static int mov_write_tfxd_tag(AVIOContext *pb, MOVTrack *track)
{
    int64_t pos = avio_tell(pb);
    static const uint8_t uuid[] = {
        0x6d, 0x1d, 0x9b, 0x05, 0x42, 0xd5, 0x44, 0xe6,
        0x80, 0xe2, 0x14, 0x1d, 0xaf, 0xf7, 0x57, 0xb2
    };

    avio_wb32(pb, 0); /* size placeholder */
    ffio_wfourcc(pb, "uuid");
    avio_write(pb, uuid, sizeof(uuid));
    avio_w8(pb, 1);
    avio_wb24(pb, 0);
    avio_wb64(pb, track->start_dts + track->frag_start +
                  track->cluster[0].cts);
    avio_wb64(pb, track->end_pts -
                  (track->cluster[0].dts + track->cluster[0].cts));

    return update_size(pb, pos);
}

The product divides a value by zero.