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• Matplotlib : Live animation works fine but displays a blank plot when being saved

  18 juillet 2017, par Loïc Poncin

  I made a little forest fire animation. My code is at the end of the question.

  Here is some information before I ask my question :

  • No tree : forest[i,j] = 0
  • A tree : forest[i,j] = 1
  • A tree on fire : forest[i,j] = 2

  Basically what happens is that constructforest creates a 2 dimensional array called forest of size n by m with a probability of tree occupancy called p. After that setonfire sets on fire the forest and while the forest can burn spreadfire spread the fire.

  When I run forestfire with the Python prompt or the IPython prompt I get a nice animation but when I go check the video file that I saved I only see a blank plot.

  I did some research, I found many questions about this issue but none of the advice I read was helpful :

  • matplotlib animation produces a blank
  • Matplotlib animation not working in IPython Notebook (blank plot)
  • Animation from matplotlib not working in spyder
  • Spyder Python Animation not working

  Can someone tell me what is going on please ?

  forestfire.py

  from random import random
  
  
  
  import numpy as np
  
  
  
  import matplotlib.pylab as plt
  
  import matplotlib.colors as mcolors
  
  import matplotlib.animation as animation
  
  
  
  
  
  def hazard(p):
  
      r=random()
  
      assert p>=0 and p<=1
  
      return r <= p
  
  
  
  
  
  def constructforest(n,m,p):
  
      forest = np.zeros((n,n))
  
      for i in xrange(n):
  
          for j in xrange(m):
  
              if hazard(p):
  
                  forest[i,j] = 1
  
      return forest
  
  
  
  
  
  def setfire(forest,i,j):
  
      forest[i,j] = 2
  
      return forest
  
  
  
  
  
  def spreadfire(forest):    
  
  
  
      n,m=forest.shape
  
      c = np.copy(forest)
  
  
  
      for i in xrange(n):
  
          for j in xrange(m):
  
  
  
              if c[i,j] == 1:
  
  
  
                  Y, X = xrange(max(0,i-1),min(n,i+2)), xrange(max(0,j-1),min(m,j+2))
  
  
  
                  for y in Y:
  
                      for x in X:
  
  
  
                          if c[y,x] == 2:
  
                              forest[i,j] = 2                        
  
      return forest
  
  
  
  
  
  def canburn(forest):    
  
  
  
      n,m=forest.shape
  
      c = np.copy(forest)
  
  
  
      for i in xrange(n):
  
          for j in xrange(m):
  
  
  
              if c[i,j] == 1:
  
  
  
                  Y, X = xrange(max(0,i-1),min(n,i+2)), xrange(max(0,j-1),min(m,j+2))
  
  
  
                  for y in Y:
  
                      for x in X:
  
  
  
                          if c[y,x] == 2:
  
                              return True                      
  
      return False
  
  
  
  
  
  def forestfire(forest):
  
  
  
      fig, ax = plt.subplots()
  
  
  
      movie = []    
  
  
  
      # Colormap
  
      red, green, blue = [(1,0,0,1)], [(0,1,0,1)], [(0,0,1,1)]   
  
  
  
      colors = np.vstack((blue, green, red))
  
      mycmap = mcolors.LinearSegmentedColormap.from_list('my_colormap', colors)
  
  
  
      # Initialization
  
      k = 0
  
  
  
      forest = spreadfire(forest)
  
  
  
      im = plt.imshow(forest, animated=True, cmap = mycmap, interpolation="none", origin='lower')
  
      movie.append([im])
  
  
  
      # Fire propagation
  
      while canburn(forest):
  
          k += 1
  
          print k
  
  
  
          forest = spreadfire(forest)
  
  
  
          im = plt.imshow(forest, animated=True, cmap = mycmap, interpolation="none", origin='lower')
  
          movie.append([im])
  
  
  
      return animation.ArtistAnimation(fig, movie, blit=True, repeat_delay=100)
  
  
  
  
  
  
  
  ani = forestfire(setfire(constructforest(101,101,0.4),50,50))
  
  
  
  ani.save("forestfire_test.mp4", writer = 'ffmpeg', fps=5, dpi=500)

  EDIT

  As requested by @Y.Luo by @ImportanceOfBeingErnest in the comments I downgraded matplotlib to 2.0.0 and I changed the framerate of the animation but forestfire_test.mp4 still displays a blank plot.

  Here are my settings :
  
  

• ffmpeg progess bar not giving percent

  3 décembre 2014, par Brett

  Hi im trying to create a java program that shows the percent of a ffmpeg command , Im not sure where i am going wrong.

  Its keeps giving me these results

  run :
  Total duration : 857.44 seconds.
  Progress : 0.85%
  Progress : 1.76%
  Progress : 2.79%
  Progress : 3.93%
  Progress : 5.04%
  Progress : 6.21%
  Progress : 6000.27%
  Progress : 6001.29%
  Progress : 6002.46%
  Progress : 6003.58%
  Progress : 6004.59%
  Progress : 6005.70%
  Progress : 6006.77%
  Progress : 12000.86%
  Progress : 12001.97%
  Progress : 12002.97%
  Progress : 12004.03%
  Progress : 12005.15%
  Progress : 12006.27%
  Progress : 18000.34%
  Progress : 18001.46%
  Progress : 18002.29%
  Progress : 18003.41%
  Progress : 18004.41%
  Progress : 18005.50%
  Progress : 18006.55%
  Progress : 24000.52%
  Progress : 24001.62%
  Progress : 24002.74%
  Progress : 24003.69%
  Progress : 24004.76%
  Progress : 24005.88%
  Progress : 24006.94%
  Progress : 30001.01%
  Progress : 30002.16%
  Progress : 30003.24%
  Progress : 30004.25%
  Progress : 30005.37%
  Progress : 30006.44%
  Progress : 36000.56%
  Progress : 36001.60%
  Progress : 36002.69%
  Progress : 36003.73%
  Progress : 36004.81%
  Progress : 36005.93%
  Progress : 42000.05%
  Progress : 42001.18%
  Progress : 42002.30%
  Progress : 42003.41%
  Progress : 42004.50%
  Progress : 42005.60%
  Progress : 42006.72%
  Progress : 48000.84%
  Progress : 48001.96%
  Progress : 48003.08%
  Progress : 48004.18%
  Progress : 48005.09%
  Progress : 48006.16%
  Progress : 54000.22%
  Progress : 54001.15%
  Progress : 54002.20%
  Progress : 54003.30%
  Progress : 54004.42%
  Progress : 54005.49%
  Progress : 54006.38%
  Progress : 60000.45%
  Progress : 60001.57%
  Progress : 60002.55%
  Progress : 60003.64%
  Progress : 60004.66%
  Progress : 60005.62%
  Progress : 60006.72%
  Progress : 66000.67%
  Progress : 66001.73%
  Progress : 66002.75%
  Progress : 66003.61%
  Progress : 66004.71%
  Progress : 66005.82%
  Progress : 66006.81%
  Progress : 72000.67%
  Progress : 72001.73%
  Progress : 72002.80%
  Progress : 72003.87%
  Progress : 72004.81%
  Progress : 72005.71%
  Progress : 72006.69%
  Progress : 78000.73%
  Progress : 78001.82%
  Progress : 78002.91%
  Progress : 78003.91%
  Progress : 78004.98%
  Progress : 78005.88%
  Progress : 78006.49%
  Progress : 84000.37%
  Progress : 84001.12%
  Progress : 84002.04%
  BUILD SUCCESSFUL (total time : 49 seconds)

  But the file is created , i don’t know why im getting 0.00% any help would be awsome
  ..
  It also complains some imports a not being used here are the imports.

  here is my code

  import java.io.IOException;
  
  import java.util.Scanner;
  
  import static java.util.logging.Level.parse;
  
  import java.util.regex.Pattern;
  
  import javafx.util.Duration;
  
  import static javax.management.Query.lt;
  
  /**
  
   *
  
   * @author brett
  
   */
  
  
  
  public class MashMeUp {
  
  
  
      public static void main(String[] args) throws IOException {
  
          ProcessBuilder pb = new ProcessBuilder("ffmpeg", "-i", "C:\\Users\\brett\\Documents\\Telegraph_Road.mp4", "C:\\Users\\brett\\Documents\\out.mp4");
  
  
  
          // ProcessBuilder pb = new ProcessBuilder(args);  
  
          final Process p = pb.start();
  
  
  
      // create a new thread to get progress from ffmpeg command , override  
  
          // it's run method, and start it!  
  
          new Thread() {
  
              public void run() {
  
  
  
                  Scanner sc = new Scanner(p.getErrorStream());
  
  
  
                  // Find duration  
  
                  Pattern durPattern = Pattern.compile("(?<=Duration: )[^,]*");
  
                  String dur = sc.findWithinHorizon(durPattern, 0);
  
                  if (dur == null) {
  
                      throw new RuntimeException("Could not parse duration.");
  
                  }
  
                  String[] hms = dur.split(":");
  
                  double totalSecs = Integer.parseInt(hms[0]) * 3600
  
                          + Integer.parseInt(hms[1]) * 60
  
                          + Double.parseDouble(hms[2]);
  
                  System.out.println("Total duration: " + totalSecs + " seconds.");
  
  
  
                  // Find time as long as possible.  
  
                  Pattern timePattern = Pattern.compile("(?<=time=)[\\d:.]*");
  
                  // TODO make regex that works with ffmpeg static build  
  
                  String match;
  
                  String[] matchSplit;
  
  while (null != (match = sc.findWithinHorizon(timePattern, 0))) {
  
      matchSplit = match.split(":");
  
      double progress = Double.parseDouble(matchSplit[2]) / totalSecs +  Integer.parseInt(matchSplit[0]) * 3600 + Integer.parseInt(matchSplit[1]) * 60;
  
                      System.out.printf("Progress: %.2f%%%n", progress * 100);
  
                  }
  
              }
  
          }.start();
  
      }
  
  }

• ffmpeg : how to extract 1st video, english audio and french subtitle from video file in one command line ?

  15 mai 2020, par Sxilderik

  I have read many posts related to extracting streams per language with ffmpeg, but it seems that the -map 0:m:language:xxx is global, and goes for all streams.

  



  Let’s say I have a video file that contains hopefully one english audio stream and some french subtitle streams, among possibly many other streams. I want to get a smaller file with the first video track, the (first) english audio stream and all the french subtitle streams.

  



  If I run

  



  ffmpeg -i "$file" -map 0:v:0 -vcodec copy -map 0:m:language:eng -acodec copy -map 0:m:language:fre -scodec copy -f matroska "${file%.*}.mkv_out"


  



  I get in file.mkv_out all audio and subtitle tracks which are either french or english.

  



  Is there a way to achieve this, without having any prior knowledge of track numbers in the original file ?

  



  Thanks.