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• ffmpeg direct show obvoius problem. ffmpeg is not letting to reconnect to camera

  11 avril 2021, par josh joyer

  I use ffmpeg with command

  


  ffmpeg -f dshow -i video="@device_pnp_\\?\usb#vid_1908&pid_2311&mi_00#6&353461d3&0&0000#{65e8773d-8f56-`11d0-a3b9-00a0c9223196}\global" output.mkv`


  


  It is fine to record camera but it uses direct show standard
Microsoft Windows library that is faulty.
Once connected to camera one is unable to use camera again or disconnect from it.
One should restart computer to connect to camera again.
Microsoft tells not to use direct show (dshow) for camera but
to use AForge or VisioForge libraries.

  


  But ffpmeg uses faulty dshow library. Is there any way to
change direct show to some other so one could connect to camer multiple times ?

  


• 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.

  


• 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()