fix ctts index computation when seeking, check must be done against next ctts...

fix ctts index computation when seeking, check must be done against next ctts sample, thanks to Uoti

Originally committed as revision 9007 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/mov.c

@@ -1525,12 +1525,13 @@ static int mov_seek_stream(AVStream *st, int64_t timestamp, int flags)
     if (sc->ctts_data) {
         time_sample = 0;
         for (i = 0; i < sc->ctts_count; i++) {
-            time_sample += sc->ctts_data[i].count;
-            if (time_sample >= sc->current_sample) {
+            int next = time_sample + sc->ctts_data[i].count;
+            if (next > sc->current_sample) {
                 sc->sample_to_ctime_index = i;
-                sc->sample_to_ctime_sample = time_sample - sc->current_sample;
+                sc->sample_to_ctime_sample = sc->current_sample - time_sample;
                 break;
             }
+            time_sample = next;
         }
     }
     return sample;