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• avcodec/vqcdec : Check init_get_bits8() for failure

  18 mai 2024, par Michael Niedermayer

  avcodec/vqcdec : Check init_get_bits8() for failure
  Fixes : CID1516090 Unchecked return value
  Sponsored-by : Sovereign Tech Fund
  
  Reviewed-by : Peter Ross <pross@xvid.org>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/vqcdec.c

• avcodec/mpegvideo_enc : Fix potential overflow in RD

  11 mai 2024, par Michael Niedermayer

  avcodec/mpegvideo_enc : Fix potential overflow in RD
  Fixes : CID1500285 Unintentional integer overflow
  Sponsored-by : Sovereign Tech Fund
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/mpegvideo_enc.c

• Why is image loading from ffmpeg using stdout slow ?

  23 octobre 2017, par Jirka Šáda

  I was just experimenting with FFMPEG, and wrote this testing piece of code, that is reading frames from FFMPEG and displaying them :

  public partial class MainWindow : Window
  
  {
  
      private WriteableBitmap wbm = new WriteableBitmap(1920, 1080, 96, 96, PixelFormats.Rgb24, null);
  
      private IntPtr backBuffer;
  
      private int totalFrames = 0;
  
      private bool drawing = false;
  
  
  
      public MainWindow()
  
      {
  
          InitializeComponent();
  
  
  
          backBuffer = wbm.BackBuffer;
  
  
  
          Thread t = new Thread(new ThreadStart(RunFFMPEG));
  
          t.Start();
  
  
  
          Thread measurer = new Thread(new ThreadStart(Measure));
  
          measurer.Start();
  
      }
  
  
  
      private void Measure()
  
      {
  
          while(true)
  
          {
  
              Thread.Sleep(1000);
  
              Console.Title = "FPS: " + totalFrames;
  
              totalFrames = 0;
  
          }
  
      }
  
  
  
      private void UpdateBitmap()
  
      {
  
          drawing = true;
  
  
  
          wbm.Lock();
  
          wbm.AddDirtyRect(new Int32Rect(0, 0, 1920, 1080));
  
          wbm.Unlock();
  
  
  
          mainImage.Source = wbm;
  
  
  
          drawing = false;
  
      }
  
  
  
      private void RunFFMPEG()
  
      {
  
          totalFrames = 0;
  
  
  
          int length = 1920 * 1080 * 3;
  
  
  
          // start FFMPEG process and pipe standart output
  
          ProcessStartInfo info = new ProcessStartInfo("ffmpeg.exe", "-f dshow -vcodec mjpeg -video_size 1920x1080 -framerate 30 -i video=\"A4 TECH HD PC Camera\" -y -pix_fmt rgb24 -f rawvideo -framerate 30 pipe:1");
  
          info.WindowStyle = ProcessWindowStyle.Hidden;
  
          info.UseShellExecute = false;
  
          info.CreateNoWindow = true;
  
          info.RedirectStandardOutput = true;
  
  
  
          Process p = new Process();
  
          p.StartInfo = info;
  
          p.Start();
  
  
  
          while (true) // read frames from standart output
  
          {
  
  
  
              byte[] data = new byte[length];
  
  
  
              for (int i = 0; i < length; i++) // read byte by byte, if we call normal Read(), the returned array is always mostly empty
  
                  data[i] = (byte)p.StandardOutput.BaseStream.ReadByte();
  
  
  
              if (!drawing)
  
              {
  
                  Marshal.Copy(data, 0, backBuffer, length);
  
                  Dispatcher.Invoke(() => UpdateBitmap()); // we are not in UI thread
  
              }
  
  
  
              totalFrames++;
  
          }
  
      }   
  
  }

  The problem is, although I get around 17-20 FPS reported, the Image is redrawing very very slowly (once or twice per a second) and even though the mainImage.Source =... line takes always similar amount of time, the speed at which the Image visually updates itself is getting progressively slower. What could be the cause ?? Thanks for any tips

  PS : I know the code is ugly and not following MVVM pattern, but it’s just and only for testing, please don’t hate me :-)

  Edit : The problem is not speed at which I’m reading from stdout, that’s fine (20 FPS), the problem is, that WPF Image is visually updating very slowly