mCodecContext->bit_rate = 5000000;
            mCodecContext->width = 640;
            mCodecContext->height = 360;
            mCodecContext->pix_fmt = PIX_FMT_YUV420P;
            mCodecContext->time_base =AVRational{1,31};
            mCodecContext->gop_size = 10;
            mCodecContext->max_b_frames = 1;
            int  ret= avcodec_open2(mCodecContext, mCodec, NULL);