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• Segmentation Fault error when trying to compare two videos with pHash library and its ruby bindings

  10 juillet 2014, par anado1771

  I have set up my system with the latest ffmpeg and pHash libraries (ffmpeg-2.2.1 and pHash-0.9.6) as well as the pHash ruby gem (https://github.com/toy/pHash).

  I am using ruby and attempting to compare two video files like this :

  require 'phash/video'
  
  
  
  video1 = Phash::Video.new('video1.mp4')
  
  video2 = Phash::Video.new('video2.mp4')
  
  
  
  video1 % video2

  Executing this script results in a Segmentation fault :

  ..../gems/pHash-1.1.4/lib/phash/video.rb:20: [BUG] Segmentation fault
  
  ruby 1.9.3p545 (2014-02-24 revision 45159) [x86_64-darwin13.1.0]
  
  
  
  -- Control frame information -----------------------------------------------
  
  c:0008 p:---- s:0029 b:0029 l:000028 d:000028 CFUNC  :ph_dct_videohash
  
  c:0007 p:0042 s:0024 b:0024 l:000023 d:000023 METHOD .../gems/pHash-1.1.4/lib/phash/video.rb:20
  
  c:0006 p:0038 s:0017 b:0017 l:000016 d:000016 METHOD .../gems/pHash-1.1.4/lib/phash.rb:43
  
  c:0005 p:0025 s:0014 b:0014 l:000013 d:000013 METHOD .../gems/pHash-1.1.4/lib/phash.rb:39
  
  c:0004 p:0011 s:0011 b:0011 l:000010 d:000010 METHOD .../gems/pHash-1.1.4/lib/phash.rb:48
  
  c:0003 p:0050 s:0006 b:0006 l:000128 d:0011b8 EVAL   video_test_phash.rb:3
  
  c:0002 p:---- s:0004 b:0004 l:000003 d:000003 FINISH
  
  c:0001 p:0000 s:0002 b:0002 l:000128 d:000128 TOP   
  
  
  
  -- Ruby level backtrace information ----------------------------------------
  
  video_test_phash.rb:3:in `<main>'
  
  .../gems/pHash-1.1.4/lib/phash.rb:48:in `similarity'
  
  .../gems/pHash-1.1.4/lib/phash.rb:39:in `phash'
  
  .../gems/pHash-1.1.4/lib/phash.rb:43:in `compute_phash'
  
  .../gems/pHash-1.1.4/lib/phash/video.rb:20:in `video_hash'
  
  .../gems/pHash-1.1.4/lib/phash/video.rb:20:in `ph_dct_videohash'
  
  
  
  ...
  
  
  
  Abort trap: 6
  
  </main>

  It appears that the crash happens in the ph_dct_videohash function which is part of the pHash library. The function is in file pHash.cpp. I am copying it here in case it would make sense to someone :

  ulong64* ph_dct_videohash(const char *filename, int &Length){
  
  
  
      CImgList *keyframes = ph_getKeyFramesFromVideo(filename);
  
      if (keyframes == NULL)
  
      return NULL;
  
  
  
      Length = keyframes->size();
  
  
  
      ulong64 *hash = (ulong64*)malloc(sizeof(ulong64)*Length);
  
      CImg<float> *C = ph_dct_matrix(32);
  
      CImg<float> Ctransp = C->get_transpose();
  
      CImg<float> dctImage;
  
      CImg<float> subsec;
  
      CImg currentframe;
  
  
  
      for (unsigned int i=0;i &lt; keyframes->size(); i++){
  
      currentframe = keyframes->at(i);
  
      currentframe.blur(1.0);
  
      dctImage = (*C)*(currentframe)*Ctransp;
  
      subsec = dctImage.crop(1,1,8,8).unroll('x');
  
      float med = subsec.median();
  
      hash[i] =     0x0000000000000000;
  
      ulong64 one = 0x0000000000000001;
  
      for (int j=0;j&lt;64;j++){
  
          if (subsec(j) > med)
  
          hash[i] |= one;
  
          one = one &lt;&lt; 1;
  
      }
  
      }
  
  
  
      keyframes->clear();
  
      delete keyframes;
  
      keyframes = NULL;
  
      delete C;
  
      C = NULL;
  
      return hash;
  
  }
  
  </float></float></float></float>

  Any help is very much appreciated !

• Combine video using ffmpeg took long time

  19 septembre 2019, par Shijin

  I have two video files,I am trying to mix the video to create a single video with one video on the left and another at the right. For this, I was used FFMPEG with the following command.

  ffmpeg -y -threads 4 -loglevel debug -ss 4.22 -t 6127.514 -i left.webm -ss 0 -t 6131.734 -i right.webm -filter_complex "[0]scale=320:-1,pad=2*iw:2*ih:0:120[left];[1]scale=320:-1[right];[left][right]overlay=main_w/2:120,scale=640:480;[0][1]amix" -shortest composed.mp4

  It is working, But it took a long time and i need to wait for hours to complete the task with large files.
  Anyone can suggest a method to improve performance or an alternative solution ?
  I have already upgraded my server with maximum resources, But not improved.

• ffmpeg list video devices with batch script to variables

  5 août 2020, par ubul

  I use the ffmpeg -stats -hide_banner -list_devices true -f dshow -i dummy command to list all video and audio devices, and I need to get all Alternative name From "DirectShow video devices" (just video devices) with batch script.

  


  I'm start with this : ffmpeg output parse in batch script (first answer)

  


  Can someone more experienced to help me with this task ? Thanks in advance !