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• Having trouble obtaining the time from RTP Timestamps obtained through OpenCV

  24 août 2019, par Fr0sty

  I am finding it a bit difficult trying to understand whether or not the hack around with FFmpeg and OpenCV really provided a RTP timestamp. My last post helped a little bit but got me stuck in trying to validate the timestamps obtained through this work around by modifying ffmpeg and opencv.

  FFmpeg version : 4.1.0
  OpenCV version : 3.4.1

  import cv2
  
  import time
  
  from datetime import datetime, date
  
  
  
  uri = 'rtsp://admin:password@192.168.1.66:554/Streaming/Channels/101'
  
  cap = cv2.VideoCapture(uri)
  
  '''One is the offset between the two epochs. Unix uses an epoch located at 1/1/1970-00:00h (UTC) and NTP uses 1/1/1900-00:00h.
  
  This leads to an offset equivalent to 70 years in seconds (there are 17 leap years between the two dates so the offset is'''
  
  time_offset = 2208988800 # (70*365 + 17)*86400 = 2208988800 (in seconds)
  
  # offset = 3775484294
  
  days = 43697
  
  pdat = "1900-01-01 00:00:00:00"
  
  mdat = "2019-08-23 22:02:44:00" # str(datetime.now()) + str(datetime.now().time())
  
  pdate = datetime.strptime(pdat, "%Y-%m-%d %H:%M:%S:%f").date()
  
  mdate = datetime.strptime(mdat, "%Y-%m-%d %H:%M:%S:%f").date()
  
  delta = (mdate - pdate).days
  
  offset = delta * 86400
  
  def time_delta(s):
  
      return (s - time_offset)
  
  
  
  while True:
  
      frame_exists, curr_frame = cap.read()
  
      if frame_exists:
  
          seconds = cap.getRTPTimeStampSeconds()
  
          fraction = cap.getRTPTimeStampFraction()
  
          timestamp = cap.getRTPTimeStampTs()
  
          unix_offset = seconds - time_offset
  
          msec = int((int(fraction) / 0xFFFFFFFF) * 1000.0)
  
          ts = float(str(unix_offset) + "." + str(msec))
  
          # print("Timestamp per Frame:%i" % timestamp)
  
          print((datetime.fromtimestamp(float(ts) + offset)))
  
  cap.release()

  My Output :

  On August 23, 2019 at 22:02

  ...
  
  2019-08-23 13:59:52.781000
  
  2019-08-23 13:59:52.726000
  
  2019-08-23 13:59:52.671000
  
  2019-08-23 13:59:52.616000
  
  2019-08-23 13:59:52.561000
  
  2019-08-23 13:59:52.506000
  
  2019-08-23 13:59:52.451000
  
  2019-08-23 13:59:52.396000
  
  2019-08-23 13:59:52.342000
  
  2019-08-23 13:59:52.287000
  
  2019-08-23 13:59:52.232000
  
  2019-08-23 13:59:52.177000
  
  2019-08-23 13:59:52.122000
  
  2019-08-23 13:59:52.067000
  
  2019-08-23 13:59:52.012000
  
  2019-08-23 13:59:53.570000
  
  2019-08-23 13:59:53.020000
  
  2019-08-23 13:59:53.847000
  
  2019-08-23 13:59:53.792000

  I’ve noticed how the time increments weirdly (that’s not suppose to happen in the real, current time), such as the last two lines and a few others in between in the output. A bit flabbergasted as to what went wrong. Also trying this out on multiple IP cameras, with each showing a different timestamp probably related to when they were turned on.

• Dreamcast Development Desktop

  28 mars 2011, par Multimedia Mike — Sega Dreamcast

  Some people are curious about what kind of equipment is required to program a Sega Dreamcast. This is my setup :

  
  
  

  It’s a bit overcomplicated. The only piece in that picture which doesn’t play a role in the Dreamcast development process is the scanner. The Eee PC does the heavy lifting of development (i.e., text editing and cross compilation) and uploads to the Dreamcast via a special serial cable. Those are the most essential parts and are really the only pieces necessary for a lot of algorithmic stuff (things that can be validated via a serial console). But then I have to go up a level where I output video. That’s where things get messy.

  
  
  

  The Mac Mini and giant monitor really just act as a glorified TV in this case. Ideally, it will be more than that. The DC outputs audio and video via composite cables to a Canopus DV capture bridge. That’s connected via FireWire to the external hard drive underneath the Mac Mini, which is connected to the Mac. Adobe Premiere Pro handles the DV capture / display.

  One day I hope to have something worthwhile to capture.

• Evolution #4768 : Sus aux préfixes navigateurs

  5 mai 2021, par cedric -

  je suis pas fan du prefixeur JS :(

  Dans le plugin BS4 j’ai fait un mini-prefixeur utilisable en filtre, soit dans le squelette lui même en ajoutant le filtre à la fin, soit dans le head en l’utilisant en filtre sur le nom du fichier.

  Je dis "mini-prefixeur" car il a pas la prétention de traiter tous les cas, je me suis concentré sur "tous les cas utilisés dans BS4", ce qui couvre quand même les cas les plus courants... (mais pas les css grids par exemple donc)

  J’avais fait une recherche sur les prefixeurs PHP, mais rien trouvé de super convaincant. Cela dit, si quelqu’un a une lib propre et à peu près à jour sous la main, on peut facilement l’intégrer au lieu du truc à la main, et ainsi avoir donc un prefixeur PHP facile à utiliser...