public static extern AVError avformat_open_input(out IntPtr ps, string filename, AVInputFormat* fmt, AVDictionary* options);
public static extern AVError avformat_write_header(ref AVFormatContext pAVFormatContext, AVDictionary** options);
public static extern AVError avformat_find_stream_info(ref AVFormatContext pAVFormatContext, AVDictionary** options);