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• VideoCapture is not working in OpenCV 2.4.2

  31 mai 2016, par Froyo

  I recently installed OpenCV 2.4.2 in Ubuntu 12.04.

  cap = VideoCapture(0)

  is working. but I can’t grab frames from some video source.

  cap = VideoCapture("input.avi")
  
  img = cap.read() 

  gives me a numpy with all zero elements.

  I have also installed ffmpeg 0.11, Latest snapshot of x264, v4l-0.8.8 (All are latest stable versions)

  cmake -D WITH_QT=ON -D WITH_FFMPEG=ON -D WITH_OPENGL=ON -D WITH_TBB=ON -D BUILD_EXAMPLES=OFF WITH_V4L=ON .. 
  
  make
  
  sudo make install

  When I do cmake, I get this

  — Detected version of GNU GCC : 46 (406)
  — Found OpenEXR : /usr/lib/libIlmImf.so
  — Looking for linux/videodev.h
  — Looking for linux/videodev.h - not found
  — Looking for linux/videodev2.h
  — Looking for linux/videodev2.h - found
  — Looking for libavformat/avformat.h
  — Looking for libavformat/avformat.h - found
  — Looking for ffmpeg/avformat.h
  — Looking for ffmpeg/avformat.h - not found
  — checking for module ’tbb’
  — package ’tbb’ not found

  And

  --   Video I/O:  
  
  --     DC1394 1.x:                  NO  
  
  --     DC1394 2.x:                  YES (ver 2.2.0)  
  
  --     FFMPEG:                      YES  
  
  --       codec:                     YES (ver 54.23.100)  
  
  --       format:                    YES (ver 54.6.100)  
  
  --       util:                      YES (ver 51.54.100)  
  
  --       swscale:                   YES (ver 2.1.100)  
  
  --       gentoo-style:              YES  
  
  --     GStreamer:                   
  
  --       base:                      YES (ver 0.10.36)  
  
  --       app:                       YES (ver 0.10.36)  
  
  --       video:                     YES (ver 0.10.36)  
  
  --     OpenNI:                      NO  
  
  --     OpenNI PrimeSensor Modules:  NO  
  
  --     PvAPI:                       NO  
  
  --     UniCap:                      NO  
  
  --     UniCap ucil:                 NO  
  
  --     V4L/V4L2:                    Using libv4l (ver 0.8.8)  
  
  --     XIMEA:                       NO  
  
  --     Xine:                        NO

  I looked for videodev.h, etc

  • /usr/include/linux/videodev2.h exists
  • /usr/include/libavformat/avformat.h exists
  • /usr/local/include/libavformat/avformat.h exists

  But I couldn’t find ffmpeg/avformat.h

  What’s the problem here ?

• Convert AAC (.m4a) files to .mp3 in directory

  25 juillet 2012, par elithrar

  I'm writing a script to convert AAC files to MP3 - specifically so I can burn them to MP3 CD's as iTunes won't transcode on the fly. I've adapted the code from Write a simple python script to convert all .wav files in a specific folder to .mp3 using lame

  It currently converts the first file in the directory and then stops.

  I have a cursory knowledge of Python, but not the subprocess module. Went through the docs and can't see why it is not continuing to process the files.

  #!/usr/bin/env python
  
  
  
  import os
  
  import os.path
  
  import sys
  
  import subprocess
  
  
  
  OUTPUT_DIR = '/Users/matt/Desktop/mp3/'
  
  
  
  def main():
  
      path = os.getcwd()
  
      filenames = [
  
          filename
  
          for filename
  
          in os.listdir(path)
  
          if filename.endswith('.m4a')
  
          ]
  
  
  
      for filename in filenames:
  
          subprocess.call([
  
              "ffmpeg", "-i",
  
              os.path.join(path, filename),
  
              "-acodec", "libmp3lame", "-ab", "256k",
  
              os.path.join(OUTPUT_DIR, '%s.mp3' % filename[:-4])
  
              ])
  
          return 0
  
  
  
  if __name__ == '__main__':
  
      status = main()
  
      sys.exit(status)

• FFmpeg and Ruby linkage

  9 août 2012, par Thomas Kobber Panum

  I'm getting this error :

  Failed encoding. Errors: no output file created. Full output: dyld: Library not loaded: /usr/local/lib/libogg.0.dylib
  
   Referenced from: /usr/local/bin/ffmpeg
  
   Reason: Incompatible library version: ffmpeg requires version 9.0.0 or later, but libogg.0.dylib provides version 6.0.0

  I've installed ffmpeg through brew, and installed both the 'ffmpeg' gem and the 'streamio-ffmpeg' gem.

  Running :

  otool -L /usr/local/lib/libogg.0.dylib

  gives me this output :

  /usr/local/lib/libogg.0.dylib:
  
      /usr/local/lib/libogg.0.dylib (compatibility version 9.0.0, current version 9.0.0)
  
      /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 159.1.0)

  The file I'm using ffmpeg in, looks like this :

  # lib/carrierwave/ffmpeg.rb
  
  require 'streamio-ffmpeg'
  
  module CarrierWave
  
    module FFMPEG
  
      module ClassMethods
  
        def resample( bitrate )
  
          process :resample => bitrate
  
        end
  
      end
  
  
  
      def resample( bitrate )
  
        directory = File.dirname( current_path )
  
        tmpfile   = File.join( directory, "tmpfile" )
  
  
  
        FileUtils.mv( current_path, tmpfile )
  
  
  
        file = ::FFMPEG::Movie.new(tmpfile)
  
        file.transcode( current_path, :audio_bitrate => bitrate)
  
  
  
        File.delete( tmpfile )
  
      end
  
    end
  
  end