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• Python PyQT : How to call a GUI function from a worker thread ?

  18 juillet 2014, par rainer

  I have a pyqt gui and calling a long process (ffmpeg) which I put on a separate thread to not block the gui. I then want to update a progress bar when one command of a longer list of commands finishes. The problem is, that I can’t call a function in the gui thread out of the worker thread. So I let run a ticker in the worker thread, but when I update the progress bar with a while loop and reading the ticker value, the gui gets blocked again. How can I solve this. I used currently python threading and not Qthread.
  Thx for any help !

  import threading, pexpect
  
  
  
  self.cmd_list = ['ffmpeg -i file outfile','and so on']
  
  
  
  self.stop_proc = False
  
  self.executeCMD()
  
  
  
  def spawn_ffmpeg_cmd(self):
  
      for cmd in self.cmd_list:
  
          if self.stop_proc == False:
  
              thread = pexpect.spawn(cmd)
  
              print "\nstarted: %s" % cmd
  
              cpl = thread.compile_pattern_list([pexpect.EOF,"frame= *\d+ fps=*\d+",'(.+)'])
  
  
  
              while True:
  
                  i = thread.expect_list(cpl, timeout=None)
  
                  if i == 0: # EOF
  
                      print "the sub process exited"
  
                      self.pgticker += 1
  
                      break
  
                  elif i == 1:
  
                      frame_number_fps = thread.match.group(0)
  
                      print frame_number_fps
  
                      thread.close
  
                  elif i == 2:
  
                      pass
  
      self.startButton.setEnabled(True)
  
  
  
  
  
  def executeCMD(self):
  
      self.startButton.setEnabled(False)
  
      self.pgticker = 0
  
      threading.Thread(target=self.spawn_ffmpeg_cmd, name="_proc").start()
  
  
  
  
  
  def stopprocess(self):
  
      self.stop_proc = True
  
      self.cmd_list = []
  
      os.system('pkill ffmpeg') 
  
      self.pgticker = len(self.cmd_list)
  
      self.startButton.setEnabled(True)
  
  
  
  
  
  def updateProgress(self):  
  
      pgfactor = 100 / len(self.cmd_list)
  
      progress = 0.0
  
      progress = pgfactor*int(self.pgticker)
  
      self.progressBar.setProperty("value", progress)

• altivec : perform an explicit unaligned load

  14 août 2013, par Kostya Shishkov

  altivec : perform an explicit unaligned load
  Implicit vector loads on POWER7 hardware can use the VSX
  
  instruction set instead of classic Altivec/VMX. Let’s force
  
  a VMX load in this case.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/ppc/int_altivec.c

• Playing H.264 video in an application through ffmpeg using DXVA2 acceleration

  28 avril 2012, par cloudraven

  I am trying to output H.264 video in a Windows application. I am moderately familiar with FFMPEG and I have been successful at getting it to play H.264 in a SDL window without a problem. Still, I would really benefit from using Hardware Acceleration (probably through DXVA2)

  I am reading raw H264 video, no container, no audio ... just raw video (and no B-frames, just I and P). Also, I know that all the systems that will use this applications have Nvidia GPUs supporting at least VP3.
  Given that set of assumptions I was hoping to cut some corners, make it simple instead of general, just have it working for my particular scenario.

  So far I know that I need to set the hardware acceleration in the codec context by filling the hwaccel member through a call to ff_find_hwaccel. My plan is to look at Media Player Classic Home Cinema which does a pretty good job at supporting DXVA2 using FFMPEG when decoding H.264. However, the code is quite large and I am not exactly sure where to look. I can find the place where ff_find_hwaccel is called in h264.c, but I was wondering where else should I be looking at.

  More specifically, I would like to know what is the minimum set of steps that I have to code to get DXVA2 through FFMPEG working ?

  EDIT : I am open to look at VLC or anything else if someone knows where I can find the "important" piece of code that does the trick. I just mentioned MPC-HC because I think it is the easiest to get to compile in Windows.