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• Difficulties saving an animation (matplotlib)

  14 avril 2020, par Ben C.

  I have a simple animation that I want to save. I followed the example : https://matplotlib.org/examples/animation/basic_example_writer.html

  



  But I get the following error : RuntimeError : Requested MovieWriter (ffmpeg) not available

  



  I installed ffmpeg and checked via ffmpeg -version that it really is installed and the path correct.

  



  Here is my code :

  



  import numpy as np
import matplotlib.animation as animation
import matplotlib.pyplot as plt

# Set up formatting for the movie files
Writer = animation.writers['ffmpeg']
writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)

fig, ax = plt.subplots()

x = np.random.uniform(0,1)
y = np.random.uniform(0,1)


scat = ax.scatter(x,y, color= 'blue')
circle = plt.Circle((x,y), radius=0.1, color='blue', fill=False, lw=0.5)
ax.add_patch(circle)

def init():
    scat = ax.scatter(x, y, color = 'blue')
    circle = plt.Circle((x,y), radius=0.1, color='blue', fill=False, lw=0.5)

def animate(i):
    random = np.random.uniform(0,1)
    if random < 0.5:
        scat.set_color('red')
        circle.set_edgecolor('blue')
    else:
        scat.set_color('blue')
        circle.set_edgecolor('red')
    return circle, scat,


ani = animation.FuncAnimation(fig, animate, init_func=init(), interval=1000, blit=True)
ani.save('test.mp4', writer=writer)


  



  None of the proposed solution in RuntimeError : No MovieWriters available in Matplotlib animation worked for me. Any ideas ?

  



  Edit : I am using Windows (10)

  


• Saving scatterplot animations with matplotlib produces blank video file

  1er avril 2013, par user2175850

  I am having a very similar problem to this question

  but the suggested solution doesn't work for me.

  I have set up an animated scatter plot using the matplotlib animation module. This works fine when it is displaying live. I would like to save it to an avi file or something similar. The code I have written to do this does not error out but the video it produces just shows a blank set of axes or a black screen. I've done several checks and the data is being run and figure updated it's just not getting saved to video...

  I tried removing "animated=True" and "blit=True" as suggested in this question but that did not fix the problem.

  I have placed the relevant code below but can provide more if necessary. Could anyone suggest what I should do to get this working ?

  def initAnimation(self):
  
          rs, cfgs = next(self.jumpingDataStreamIterator)     
  
          #self.scat = self.axAnimation.scatter(rs[0], rs[1], c=cfgs[0], marker='o')
  
          self.scat = self.axAnimation.scatter(rs[0], rs[1], c=cfgs[0], marker='o', animated=True)
  
          return self.scat,
  
  
  
  
  
  def updateAnimation(self, i):
  
      """Update the scatter plot."""
  
      rs, cfgs = next(self.jumpingDataStreamIterator)
  
      # Set x and y data...
  
      self.scat.set_offsets(rs[:2,].transpose()) 
  
      #self.scat = self.axAnimation.scatter(rs[0], rs[1], c=cfgs[0], animated=True)
  
      # Set sizes...
  
      #self.scat._sizes = 300 * abs(data[2])**1.5 + 100
  
      # Set colors..
  
      #self.scat.set_array(cfgs[0])
  
      # We need to return the updated artist for FuncAnimation to draw..
  
      # Note that it expects a sequence of artists, thus the trailing comma.
  
      matplotlib.pyplot.draw()
  
      return self.scat,
  
  
  
  def animate2d(self, steps=None, showEvery=50, size = 25):
  
      self.figAnimation, self.axAnimation = matplotlib.pyplot.subplots()
  
      self.axAnimation.set_aspect("equal")
  
      self.axAnimation.axis([-size, size, -size, size])
  
      self.jumpingDataStreamIterator = self.jumpingDataStream(showEvery)
  
  
  
      self.univeseAnimation = matplotlib.animation.FuncAnimation(self.figAnimation, 
  
                              self.updateAnimation, init_func=self.initAnimation,
  
                              blit=True)
  
      matplotlib.pyplot.show()
  
  
  
  def animate2dVideo(self,fileName=None, steps=10000, showEvery=50, size=25):
  
      self.figAnimation, self.axAnimation = matplotlib.pyplot.subplots()
  
      self.axAnimation.set_aspect("equal")
  
      self.axAnimation.axis([-size, size, -size, size])
  
      self.Writer = matplotlib.animation.writers['ffmpeg']
  
      self.writer = self.Writer(fps=1, metadata=dict(artist='Universe Simulation'))
  
      self.jumpingDataStreamIterator = self.jumpingDataStream(showEvery)
  
  
  
      self.universeAnimation = matplotlib.animation.FuncAnimation(self.figAnimation, 
  
                              self.updateAnimation, scipy.arange(1, 25), init_func=self.initAnimation)
  
  
  
      self.universeAnimation.save('C:/universeAnimation.mp4', writer = self.writer)

• Windows batch - unable to assign a variable within an iterative for loop

  17 janvier 2024, par user23254772

  I am using ffprobe to get the codec_name of subtitles in media files. But when I try to get the codec extension it fails. What am I doing wrong ?

  


  I have edited this post to address the comments and include the complete batch file

  


  Re : ns.txt - this command outputs the stream number of the subtitles :

  


  C:\ffmpeg\bin\ffprobe -loglevel error -select_streams s -show_entries stream=index:stream_tags=language -of csv=p=0 -i "%~dpnx1">ns.txt


  


  and the output in the txt file is :

  


  2
3


  


  Now I need to count the number of lines in this text file which will tell me how many subtitles my media file has :

  


  set "cmd=findstr /R /N "^^" ns.txt | find /C ":""
for /f %%a in ('!cmd!') do set nums=%%a
set /A nums=%nums%-1


  


  In this case nums = 2 but in ffprobe the first subtitle is s:0, so I subtract 1 from nums

  


  My iterative loop is :

  


  FOR %%i in (1,1,%nums%) DO (
C:\ffmpeg\bin\ffprobe.exe -v quiet -select_streams s:%%i -show_entries stream=%arg% -of default=noprint_wrappers=1:nokey=1 -i "%~dpnx1" >sub.txt
set /p codecs=code>

  


  Which puts the codec name in sub.txt and I create the variable codecs to store this value.

  


  Then I need to determine the appropriate container [extension] for the subtitle - here I changed my code from what I posted earlier :

  


  if !codecs! == mov_text set codecs1=srt
if !codecs! == subrip set codecs1=srt
if !codecs! == ass set codecs1=ass
if !codecs! == webvtt set codecs1=vtt
if !codecs! == ttml set codecs1=ttml
if !codecs! == dvb_subtitle set codecs1=dvbsub
if !codecs! == dvd_subtitle set codecs1=dvdsub
if !codecs! == hdmv_pgs_subtitle setcodecs1=sup
if !codecs! == xsub set codecs1=xsub


  


  Then I demux [extract] the subtitle using ffmpeg :

  


  c:\ffmpeg\bin\ffmpeg -i "%~dpnx1" -an -vn -c:s "!codecs!" "%~n1_d."!codecs1!"


  


  This is working, except I have an extra iteration, my output is :

  


  Mediafile: C:\Users\UNOIT\Desktop\Tears of Steel_2sub.mkv
subtile: Tears of Steel_2sub_d.srt
subtile: Tears of Steel_2sub_d.ass
subtile: Tears of Steel_2sub_d.ass
File 'Tears of Steel_2sub_d.ass' already exists. Overwrite? [y/N]


  


  And if the media file has only one subtitle, my ffmpeg output is :

  


  Mediafile: C:\Users\UNOIT\Desktop\_Jan2024-Media\mkv\Tears of Steel_ass.mkv
subtile: Tears of Steel_ass_d.ass
subtile: Tears of Steel_ass_d.ass
File 'Tears of Steel_ass_d.ass' already exists. Overwrite? [y/N]
subtile: Tears of Steel_ass_d.ass
File 'Tears of Steel_ass_d.ass' already exists. Overwrite? [y/N]


  


  I can choose not to overwrite the file - but obviously there is a problem with my iterative loop - maybe a subroutine would work

  


  Here is the batch file :

  


  ECHO OFF
SETLOCAL ENABLEDELAYEDEXPANSION
set "arg=codec_name"
set "arg1=codec_name"
set "arg2=codec_name"
echo Mediafile: %~dpnx1
C:\ffmpeg\bin\ffprobe -v quiet -loglevel error -select_streams s -show_entries stream=index:stream_tags=language -of csv=p=0 -i "%~dpnx1" >ns.txt
set "cmd=findstr /R /N "^^" ns.txt | find /C ":""
for /f %%a in ('!cmd!') do set nums=%%a
set /A nums=%nums%-1
FOR %%i in (0,1,%nums%) DO (
    C:\ffmpeg\bin\ffprobe.exe -v quiet -select_streams s:%%i -show_entries stream=%arg% -of default=noprint_wrappers=1:nokey=1 -i "%~dpnx1" >sub%%i.txt
    set /p codecs=code>