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• ValueError : I/O operation on closed file when making animation

  3 juillet 2018, par user3851187

  I am using matplotlib and ffmpeg to do some animations. I usually code on a remote server because the code runs faster ; we are having some issues making animations on the remote server. Here is an example of code that works perfectly on my local mac but does not work remotely.

  import matplotlib as mpl
  
  mpl.use('agg')
  
  import matplotlib as mpl 
  
  from matplotlib import animation
  
  import pylab
  
  
  
  def init():
  
      pylab.plot(pylab.arange(10), [0]*10)
  
  
  
  def redraw(frame):
  
      pylab.plot(pylab.arange(10), pylab.arange(10) * frame)
  
  
  
  fig = pylab.figure()
  
  ani = animation.FuncAnimation(fig, redraw, frames=10, interval=1000, init_func=init)
  
  ani.save('animation.mp4')

  I get the animation I want on my local machine (macOS Sierra). When I run it on the remote host (Debian GNU/Linux 8 (jessie)), I get the following error message after 5 frames

  Traceback (most recent call last):
  
    File "animation.py", line 14, in <module>
  
      ani.save('animation.mp4')
  
    File "/usr/local/lib/python2.7/dist-packages/matplotlib/animation.py", line 1200, in save
  
      writer.grab_frame(**savefig_kwargs)
  
    File "/usr/lib/python2.7/contextlib.py", line 35, in __exit__
  
      self.gen.throw(type, value, traceback)
  
    File "/usr/local/lib/python2.7/dist-packages/matplotlib/animation.py", line 241, in saving
  
      self.finish()
  
    File "/usr/local/lib/python2.7/dist-packages/matplotlib/animation.py", line 367, in finish
  
      self.cleanup()
  
    File "/usr/local/lib/python2.7/dist-packages/matplotlib/animation.py", line 405, in cleanup
  
      out, err = self._proc.communicate()
  
    File "/usr/local/lib/python2.7/dist-packages/subprocess32.py", line 724, in communicate
  
      stdout, stderr = self._communicate(input, endtime, timeout)
  
    File "/usr/local/lib/python2.7/dist-packages/subprocess32.py", line 1535, in _communicate
  
      orig_timeout)
  
    File "/usr/local/lib/python2.7/dist-packages/subprocess32.py", line 1591, in _communicate_with_poll
  
      register_and_append(self.stdout, select_POLLIN_POLLPRI)
  
    File "/usr/local/lib/python2.7/dist-packages/subprocess32.py", line 1570, in register_and_append
  
      poller.register(file_obj.fileno(), eventmask)
  
  ValueError: I/O operation on closed file
  
  </module>

  My local machine uses matplotlib version 2.0.0 ; the remote machine uses matplotlib version 2.2.2

  On my local machine I have ffmpeg version 3.2.4

  $ ffmpeg -version
  
  ffmpeg version 3.2.4 Copyright (c) 2000-2017 the FFmpeg developers
  
  built with Apple LLVM version 8.0.0 (clang-800.0.42.1)
  
  configuration: --prefix=/usr/local/Cellar/ffmpeg/3.2.4 --enable-shared - 
  
  -enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables 
  
  --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable libmp3lame --enable-libx264 --enable-libxvid --enable-opencl --disable-lzma --enable-vda
  
  libavutil      55. 34.101 / 55. 34.101
  
  libavcodec     57. 64.101 / 57. 64.101
  
  libavformat    57. 56.101 / 57. 56.101
  
  libavdevice    57.  1.100 / 57.  1.100
  
  libavfilter     6. 65.100 /  6. 65.100
  
  libavresample   3.  1.  0 /  3.  1.  0
  
  libswscale      4.  2.100 /  4.  2.100
  
  libswresample   2.  3.100 /  2.  3.100
  
  libpostproc    54.  1.100 / 54.  1.100 

  On the remote host i have ffmpeg version 4.0.1

  ffmpeg -version
  
  ffmpeg version 4.0.1 Copyright (c) 2000-2018 the FFmpeg developers
  
  built with gcc 4.9.2 (Debian 4.9.2-10+deb8u1)
  
  configuration: --prefix=/usr/local
  
  libavutil      56. 14.100 / 56. 14.100
  
  libavcodec     58. 18.100 / 58. 18.100
  
  libavformat    58. 12.100 / 58. 12.100
  
  libavdevice    58.  3.100 / 58.  3.100
  
  libavfilter     7. 16.100 /  7. 16.100
  
  libswscale      5.  1.100 /  5.  1.100
  
  libswresample   3.  1.100 /  3.  1.100

  If I recall correctly I installed ffmpeg locally through homebrew ; I have the anaconda distribution of python. On the remote machine we have the default version of python that comes with Jessie ; I’m not sure how the sysadmin installed ffmpeg.

  I am by no means an expert on ffmpeg, but I have generally never had issues with making animations in matplotlib on my local machine and I would really like to be able to make videos more quickly on the remote machine. Any help would be appreciated !

  Edit
  On the remote machine, the animation works if I use avconv as the writer instead of ffmpeg. I installed avconv locally...which led me to get the same ffmpeg issues locally (probably due to updating shared dependencies). However, I uninstalled ffmpeg and reinstalled it with x264 codec enables Animations in ipython (jupyter) notebook - ValueError : I/O operation on closed file

• Difference between ffmpeg and avconv for rawvideo image2pipe

  15 août 2016, par NHDaly

  I’m not sure why, but avconv does not seem to be piping raw video like I would expect.

  I’m trying pipe a video from ffmpeg into python (eventually I want to read from x11grab, not a video file). It works just fine on my Macbook using ffmpeg, but when I use avconv on Debian Jessie, the stream cuts off early !

  Here’s my basic python, which is following this guide :

  input_resolution_shape = (1280,800,3)
  
  input_bytes = reduce(mul, input_resolution_shape, 1)
  
  print input_bytes
  
  
  
  # Prints 3072000
  
  
  
  import subprocess as sp
  
  command = [ FFMPEG_BIN,   # This is either "avconv" or "ffmpeg".
  
              '-i', 'test_video.mp4',
  
              '-f', 'image2pipe',
  
              '-pix_fmt', 'rgb24',
  
              '-vcodec', 'rawvideo', '-']
  
  pipe = sp.Popen(command, stdout = sp.PIPE, bufsize=10**8)
  
  
  
  import numpy
  
  for _ in range(100):  # read 100 frames
  
      # read 1280*800*3 bytes (= 1 frame)
  
      raw_image = pipe.stdout.read(input_bytes)
  
      # transform the byte read into a numpy array
  
      image = numpy.fromstring(raw_image, dtype='uint8')
  
      if image.size != 0:
  
          print image.size
  
  
  
          # Prints 1015808

  On the mac, the image.size printed is the same as the input_bytes, 3072000. But on debian, it’s 1015808. Any ideas why that could be happening ?

  Interestingly, 3072000/1015808 is just about 3 :

  In [1]:    3072000./1015808.
  
  Out[1]:    3.024193548387097

• How to wrap an h.264 file as mp4 on iOS

  27 octobre 2016, par buildsucceeded

  I have a bare h.264 file (from a raspberry pi camera), and I’d like to wrap it as an mp4. I don’t need to play it, edit it, add or remove anything, or access the pixels.

  Lots of people have asked about compiling ffmpeg for iOS, or streaming live data. But given the lack of easy translation between the ffmpeg command line and its iOS build, it’s very difficult for me to figure out how to implement this simple command :

  ffmpeg -i input.h264 -vcodec copy out.mp4

  I don’t specifically care whether this happens via ffmpeg, avconv, or AVFoundation (or something else). It just seems like it should be not-this-hard to do on a device.