addresses (from SDP content) */
diff --git a/libavformat/sdp.c b/libavformat/sdp.c
index 34e9839b67..c3c2909090 100644
--- a/libavformat/sdp.c
+++ b/libavformat/sdp.c
@@ -26,11 +26,13 @@ 
 #include "libavutil/opt.h"
 #include "libavcodec/xiph.h"
 #include "libavcodec/mpeg4audio.h"
+#include "avio_internal.h"
 #include "avformat.h"
 #include "internal.h"
 #include "avc.h"
 #include "hevc.h"
 #include "rtp.h"
+#include "rtpproto.h"
 #if CONFIG_NETWORK
 #include "network.h"
 #endif
@@ -480,10 +482,16 @@  static char *latm_context2config(AVFormatContext *s, AVCodecParameters *par)
     return config;
 }
 
-static char *sdp_write_media_attributes(char *buff, int size, AVStream *st, int payload_type, AVFormatContext *fmt)
+static char *sdp_write_media_attributes(char *buff, int size, AVStream *st, int payload_type, AVFormatContext *fmt, int port)
 {
     char *config = NULL;
     AVCodecParameters *p = st->codecpar;
+    URLContext* url_ctx = ffio_geturlcontext(fmt->pb);
+    if (url_ctx) {
+        int rtcp_port = ff_rtp_get_remote_rtcp_port(url_ctx);
+        if (rtcp_port > 0 && rtcp_port != port+1)
+            av_strlcatf(buff, size, "a=rtcp:%d\r\n", rtcp_port);
+    }
 
     switch (p->codec_id) {
         case AV_CODEC_ID_DIRAC:
@@ -766,7 +774,7 @@  void ff_sdp_write_media(char *buff, int size, AVStream *st, int idx,
         av_strlcatf(buff, size, "b=AS:%"PRId64"\r\n", p->bit_rate / 1000);
     }
 
-    sdp_write_media_attributes(buff, size, st, payload_type, fmt);
+    sdp_write_media_attributes(buff, size, st, payload_type, fmt, port);
 }
 
 int av_sdp_create(AVFormatContext *ac[], int n_files, char *buf, int size)