[FFmpeg-devel] [PATCH] avformat/whip: set the first sequence number for video and audio (PR #20332)

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

PR #20332 opened by Jack Lau (JackLau)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20332
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20332.patch

this patch will make whip be able to get the first
rtp seq easily and compute something sequence-based
(e.g. NACK and RTX handling)

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


From 3109374df9e00e1c8c5e199809ffc2a95c4a9b6e Mon Sep 17 00:00:00 2001
From: Jack Lau <jacklau1222@qq.com>
Date: Mon, 25 Aug 2025 05:52:34 +0800
Subject: [PATCH] avformat/whip: set the first sequence number for video and
 audio

this patch will make whip be able to get the first
rtp seq easily and compute something sequence-based
(e.g. NACK and RTX handling)

Signed-off-by: Jack Lau <jacklau1222@qq.com>
---
 libavformat/whip.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libavformat/whip.c b/libavformat/whip.c
index 69f1010ee8..ae0e98052b 100644
--- a/libavformat/whip.c
+++ b/libavformat/whip.c
@@ -219,6 +219,9 @@ typedef struct WHIPContext {
     /* The SSRC of the audio and video stream, generated by the muxer. */
     uint32_t audio_ssrc;
     uint32_t video_ssrc;
+
+    uint16_t audio_first_seq;
+    uint16_t video_first_seq;
     /* The PT(Payload Type) of stream, generated by the muxer. */
     uint8_t audio_payload_type;
     uint8_t video_payload_type;
@@ -379,6 +382,9 @@ static av_cold int initialize(AVFormatContext *s)
     seed = av_get_random_seed();
     av_lfg_init(&whip->rnd, seed);
 
+    whip->audio_first_seq = av_lfg_get(&whip->rnd) & 0x0fff;
+    whip->video_first_seq = av_lfg_get(&whip->rnd) & 0x0fff;
+
     if (whip->pkt_size < ideal_pkt_size)
         av_log(whip, AV_LOG_WARNING, "pkt_size=%d(<%d) is too small, may cause packet loss\n",
                whip->pkt_size, ideal_pkt_size);
@@ -1536,6 +1542,7 @@ static int create_rtp_muxer(AVFormatContext *s)
         av_dict_set(&opts, "payload_type", buf, 0);
         snprintf(buf, sizeof(buf), "%d", is_video? whip->video_ssrc : whip->audio_ssrc);
         av_dict_set(&opts, "ssrc", buf, 0);
+        av_dict_set_int(&opts, "seq", is_video ? whip->video_first_seq : whip->audio_first_seq, 0);
 
         ret = avformat_write_header(rtp_ctx, &opts);
         if (ret < 0) {
-- 
2.49.1

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