ffmpeg: fix get_fps()

modules/videoio/src/cap_ffmpeg_impl.hpp

@@ -1135,7 +1135,14 @@ int CvCapture_FFMPEG::get_bitrate() const
 
 double CvCapture_FFMPEG::get_fps() const
 {
+#if 0 && 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)
+    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 (fps < eps_zero)
@@ -1148,7 +1155,7 @@ double CvCapture_FFMPEG::get_fps() const
     {
         fps = 1.0 / r2d(ic->streams[video_stream]->codec->time_base);
     }
-
+#endif
     return fps;
 }