avformat/rtsp: support buffer_size and pkt_size options for RTP

And forward it to the underlying UDP protocol.

Fixes ticket #7517.

Signed-off-by: Jiangjie Gao <gaojiangjie@live.com>
Signed-off-by: Marton Balint <cus@passwd.hu>

doc/protocols.texi

@@ -1033,6 +1033,9 @@ Set the local RTCP port to @var{n}.
 @item pkt_size=@var{n}
 Set max packet size (in bytes) to @var{n}.
 
+@item buffer_size=@var{size}
+Set the maximum UDP socket buffer size in bytes.
+
 @item connect=0|1
 Do a @code{connect()} on the UDP socket (if set to 1) or not (if set
 to 0).

libavformat/rtsp.c

@@ -2506,12 +2506,15 @@ static int rtp_read_header(AVFormatContext *s)
     RTSPState *rt = s->priv_data;
     const char *p;
     AVBPrint sdp;
+    AVDictionary *opts = NULL;
 
     if (!ff_network_init())
         return AVERROR(EIO);
 
+    opts = map_to_opts(rt);
     ret = ffurl_open_whitelist(&in, s->url, AVIO_FLAG_READ,
-                     &s->interrupt_callback, NULL, s->protocol_whitelist, s->protocol_blacklist, NULL);
+                     &s->interrupt_callback, &opts, s->protocol_whitelist, s->protocol_blacklist, NULL);
+    av_dict_free(&opts);
     if (ret)
         goto fail;