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• Although ffmpeg installed, unable to save mp4 file on disk

  2 janvier 2020, par yannis

  Although I have installed ffmpeg, matplotlib reports that MovieWriter ffmpeg is unavailable and the MP4 file created is empty.

  import numpy as np
  
  from matplotlib import pyplot as plt
  
  from matplotlib import animation
  
  
  
  # First set up the figure, the axis, and the plot element we want to animate
  
  fig = plt.figure()
  
  ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
  
  line, = ax.plot([], [], lw=2)
  
  
  
  # initialization function: plot the background of each frame
  
  def init():
  
      line.set_data([], [])
  
      return line,
  
  
  
  # animation function.  This is called sequentially
  
  def animate(i):
  
      x = np.linspace(0, 2, 1000)
  
      y = np.sin(2 * np.pi * (x - 0.01 * i))
  
      line.set_data(x, y)
  
      return line,
  
  
  
  # call the animator.  blit=True means only re-draw the parts that have changed.
  
  anim = animation.FuncAnimation(fig, animate, init_func=init,
  
                                 frames=200, interval=20, blit=True)
  
  
  
  # save the animation as an mp4.  This requires ffmpeg or mencoder to be
  
  # installed.  The extra_args ensure that the x264 codec is used, so that
  
  # the video can be embedded in html5.  You may need to adjust this for
  
  # your system: for more information, see
  
  # http://matplotlib.sourceforge.net/api/animation_api.html
  
  anim.save('basic_animation.mp4', fps=30, extra_args=['-vcodec', 'libx264'])
  
  
  
  plt.show()

  I have even added the line plt.switch_backend('TkAgg') proposed in another post, nothing changed. Here is my matplotlib :

  Name: matplotlib
  
  Version: 2.1.0
  
  Summary: Python plotting package
  
  Home-page: http://matplotlib.org

  my ffmpeg :

  Name: ffmpeg
  
  Version: 1.4
  
  Summary: ffmpeg python package url [https://github.com/jiashaokun/ffmpeg]
  
  Home-page: https://github.com/jiashaokun/ffmpeg

  and my Python version :

  Python 3.6.5

  The error I get is :

  /usr/local/lib/python3.6/site-packages/matplotlib/animation.py:1218: UserWarning: MovieWriter ffmpeg unavailable
  
    warnings.warn("MovieWriter %s unavailable" % writer)

  This error has been reported many times on stackoverflow, each time the solution is either to install ffmpeg (mine is installed) or to add that extra line about the backend, which hasn’t changed anything for me.

  Curiously enough the plt.show()command works and I do preview an animation, but the only file format to save it is (nonanimated) PNG.

• avformat/jvdec : Make sizeof(JVFrame) smaller to save memory

  23 septembre 2021, par Andreas Rheinhardt

  avformat/jvdec : Make sizeof(JVFrame) smaller to save memory
  Reviewed-by : Peter Ross <pross@xvid.org>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavformat/jvdec.c

• How to convert mp3 data to wav data ?

  12 mai 2023, par Yali

  I have a wav audio file and i extracted data from that wav using python pydub module and i got this data

  


  [-139 18 -215 34 -196 6 -295 -31 -301 -35 -211 13 -93 47
-60 39 -58 7 -17 2]

  


  (this is first 10 data i got more than 1 million data)

  


  from pydub import AudioSegment
import numpy as np

song = AudioSegment.from_file("test.wav")
extract_data = np.array(song.get_array_of_samples())
print(extract_data[:10])


  


  then i converted wav to mp3 using that module and again extracted data from mp3 file and i got this data

  


  [-108 7 -193 24 -223 11 -239 -31 -248 -43 -203 -10 -101 23
-14 24 10 15 24 16]

  


  (this is first 10 data i got more than 1 million data)

  


  song = AudioSegment.from_file("test.wav")
song.export("test.mp3")
mp3_song = AudioSegment.from_file("test.mp3")
extract_data = np.array(mp3_song.get_array_of_samples())
print(extract_data[:10])


  


  and again i converted mp3 to wav now i got mp3 data instead of wav data.

  


  mp3_song = AudioSegment.from_file("test.mp3")
mp3_song.export("test1.wav", format="wav")

song = AudioSegment.from_file("test1.wav")
extract_data = np.array(song.get_array_of_samples())
print(extract_data[:10])


  


  My point is how to convert mp3 data to original wav data ?

  


  please help me,

  


  Thanks.