h264.cpp

if(framefinished && nres > 0 && nres == sz)
  {
      if (is_first_successful_frame){
          is_first_successful_frame = false;

          img_conv_ctx = sws_getContext(m_pCodecCtx->width, m_pCodecCtx->height, m_pCodecCtx->pix_fmt,
                                          m_pCodecCtx->width, m_pCodecCtx->height, PIX_FMT_BGR24,
                                          SWS_BICUBIC, nullptr, nullptr, nullptr);

          auto bytes = avpicture_get_size(m_pCodecCtx->pix_fmt, m_pCodecCtx->width, m_pCodecCtx->height);
          auto buffer = reinterpret_cast<uint8_t *>(av_malloc(bytes * sizeof(uint8_t)));

          avpicture_fill(reinterpret_cast<AVPicture*>(temp_frame), buffer, PIX_FMT_BGR24, m_pCodecCtx->width, m_pCodecCtx->height);

          if (img_conv_ctx == nullptr){
              printf("Failed to create conversion context\n");
              throw 1;
          }

          cv::namedWindow( "frame", cv::WINDOW_AUTOSIZE );

      }

      nres = sws_scale(img_conv_ctx, m_pFrame->data, m_pFrame->linesize, 0, m_pCodecCtx->height, temp_frame->data, temp_frame->linesize);
      cv::Mat img(m_pCodecCtx->height, m_pCodecCtx->width, CV_8UC3, temp_frame->data[0], temp_frame->linesize[0]);

      cv::imshow("frame", img);
      cv::waitKey(15);
    }
  }