avformat: replace some odd 30-60 rates by higher less odd ones in get_std_framerate()

Fixes Ticket4012

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/avformat.h

@@ -916,7 +916,7 @@ typedef struct AVStream {
     /**
      * Stream information used internally by av_find_stream_info()
      */
-#define MAX_STD_TIMEBASES (60*12+6)
+#define MAX_STD_TIMEBASES (30*12+7+6)
     struct {
         int64_t last_dts;
         int64_t duration_gcd;