Merge pull request #19665 from alalek:update_ffmpeg_3.4

3rdparty/ffmpeg/ffmpeg.cmake

-# Binaries branch name: ffmpeg/3.4_20200907
-# Binaries were created for OpenCV: 03bee14372f5537daa56c62e771ec16181ca1f98
-ocv_update(FFMPEG_BINARIES_COMMIT "2a96257b743695a47f8012aab1ffb995a1dee8b4")
-ocv_update(FFMPEG_FILE_HASH_BIN32 "5e68a3ff82f43ac6524e50e448a34c9c")
-ocv_update(FFMPEG_FILE_HASH_BIN64 "205db629d893e7d4865fd1459807ff47")
+# Binaries branch name: ffmpeg/3.4_20210302
+# Binaries were created for OpenCV: 2ab1f3f166fccc3a01497209cc01c5cea44ff201
+ocv_update(FFMPEG_BINARIES_COMMIT "e99214251d9f3cde7c48abd46b2259bddc9885b6")
+ocv_update(FFMPEG_FILE_HASH_BIN32 "fad5ada9be36120bba8966709e7953a8")
+ocv_update(FFMPEG_FILE_HASH_BIN64 "650e2272728491923e566f784f79cfef")
 ocv_update(FFMPEG_FILE_HASH_CMAKE "3b90f67f4b429e77d3da36698cef700c")
 
 function(download_win_ffmpeg script_var)