[solved] Stopping a video with a key release?

Comments

• adamstone

  December 2014 edited December 2014

  Hello,

  I did some more work on this via a lot of googling through this forum. I now think a parallel structure might work, where one side looks for the key release event, while the other side presents the video.

  I talked with my colleague and we no longer need the video to actually stop when the key is released. So the problem is simpler now...I just need it to record the time when a key is pressed and held down, starting a video, to the time the key is released.

  I am able to make the first part work using an inline script polling for pygame.KEYDOWN. Then the video runs. Then I have a second inline script that measures RT but it does not continue from when the video started...I have to release the key and then press it down and then release it again and then a RT is recorded but that's not what I want at all.

  (Instruction - "hold down key to play") -> key is held down -> video plays -> key is released and RT is recorded from key_down. (video can keep playing; it's very short anyway)

  Here's my latest attempt at this--Dropbox link

  I am thinking maybe I need to replace the loop/sequence with one big long inline script that calls for the video player and pygame.KEYDOWN and pygame.KEYUP but I am having difficulty finding documentation on how to call video player in the inline script??

  Thanks again,
  Adam
• eduard

  December 2014 edited 4:44PM

  Hi Adam,

  Your last idea is just what I had in mind. So, what you probably want the do is getting an inline_script in which you have your loop waiting for key presses and releases. As soon as you hold on specific key you start your video and wait until the key release. The only thing I am unsure about is, whether you can continue monitorring the keypress situation while the video is playing, or you have to wait until the video stops to be able to continue looping. I think it should be fine though.
  I recommend you're loading on of the 'backends' in the inline_scripts and use its functionality to present videos. I can't really tell you which backend is the best for video presentation. Xpyriment has at least video functionality

  Here is a small description how to load the libraries into opensesame.
  Basically, it boils down to:

  from expyriment import stimuli
  video = stimuli.Video(file)
  

  I hope this helps. Sorry for not giving more detailed information, but I haven't work with it yet myself.

  Good luck,

  Eduard

  
• adamstone

  December 2014 edited December 2014

  Eduard,

  Thanks for your help. I tried those two lines you gave me, and it didn't work - so I went for some more searching on how to build while loops with videos and got pretty overwhelmed.

  Then I had an idea. I looked in video_player.py (the plugin file itself) and found a line that referenced to KEYDOWN - so I changed that to KEYUP and also added a few more lines to print out reaction time in the debug window.

  IT WORKED PERFECTLY! Yes, I know, this basically breaks video_player's normal functionality, but it will do for now. This approach seems easier than any other approach I've tried.

  Now the issue is, it logs the reaction times as NA...I find this puzzling as it prints out just fine (and very accurately) to the debug window, but in the log file it's NA. I feel I'm missing something simple here. Shouldn't self.set('keydowntime', start_t) work fine? I tried exp.set() and set() and self.log() and exp.log() and log() but all throw errors. I'm sure I'm missing something simple here.

  Here's my mods to the code in video_player.py:

  """
  Handles the actual video playback
  """
  
  # Log the onset time of the item
  self.set_item_onset()
  
  t = pygame.time.get_ticks()
  start_t = t
  self.set('keydowntime', start_t)
  
  
  # Loop until a key is pressed
  go = True
  while go:
  
      # Get the frame     
      self.src = cv.QueryFrame(self.video)
  
      # Check for the end of the video
      if self.src == None:
          break       
  
      # Resize if requested and convert the resulting image to
      # RGB format, which is compatible with PyGame
      if self._fullscreen:
          cv.Resize(self.src, self.src_tmp)
          cv.CvtColor(self.src_tmp, self.src_rgb, cv.CV_BGR2RGB)
      else:
          cv.CvtColor(self.src, self.src_rgb, cv.CV_BGR2RGB)
  
      # Convert the image to PyGame format
      pg_img = pygame.image.frombuffer(self.src_rgb.tostring(), cv.GetSize(self.src_rgb), "RGB")
  
      # Show the video frame!
      self.experiment.surface.blit(pg_img, (self._x, self._y))    
      pygame.display.flip()
  
      # Pause before jumping to the next frame
      pygame.time.wait(self.frame_dur - pygame.time.get_ticks() + t)
      t = pygame.time.get_ticks()
  
      if type(self.duration) == int:          
          # Wait for a specified duration
          if t - start_t >= self.duration:
              go = False
  
      # Catch escape presses
      for event in pygame.event.get():        
  
          if event.type == KEYUP:                 
              if event.key == pygame.K_ESCAPE:
                  raise exceptions.runtime_error("The escape key was pressed.")
              if self.duration == "keypress": 
                  keyup_t = pygame.time.get_ticks()
                  self.set('keyuptime', keyup_t)
                  keyreleasert = keyup_t - start_t
                  self.set('keyreleasert', keyreleasert)
                  print 'key was released at %d ms' % (keyreleasert)
                  go = False
  
  
  
          if event.type == MOUSEBUTTONDOWN and self.duration == "mouseclick":
              go = False
  
• eduard

  December 2014 edited 4:44PM

  Sorry for the confusion, Adam. The two lines were not supposed to work (well, I wouldn't mind if they did, though). It should just demonstrate how you can access expyriments functionality, in general. You would have to check their documentation to make it work, but I am quite sure it should be possible.

  I think the reason why you're not logging anything right now is that you're trying to set experiment variables outside an experiment. At the position where you modified the file, self doesn't refer to the experiment, but to the video player class. The actual experiment is an attribute of the class, though, so you should be able to set its variables if you use: self.experiment.set('keydowntime', start_t). Can you check that?

  Best,
  Eduard

  
• adamstone

  December 2014 edited 4:44PM

  That works perfectly. THANK YOU, Eduard! I really, really appreciate this. Now we can do our study. Let me know if there's anything I can do for you!

  Adam