FFmpeg sws_scale stretching frame and pixel conversion

void ConvertYUVFrameToBGRFrame(AVFrame* pYUVFrame, AVFrame* pBGRFrame)
{
 int nBGRFrameSize = av_image_get_buffer_size(AV_PIX_FMT_BGR24, pBGRFrame->width, pBGRFrame->height, 1);
 uint8_t* pszBGRBuffer = (uint8_t*)av_malloc(nBGRFrameSize);

 // The picture buffer pointers pszBGRBuffer pBGRFrame mount frame, it is necessary to manually remove
 av_image_fill_arrays (pBGRFrame-> data, pBGRFrame-> linesize, pszBGRBuffer, AV_PIX_FMT_BGR24, pBGRFrame-> width, pBGRFrame-> height, 1);

 struct SwsContext *pSwsCtx = sws_getContext(pYUVFrame->width, pYUVFrame->height, AV_PIX_FMT_YUVJ420P,
  pBGRFrame->width, pBGRFrame->height, AV_PIX_FMT_BGR24,
  SWS_BICUBIC, NULL, NULL, NULL);

 0 // Note need to fill srcSliceY, or the call fails
 sws_scale (pSwsCtx, pYUVFrame-> Data,
  pYUVFrame-> LINESIZE, 0, pYUVFrame-> height,
  pBGRFrame-> Data, pBGRFrame-> LINESIZE);
}

Examples of call

  AVFrame *pBGRFrame = NULL;
  pBGRFrame = av_frame_alloc();
  pBGRFrame->width = 1920 / 2;
  pBGRFrame->height = 1080 / 2;
  pBGRFrame->format = AV_PIX_FMT_BGR24;
  pVideoc->ConvertYUVFrameToBGRFrame(pFrame, pBGRFrame);

Description: The size of the image to zoom out, then converts the pixel format BGR24