[FFmpeg-cvslog] lavf/rtmp: Add option to set TCP_NODELAY for rtmp

[Nick Ruff]

ffmpeg | branch: master | Nick Ruff <nickruff at devvm32779.prn1.facebook.com> | Fri Jun 11 21:02:02 2021 +0200| [ea24781a9b508f92b6b2bb97ffca386898b70193] | committer: Thilo Borgmann

lavf/rtmp: Add option to set TCP_NODELAY for rtmp

Suggested-By: ffmpeg at fb.com

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ea24781a9b508f92b6b2bb97ffca386898b70193
---

 doc/protocols.texi      | 5 +++++
 libavformat/rtmppkt.c   | 6 ++++++
 libavformat/rtmpproto.c | 8 +++++---
 libavformat/tcp.c       | 3 +++
 4 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/doc/protocols.texi b/doc/protocols.texi
index d3095c88c6..6b5a9cfbd5 100644
--- a/doc/protocols.texi
+++ b/doc/protocols.texi
@@ -843,6 +843,11 @@ URL to player swf file, compute hash/size automatically.
 @item rtmp_tcurl
 URL of the target stream. Defaults to proto://host[:port]/app.
 
+ at item tcp_nodelay=@var{1|0}
+Set TCP_NODELAY to disable Nagle's algorithm. Default value is 0.
+
+ at emph{Remark: Writing to the socket is currently not optimized to minimize system calls and reduces the efficiency / effect of TCP_NODELAY.}
+
 @end table
 
 For example to read with @command{ffplay} a multimedia resource named
diff --git a/libavformat/rtmppkt.c b/libavformat/rtmppkt.c
index 00eb0873b2..4b97c0833f 100644
--- a/libavformat/rtmppkt.c
+++ b/libavformat/rtmppkt.c
@@ -374,6 +374,12 @@ int ff_rtmp_packet_write(URLContext *h, RTMPPacket *pkt,
     prev_pkt[pkt->channel_id].ts_field   = pkt->ts_field;
     prev_pkt[pkt->channel_id].extra      = pkt->extra;
 
+    // FIXME:
+    // Writing packets is currently not optimized to minimize system calls.
+    // Since system calls flush on exit which we cannot change in a system-independant way.
+    // We should fix this behavior and by writing packets in a single or in as few as possible system calls.
+    // Protocols like TCP and RTMP should benefit from this when enabling TCP_NODELAY.
+
     if ((ret = ffurl_write(h, pkt_hdr, p - pkt_hdr)) < 0)
         return ret;
     written = p - pkt_hdr + pkt->size;
diff --git a/libavformat/rtmpproto.c b/libavformat/rtmpproto.c
index 5a540e3240..b14d23b919 100644
--- a/libavformat/rtmpproto.c
+++ b/libavformat/rtmpproto.c
@@ -123,6 +123,7 @@ typedef struct RTMPContext {
     int           listen_timeout;             ///< listen timeout to wait for new connections
     int           nb_streamid;                ///< The next stream id to return on createStream calls
     double        duration;                   ///< Duration of the stream in seconds as returned by the server (only valid if non-zero)
+    int           tcp_nodelay;                ///< Use TCP_NODELAY to disable Nagle's algorithm if set to 1
     char          username[50];
     char          password[50];
     char          auth_params[500];
@@ -2653,10 +2654,10 @@ static int rtmp_open(URLContext *s, const char *uri, int flags, AVDictionary **o
             port = RTMP_DEFAULT_PORT;
         if (rt->listen)
             ff_url_join(buf, sizeof(buf), "tcp", NULL, hostname, port,
-                        "?listen&listen_timeout=%d",
-                        rt->listen_timeout * 1000);
+                        "?listen&listen_timeout=%d&tcp_nodelay=%d",
+                        rt->listen_timeout * 1000, rt->tcp_nodelay);
         else
-            ff_url_join(buf, sizeof(buf), "tcp", NULL, hostname, port, NULL);
+            ff_url_join(buf, sizeof(buf), "tcp", NULL, hostname, port, "?tcp_nodelay=%d", rt->tcp_nodelay);
     }
 
 reconnect:
@@ -3115,6 +3116,7 @@ static const AVOption rtmp_options[] = {
     {"rtmp_tcurl", "URL of the target stream. Defaults to proto://host[:port]/app.", OFFSET(tcurl), AV_OPT_TYPE_STRING, {.str = NULL }, 0, 0, DEC|ENC},
     {"rtmp_listen", "Listen for incoming rtmp connections", OFFSET(listen), AV_OPT_TYPE_INT, {.i64 = 0}, INT_MIN, INT_MAX, DEC, "rtmp_listen" },
     {"listen",      "Listen for incoming rtmp connections", OFFSET(listen), AV_OPT_TYPE_INT, {.i64 = 0}, INT_MIN, INT_MAX, DEC, "rtmp_listen" },
+    {"tcp_nodelay", "Use TCP_NODELAY to disable Nagle's algorithm", OFFSET(tcp_nodelay), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, DEC|ENC},
     {"timeout", "Maximum timeout (in seconds) to wait for incoming connections. -1 is infinite. Implies -rtmp_listen 1",  OFFSET(listen_timeout), AV_OPT_TYPE_INT, {.i64 = -1}, INT_MIN, INT_MAX, DEC, "rtmp_listen" },
     { NULL },
 };
diff --git a/libavformat/tcp.c b/libavformat/tcp.c
index 2198e0f00e..1c19aed887 100644
--- a/libavformat/tcp.c
+++ b/libavformat/tcp.c
@@ -135,6 +135,9 @@ static int tcp_open(URLContext *h, const char *uri, int flags)
         if (av_find_info_tag(buf, sizeof(buf), "listen_timeout", p)) {
             s->listen_timeout = strtol(buf, NULL, 10);
         }
+        if (av_find_info_tag(buf, sizeof(buf), "tcp_nodelay", p)) {
+            s->tcp_nodelay = strtol(buf, NULL, 10);
+        }
     }
     if (s->rw_timeout >= 0) {
         s->open_timeout =