[FFmpeg-devel] [PATCH] avformat/whip: remind user increase -buffer_size (PR #20579)

[Jack Lau via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20579 opened by Jack Lau (JackLau)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20579
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20579.patch

The udp buffer size might be too small to easily
be full temporarily and return WSAEWOULDBLOCK.
The udp code will handle the windows error code
and convert it to AVERROR(EAGAIN).

This issue just can be reproduced on windows.

If sleep a interval and retry to send pkt when hit
EAGAIN, it will increase latency, and appropriate
interval is hard to define.

So this patch just remind user increase the buffer
size via -buffer_size to avoid this issue.

Signed-off-by: Jack Lau <jacklau1222@qq.com>


>From 07c0ee59f237e7f47e12224d1948c7f688a36ed7 Mon Sep 17 00:00:00 2001
From: Jack Lau <jacklau1222@qq.com>
Date: Wed, 17 Sep 2025 10:25:41 +0800
Subject: [PATCH 1/3] avformat/whip: pass through buffer_size option to udp

Signed-off-by: Jack Lau <jacklau1222@qq.com>
---
 doc/muxers.texi    | 3 +++
 libavformat/whip.c | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/doc/muxers.texi b/doc/muxers.texi
index 8c45b7d47a..f4caa4d7cb 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -3955,6 +3955,9 @@ Default value is 5000.
 Set the maximum size, in bytes, of RTP packets that send out.
 Default value is 1500.
 
+@item buffer_size @var{integer}
+Set the buffer size, in bytes, of underlying protocol.
+
 @item authorization @var{string}
 The optional Bearer token for WHIP Authorization.
 
diff --git a/libavformat/whip.c b/libavformat/whip.c
index cfdc861c5b..e4386016a9 100644
--- a/libavformat/whip.c
+++ b/libavformat/whip.c
@@ -306,6 +306,7 @@ typedef struct WHIPContext {
      * Note that pion requires a smaller value, for example, 1200.
      */
     int pkt_size;
+    int buffer_size;/* Underlying protocol send/receive buffer size */
     /**
      * The optional Bearer token for WHIP Authorization.
      * See https://www.ietf.org/archive/id/draft-ietf-wish-whip-08.html#name-authentication-and-authoriz
@@ -1191,8 +1192,9 @@ static int udp_connect(AVFormatContext *s)
 
     av_dict_set_int(&opts, "connect", 1, 0);
     av_dict_set_int(&opts, "fifo_size", 0, 0);
-    /* Set the max packet size to the buffer size. */
+    /* Pass through the pkt_size and buffer_size to underling protocol */
     av_dict_set_int(&opts, "pkt_size", whip->pkt_size, 0);
+    av_dict_set_int(&opts, "buffer_size", whip->buffer_size, 0);
 
     ret = ffurl_open_whitelist(&whip->udp, url, AVIO_FLAG_WRITE, &s->interrupt_callback,
         &opts, s->protocol_whitelist, s->protocol_blacklist, NULL);
@@ -1954,6 +1956,7 @@ static int whip_check_bitstream(AVFormatContext *s, AVStream *st, const AVPacket
 static const AVOption options[] = {
     { "handshake_timeout",  "Timeout in milliseconds for ICE and DTLS handshake.",      OFFSET(handshake_timeout),  AV_OPT_TYPE_INT,    { .i64 = 5000 },    -1, INT_MAX, ENC },
     { "pkt_size",           "The maximum size, in bytes, of RTP packets that send out", OFFSET(pkt_size),           AV_OPT_TYPE_INT,    { .i64 = 1200 },    -1, INT_MAX, ENC },
+    { "buffer_size",        "The buffer size, in bytes, of underlying protocol",        OFFSET(buffer_size),        AV_OPT_TYPE_INT,    { .i64 = -1 },      -1, INT_MAX, ENC },
     { "authorization",      "The optional Bearer token for WHIP Authorization",         OFFSET(authorization),      AV_OPT_TYPE_STRING, { .str = NULL },     0,       0, ENC },
     { "cert_file",          "The optional certificate file path for DTLS",              OFFSET(cert_file),          AV_OPT_TYPE_STRING, { .str = NULL },     0,       0, ENC },
     { "key_file",           "The optional private key file path for DTLS",              OFFSET(key_file),      AV_OPT_TYPE_STRING, { .str = NULL },     0,       0, ENC },
-- 
2.49.1


>From 4915fd78ba45f871ec750226b21ae2e5d0a1636e Mon Sep 17 00:00:00 2001
From: Jack Lau <jacklau1222@qq.com>
Date: Wed, 17 Sep 2025 10:50:18 +0800
Subject: [PATCH 2/3] avformat/whip: remind user increase -buffer_size

The udp buffer size might be too small to easily
be full temporarily and return WSAEWOULDBLOCK.
The udp code will handle the windows error code
and convert it to AVERROR(EAGAIN).

This issue just can be reproduced on windows.

If sleep a interval and retry to send pkt when hit
EAGAIN, it will increase latency, and appropriate
interval is hard to define.

So this patch just remind user increase the buffer
size via -buffer_size to avoid this issue.

Signed-off-by: Jack Lau <jacklau1222@qq.com>
---
 libavformat/whip.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libavformat/whip.c b/libavformat/whip.c
index e4386016a9..887df5ad41 100644
--- a/libavformat/whip.c
+++ b/libavformat/whip.c
@@ -1877,8 +1877,10 @@ write_packet:
         if (ret == AVERROR(EINVAL)) {
             av_log(whip, AV_LOG_WARNING, "Ignore failed to write packet=%dB, ret=%d\n", pkt->size, ret);
             ret = 0;
+        } else if (ret == AVERROR(EAGAIN)) {
+            av_log(whip, AV_LOG_ERROR, "UDP send blocked, please increase the buffer via -buffer_size\n");
         } else
-            av_log(whip, AV_LOG_ERROR, "Failed to write packet, size=%d\n", pkt->size);
+            av_log(whip, AV_LOG_ERROR, "Failed to write packet, size=%d, ret=%d\n", pkt->size, ret);
         goto end;
     }
 
-- 
2.49.1


>From a9690e6522287faa5a9697d506eec06703507ad4 Mon Sep 17 00:00:00 2001
From: Jack Lau <jacklau1222@qq.com>
Date: Mon, 22 Sep 2025 16:48:12 +0800
Subject: [PATCH 3/3] doc/muxers: correct default pkt_size value of whip

Signed-off-by: Jack Lau <jacklau1222@qq.com>
---
 doc/muxers.texi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/muxers.texi b/doc/muxers.texi
index f4caa4d7cb..6ad7dad554 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -3953,7 +3953,7 @@ Default value is 5000.
 
 @item pkt_size @var{integer}
 Set the maximum size, in bytes, of RTP packets that send out.
-Default value is 1500.
+Default value is 1200.
 
 @item buffer_size @var{integer}
 Set the buffer size, in bytes, of underlying protocol.
-- 
2.49.1

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