Avcodec: add a macro for version check working for libav and FFmpeg

modules/codec/avcodec/fourcc.c

@@ -36,6 +36,14 @@
 #endif
 #include "avcodec.h"
 
+/* LIBAVCODEC_VERSION_CHECK checks for the right version of libav and FFmpeg
+ * a is the major version
+ * b and c the minor and micro versions of libav
+ * d and e the minor and micro versions of FFmpeg */
+#define LIBAVCODEC_VERSION_CHECK( a, b, c, d, e ) \
+    (LIBAVCODEC_VERSION_MICRO <  100 && LIBAVCODEC_VERSION_INT >= AV_VERSION_INT( a, b, c ) ) || \
+    (LIBAVCODEC_VERSION_MICRO >= 100 && LIBAVCODEC_VERSION_INT >= AV_VERSION_INT( a, d, e ) )
+
 /*****************************************************************************
  * Codec fourcc -> ffmpeg_id mapping
  *****************************************************************************/