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• arm : vp9mc : Calculate less unused data in the 4 pixel wide horizontal filter

  17 décembre 2016, par Martin Storsjö

  arm : vp9mc : Calculate less unused data in the 4 pixel wide horizontal filter
  Before :                    Cortex A7      A8     A9     A53
  
  vp9_put_8tap_smooth_4h_neon :   378.1   273.2  340.7   229.5
  
  After :
  
  vp9_put_8tap_smooth_4h_neon :   352.1   222.2  290.5   229.5
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/arm/vp9mc_neon.S

• Calculate frames to remove to get timelapse of desired length

  12 juin 2016, par Espen Birk

  I’ve got lots of images stored on a server, and a reference in a MySQL database so that i can easily query it for image from specific dates/time.

  Images is taken with an interval of 7 images/hour.

  Lets say i want to create a timelapse from the last 4 days, and make a 5 sec movie. How can i calculate how to evenly drop frames to get to that desired length of 5 seconds ?

  This is what i got so far.

  Total images : 4 Days * 24 hours * 7 images/hour = 672 images
  Required images at 24 fps : 24 * 5 = 120 images

  Divide the total images with the required images to find out which/every frame i need to keep

  672 / 120 = 5.6

  Then i loop trough all 672 images, and every 5th or 6th time i store a reference to the image in an array.

  Here is my problem. If i round up i get a video thats longer than i want, and if i round down i get a video thats shorter.

  If i keep every 5th image when looping : 134 images / 24 fps = 5.6 sec video
  If i keep every 6th image when looping : 112 images / 24 fps = 4.6 sec video

  Is it possible to get it better, and still skip images evenly ?

  Solved this using xxfelixxx’s answer in PHP
  Heres the code in PHP :

  $start  = 1;
  
  $stop   = 672; // Total Images
  
  
  
  $dur    = 5;   // Video Duration
  
  $n      = 24 * $dur; // Required frames - 24 FPS * Duration
  
  $next   = $start;
  
  $step = ( $stop - $start ) / $n;
  
  
  
  $frames = array();
  
  
  
  for ($i = 1; $i <= $n; $i++) {
  
      $frames[] = round($next);
  
      $next += $step;
  
  };
  
  
  
  var_dump($frames);

• calculate delay time between 2 videos using ffprobe

  10 mars 2017, par Hanqing Wang

  So here is the thing. I am streaming a mpg video using live555 server(/mediaServer). Then I have a python program that open the ffserver. Then I can have 2 videos by using

  ffplay rtsp://192.168.1.7:8554/counter.mpg 
  
  
  
  ffplay http://192.168.1.7:8090/live.ts

  the problem is that the two videos have a delay from each other, like 5-10 seconds. Now I want to use ffprobe to calculate the delay time. How can I do it with a command in the terminal ?

  Here is th python code :

  from subprocess import call
  
  import os
  
  
  
  URLCamera = "rtsp://192.168.1.7:8554/counter.mpg"
  
  
  
  def ipCamera_to_URL(ipCamera): 
  
  return URLCamera
  
  
  
  def define_URL_output(ipCamera, portOutput): 
  
  return "http://localhost:"+str(portOutput)+"/feed.ffm"
  
  
  
  def run_ffserver(portOutput):
  
  os.system("sh runserver.sh ffserver_"+str(portOutput)+".conf")
  
  
  
  def connect_camera(ipCamera, portOutput):
  
  os.system("sh connect_camera.sh "+str(ipCamera_to_URL(ipCamera))+" "+str(define_URL_output(ipCamera,portOutput)))
  
  
  
  if __name__=="__main__":
  
  run_ffserver("8090") # Run a first process which will forward video stream to http://localhost:8090/feed.ffm
  
  connect_camera("1","8090")
  
  run_ffserver("8091") # Run a first process which will forward video stream to http://localhost:8091/feed.ffm
  
  connect_camera("2","8091")