avutil/timecode: use timecode fps for number of frame digits

Signed-off-by: Marton Balint <cus@passwd.hu>

libavutil/timecode.c

@@ -104,7 +104,7 @@ char *av_timecode_make_string(const AVTimecode *tc, char *buf, int framenum)
 {
     int fps = tc->fps;
     int drop = tc->flags & AV_TIMECODE_FLAG_DROPFRAME;
-    int hh, mm, ss, ff, neg = 0;
+    int hh, mm, ss, ff, ff_len, neg = 0;
 
     framenum += tc->start;
     if (drop)
@@ -119,9 +119,10 @@ char *av_timecode_make_string(const AVTimecode *tc, char *buf, int framenum)
     hh = framenum / (fps*3600LL);
     if (tc->flags & AV_TIMECODE_FLAG_24HOURSMAX)
         hh = hh % 24;
-    snprintf(buf, AV_TIMECODE_STR_SIZE, "%s%02d:%02d:%02d%c%02d",
+    ff_len = fps > 10000 ? 5 : fps > 1000 ? 4 : fps > 100 ? 3 : fps > 10 ? 2 : 1;
+    snprintf(buf, AV_TIMECODE_STR_SIZE, "%s%02d:%02d:%02d%c%0*d",
              neg ? "-" : "",
-             hh, mm, ss, drop ? ';' : ':', ff);
+             hh, mm, ss, drop ? ';' : ':', ff_len, ff);
     return buf;
 }