mCodecContext= m_outputVideoStream->codec;
    mCodecContext->bit_rate = 500000;
    mCodecContext->width= m_size.width();
    mCodecContext->height=  m_size.height();
    mCodecContext->pix_fmt = AV_PIX_FMT_YUV420P;
    mCodecContext->time_base =AVRational{1,31};
    mCodecContext->gop_size= 12; /* emit one intra frame every twelve frames at most */
    //av_opt_set(mCodecContext->priv_data, "preset", "ultrafast", 0);
    av_dict_set(&m_dictionary, "preset","veryslow",0);
    if (m_FormatContext->oformat->flags & AVFMT_GLOBALHEADER)
        mCodecContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
      avcodec_open2(mCodecContext, mCodec, &m_dictionary);