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• VideoWriter do not write anything

  29 avril 2015, par Nelson

  When I try to use VideoWriter to write a frame it does not work. I already tried lots of FOURCC codes, like the defaul, h264, mjpg, divx, xvid, etc. And yes, I have installed ffmpeg with all the necessary configurations (—enable-shared, —enable-libx264, ...) and the opencv installation is with ffmpeg support on.

  I already google it a lot and everything that I found do not even nearly solve this problem, that is recurrent in OpenCV. The code is the simplest possible, and it worked a few weeks back, but not it does not.

  A few insights : get(CV_CAP_PROP_FPS) returns the unknown option message, with the -1 value (the same happens for the set). The following part of the cmake process of opencv is also interesting :

  -- Could NOT find Jasper (missing:  JASPER_LIBRARIES JASPER_INCLUDE_DIR) 
  
  -- checking for module 'gstreamer-video-1.0'
  
  --   package 'gstreamer-video-1.0' not found
  
  -- checking for module 'gstreamer-app-1.0'
  
  --   package 'gstreamer-app-1.0' not found
  
  -- checking for module 'gstreamer-riff-1.0'
  
  --   package 'gstreamer-riff-1.0' not found
  
  -- checking for module 'gstreamer-pbutils-1.0'
  
  --   package 'gstreamer-pbutils-1.0' not found
  
  -- checking for module 'gstreamer-base-0.10'
  
  --   package 'gstreamer-base-0.10' not found
  
  -- checking for module 'gstreamer-video-0.10'
  
  --   package 'gstreamer-video-0.10' not found
  
  -- checking for module 'gstreamer-app-0.10'
  
  --   package 'gstreamer-app-0.10' not found
  
  -- checking for module 'gstreamer-riff-0.10'
  
  --   package 'gstreamer-riff-0.10' not found
  
  -- checking for module 'gstreamer-pbutils-0.10'
  
  --   package 'gstreamer-pbutils-0.10' not found
  
  -- 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 sys/videoio.h
  
  -- Looking for sys/videoio.h - not found
  
  -- Looking for libavformat/avformat.h
  
  -- Looking for libavformat/avformat.h - found
  
  -- Looking for ffmpeg/avformat.h
  
  -- Looking for ffmpeg/avformat.h - not found

  Opencv 2.4.10
  Ubuntu 14.04

  EDIT : I found out that the problem is that the VideoWriter object isn’t open, even after the constructor call :

  VideoWriter wr(outputFile, CV_FOURCC('D','I','V','X'), capture.get(CV_CAP_PROP_FPS,Size(capture.get(CV_CAP_PROP_FRAME_WIDTH),capture.get(CV_CAP_PROP_FRAME_HEIGHT)));

  And using the CV_CAP_PROP_FPS makes OpenCV show the following message in secution time :

  HIGHGUI ERROR: V4L2: Unable to get property <unknown property="property" string="string">(5) - Invalid argument
  
  </unknown>

  Why this hqppen, how can I fix that ?

• MoviePy : Concatenating video clips causes weird glitches in final video

  16 mai 2022, par JohnSmithy1266

  Is there a way to successfully always patch up any clips together in such a way that prevents weird glitches ? I put together a .mp4 from smaller .mp4 files and I got a final video with weird glitches. I am running Python 3.6.1 on Windows 10 through Sublime Text 3. I used MoviePy to do the concatenation.

  



  The code :

  



  from moviepy.editor import VideoFileClip, concatenate_videoclips
import os.path

path = "C:/Users/blah/videos/out/"

cliparray = []

for filename in os.listdir(path):
    cliparray.append(VideoFileClip(path + filename))

final_clip = concatenate_videoclips(cliparray)

final_clip.write_videofile(path + "concatenatedvideo.mp4", codec = "libx264")


  



  The weird glitches :

  



  

  1. One of the clips turns into a 3x3 grid of smaller clips.

  


  2. Another has the audio not lined up with the video

  


  3. Another is sped up faster than what was normal.

  


  


• Compression rate (final size) ffmpeg with h263 as codec, can be improved ?

  29 août 2013, par voskyc

  With the following data :

  Sample 1 :
  vcodec : H263
  Duration : 4seconds
  Resolution:1288/720
  FR : 30fps/s
  datarate : 195.135 kB/s
  MP3 : 44HZ, 16bits

  ---

  Size file : 5.84MB.

  Sample 2 :
  vcodec : H263
  Duration : 4seconds
  Resolution:640/480
  FR : 30fps/s
  datarate : 195.135 kB/s
  MP3 : 44HZ, 16bits

  ---

  Size file = 3.34MB.

  Both in flv container.

  Aren't those sizes a little bit high for 4 second video ?

  I believe we are doing some kind of error or missing an optimization.
  Should we decrease the datarate ?
  Maybe we are missing some option for h263 encoding with FFMPEG ?.

  Thanks a lot in advance for your suggestions.

  Note : no, we "can not" use h264. :-)