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• Generating movie from python without saving individual frames to files

  8 avril 2015, par Paul

  I would like to create an h264 or divx movie from frames that I generate in a python script in matplotlib. There are about 100k frames in this movie.

  In examples on the web [eg. 1], I have only seen the method of saving each frame as a png and then running mencoder or ffmpeg on these files. In my case, saving each frame is impractical. Is there a way to take a plot generated from matplotlib and pipe it directly to ffmpeg, generating no intermediate files ?

  Programming with ffmpeg’s C-api is too difficult for me [eg. 2]. Also, I need an encoding that has good compression such as x264 as the movie file will otherwise be too large for a subsequent step. So it would be great to stick with mencoder/ffmpeg/x264.

  Is there something that can be done with pipes [3] ?

  [1] http://matplotlib.sourceforge.net/examples/animation/movie_demo.html

  [2] http://stackoverflow.com/questions/2940671

  [3] http://www.ffmpeg.org/ffmpeg-doc.html#SEC41

• Permissions issue with Python and ffmpeg on a Mac

  13 avril 2020, par EventHorizon

  I am fairly new to Python ( 4 weeks), and I have been struggling with this all day.

  



  I am using MacOS 10.13, Python 3.7 via Anaconda Navigator 1.9.12 and Spyder 4.0.1.

  



  Somehow (only a noob, remember) I had 2 Anaconda environments. I don't do production code, just research, so I figured I would make life simple and just use the base environment. I deleted the other environment.

  



  I had previously got FFmpeg working and was able to do frame grabs, build mpeg animations, and convert them to gifs for blog posts and such. I had FFmpeg installed in the directories associated with the deleted environment, so it went away.

  



  No worries, I got the git URL, used Terminal to install it in /opt/anaconda3/bin. It's all there and I can run FFmpeg from the Terminal.

  



  My problem : When I attempt to run a module that previously worked fine, I get the following message :

  



  [Errno 13] Permission denied : '/opt/anaconda3/bin/ffmpeg'

  



  In my module I set the default location of FFmpeg : plt.rcParams['animation.ffmpeg_path'] = '/opt/anaconda3/bin/ffmpeg'

  



  In my module I have the following lines :

  



  writer = animation.FFMpegWriter(fps=frameRate, metadata=metadata)
writer.setup(fig, "animation.mp4", 100)


  



  This calls matplotlib's 'animation.py', which runs the following :

  



  def setup(self, fig, outfile, dpi=None):
    '''
    Perform setup for writing the movie file.

    Parameters
    ----------
    fig : `~matplotlib.figure.Figure`
        The figure object that contains the information for frames
    outfile : str
        The filename of the resulting movie file
    dpi : int, optional
        The DPI (or resolution) for the file.  This controls the size
        in pixels of the resulting movie file. Default is fig.dpi.
    '''
    self.outfile = outfile
    self.fig = fig
    if dpi is None:
        dpi = self.fig.dpi
    self.dpi = dpi
    self._w, self._h = self._adjust_frame_size()

    # Run here so that grab_frame() can write the data to a pipe. This
    # eliminates the need for temp files.
    self._run()

def _run(self):
    # Uses subprocess to call the program for assembling frames into a
    # movie file.  *args* returns the sequence of command line arguments
    # from a few configuration options.
    command = self._args()
    _log.info('MovieWriter.run: running command: %s', command)
    PIPE = subprocess.PIPE
    self._proc = subprocess.Popen(
        command, stdin=PIPE, stdout=PIPE, stderr=PIPE,
        creationflags=subprocess_creation_flags)


  



  Everything works fine up to the last line (i.e. 'command' looks like a well-formatted FFmpeg command line, PIPE returns -1) but subprocess.Popen() bombs out with the error message above.

  



  I have tried changing file permissions - taking a sledgehammer approach and setting everything in /opt/anaconda3/bin/ffmpeg to 777, read, write, and execute. But that doesn't seem to make any difference. I really am clueless when it comes to Apple's OS, file permissions, etc. Any suggestions ?

  


• Generating movie from python without saving individual frames to files

  31 juillet 2022, par Paul

  I would like to create an h264 or divx movie from frames that I generate in a python script in matplotlib. There are about 100k frames in this movie.

  



  In examples on the web [eg. 1], I have only seen the method of saving each frame as a png and then running mencoder or ffmpeg on these files. In my case, saving each frame is impractical. Is there a way to take a plot generated from matplotlib and pipe it directly to ffmpeg, generating no intermediate files ?

  



  Programming with ffmpeg's C-api is too difficult for me [eg. 2]. Also, I need an encoding that has good compression such as x264 as the movie file will otherwise be too large for a subsequent step. So it would be great to stick with mencoder/ffmpeg/x264.

  



  Is there something that can be done with pipes [3] ?

  



  [1] http://matplotlib.sourceforge.net/examples/animation/movie_demo.html

  



  [2] How does one encode a series of images into H264 using the x264 C API ?

  



  [3] http://www.ffmpeg.org/ffmpeg-doc.html#SEC41