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• OpenCV VideoWriter will not open

  21 février 2015, par ChrisC

  I’m having trouble instantiating and opening an OpenCV VideoWriter for recording video on a Raspberry Pi (Raspbian Weezy).

  My project is written in C++, but I’ve written a minimal Python program that demonstrates the problem.

  https://gist.github.com/chriscollins/11ff2f43852e1c93dae8

  Both my C++ code and the Python code above run without problem on my Windows machine. Sometimes the writer does not open, but that’s to be expected - I don’t have all of the listed codecs installed (the list of codecs comes from the Open CV source), but a good number of them work correctly. However, on a Raspberry Pi, both the C++ code and the Python code fail with the VideoWriter never being opened. In the above Python code, writer.isOpened() returns false for every single codec, when run on a Raspberry Pi.

  I’ve chowned the destination directory to the user I’m running the Python script as, and chmodded it to 777 so I don’t believe that it is a permissions problem. I think it may be connected with how I’ve installed OpenCV or some of its dependencies, but I’m not sure how to rectify it.

  The install process I’ve used is as follows :

  1. Update firmware/packages via rpi-update, apt-get update and apt-get upgrade.

  2. Install the following dependencies via apt-get :

     libjpeg8
libjpeg8-dev
libjpeg8-dbg
libjpeg-progs
ffmpeg
libavcodec-dev
libavcodec53
libavformat53
libavformat-dev
libgstreamer0.10-0-dbg
libgstreamer0.10-0
libgstreamer0.10-dev
libxine1-ffmpeg
libxine-dev
libxine1-bin
libunicap2
libunicap2-dev
swig
libv4l-0
libv4l-dev
python-numpy
libpython2.6
python-dev
python2.6-dev
libgtk2.0-dev

  3. Download and unzip http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/2.4.9/opencv-2.4.9.zip to /root/opencv-2.4.9.

  4. cd /root/opencv-2.4.9 and run cmake -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_INSTALL_PREFIX=/usr/local -DBUILD_PERF_TESTS=OFF -DBUILD_opencv_gpu=OFF -DBUILD_opencv_ocl=OFF. Output of cmake is available at https://gist.github.com/chriscollins/d8060e03a6acd6d4336c

  5. make and make install from the same directory.

  Various other OpenCV functionality works correctly on the Raspberry Pi (in C++ or in Python) - e.g. viewing a webcam via VideoCapture, but I can’t get the VideoWriter to work. I’m tempted to try installing FFMPEG from source instead of via apt-get, but as make takes 5+ hours to run on a Raspberry Pi, I was hoping I’d find the answer here, rather than proceeding with a trial and error approach !

  Any advice on how to solve (or debug) this is appreciated.

  EDIT : Added output of cmake command (https://gist.github.com/chriscollins/d8060e03a6acd6d4336c)

• fftools/ffmpeg : add thread-aware transcode scheduling infrastructure

  18 mai 2023, par Anton Khirnov

  fftools/ffmpeg : add thread-aware transcode scheduling infrastructure
  See the comment block at the top of fftools/ffmpeg_sched.h for more
  
  details on what this scheduler is for.
  This commit adds the scheduling code itself, along with minimal
  
  integration with the rest of the program :
  
  * allocating and freeing the scheduler
  
  * passing it throughout the call stack in order to register the
  
    individual components (demuxers/decoders/filtergraphs/encoders/muxers)
  
    with the scheduler
  The scheduler is not actually used as of this commit, so it should not
  
  result in any change in behavior. That will change in future commits.
  

  • [DH] fftools/Makefile
  • [DH] fftools/ffmpeg.c
  • [DH] fftools/ffmpeg.h
  • [DH] fftools/ffmpeg_dec.c
  • [DH] fftools/ffmpeg_demux.c
  • [DH] fftools/ffmpeg_enc.c
  • [DH] fftools/ffmpeg_filter.c
  • [DH] fftools/ffmpeg_mux.c
  • [DH] fftools/ffmpeg_mux.h
  • [DH] fftools/ffmpeg_mux_init.c
  • [DH] fftools/ffmpeg_opt.c
  • [DH] fftools/ffmpeg_sched.c
  • [DH] fftools/ffmpeg_sched.h

• ValueError : I/O operation on closed file with ffmpeg

  22 mars 2018, par AstroCoda

  I’m trying to get this (minimal working example) code to compile in a virtual environment on Anaconda which I’ve set up in a supercomputing cluster :

  import numpy as np
  
  import matplotlib
  
  matplotlib.use("Agg")
  
  import matplotlib.pyplot as plt
  
  import matplotlib.animation as manimation
  
  
  
  FFMpegWriter = manimation.writers['ffmpeg']
  
  metadata = dict(title='Movie Test', artist='Matplotlib',
  
              comment='Movie support!')
  
  writer = FFMpegWriter(fps=15, metadata=metadata)
  
  
  
  fig = plt.figure()
  
  l, = plt.plot([], [], 'k-o')
  
  
  
  plt.xlim(-5, 5)
  
  plt.ylim(-5, 5)
  
  
  
  x0, y0 = 0, 0
  
  
  
  with writer.saving(fig, "writer_test.mp4", 100):
  
      for i in range(100):
  
          x0 += 0.1 * np.random.randn()
  
          y0 += 0.1 * np.random.randn()
  
          l.set_data(x0, y0)
  
          writer.grab_frame()

  The thing is, this code works absolutely fine on my local machine (MacOSX) - Anaconda distribution ; Python 2.7 ; same matplotlib and numpy version, and I have ffmpeg on Anaconda ; I have ffmpeg on the cluster as well, albeit at a different version to the one on Python (but no issue with this on my local machine). When I run the code on the cluster, I get :

  Traceback (most recent call last):
  
    File "movie_test.py", line 25, in <module>
  
      writer.grab_frame()
  
    File "~/anaconda2/envs/test_movie/lib/python2.7/contextlib.py", line 35, in __exit__
  
      self.gen.throw(type, value, traceback)
  
    File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/matplotlib/animation.py", line 241, in saving
  
      self.finish()
  
    File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/matplotlib/animation.py", line 367, in finish
  
      self.cleanup()
  
    File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/matplotlib/animation.py", line 405, in cleanup
  
      out, err = self._proc.communicate()
  
    File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/subprocess32.py", line 927, in communicate
  
      stdout, stderr = self._communicate(input, endtime, timeout)
  
    File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/subprocess32.py", line 1713, in _communicate
  
      orig_timeout)
  
    File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/subprocess32.py", line 1769, in _communicate_with_poll
  
      register_and_append(self.stdout, select_POLLIN_POLLPRI)
  
    File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/subprocess32.py", line 1748, in register_and_append
  
      poller.register(file_obj.fileno(), eventmask)
  
  ValueError: I/O operation on closed file
  
  </module>

  All the searches I’ve made correspond to relatively simple text write in/out operations, but not for videos. Thanks in advance for the help !