avcodec/h264_slice: respect side data preference

If the time code side data is overridden by the packet level, we also
make sure not to update `out->metadata` to a mismatched timecode.

libavcodec/h264_slice.c

@@ -1252,26 +1252,27 @@ static int h264_export_frame_props(H264Context *h)
     if (h->sei.picture_timing.timecode_cnt > 0) {
         uint32_t *tc_sd;
         char tcbuf[AV_TIMECODE_STR_SIZE];
+        AVFrameSideData *tcside;
+        ret = ff_frame_new_side_data(h->avctx, out, AV_FRAME_DATA_S12M_TIMECODE,
+                                     sizeof(uint32_t)*4, &tcside);
+        if (ret < 0)
+            return ret;
+
+        if (tcside) {
+            tc_sd = (uint32_t*)tcside->data;
+            tc_sd[0] = h->sei.picture_timing.timecode_cnt;
 
-        AVFrameSideData *tcside = av_frame_new_side_data(out,
-                                                         AV_FRAME_DATA_S12M_TIMECODE,
-                                                         sizeof(uint32_t)*4);
-        if (!tcside)
-            return AVERROR(ENOMEM);
-
-        tc_sd = (uint32_t*)tcside->data;
-        tc_sd[0] = h->sei.picture_timing.timecode_cnt;
-
-        for (int i = 0; i < tc_sd[0]; i++) {
-            int drop = h->sei.picture_timing.timecode[i].dropframe;
-            int   hh = h->sei.picture_timing.timecode[i].hours;
-            int   mm = h->sei.picture_timing.timecode[i].minutes;
-            int   ss = h->sei.picture_timing.timecode[i].seconds;
-            int   ff = h->sei.picture_timing.timecode[i].frame;
-
-            tc_sd[i + 1] = av_timecode_get_smpte(h->avctx->framerate, drop, hh, mm, ss, ff);
-            av_timecode_make_smpte_tc_string2(tcbuf, h->avctx->framerate, tc_sd[i + 1], 0, 0);
-            av_dict_set(&out->metadata, "timecode", tcbuf, 0);
+            for (int i = 0; i < tc_sd[0]; i++) {
+                int drop = h->sei.picture_timing.timecode[i].dropframe;
+                int   hh = h->sei.picture_timing.timecode[i].hours;
+                int   mm = h->sei.picture_timing.timecode[i].minutes;
+                int   ss = h->sei.picture_timing.timecode[i].seconds;
+                int   ff = h->sei.picture_timing.timecode[i].frame;
+
+                tc_sd[i + 1] = av_timecode_get_smpte(h->avctx->framerate, drop, hh, mm, ss, ff);
+                av_timecode_make_smpte_tc_string2(tcbuf, h->avctx->framerate, tc_sd[i + 1], 0, 0);
+                av_dict_set(&out->metadata, "timecode", tcbuf, 0);
+            }
         }
         h->sei.picture_timing.timecode_cnt = 0;
     }