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• Picturebox from AForge FFMPEG empty - C#/WinForms

  1er août 2017, par Jake Delson

  I’ve done a ton of research and looked at a lot of questions here but can’t seem to find anything to help me. I should preface I’m very new to C#, Windows Forms, and SO ! I’m a 1st year CompSci student coming from C++ experimenting with my own projects for the summer. I’m trying to display a series of bitmaps from a .avi using the AForge.Video.FFMPEG video file reader.

  It seems to be finding the file, getting its’ data (console prints dimensions, framerate, and codec) and creating the picturebox, but the picturebox comes up blank/empty. I get the bitmap from the frames of a .avi :

  From AForge example code here

  Then I’m trying to display it with a picture box :

  From MS example code here as well

  And here’s my code. Essentially a combination of the two :

      public class Simple : Form
  
  {
  
      Bitmap videoFrame;
  
  
  
      public Simple()
  
      {
  
          try
  
          {
  
              // create instance of video reader
  
              VideoFileReader reader = new VideoFileReader();
  
              // open video file
  
              reader.Open(@"C:\Users\User\Desktop\ScanTest3.AVI");
  
              // check some of its attributes
  
              Console.WriteLine("width:  " + reader.Width);
  
              Console.WriteLine("height: " + reader.Height);
  
              Console.WriteLine("fps:    " + reader.FrameRate);
  
              Console.WriteLine("codec:  " + reader.CodecName);
  
  
  
              PictureBox pictureBox1 = new PictureBox();
  
  
  
              // read 100 video frames out of it
  
              for (int i = 0; i < 100; i++)
  
              {
  
                  videoFrame = reader.ReadVideoFrame();
  
  
  
                  pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
  
                  pictureBox1.ClientSize = new Size(videoFrame.Width, videoFrame.Height);
  
                  pictureBox1.Image = videoFrame;
  
  
  
                  // dispose the frame when it is no longer required
  
                  videoFrame.Dispose();
  
              }
  
  
  
              reader.Close();
  
          }
  
  
  
          catch
  
          {
  
              Console.WriteLine("Nope");
  
          }
  
  
  
      }
  
  }
  
  
  
  class MApplication
  
  {
  
      public static void Main()
  
      {
  
          Application.Run(new Simple());
  
      }
  
  }

  So that’s it pretty much. Just a blank picture box coming up, when it should have the first frame of the video, even though no exception caught (though I’m pretty confident I’m using the try/catch very poorly), and the console printing the correct data for the file :

  width:  720
  
  height: 480
  
  fps:    29
  
  codec:  dvvideo
  
  [swscaler @ 05E10060] Warning: data is not aligned! This can lead to a speedloss

  Though if anyone could tell me what that warning means, that would be great as well, but I’m mainly just lost as to why there’s no picture printing to the screen.

  Thanks !

• avutil/mathematics : speed up av_gcd by using Stein’s binary GCD algorithm

  11 octobre 2015, par Ganesh Ajjanagadde

  avutil/mathematics : speed up av_gcd by using Stein’s binary GCD algorithm
  This uses Stein’s binary GCD algorithm :
  
  https://en.wikipedia.org/wiki/Binary_GCD_algorithm
  
  to get a roughly 4x speedup over Euclidean GCD on standard architectures
  
  with a compiler intrinsic for ctzll, and a roughly 2x speedup otherwise.
  
  At the moment, the compiler intrinsic is used on GCC and Clang due to
  
  its easy availability.
  Quick note regarding overflow : yes, subtractions on int64_t can, but the
  
  llabs takes care of that. The llabs is also guaranteed to be safe, with
  
  no annoying INT64_MIN business since INT64_MIN being a power of 2, is
  
  shifted down before being sent to llabs.
  The binary GCD needs ff_ctzll, an extension of ff_ctz for long long (int64_t). On
  
  GCC, this is provided by a built-in. On Microsoft, there is a
  
  BitScanForward64 analog of BitScanForward that should work ; but I can’t confirm.
  
  Apparently it is not available on 32 bit builds ; so this may or may not
  
  work correctly. On Intel, per the documentation there is only an
  
  intrinsic for _bit_scan_forward and people have posted on forums
  
  regarding _bit_scan_forward64, but often their documentation is
  
  woeful. Again, I don’t have it, so I can’t test.
  As such, to be safe, for now only the GCC/Clang intrinsic is added, the rest
  
  use a compiled version based on the De-Bruijn method of Leiserson et al :
  
  http://supertech.csail.mit.edu/papers/debruijn.pdf.
  Tested with FATE, sample benchmark (x86-64, GCC 5.2.0, Haswell)
  
  with a START_TIMER and STOP_TIMER in libavutil/rationsl.c, followed by a
  
  make fate.
  aac-am00_88.err :
  
  builtin :
  
  714 decicycles in av_gcd,    4095 runs,      1 skips
  de-bruijn :
  
  1440 decicycles in av_gcd,    4096 runs,      0 skips
  previous :
  
  2889 decicycles in av_gcd,    4096 runs,      0 skips
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavutil/intmath.h
  • [DH] libavutil/mathematics.c

• avformat/mov : Only read the primary item for AVIF

  28 juin 2022, par Vignesh Venkatasubramanian

  avformat/mov : Only read the primary item for AVIF
  Update the still AVIF parser to only read the primary item. With this
  
  patch, AVIF still images with exif/icc/alpha channel will no longer
  
  fail to parse.
  For example, this patch enables parsing of files in :
  
  https://github.com/AOMediaCodec/av1-avif/tree/master/testFiles/Microsoft
  Adding two fate tests :
  
  1) demuxing of still image with 1 item - this test will pass regardless
  
     of this patch.
  
  2) demuxing of still image with 2 items - this test will fail without
  
     this patch and will pass with patch applied.
  Partially fixes trac ticket #7621
  Signed-off-by : Vignesh Venkatasubramanian <vigneshv@google.com>
  
  Signed-off-by : James Zern <jzern@google.com>
  

  • [DH] libavformat/isom.h
  • [DH] libavformat/mov.c
  • [DH] tests/fate/mov.mak
  • [DH] tests/ref/fate/mov-avif-demux-still-image-1-item
  • [DH] tests/ref/fate/mov-avif-demux-still-image-multiple-items