static int mov_metadata_track_or_disc_number(MOVContext *c, AVIOContext *pb,
                                             unsigned len, const char *key)
{
    char buf[16];

    short current, total = 0;
    avio_rb16(pb); // unknown
    current = avio_rb16(pb);
    if (len >= 6)
        total = avio_rb16(pb);
    if (!total)
        snprintf(buf, sizeof(buf), "%d", current);
    else
        snprintf(buf, sizeof(buf), "%d/%d", current, total);
    c->fc->event_flags |= AVFMT_EVENT_FLAG_METADATA_UPDATED;
    av_dict_set(&c->fc->metadata, key, buf, 0);

    return 0;
}