avfilter/vf_showinfo: limit the max number of timecode

Signed-off-by: Limin Wang <lance.lmwang@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/vf_showinfo.c

@@ -318,14 +318,15 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
             break;
         case AV_FRAME_DATA_S12M_TIMECODE: {
             uint32_t *tc = (uint32_t*)sd->data;
+            int m = FFMIN(tc[0],3);
             if (sd->size != 16) {
                 av_log(ctx, AV_LOG_ERROR, "invalid data");
                 break;
             }
-            for (int j = 1; j <= tc[0]; j++) {
+            for (int j = 1; j <= m; j++) {
                 char tcbuf[AV_TIMECODE_STR_SIZE];
                 av_timecode_make_smpte_tc_string(tcbuf, tc[j], 0);
-                av_log(ctx, AV_LOG_INFO, "timecode - %s%s", tcbuf, j != tc[0] ? ", " : "");
+                av_log(ctx, AV_LOG_INFO, "timecode - %s%s", tcbuf, j != m ? ", " : "");
             }
             break;
         }