Recherche avancée

Sur d’autres sites (10990)

• how to use FFmpeg Multiple outputs using Named Pipes and use all in one command

  28 mars 2016, par user2542111

  I am working with FFmpeg and I want to do the following with named pipes :

  1. I have source video (video.mp4) and I want to convert it to 2 outputs in one command. this is accomplish with normal file system writing files. but to save disk I/O I want to use named pipes.

  I can’t succeed to do it with named pipes and make them get the data as multiple ffmpeg output. An example :

  ffmpeg -y -i video.mp4 -t 1 -an video_part1.mov -ss 1 -an video_part2.mov

  2. compose the 2 files to one. again, done with the 2 file system written on disk, but I want to do it from the named pipes concatenated to #1 above.

  ffmpeg -y -i video_part1.mov -i video_part2.mov —ffmpeg params— video_final.mov

  Any idea how to do it and do so in single command in-memory using pipes ?

• Redirect ffmpeg stdout to memorystream and convert it to image c#

  2 février 2016, par Zed Machine

  I want to get an image from ffmpeg stdout without saving it to disk.

  here is the code :

       public void GetFrame(string video, long millisectoseek)
  
      {
  
          panel1.BackgroundImage = null;
  
          this.Update();
  
  
  
          Process process = new Process();
  
  
  
          long seconds = millisectoseek / 1000;
  
          long millisec = millisectoseek % 1000;
  
  
  
          var cmd = String.Format(" -ss {0}.{1} -i \"{2}\" -vframes 1 -an -f image2pipe pipe:1", seconds, millisec.ToString("000"), video);
  
  
  
          process.StartInfo.RedirectStandardOutput = true;
  
          process.StartInfo.UseShellExecute = false;
  
          process.StartInfo.CreateNoWindow = true;
  
          process.StartInfo.FileName = "\"" + Application.StartupPath + "\\ffmpeg.exe\"";
  
          process.StartInfo.Arguments = cmd;
  
  
  
          process.Start();
  
          process.WaitForExit(100);
  
  
  
          try
  
          {
  
             Bitmap myimg = (Bitmap)Image.FromStream(process.StandardOutput.BaseStream);
  
  
  
              panel1.BackgroundImage = myimg;
  
  
  
              this.Update();
  
          }
  
          catch (Exception ex) {
  
              MessageBox.Show(ex.Message);
  
          }
  
      }

  The problem is that I get an ArgumentException (Parameters is not valid.) in Image.FromStream().. what is the problem ?
  Seems that the process stdout stream is empty, or a least it looks like from the debugging. I tried using CopyToAsync with another declared memory stream just before process.WaitForExit() ; but it gave me the same exception every time.

  If I use the console with the same command line and I redirect all stdout to a file (1> image.png) the image is readable... so I cannot understand why it does not work properly.

  Thanks in advance.

• Matplotlib animation is not saved correctly

  21 décembre 2015, par Spiros

  I produced an animation of a contour field with pyplot and would like to save it as movie file. Unfortunately, when I save it I get a file of the right format and I can open it with, say, VLC, but it contains just one or two frames.

  This a simplified version of the code I’m using :

  import numpy as np
  
  import matplotlib.pyplot as plt
  
  from matplotlib.animation import FuncAnimation
  
  
  
  # Initialize figure and axes
  
  fig = plt.figure()
  
  ax = fig.add_subplot(111)
  
  
  
  # Initialize mesh
  
  x = np.r_[-5:5:100j]
  
  X, Y = np.meshgrid(x, x)
  
  
  
  # Computes the data and yields them
  
  def data_generator(X, Y, dt):
  
      for t in np.r_[:10:dt]:
  
          yield t, np.tanh(Y*(2+t)) + np.sqrt(np.abs(X))
  
  
  
  # Plots the given solution on the given axes
  
  def plotter(data, ax, X, Y):
  
      ax.clear()
  
      t, field = data
  
      C = ax.contour(X, Y, field)
  
      ax.set_title('Time: {0:.1f}'.format(t))
  
      return C
  
  
  
  # Animation object
  
  anim = FuncAnimation(fig, plotter, frames=data_generator(X, Y, 0.1),
  
                       interval=100, repeat=False, fargs=(ax,X,Y))
  
  anim.save('animation.mp4')
  
  plt.show()

  I’m using python-3.5.0 on Arch linux, with matplotlib-1.5.0. I have ffmpeg-2.8.2 installed. I tried with different formats (e.g. avi, mkv, mov), and I also tried with explicitly selecting the ffmpeg and ffmpeg_file writers. The problem is not with my hard disk running out of space. What else should I check ?