Recherche avancée

Sur d’autres sites (5013)

• Python : What's the fastest way to load a video file into memory ?

  8 juillet 2017, par michaelh

  First some background

  I am trying to write my own set of tools for video analysis, mainly for detecting render errors like flashing frames and possibly some other stuff in the future.

  The (obvious) goal is to write a script, that is faster and more accurate than me watching the file in real time.

  Using OpenCV, I have something that looks like this :

  import cv2
  
  
  
  
  
  vid = cv2.VideoCapture("Video/OpenCV_Testfile.mov", cv2.CAP_FFMPEG)
  
  width = 1024
  
  height = 576
  
  length = vid.get(cv2.CAP_PROP_FRAME_COUNT)
  
  
  
  for f in range(length):
  
      blue_values = []
  
      vid.set(cv2.CAP_PROP_POS_FRAMES, f)
  
      is_read, frame = vid.read()
  
      if is_read:
  
          for row in range(height):
  
              for col in range(width):
  
                  blue_values.append(frame[row][col][0])
  
      print(blue_values)
  
  vid.release()

  This just prints out a list of all blue values of every frame.
   Just for simplicity (My actual script compares a few values across each frame and only saves the frame number when all are equal)

  Although this works, it is not a very fast operation. (Nested loops, but most important, the read() method has to be called for every frame, which is rather slow.
  I tried to use multiprocessing but basically ended up having the same crashes as described here :

  how to get frames from video in parallel using cv2 & multiprocessing in python

  I have a 20s long 1024x576@25fps Testfile which performs as follows :

  • mov, ProRes : 15s
  • mp4, h.264 : 30s (too slow)

  My machine is capable of playing back h.264 in 1920x1080@50fps with mplayer (which uses ffmpeg to decode). So, I should be able to get more out of this. Which leads me to

  my Question

  How can I decode a video and simply dump all pixel values into a list for further (possibly multithreaded) operations ? Speed is really all that matters. Note : I’m not fixated on OpenCV. Whatever works best.

  Thanks !

• running ffmpeg from Popen inside (twisted) timer.LoopingCall() stalls

  14 février 2014, par user1913115

  I have an RTSP stream which i need to re-stream as HLS. When RTSP stream goes down (e.g. camera disconnects) I put a blue screen to let the user know that the camera went offline. HLS segmenter is running separately, listening on port 22200 for incoming packets.

  in python the code essentially boils down to this :

  import psutil, subprocess as sb
  
  from twisted.internet import reactor, task
  
  from cameraControls import camStatus, camURL
  
  ffOn = False
  
  psRef = False
  
  def monitor():
  
   print "TIMER TICK"
  
   if camStatus()=='ON' and not ffOn: #camera just came online
  
    cmd = ["ffmpeg", "-i", camURL, "-codec", "copy", "-f", "mpegts", "udp://127.0.0.1:22200"]
  
    ps = sb.Popen(cmd,stderr=sb.PIPE)
  
    psRef=ps
  
   #check the stream:
  
   psmon = psutil.Process(psRef.pid)
  
   if psmon.status!=psutil.STATUS_RUNNING: 
  
    print "FFMPEG STOPPED"
  
  
  
  tmr = task.LoopingCall(monitor)
  
  tmr.start(2)
  
  reactor.run()

  it works fine for 5-6 minutes, then i see the video stall and if i check the cpu usage of the ffmpeg it shows 0, the ffmpeg output doesn't change, as if paused. however psmon.status shows as running, and the timer is still going (i see "TIMER TICK" message pop up every 2 seconds in the command line.

  if i simply run the ffmpeg command from the command line (not from python) then it works for hours no problem.

  does anybody know if the twisted reactor is stalling the process ? or is it the subprocess.Popen itself issue ? or the timer itself is glitching somehow(even though it gets to the 'monitor' function) ? i have other timers running also in the same reactor (same thread), could that be an issue ?

• How to make videos .mp4 for a Phillips Media Player GO GEAR VIBE models ? [closed]

  14 avril 2023, par Ivan Rojas Calvo

  Here is the answer by steps (4/13/23) :

  


  


  1. First download and install the software WinFF here

     


  


  2. Check the specificacions of your media player, mine is the GoGearVibe SA2VBE08K/55 model

     


  


  3. Look for the video specification : mine says that the video format needs to match this specifications :

     


     Format = MJPEG (.mp4)

     


     Resolution = 128 x 128 píxeles

     


     Frames per second = 30 cps (fps)

     


     Bitrate = 512 kpbs

     


  


  4. Read this tutorial to create a preset in WinFF here

     


  


  5. Create a preset that turns ANY mp4 video you have into an MJPEG video with the properties shown above with this info :

     


     name : GoGearVibe55

     


     preset label : MJPEG GOGEAR

     


     Preset command line :

     


     -f mov -vf scale=128:128 -c:v mjpeg -b:v 512k -r 25 -c:a adpcm_ima_wav -b:a 192k -ar 22050 -ac 2


     


     output file : mp4

     


  


  6. Understand how to adapt the code to your necessities with this image
enter image description here

     


  


  


  Do not change what is mark in red, that's the resolution of the screen and the encoder of the video. You can change the value mark in blue, which means the bitrate, more bitrate the video will have more definition without changing the resolution. Tha value in green refers to the fps and the ones marked in yellow is the audio settings, don't worry about that, are good audio settings.

  


  Done. I did'n know how to create an article so I let you try this solution, good luck !