avformat/vividas use avpriv_set_pts_info()

Fixes: assertion failure
Fixes: 26482/clusterfuzz-testcase-minimized-ffmpeg_dem_VIVIDAS_fuzzer-4905102324006912
Fixes: 26491/clusterfuzz-testcase-minimized-ffmpeg_dem_VIVIDAS_fuzzer-6002953141616640

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/vividas.c

@@ -319,6 +319,8 @@ static int track_header(VividasDemuxContext *viv, AVFormatContext *s,  uint8_t *
 
     for (i = 0; i < num_video; i++) {
         AVStream *st = avformat_new_stream(s, NULL);
+        int num, den;
+
         if (!st)
             return AVERROR(ENOMEM);
 
@@ -331,8 +333,9 @@ static int track_header(VividasDemuxContext *viv, AVFormatContext *s,  uint8_t *
         off += ffio_read_varlen(pb);
         avio_r8(pb); // '3'
         avio_r8(pb); // val_7
-        st->time_base.num = avio_rl32(pb); // frame_time
-        st->time_base.den = avio_rl32(pb); // time_base
+        num = avio_rl32(pb); // frame_time
+        den = avio_rl32(pb); // time_base
+        avpriv_set_pts_info(st, 64, num, den);
         st->nb_frames = avio_rl32(pb); // n frames
         st->codecpar->width = avio_rl16(pb); // width
         st->codecpar->height = avio_rl16(pb); // height