From 6a656785929e50c352855391ef17177206896067 Mon Sep 17 00:00:00 2001
From: Alexander Smorkalov <alexander.smorkalov@xperience.ai>
Date: Fri, 3 Nov 2023 13:59:31 +0300
Subject: [PATCH] Use video stream fps first in FFmpeg backend for
 VideoCapture.

---
 modules/videoio/src/cap_ffmpeg_impl.hpp | 13 +++++++------
 modules/videoio/test/test_ffmpeg.cpp    |  2 +-
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/modules/videoio/src/cap_ffmpeg_impl.hpp b/modules/videoio/src/cap_ffmpeg_impl.hpp
index bf259b4daf..17d02df95a 100644
--- a/modules/videoio/src/cap_ffmpeg_impl.hpp
+++ b/modules/videoio/src/cap_ffmpeg_impl.hpp
@@ -1877,15 +1877,16 @@ int64_t CvCapture_FFMPEG::get_bitrate() const
 
 double CvCapture_FFMPEG::get_fps() const
 {
-#if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(55, 1, 100) && LIBAVFORMAT_VERSION_MICRO >= 100
-    double fps = r2d(av_guess_frame_rate(ic, ic->streams[video_stream], NULL));
-#else
+#if LIBAVCODEC_BUILD >= CALC_FFMPEG_VERSION(54, 1, 0) || LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(52, 111, 0)
     double fps = r2d(ic->streams[video_stream]->avg_frame_rate);
+#else
+    double fps = r2d(ic->streams[video_stream]->r_frame_rate);
+#endif
 
-#if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(52, 111, 0)
+#if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(55, 1, 100) && LIBAVFORMAT_VERSION_MICRO >= 100
     if (fps < eps_zero)
     {
-        fps = r2d(ic->streams[video_stream]->avg_frame_rate);
+        fps = r2d(av_guess_frame_rate(ic, ic->streams[video_stream], NULL));
     }
 #endif
 
@@ -1893,7 +1894,7 @@ double CvCapture_FFMPEG::get_fps() const
     {
         fps = 1.0 / r2d(ic->streams[video_stream]->time_base);
     }
-#endif
+
     return fps;
 }
 
diff --git a/modules/videoio/test/test_ffmpeg.cpp b/modules/videoio/test/test_ffmpeg.cpp
index 9f59480c9c..338138518b 100644
--- a/modules/videoio/test/test_ffmpeg.cpp
+++ b/modules/videoio/test/test_ffmpeg.cpp
@@ -296,7 +296,7 @@ TEST_P(videoio_encapsulate, write)
         ASSERT_TRUE(capActualRaw.isOpened());
         const double fpsReference = capReference.get(CAP_PROP_FPS);
         const double fpsActual = capActual.get(CAP_PROP_FPS);
-        ASSERT_EQ(fpsReference, fpsActual);
+        ASSERT_NEAR(fpsReference, fpsActual, 1e-2);
         const int nFramesActual = static_cast<int>(capActual.get(CAP_PROP_FRAME_COUNT));
         ASSERT_EQ(nFrames, nFramesActual);