From 2ad8a934e0ea0862f2c0a98e45efb3bfa811fd4c Mon Sep 17 00:00:00 2001
From: sladro <sladro@163.com>
Date: Tue, 6 Jan 2026 16:42:13 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BC=98=E5=8C=96=E6=80=A7=E8=83=BD=EF=BC=8C?=
 =?UTF-8?q?=E4=BF=AE=E5=A4=8Dmp4=E6=92=AD=E6=94=BE=E9=80=9F=E5=BA=A6?=
 =?UTF-8?q?=E4=B8=8D=E5=AF=B9?=
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---
 plugins/alarm/actions/clip_action.cpp | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/plugins/alarm/actions/clip_action.cpp b/plugins/alarm/actions/clip_action.cpp
index d95ff25..6fe25fb 100644
--- a/plugins/alarm/actions/clip_action.cpp
+++ b/plugins/alarm/actions/clip_action.cpp
@@ -251,8 +251,10 @@ std::string ClipAction::ProcessClipFromPackets(const std::vector<std::shared_ptr
         return "";
     }
 
-    stream->time_base = AVRational{1, 1000};
-    stream->avg_frame_rate = AVRational{std::max(1, fps_), 1};
+    const int fps_eff = std::max(1, (first->codec->fps > 0 ? first->codec->fps : fps_));
+    // Use a stable timescale to avoid rounding drift and "fast playback" caused by bad source PTS.
+    stream->time_base = AVRational{1, 90000};
+    stream->avg_frame_rate = AVRational{fps_eff, 1};
     stream->r_frame_rate = stream->avg_frame_rate;
     stream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
     stream->codecpar->codec_id = cid;
@@ -312,10 +314,8 @@ std::string ClipAction::ProcessClipFromPackets(const std::vector<std::shared_ptr
         }
     }
 
-    int64_t first_pts = 0;
-    bool have_first = false;
-    int64_t last_pts = -1;
-    const int64_t frame_dur = (fps_ > 0) ? (1000LL / std::max(1, fps_)) : 40;
+    const int64_t frame_dur = av_rescale_q(1, AVRational{1, fps_eff}, stream->time_base);
+    int64_t frame_idx = 0;
 
     for (size_t i = start_idx; i < metas.size(); ++i) {
         const auto& m = metas[i];
@@ -323,14 +323,7 @@ std::string ClipAction::ProcessClipFromPackets(const std::vector<std::shared_ptr
         if (!m->codec || m->pkt.data.empty()) continue;
         if (m->pkt.pts_ms <= 0) continue;
 
-        if (!have_first) {
-            first_pts = m->pkt.pts_ms;
-            have_first = true;
-        }
-        int64_t pts = m->pkt.pts_ms - first_pts;
-        if (pts < 0) pts = 0;
-        if (pts <= last_pts) pts = last_pts + 1;
-        last_pts = pts;
+        const int64_t pts = av_rescale_q(frame_idx, AVRational{1, fps_eff}, stream->time_base);
 
         std::vector<uint8_t> sample = m->pkt.data;
         if (cid == AV_CODEC_ID_H264 && HasAnnexBStartCode(sample.data(), sample.size())) {
@@ -353,6 +346,8 @@ std::string ClipAction::ProcessClipFromPackets(const std::vector<std::shared_ptr
 
         (void)av_interleaved_write_frame(fmt_ctx, pkt);
         av_packet_free(&pkt);
+
+        ++frame_idx;
     }
 
     av_write_trailer(fmt_ctx);