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• Evolution #4427 (En cours) : Permettre (via une constante) de passer de 65 536 à 4096 le nombre ma...

  24 janvier 2020, par - Equipement

  Bonjour,
  Concernant le cache de second niveau de SPIP, c’est-à-dire celui qui contient le résultat du calcul des squelettes :

  Jusqu’à la branche 3.0 de SPIP la taille maximum du cache était par défaut de 10 Mo.

  A partir de la branche 3.1 de SPIP, le nombre maximal de fichier dans le cache est de 65 536 (et il n’y a plus de limite sur la taille du cache).
  Sur un cas réel, le cache a atteint 2 Go (soit une moyenne de 31 Ko par fichier).
  Certains hébergeurs ont un quota sur la taille, mais également sur le nombre d’inodes.
  Dans un cas réel, des sites ont ainsi atteint le quota d’inodes, ce qui empêchait l’accès à l’espace privé des sites (cf. contrib.spip.net/Plugins-Giseh#comment502510).

  Remarque : L’expérience montre que le passage d’un robot, qui n’est pas identifié par SPIP, peut suffit à garnir le cache. Or la liste des robots détectés par SPIP ne sera jamais exhaustive. Par ailleurs, pour certains robots (aspirateurs de sites ou autre) il est possible de modifier leur user-agent.

  Aussi, je propose que, via l’ajout d’une constante dans le fichier mes_options, il soit possible de fixer le nombre maximal de fichier dans le cache à 4096 (au lieu de 65 536). Cette approche, par constante optionnelle, évite d’impacter les sites qui veulent conserver la limite de 65 536 fichiers.

  En pratique, il s’agit d’offrir la possibilité de mettre dans le fichier mes_options la constante suivante :
  

  <span class="CodeRay"><span class="predefined">define</span>(<span class="string"><span class="delimiter">'</span><span class="content">_CACHE_MAX_4096_FILES</span><span class="delimiter">'</span></span>,<span class="predefined-constant">true</span>) ;
  </span>
  Télécharger

  et de prendre en compte cette constante dans le fichier ecrire/public/cacher.php de la manière suivante :

  <span class="CodeRay"><span class="keyword">function</span> <span class="function">ecrire_cache</span>(<span class="local-variable">$nom_cache</span>, <span class="local-variable">$valeur</span>) {
  <span class="comment">//    $d = substr($nom_cache, 0, 2);</span>
  <span class="comment">//    $u = substr($nom_cache, 2, 2);</span>
    <span class="local-variable">$longueur_d</span> = <span class="integer">2</span>;
    <span class="keyword">if</span> (<span class="predefined">defined</span>(<span class="string"><span class="delimiter">'</span><span class="content">_CACHE_MAX_4096_FILES</span><span class="delimiter">'</span></span>) <span class="keyword">AND</span> _CACHE_MAX_4096_FILES){
      <span class="local-variable">$longueur_d</span> = <span class="integer">1</span>;
    }
      <span class="local-variable">$d</span> = <span class="predefined">substr</span>(<span class="local-variable">$nom_cache</span>, <span class="integer">0</span>, <span class="local-variable">$longueur_d</span>);
      <span class="local-variable">$u</span> = <span class="predefined">substr</span>(<span class="local-variable">$nom_cache</span>, <span class="local-variable">$longueur_d</span>, <span class="integer">2</span>);
   
      <span class="local-variable">$rep</span> = _DIR_CACHE;
      <span class="local-variable">$rep</span> = sous_repertoire(<span class="local-variable">$rep</span>, <span class="string"><span class="delimiter">'</span><span class="delimiter">'</span></span>, <span class="predefined-constant">false</span>, <span class="predefined-constant">true</span>);
      <span class="local-variable">$rep</span> = sous_repertoire(<span class="local-variable">$rep</span>, <span class="local-variable">$d</span>, <span class="predefined-constant">false</span>, <span class="predefined-constant">true</span>);
   
      <span class="keyword">return</span> ecrire_fichier(<span class="local-variable">$rep</span> . <span class="local-variable">$u</span> . <span class="string"><span class="delimiter">"</span><span class="content">.cache</span><span class="delimiter">"</span></span>, <span class="predefined">serialize</span>(<span class="predefined">array</span>(<span class="string"><span class="delimiter">"</span><span class="content">nom_cache</span><span class="delimiter">"</span></span> => <span class="local-variable">$nom_cache</span>, <span class="string"><span class="delimiter">"</span><span class="content">valeur</span><span class="delimiter">"</span></span> => <span class="local-variable">$valeur</span>)));
  }
   
  <span class="keyword">function</span> <span class="function">lire_cache</span>(<span class="local-variable">$nom_cache</span>) {
  <span class="comment">//    $d = substr($nom_cache, 0, 2);</span>
  <span class="comment">//    $u = substr($nom_cache, 2, 2);</span>
    <span class="local-variable">$longueur_d</span> = <span class="integer">2</span>;
    <span class="keyword">if</span> (<span class="predefined">defined</span>(<span class="string"><span class="delimiter">'</span><span class="content">_CACHE_MAX_4096_FILES</span><span class="delimiter">'</span></span>) <span class="keyword">AND</span> _CACHE_MAX_4096_FILES){
      <span class="local-variable">$longueur_d</span> = <span class="integer">1</span>;
    }
      <span class="local-variable">$d</span> = <span class="predefined">substr</span>(<span class="local-variable">$nom_cache</span>, <span class="integer">0</span>, <span class="local-variable">$longueur_d</span>);
      <span class="local-variable">$u</span> = <span class="predefined">substr</span>(<span class="local-variable">$nom_cache</span>, <span class="local-variable">$longueur_d</span>, <span class="integer">2</span>);
   
      <span class="keyword">if</span> (<span class="predefined">file_exists</span>(<span class="local-variable">$f</span> = _DIR_CACHE . <span class="string"><span class="delimiter">"</span><span class="local-variable">$d</span><span class="content">/</span><span class="local-variable">$u</span><span class="content">.cache</span><span class="delimiter">"</span></span>)
          <span class="keyword">and</span> lire_fichier(<span class="local-variable">$f</span>, <span class="local-variable">$tmp</span>)
          <span class="keyword">and</span> <span class="local-variable">$tmp</span> = <span class="predefined">unserialize</span>(<span class="local-variable">$tmp</span>)
          <span class="keyword">and</span> <span class="local-variable">$tmp</span>[<span class="string"><span class="delimiter">'</span><span class="content">nom_cache</span><span class="delimiter">'</span></span>] == <span class="local-variable">$nom_cache</span>
          <span class="keyword">and</span> <span class="predefined">isset</span>(<span class="local-variable">$tmp</span>[<span class="string"><span class="delimiter">'</span><span class="content">valeur</span><span class="delimiter">'</span></span>])
      ) {
          <span class="keyword">return</span> <span class="local-variable">$tmp</span>[<span class="string"><span class="delimiter">'</span><span class="content">valeur</span><span class="delimiter">'</span></span>];
      }
   
      <span class="keyword">return</span> <span class="predefined-constant">false</span>;
  }
  </span>
  Télécharger

  Cordialement
  Equipement

• Is there a way to extract a video frame, encode a sentence behind it, put it back, and then decode it ?

  29 juillet 2021, par Jesse Hix

  I am trying to do stenography on an MP4 video where I am pulling a frame out at a certain time, 5.52 sec, saving that frame as a jpg or jpeg using any image stenography tool, in this case stegosuite, to encode a sentence behind the image and then reinsert that image back into the video at the same time and then extract it again with the same command and using the same steno tool read the message.

  


  Up until decoding the message everything runs without issue.
I know that it is not working because the videos are not the same in size meaning that the frankenstein video is not the same as the original and thus messing up the frame extraction.

  


  Question :
  Is there a way to extract a frame encode a sentence behind it put it back and then decode it ?

  


  What I tried :
  
Used to extract the frame both times :

  


  ffmpeg -ss 5.52 -i original.mp4 -vframes 1 frames_%d.jpg


  


  Used to combine the image back into the video :

  


  ffmpeg -i original.mp4 -i frames_1_embed.jpg -filter_complex "[1]setpts=5.52/TB[im];[0][im]overlay=eof_action=pass" -c:a copy out_1.mp4


  


• Extract all keyframe frome a video and inject them back [on hold]

  7 octobre 2019, par viewv

  Is there any way to extract all keyframe from a video then edit them or just do small changes even not change at all, and later inject them back to the video without changing other parts of the video ? I want to keep the video format so I can still play it although the predict-frame or other thing is not right.