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• Dreamcast Operating Systems

  16 septembre 2010, par Multimedia Mike — Sega Dreamcast

  The Sega Dreamcast was famously emblazoned with a logo proudly announcing that it was compatible with Windows CE :

  
  
  

  It’s quite confusing. The console certainly doesn’t boot into some version of Windows to launch games. Apparently, there was a special version of CE developed for the DC and game companies had the option to leverage it. I do recall that some game startup screens would similarly advertise Windows CE.

  Once the homebrew community got ahold of the device, the sky was the limit. I think NetBSD was the first alternative OS to support the Dreamcast. Meanwhile, I have recollections of DC Linux and LinuxDC projects along with more generic Linux-SH and SH-Linux projects.

  
  
  

  DC Evolution hosts a disc image available for download with an unofficial version of DC Linux, assembled by one Adrian O’Grady. I figured out how to burn the disc (burning DC discs is a blog post of its own) and got it working in the console.

  It’s possible to log in directly via the physical keyboard or through a serial terminal provided that you have a coder’s cable. That reminds me– my local Fry’s had a selection of USB-to-serial cables. I think this is another area that is sufficiently commoditized that just about any cable ought to work with Linux out of the box. Or maybe I’m just extrapolating from the experience of having the cheapest cable in the selection (made by io connect) plug and play with Linux.

  
  
  

  Look ! No messy converter box in the middle as in the Belkin case. The reason I went with this cable is that the packaging claimed it was capable of up to 500 Kbits/sec. Most of the cables advertised a max of 115200 bps. I distinctly recall being able to use the DC coder’s cable at 230400 bps a long time ago. Alas, 115200 seems to be the speed limit, even with this new USB cable.

  Anyway, the distribution is based on a 2.4.5 kernel circa 2001. I tried to make PPP work over the serial cable but the kernel doesn’t have support. If you’re interested, here is some basic information about the machine from Linux’s perspective, gleaned from some simple commands. This helps remind us of a simpler time when Linux was able to run comfortably on a computer with 16 MB of RAM.

  Debian GNU/Linux testing/unstable dreamcast ttsc/1
  dreamcast login : root
  
  Linux dreamcast 2.4.5 #27 Thu May 31 07:06:51 JST 2001 sh4 unknown
  Most of the programs included with the Debian GNU/Linux system are
  
  freely redistributable ; the exact distribution terms for each program
  
  are described in the individual files in /usr/share/doc/*/copyright
  Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
  
  permitted by applicable law.
  dreamcast : # uname -a
  
  Linux dreamcast 2.4.5 #27 Thu May 31 07:06:51 JST 2001 sh4 unknown
  dreamcast : # cat /proc/cpuinfo 
  
  cpu family : SH-4
  
  cache size : 8K-byte/16K-byte
  
  bogomips : 199.47
  Machine : dreamcast
  
  CPU clock : 200.00MHz
  
  Bus clock : 100.00MHz
  
  Peripheral module clock : 50.00MHz
  dreamcast : # top -b
   09:14:54 up 14 min,  1 user,  load average : 0.04, 0.03, 0.03
  
  15 processes : 14 sleeping, 1 running, 0 zombie, 0 stopped
  
  CPU states :   1.1% user,   5.8% system,   0.0% nice,  93.1% idle
  
  Mem :     14616K total,    11316K used,     3300K free,     2296K buffers
  
  Swap :        0K total,        0K used,        0K free,     5556K cached
    PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME COMMAND
  
    219 root      18   0  1072 1068   868 R     5.6  7.3   0:00 top
  
      1 root       9   0   596  596   512 S     0.0  4.0   0:01 init
  
      2 root       9   0     0    0     0 SW    0.0  0.0   0:00 keventd
  
      3 root       9   0     0    0     0 SW    0.0  0.0   0:00 kswapd
  
      4 root       9   0     0    0     0 SW    0.0  0.0   0:00 kreclaimd
  
      5 root       9   0     0    0     0 SW    0.0  0.0   0:00 bdflush
  
      6 root       9   0     0    0     0 SW    0.0  0.0   0:00 kupdated
  
      7 root       9   0     0    0     0 SW    0.0  0.0   0:00 kmapled
  
     39 root       9   0   900  900   668 S     0.0  6.1   0:00 devfsd
  
     91 root       8   0   652  652   556 S     0.0  4.4   0:00 pump
  
     96 daemon     9   0   524  524   420 S     0.0  3.5   0:00 portmap
  
    149 root       9   0   944  944   796 S     0.0  6.4   0:00 syslogd
  
    152 root       9   0   604  604   456 S     0.0  4.1   0:00 klogd
  
    187 root       9   0   540  540   456 S     0.0  3.6   0:00 getty
  
    201 root       9   0  1380 1376  1112 S     0.0  9.4   0:01 bash
  

  Note that at this point I had shutdown both gpm and inetd. The rest of the processes, save for bash, are default. The above stats only report about 14 MB of RAM ; where are the other 2 MB ?

  dreamcast : # df -h
  Filesystem            Size  Used Avail Use% Mounted on
  /dev/rd/1             2.0M  560k  1.4M  28% /
  

• Memory Leak in c++/cli application

  10 décembre 2013, par Ankush

  I am passing bitmap from my c# app to c++/cli dll that add it to video.
  The problem is program slowly leaking memory. I tried _CrtDumpMemoryLeaks() shows me leak of bitmap & another 40 byte leak but i am disposing bitmap.
  Can anyone see memory leak, Here is code..

  Flow :

  1) Capture screenshot by takescreenshot()

  2) pass it to c++/cli function

  3) dispose bitmap

  lines from my c# app

  Bitmap snap = takescreeshot();
  
  vencoder.AddBitmap(snap);
  
  snap.Dispose();
  
  vencoder.printleak();
  
  
  
  private static Bitmap takescreeshot()
  
      {
  
          System.Drawing.Bitmap bitmap = null;
  
          System.Drawing.Graphics graphics = null;
  
  
  
          bitmap = new Bitmap
  
          (
  
              System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width,
  
              System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height,
  
              System.Drawing.Imaging.PixelFormat.Format24bppRgb
  
          );
  
  
  
          graphics = System.Drawing.Graphics.FromImage(bitmap);
  
  
  
          graphics.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, 0, 0, Screen.PrimaryScreen.Bounds.Size);
  
  
  
          //Write TimeSpamp
  
          Rectangle rect = new Rectangle(1166, 738, 200, 20);
  
          String datetime= System.String.Format("{0:dd:MM:yy  hh:mm:ss}",DateTime.Now);
  
          System.Drawing.Font sysfont = new System.Drawing.Font("Times New Roman", 14, FontStyle.Bold);
  
          graphics.DrawString(datetime, sysfont, Brushes.Red,rect);
  
          //
  
  
  
          Grayscale filter = new Grayscale(0.2125, 0.7154, 0.0721);
  
          Bitmap grayImage = filter.Apply(bitmap);
  
  
  
          //Dispose
  
          bitmap.Dispose();
  
          graphics.Dispose();
  
  
  
          return grayImage;
  
      }

  now in c++/cli dll

  bool VideoEncoder::AddBitmap(Bitmap^ bitmap)
  
      {
  
          BitmapData^ bitmapData = bitmap->LockBits( System::Drawing::Rectangle( 0, 0,bitmap->Width, bitmap->Height ),ImageLockMode::ReadOnly,PixelFormat::Format8bppIndexed);
  
          uint8_t* ptr = reinterpret_cast( static_cast( bitmapData->Scan0 ) );
  
          uint8_t* srcData[4] = { ptr, NULL, NULL, NULL };
  
          int srcLinesize[4] = { bitmapData->Stride, 0, 0, 0 };
  
  
  
          pCurrentPicture = CreateFFmpegPicture(pVideoStream->codec->pix_fmt, pVideoStream->codec->width, pVideoStream->codec->height);
  
  
  
          sws_scale(pImgConvertCtx, srcData, srcLinesize, 0, bitmap->Height, pCurrentPicture->data, pCurrentPicture->linesize );
  
  
  
          bitmap->UnlockBits( bitmapData );
  
  
  
          write_video_frame();
  
  
  
          bitmapData=nullptr;
  
          ptr=NULL;
  
  
  
          return true;
  
      }
  
  
  
  AVFrame * VideoEncoder::CreateFFmpegPicture(int pix_fmt, int nWidth, int nHeight)
  
      {
  
  
  
        AVFrame *picture     = NULL;
  
        uint8_t *picture_buf = NULL;
  
        int size;
  
  
  
        picture = avcodec_alloc_frame();
  
        if ( !picture)
  
        {
  
          printf("Cannot create frame\n");
  
          return NULL;
  
        }
  
  
  
        size = avpicture_get_size((AVPixelFormat)pix_fmt, nWidth, nHeight);
  
  
  
        picture_buf = (uint8_t *) av_malloc(size);
  
  
  
        if (!picture_buf) 
  
        {
  
          av_free(picture);
  
          printf("Cannot allocate buffer\n");
  
          return NULL;
  
        }
  
  
  
        avpicture_fill((AVPicture *)picture, picture_buf,
  
          (AVPixelFormat)pix_fmt, nWidth, nHeight);
  
  
  
        return picture;
  
      }
  
  
  
      void VideoEncoder::write_video_frame()
  
      {
  
          AVCodecContext* codecContext = pVideoStream->codec;
  
  
  
          int out_size, ret = 0;
  
  
  
          if ( pFormatContext->oformat->flags & AVFMT_RAWPICTURE )
  
          {
  
              printf( "raw picture must be written" );
  
          }
  
          else
  
          {
  
              out_size = avcodec_encode_video( codecContext, pVideoEncodeBuffer,nSizeVideoEncodeBuffer, pCurrentPicture );
  
  
  
              if ( out_size > 0 )
  
              {
  
                  AVPacket packet;
  
                  av_init_packet( &packet );
  
  
  
                  if ( codecContext->coded_frame->pts != AV_NOPTS_VALUE )
  
                  {
  
                      packet.pts = av_rescale_q( packet.pts, codecContext->time_base, pVideoStream->time_base );
  
                  }
  
  
  
                  if ( codecContext->coded_frame->pkt_dts != AV_NOPTS_VALUE )
  
                  {
  
                      packet.dts = av_rescale_q( packet.dts, codecContext->time_base, pVideoStream->time_base );
  
                  }
  
  
  
                  if ( codecContext->coded_frame->key_frame )
  
                  {
  
                      packet.flags |= AV_PKT_FLAG_KEY;
  
                  }
  
  
  
                  packet.stream_index = pVideoStream->index;
  
                  packet.data = pVideoEncodeBuffer;
  
                  packet.size = out_size;
  
  
  
                  ret = av_interleaved_write_frame( pFormatContext, &packet );
  
  
  
                  av_free_packet(&packet);
  
                  av_freep(pCurrentPicture);
  
              }
  
              else
  
              {
  
                  // image was buffered
  
              }
  
          }
  
  
  
          if ( ret != 0 )
  
          {
  
              throw gcnew Exception( "Error while writing video frame." );
  
          }
  
      }
  
  
  
  
  
      void VideoEncoder::printleak()
  
      {
  
          printf("No of leaks: %d",_CrtDumpMemoryLeaks());
  
          printf("\n");
  
      }

• How to extract jpeg/png images from RTSP stream without encoding the whole stream ?

  25 septembre 2020, par Rune Aspvik

  I am building a video system in Node.js based on IP cameras. They all output RTSP streams and MJPEG streams. However the Mjpeg is unreliable for web browser display snapshots and so I want to create my own snapshots. I'm using FFMPEG to record the RTSP stream so that's been my tool. So far I've tried two options :

  


  

  1. FFMPEG with two outputs :

  


  


  ffmpeg -i rtsp://.... -c copy output.ts -r 1/5 -s 640x360 -f image2 -update 1 -y snap.jpg

  


  This works really well, but it's using a lot of resources since even though I only need a low res image every 5 sec, it encodes the whole stream.

  


  

  2. Get the snapshot on demand using FFMPEG and the output.ts as input.

  


  


  ffmpeg -sseof -1 -i output.ts -frames:v 1 -f image2 pipe:1

  


  This also works really well, and doesn't require a lot of resources. However I believe it's not the most elegant solution.

  


  How can I use option 1, but without doing the resource demanding solution ?