int ff_index_search_timestamp(const AVIndexEntry *entries, int nb_entries,
                              int64_t wanted_timestamp, int flags)
{
    int a, b, m;
    int64_t timestamp;

    a = - 1;
    b = nb_entries;

    //optimize appending index entries at the end
    if(b && entries[b-1].timestamp < wanted_timestamp)
        a= b-1;

    while (b - a > 1) {
        m = (a + b) >> 1;
        timestamp = entries[m].timestamp;
        if(timestamp >= wanted_timestamp)
            b = m;
        if(timestamp <= wanted_timestamp)
            a = m;
    }
    m= (flags & AVSEEK_FLAG_BACKWARD) ? a : b;

    if(!(flags & AVSEEK_FLAG_ANY)){
        while(m>=0 && m<nb_entries && !(entries[m].flags & AVINDEX_KEYFRAME)){
            m += (flags & AVSEEK_FLAG_BACKWARD) ? -1 : 1;
        }
    }

    if(m == nb_entries)
        return -1;
    return  m;
}