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• How to extract frames from a mpeg-2 file in Python ?

  14 avril 2016, par Agnirudra

  I am trying to read and extract frames (faces detection to be precise) from a video file using python. My code is working fine with extracting frames and detecting the faces from a mp4 video file, but it can’t read a mpeg2 video file. What should be the proper approach to fix this problem ?

  import pylab
  
  import imageio
  
  import cv2
  
  import sys
  
  filename = 'c:\file.mp4'
  
  vid = imageio.get_reader("file.mp4",  'ffmpeg')
  
  nums = [10,100,190,250, 150]
  
  for num in nums:
  
      image = vid.get_data(num)
  
      fig = pylab.figure()
  
      fig.suptitle('image #{}'.format(num), fontsize=20)
  
      pylab.imshow(image)
  
  pylab.show()
  
  pic=cv2.imwrite('messigray.png',image)
  
  
  
  
  
  
  
  # Create the haar cascade
  
  faceCascade = cv2.CascadeClassifier('C:\opencv\sources\data\haarcascades\haarcascade_frontalface_default.xml')
  
  # Read the image
  
  image = cv2.imread('C:/Users/agni/Documents/Python_Devs/messigray.png')
  
  gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
  
  # Detect faces in the image
  
  faces = faceCascade.detectMultiScale(
  
      gray,
  
      scaleFactor=1.1,
  
      minNeighbors=5,
  
      minSize=(30, 30),
  
      flags = cv2.cv.CV_HAAR_SCALE_IMAGE
  
                                      )
  
  print "Found {0} faces!".format(len(faces))
  
  
  
  # Draw a rectangle around the faces
  
  for (x, y, w, h) in faces:
  
      cv2.rectangle(image, (x, y), (x+w, y+h), (0, 255, 0), 2)
  
      cv2.imshow("Faces found" ,image)
  
      cv2.waitKey(0)

• Ffmpeg and OpenCv versions incompatibility

  28 juillet 2017, par Agustin Jacob Ortiz Mendez

  I installed Python 2.7.5 and OpenCV 2.4. I’m trying to follow the instructions of this page
  http://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_gui/py_video_display/py_video_display.html
  And it suggest to install the proper version of Ffmpeg. I installed it following the instructions of this page
  http://adaptivesamples.com/how-to-install-ffmpeg-on-windows/
  Which tells the user how to add Ffmpeg to the environment variables.
  However, the sample code doesn’t work. And I don’t know if it is because the versions of OpenCv and ffmpeg are incompatible with one another.
  I’ll leave the sample code here.
  Thanks for reading :D

  import numpy as np import cv2
  
  
  
  cap = cv2.VideoCapture('vtest.avi')
  
  
  
  while(cap.isOpened()):
  
      ret, frame = cap.read()
  
  
  
      gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
  
  
  
      cv2.imshow('frame',gray)
  
      if cv2.waitKey(1) & 0xFF == ord('q'):
  
          break
  
  
  
  cap.release() cv2.destroyAllWindows()

• indeo : Refactor ff_ivi_init_tiles and ivi_decode_blocks

  3 juillet 2013, par Luca Barbato

  indeo : Refactor ff_ivi_init_tiles and ivi_decode_blocks
  Spin large and mostly self contained blocks into stand alone
  
  functions.
  

  • [DBH] libavcodec/ivi_common.c