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• Python and OpenCV - Cannot write readable avi video files

  19 avril 2016, par Hilman

  I have a code like this :

  import numpy as np
  
  import cv2
  
  
  
  
  
  cap = cv2.VideoCapture('C:/Users/Hilman/haatsu/drive_recorder/sample/3.mov')
  
  
  
  # Define the codec and create VideoWriter object
  
  fourcc = cv2.VideoWriter_fourcc(*'XVID')
  
  out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640,480))
  
  
  
  while(cap.isOpened()):
  
      ret, frame = cap.read()
  
      if ret==True:
  
          frame = cv2.flip(frame,0)
  
  
  
          # write the flipped frame
  
          out.write(frame)
  
  
  
          cv2.imshow('frame',frame)
  
          if cv2.waitKey(1) & 0xFF == ord('q'):
  
              break
  
      else:
  
          break
  
  
  
  # Release everything if job is finished
  
  cap.release()
  
  out.release()
  
  cv2.destroyAllWindows()

  But the output.avi cannot be played.

  Tried also change the out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640,480)) to something like this (as suggested by some people) out = cv2.VideoWriter('output.avi', -1, 20.0, (640,480)). But when I did this, I got this message

  OpenCV: FFMPEG: tag 0xffffffff/'    ' is not found (format 'avi / AVI (Audio Video Interleaved)')'.

  What could be the problem ? I am using Windows 10 by the way.

• Corrupted h264 mp4 using libav [on hold]

  16 juin 2014, par ArK22

  I´m compressing and muxing a video using libav, compiled with libx264 support. For this i´ve written a c++ .dll, to which i feed frames regularly :).

  Codec : h264
  Container : mp4

  Everything goes smooth, and the video gets played by VLC with no problem. But that’s it, no other video player can play it. Quicktime shows a black screen, MediaPlayer crashes, and the video itself has no thumbnail in finder (Mac) or explorer (PC). Reencoding the video using ffmpeg, works nicely and fixes this. However, i would like to know what’s wrong.

  My problem is exactly the same as the one described here.

  Comparing the two videos (before and after fixing with ffmpeg) using MediaInfo yields identical results, apart from compression settings, which vary a little bit. Both are baseline 3.1 profile, ftyp is isom, same bitrate, same duration, same fps, same everything.

  Has anyone stumbled upon similar problems using libav ? Tomorrow i´ll post my code to make things clearer, but in the meanwhile any suggestions are welcome.

  thanks !

• ffmpeg capture single window screen freezes with only mouse working

  2 septembre 2015, par Saad Abdullah

  Scenario and Problem :
  I have two machines with windows 8.1 installed. On one computer, every thing works fine with video recording by using gdigrab to capture a window by title. But on the other pc, the desktop recording works fine, but when it comes to capture single window by title, the video freezes with only mouse working. (to be exact, if i play webcam or images in the window being captured, it records the content too, but when some video is played it starts showing black screen or freezed at first frame.

  Commandline :
  here is the commandline args

  ffmpeg -f gdigrab -framerate 30 -i title="Video - VLC media player" germ.flv

  What can be the issue on the other pc ?