Merge pull request opencv#14276 from kiwixz:pr/fix_compound

Do not use compound literals (fix MSVC C4576) (opencv#14276)

* do not use compound literals (compat cpp98)

* only fix msvc path

* remove unnecessary cplusplus check

Author: kiwixz

modules/videoio/src/cap_ffmpeg_impl.hpp

@@ -1669,8 +1669,13 @@ static AVStream *icv_add_video_stream_FFMPEG(AVFormatContext *oc,
 #endif
 
 #if LIBAVCODEC_BUILD >= CALC_FFMPEG_VERSION(52, 42, 0)
+#if defined(_MSC_VER)
+    AVRational avg_frame_rate = {frame_rate, frame_rate_base};
+    st->avg_frame_rate = avg_frame_rate;
+#else
     st->avg_frame_rate = (AVRational){frame_rate, frame_rate_base};
 #endif
+#endif
 #if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(55, 20, 0)
     st->time_base = c->time_base;
 #endif