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• Get image output from python program and use ffmpeg push the real time video stream to web

  26 mai 2018, par Nick Tseng

  I have a question. How to push a real time video streaming after processing ?

  First, below program is to preprocess image from usbcamera

  Second, push the image into real time video streaming by another process (ffmpeg -r 29 -i test.avi http://ffserver IP:8090/camera.ffm)

  cap = cv2.VideoCapture(1) ##activate usbcamera
  
  
  
  frame_width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
  
  frame_height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
  
  
  
  ysize, xsize = frame_height , frame_width
  
  
  
  filepath = 'test.avi'
  
  fourcc = cv2.VideoWriter_fourcc(*'MJPG')
  
  out = cv2.VideoWriter(filepath , fourcc , 29.0 , (frame_width , frame_height),True)
  
  
  
  while(cap.isOpened()):
  
  
  
      #read camera image
  
      ret , frame = cap.read()
  
  
  
      #color selection
  
      tmp = color_select_test(frame)
  
  
  
      # Mix with original image
  
      tmp = weighted_img(tmp, frame, 0.5, 1.0, 0.0)
  
  
  
      # write in video file
  
      out.write(tmp)
  
  
  
      #cv2.imwrite('test.avi',tmp)
  
  
  
      cv2.imshow('FrameWrite' , tmp)
  
  
  
      if(cv2.waitKey(1) == 27):
  
          ##cv2.imwrite('test_blue.jpg',frame)
  
          break
  
  cap.release()
  
  cv2.destroyAllWindows()

• FFmpeg C API HLS real time timestamps

  7 septembre 2022, par Robin

  I'm using the FFmpeg C API in C++ to read from a HLS stream. I need to know the real time of each AVPacket. I can extract the pts using AVPacket::pts but that is relative to the start of the stream.

  


  This is how the .m3u8 file looks :

  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-ALLOW-CACHE:NO
#EXT-X-TARGETDURATION:10
#EXT-X-MEDIA-SEQUENCE:0

#EXT-X-PROGRAM-DATE-TIME:2022-09-07T14:01:56.612+02:00
#EXTINF:10.322561783,
1662552116.ts
#EXT-X-PROGRAM-DATE-TIME:2022-09-07T14:02:06.935+02:00
#EXTINF:10.320075936,
1662552126.ts

...


  


  The .m3u8 file contains an accurate EXT-X-PROGRAM-DATE-TIME, but how can I extract the one of the currently playing segment ?

  


  Alternatively, the file name of each .ts file is the unix timestamp in seconds. Can I extract that somehow ?

  


  If none of those are possibly, is it possible to control the exact number of preloaded segments ? I know the (approximate) segment length is 10 seconds so I could just do the following when receiving the first AVPacket :

  


  start_time = current_time - segment_count * segment_length`
start_pts = first_av_packet.pts


  


  And then to get the time of a later AVPacket, I could do :

  


  packet_time = start_time + new_packet.pts - start_pts


  


  This wouldn't give the same accuracy since the segments are not exactly the same length, but that is okay.

  


• Simplified logic of parsing sizes of rice-partitions

  2 février 2020, par Ulrik Mikaelsson

  Simplified logic of parsing sizes of rice-partitions
  > if the partition order is zero, n = frame's blocksize - predictor order
  
  > else if this is not the first partition of the subframe,
  
  >   n = (frame's blocksize / (2^partition order))
  
  > else n = (frame's blocksize / (2^partition order)) - predictor order
  if the partition order is zero, then partition_number can only be zero
  
  if the partition order is zero, then
  
    (frame's blocksize / (2^partition order))
  
    is (frame's blocksize / 1) == frame's blocksize
  

  • [DH] doc/html/format.html
  • [DH] src/libFLAC/stream_decoder.c