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• Python : How to use ffmpeg to read videos(video file or rtsp) and display them using OpenCV ?

  22 août 2019, par ToughMind

  I know that if we want to read video file or USB camera or rtsp stream, we can use cv2.VideoCapture.
  But for some reason, I want to use ffmpeg to do the thing and process obtained images using opencv. So the pseudocode would be :

  import cv2
  
  import ffmpeg
  
  
  
  videoFile = 'XXX.mp4'
  
  
  
  video = ffmpeg.XXX(videoFile)
  
  
  
  while True:
  
      frame = video.read() # this read() function is made up by me
  
      frameCV = ffmpeg2cv(frame) # this ffmpeg2cv() function is made up by me
  
  
  
      cv2.imshow('frame', frameCV)

  I have searched a something like https://github.com/kkroening/ffmpeg-python. But I still not know how to do this. I think ffmpeg is too hard and there are few online docs unlike opencv. So please help.

• How to use Python (For example, ffmpeg or moviePy) to split large video to display on multiple screen [on hold]

  27 juillet 2019, par Chen Clarence

  I am trying to find resources to split a very long (1080*15360) video into 8 1080p videos of the same time length. Is there anything that could achieve this, or even better allows control over each pixel（use a function to cover part of my video with a black circle）. Right now I have to brute force it, such as the following, but I’m sure there are much more efficient methods. Thanks in advance !

  cap=cv2.VideoCapture('sample.avi')
  
  #inputs & check for error
  
  numberOfScreens=8
  
  screenArrangement=(1,8)
  
  if (numberOfScreens!=(screenArrangement[0]*screenArrangement[1])):
  
      raise ValueError('The screen arrangement does not match the number of scrrens')
  
      exit(0)
  
  
  
  
  
  currentFrame=0
  
  originalFrames=[]
  
  while(True):
  
      #reading frames
  
      ret,frame=cap.read()
  
      if not ret:
  
          break
  
      height, width, layers = frame.shape
  
      unitHeight=(int)(height/screenArrangement[0])   #reduce this to outside loop
  
      unitWidth=(int)(width/screenArrangement[1])
  
      #cutting frames into desired size
  
      for i in range(screenArrangement[0]):
  
          for j in range(screenArrangement[1]):
  
              try:
  
                  if not os.path.exists('Screen'+str(i*screenArrangement[0]+j+1)):
  
                      os.makedirs('Screen'+str(i*screenArrangement[0]+j+1))
  
                      print('creating directory '+'Screen'+str(i*screenArrangement[0]+j+1))
  
              except OSError:
  
                  print ("Error Creating Directory")
  
              name='./Screen'+str(i*screenArrangement[0]+j+1)+'/frame'+str(currentFrame)+'.png'
  
              cropImg = frame[(i*unitHeight):((i+1)*unitHeight), (j*unitWidth):((j+1)*unitWidth)]
  
              print('creating'+name)
  
              #saving cropeed frames
  
              cv2.imwrite(name, cropImg,[cv2.IMWRITE_PNG_COMPRESSION, 0])
  
      currentFrame+=1
  
  Frames=currentFrame 
  
  
  
  #setting up the writer object
  
  fourcc = cv2.VideoWriter_fourcc(*'XVID')
  
  writer=cv2.VideoWriter('Screen1.avi', fourcc, 30, (unitWidth, unitHeight), True)
  
  #write the video
  
  for i in range(Frames):
  
      img=cv2.imread('./Screen1/frame'+str(i)+'.png')
  
      writer.write(img)
  
  writer.release()
  
  cap.release()
  
  cv2.destroyAllWindows()

• avcodec/dvbsub : add support for Display Definition Segment to DVB Subtitle encoder

  13 juillet 2019, par Jernej Fijacko

  avcodec/dvbsub : add support for Display Definition Segment to DVB Subtitle encoder
  Current version of dvbsub encoder doesn't support HD DVB subtitles. The high
  
  resolution bitmaps are muxed into the stream but without the DDS (display definition
  
  segment) the players asume that the DVB subtitles are in SD (720x576) resolution
  
  which causes them to either render the subtitles too large and misplaced or don't
  
  render them at all. By including the DDS as defined in section 7.7.1 of ETSI EN 300
  
  743 (V1.3.1) this problem is fixed.
  7.2.1 Display definition segment The display definition for a subtitle service may
  
  be defined by the display definition segment if present in the stream. Absence of a
  
  DDS implies that the stream is coded in accordance with EN 300 743 (V1.2.1) [5] and
  
  that a display width of 720 pixels and a display height of 576 lines may be assumed.
  https://www.etsi.org/deliver/etsi_en/300700_300799/300743/01.03.01_60/en_300743v010301p.pdf
  Signed-off-by : Jernej Fijacko <mikrohard@gmail.com>
  
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] libavcodec/dvbsub.c