message: videoio(mjpeg): disable parallel encoder
diff: @@ -1167,6 +1167,8 @@ public:
  fdct_qtab(_fdct_qtab),
  cat_table(_cat_table)
  {
  +#if 0 // disable parallel processing due to buffer overrun bug: https://github.com/opencv/opencv/issues/19634
  +
  //empirically found value. if number of pixels is less than that value there is no sense to parallelize it.
  const int min_pixels_count = 96*96;
  @@ -1176,6 +1178,7 @@ public:
  {
  if(height*width > min_pixels_count)
  {
  + const int default_stripes_count = 4;
  stripes_count = default_stripes_count;
  }
  }
  @@ -1191,6 +1194,12 @@ public:
  stripes_count = std::min(stripes_count, max_stripes);
  +#else
  + if (nstripes > 1)
  + CV_LOG_ONCE_WARNING(NULL, "VIDEOIO/MJPEG: parallel processing is disabled: https://github.com/opencv/opencv/issues/19634");
  + stripes_count = 1;
  +#endif
  +
  m_buffer_list.allocate_buffers(stripes_count, (height*width*2)/stripes_count);
  }
  @@ -1370,11 +1379,8 @@ private:
  const short (&fdct_qtab)[2][64];
  const uchar* cat_table;
  int stripes_count;
  - static const int default_stripes_count;
  };
  -const int MjpegEncoder::default_stripes_count = 4;
  -
  void MotionJpegWriter::writeFrameData( const uchar* data, int step, int colorspace, int input_channels )
  {
  //double total_cvt = 0, total_dct = 0;
  