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• compile opencv2.3.1 in ubuntu 11.10

  17 février 2012, par kyon

  Here is the tutorial I followed :http://thebitbangtheory.wordpress.com/2011/10/23/how-to-install-opencv-2-3-1-in-ubuntu-11-10-oneiric-ocelot-with-python-support/
  I think the problem is ffmpeg, the version I used is 0.8.10, and I installed it in /usr and enabled share, but when I complied opencv,the output was full of

  ./../lib/libopencv_highgui.so.2.3.1 : undefined reference to

  av_codec_get_id'
 ../../lib/libopencv_highgui.so.2.3.1: undefined reference to

  av_seek_frame'
  ../../lib/libopencv_highgui.so.2.3.1 : undefined reference to `avpicture_get_size

• Run ffmpeg without outputting configuration information ?

  28 mars 2014, par Matt Joiner

  I'm invoking ffmpeg with subprocess.Popen, and trying to capture the stderr output and write it to logging.

  args = ['ffmpeg', '-i', path]
  
  if start:
  
      args += ['-ss', start]
  
  if end:
  
      args += ['-t', end]
  
  args += [
  
      '-vcodec', 'copy',
  
      '-acodec', 'copy',
  
      '-scodec', 'copy',
  
      '-f', 'mpegts',
  
      '-y', '/dev/stdout']
  
  self.child = subprocess.Popen(
  
      args,
  
      stdin=open(os.devnull, 'rb'),
  
      stdout=subprocess.PIPE,
  
      stderr=subprocess.PIPE)

  ffmpeg generates a lot of configuration information like the following :

  FFmpeg version 0.6.2-4:0.6.2-1ubuntu1,
  Copyright (c) 2000-2010 the Libav
  developers built on Mar 22 2011
  15:55:04 with gcc 4.5.2
  configuration :
  —extra-version=4:0.6.2-1ubuntu1 —prefix=/usr —enable-avfilter —enable-avfilter-lavf —enable-vdpau —enable-bzlib —enable-libgsm —enable-libschroedinger —enable-libspeex —enable-libtheora —enable-libvorbis —enable-pthreads —enable-zlib —enable-libvpx —disable-stripping —enable-runtime-cpudetect —enable-vaapi —enable-gpl —enable-postproc —enable-swscale —enable-x11grab —enable-libdc1394 —enable-shared —disable-static WARNING : library configuration
  mismatch libavutil configuration :
  —extra-version=4:0.6.2-1ubuntu2 —prefix=/usr —enable-avfilter —enable-avfilter-lavf —enable-vdpau —enable-bzlib —enable-libdirac —enable-libgsm —enable-libopenjpeg —enable-libschroedinger —enable-libspeex —enable-libtheora —enable-libvorbis —enable-pthreads —enable-zlib —enable-libvpx —disable-stripping —enable-runtime-cpudetect —enable-vaapi —enable-libopenjpeg —enable-gpl —enable-postproc —enable-swscale —enable-x11grab —enable-libfaad —enable-libdirac —enable-libfaad —enable-libmp3lame —enable-librtmp —enable-libx264 —enable-libxvid —enable-libdc1394 —enable-shared —disable-static libavcodec configuration :
  —extra-version=4:0.6.2-1ubuntu2 —prefix=/usr —enable-avfilter —enable-avfilter-lavf —enable-vdpau —enable-bzlib —enable-libdirac —enable-libgsm —enable-libopenjpeg —enable-libschroedinger —enable-libspeex —enable-libtheora —enable-libvorbis —enable-pthreads —enable-zlib —enable-libvpx —disable-stripping —enable-runtime-cpudetect —enable-vaapi —enable-libopenjpeg —enable-gpl —enable-postproc —enable-swscale —enable-x11grab —enable-libfaad —enable-libdirac —enable-libfaad —enable-libmp3lame —enable-librtmp —enable-libx264 —enable-libxvid —enable-libdc1394 —enable-shared —disable-static libavutil 50.15. 1 / 50.15. 1
  libavcodec 52.72. 2 / 52.72. 2
  libavformat 52.64. 2 / 52.64. 2
  libavdevice 52. 2. 0 / 52. 2. 0
  libavfilter 1.19. 0 / 1.19. 0
  libswscale 0.11. 0 / 0.11. 0
  libpostproc 51. 2. 0 / 51. 2. 0

  Prior to finally outputting the stuff I'd like to log :

  Seems stream 0 codec frame rate
  differs from container frame rate :
  47.95 (66893/1395) -> 23.98 (66893/2790) At least one output file
  must be specified

  Is there an option to prevent this excessive output ? Should I be doing it differently ?

• Writing numpy arrays using cv2 VideoWriter

  8 juillet 2015, par JustInTime

  I have a problem with writing a toy example video using opencv2.3.1 VideoWriter, here is how I do it :

  writer = cv2.VideoWriter('test1.avi',cv.CV_FOURCC('P','I','M','1'),25,(640,480))
  
  for i in range(1000):
  
      x = np.random.randint(10,size=(480,640)).astype('uint8')
  
      writer.write(x)
  
  #del writer (with or without tested)

  I tried every possible combination resulting with a 0 bytes file if the extension was mpg, and 5.5kb if it was avi. I should say that some pointed out that I should build the ffmpeg library from source and not apt-get it. Well I did that on a fresh machine based on the help of this site http://vinayhacks.blogspot.com/2011/11/installing-opencv-231-with-ffmpeg-on-64.html. which also presented an error while compiling opencv(the error was related to ffmpeg). Now I am really out of ideas, How to generate a video using OPENCV ?

  Thanks in advance