mov: Raise ctts dts_shift threshold by 1

This fixes issue2246neu.mp4
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mov.c

@@ -1605,7 +1605,7 @@ static int mov_read_ctts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
         sc->ctts_data[i].count   = count;
         sc->ctts_data[i].duration= duration;
-        if (duration < 0 && i+1<entries)
+        if (duration < 0 && i+2<entries)
             sc->dts_shift = FFMAX(sc->dts_shift, -duration);
     }