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• pthread_frame : don’t sync items between threads for intra-only codecs.

  28 mars 2017, par Ronald S. Bultje

  pthread_frame : don’t sync items between threads for intra-only codecs.
  Intra-only codecs should either be able to read these items from the
  
  bitstream, or they should be set upon codec initialization. In both
  
  cases, syncing these items at runtime is unnecessary.
  In practice, this fixes race conditions for decoders that read these
  
  values from the bitstream.
  

  • [DH] libavcodec/pthread_frame.c

• configure : Place all temporary files in one separate directory

  21 septembre 2014, par Michał Górny

  configure : Place all temporary files in one separate directory
  Place all temporary files within a single, quasi-atomically created
  
  temporary directory rather than relying on unsafe ’mktemp -u’. This
  
  prevents possible race conditions in case two parallel ’mktemp -u’ calls
  
  returned the same path. Additionally, it reduces TMPDIR pollution by
  
  keeping all test files in a single subdirectory.
  Signed-off-by : Diego Biurrun <diego@biurrun.de>
  

  • [DBH] configure

• How do I run two indefinite loops simultaneously, while also changing variables within them ?

  11 octobre 2016, par Nyalmo

  I’m trying to write a script in Python that records a stream of an IP camera in realtime. It only keeps about a minute worth of recording, constantly overwriting the same files. Whenever an external sensor is triggered I want a variable to be set (event variable) which merges the recording with an extra 30 seconds it records after the sensor is triggered. The combined 90 seconds are then saved as the date and time for later review.

  The idea was to have 2 indefinite while loops, the first containing both the real time recording and the event. The second one would constantly read input and activate the ’event’ function. Initially I though I could just have a software version of the hardware interrupt I’ve learned before, though after some research it seems that’s only for exceptions. I’m currently using TkInter, simulating the external input with keypresses.

  When I tried it out the input wouldn’t cause the event to be triggered. So my question is : How do I run the two indefinite loops simultaneously, while also having the input loop change variables in the main loop so that the ’event’ can actually occur in real-time ?

  Since I’m using ffmpeg to record the stream, once the command is called to record it can’t be stopped, but I want the event variable to be changed as soon as possible.

  I’ve looked at several similar questions regarding multiple loops, and have tried multiprocessing(though this only seems to be used for performance, which is not that important here), making two separate files(not sure how to have them work together) and lastly, threads. None of these seem to work in my situation as I can’t get them running in the way that I want.

  Here is my latest attempt, using threads :

  i = 0
  
  event = False
  
  aboutToQuit = False
  
  someVar = 'Event Deactivated'
  
  lastVar = False
  
  
  
  def process(frame):
  
      print "Thread"
  
      i = 0    
  
      frame = frame 
  
      frame.bind("<space>", switch)
  
      frame.bind("<escape>", exit) 
  
      frame.pack()
  
      frame.focus_set()
  
  
  
  def switch(eventl):
  
      print(['Activating','Deactivating'][event])
  
      event = eventl
  
      event = not(event)
  
  
  
  def exit(eventl):
  
      print'Exiting Application'
  
      global aboutToQuit
  
      #aboutToQuit = True
  
      root.destroy()
  
  
  
  print("the imported file is", tkinter.__file__)
  
  def GetTime(): #function opens a script which saves the final merged file as date and time.
  
      time = datetime.datetime.now()
  
      subprocess.call("./GetTime.sh", shell = True)
  
      return (time)
  
  
  
  def main(root):
  
      global event, aboutToQuit, someVar,lastVar      
  
      while (not aboutToQuit):
  
          root.update() # always process new events
  
  
  
          if event == False:
  
              someVar = 'Event Deactivated'
  
              subprocess.call(Last30S_Command) #records last 30 seconds overwriting itself.
  
              print "Merge now"
  
              subprocess.call(Merge_Command) #merges last 30 seconds with the old 30 seconds       
  
              print "Shift now"
  
              subprocess.call(Shift_Command) #copies the last30s recording to the old 30 seconds, overwriting it.
  
              if lastVar == True: #Triggers only when lastVar state changes
  
                  print someVar
  
                  lastVar = False
  
              time.sleep(.1)
  
  
  
          if event == True: 
  
               someVar = 'Event Activated'
  
              print"Record Event"
  
              subprocess.call(EventRecord_Command) #records 30 seconds after event is triggered.
  
              print"EventMerge Now"
  
              subprocess.call(EventMerge_Command) # merges the 1 minute recording of Merge_Command with 30 seconds of EventRecord_Command
  
              if lastVar == False:
  
                  print someVar
  
                  lastVar = True
  
              time.sleep(.1)
  
              GetTime() #Saves 90 seconds of EventMerge_Command as date and time.
  
              subprocess.call(EventShift_Command) #Copies EventRecord file to the old 30 second recording, overwriting it
  
  
  
          if aboutToQuit:
  
             break
  
  
  
  
  
  if __name__ == "__main__":
  
      root = Tk() 
  
      frame = Frame(root, width=100, height=100)   
  
  #   maintthread = threading.Thread(target=main(root))
  
  #   inputthread = threading.Thread(target=process(frame))
  
  #   inputthread.daemon = True
  
  #   inputthread.start()
  
  #   maintthread.daemon = True
  
  #   maintthread.start()
  
  #   maintthread.join()
  
      Process(target=process(frame)).start()
  
      Process(target=main(root)).start()
  
      print "MainLoop"
  
  </escape></space>