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• Running matplotlib animation on Mac using Spyder : says to install ffmpeg

  28 avril 2017, par Addem

  I installed Anaconda on a new Mac, made a simple animation with matplotlib like

  import numpy as np
  
  from matplotlib import pyplot as plt
  
  from matplotlib import animation
  
  
  
  fig = plt.figure()
  
  ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
  
  line, = ax.plot([], [], lw=2)
  
  
  
  def init():
  
      line.set_data([], [])
  
      return line,
  
  
  
  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,
  
  
  
  anim = animation.FuncAnimation(fig, animate, init_func=init,
  
                                 frames=200, interval=20, blit=True)
  
  
  
  
  
  anim.save('basic_animation.mp4', fps=30, extra_args=['-vcodec', 'libx264'])
  
  
  
  plt.show()

  When I run it, it tells me to install ffmpeg. I tried using these instructions : http://stephenjungels.com/jungels.net/articles/ffmpeg-howto.html But the instructions were unclear about what I was supposed to download, especially when it got to the part about a "patch". This also just feels insanely complicated for something that seems like it should be much simpler. I also tried following some instructions for installing ffmpeg using Homebrew but the instructions were again poorly written so that some of the buttons it said should be there weren’t. I tried to figure it out by guessing what I should do, and it seemed to work but with a lot of warning messages. By the end of the process, when I type into a terminal

  which ffmpeg

  it returns /usr/local/bin/ffmpeg. However, even after restarting Spyder and re-running the code, it still tells me to install ffmpeg. I also navigated to /usr/local/bin and it doesn’t have a folder ffmpeg. So my guess is that ffmpeg didn’t install.

  I read in the matplotlib documentation that Anaconda doesn’t give a build for Python that is appropriate, something about a "framework" build (http://matplotlib.org/faq/osx_framework.html). But it says that in Anaconda you can install it easily by running conda install python.app which I did and it worked. It then says to use pythonw rather than python. I’m not really sure what this means, because in Spyder I don’t run scripts from the terminal. I tried navigating to the file anyway and running it with

  pythonw anim.py

  and it mysteriously gave me an I/O error.

  Do I really need to install ffmpeg or is there some simpler fix ?

  If I do need to install ffmpeg, where get I get up-to-date instructions that make the process clear ?

• Ffmpeg error : Rotate thumbnail image of video

  9 septembre 2016, par user3418135

  Iam using ffmpeg to generate thumbnail image from a video .mov (uploaded from iPhone)

  This is PHP code on live server to generate :

  public static function generateThumbnail($inputUrl, $outputUrl) {
  
      $cmd = "ffmpeg -i ".$inputUrl." -ss 00:00:01 -vframes 1 -s 200x200 ".$outputUrl;
  
      exec($cmd);
  
  }

  On live server (CentOS 6.5) : If I run this cmd in terminal, it working. But if I run by calling above function php then thumbnail image will be rotated -90 degrees.

  If i run two cases on localhost (LinuxMint 17.2) then all ok.

  Thanks all.

• FFMPEG GIF without loop, without transparency

  4 janvier 2019, par Wallie

  I use the following bash file in Terminal to transcode video files to high quality gifs.

  #!/bin/sh
  
  
  
  palette="/tmp/palette.png"
  
  
  
  filters="fps=25,scale=576:-1.78:flags=lanczos"
  
  
  
  ffmpeg -v warning -i $1 -vf "$filters,palettegen" -y $palette
  
  ffmpeg -v warning -i $1 -i $palette -lavfi "$filters [x]; [x][1:v] 
  
  paletteuse" -y $2

  Right now a 6 second video ends up as a 10 second gif. Which is a bit odd since the framerate matches. I guess it’s due to looping.

  Is it possible to add a simple filter that prevents looping.

  And also a filter that prevents transparency ?

  Source is a prores422 file.