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• FFmpeg cant recognize 3 channels with each 32 bit

  4 avril 2022, par Chryfi

  I am writing the linearized depth buffer of a game to openEXR using FFmpeg. Unfortunately, FFmpeg does not adhere to the openEXR file specification fully (like allowing unsigned integer for one channel) so I am writing one float channel to openEXR, which is put into the green channel with this command -f rawvideo -pix_fmt grayf32be -s %WIDTH%x%HEIGHT% -r %FPS% -i - -vf %DEFVF% -preset ultrafast -tune zerolatency -qp 6 -compression zip1 -pix_fmt gbrpf32le %NAME%_depth_%d.exr.

  


  The float range is from 0F to 1F and it is linear. I can confirm that the calculation and linearization is correct by testing 16 bit integer (per pixel component) PNG in Blender compositor. The 16 bit integer data is written like this short s = (short) (linearzieDepth(depth) * (Math.pow(2,16) - 1)) whereas for float the linearized value is directly written to OpenEXR without multiplying with a value.

  


  However, when viewing the openEXR file it doesn't have the same "gradient" as the 16 bit png... when viewing them side by side, it appears as if the values near 0 are not linear, and they are not as dark as they should be like in the 16 bit png.
(And yes, I set the image node to linear), and comparing it with 3d tracking data from the game I cant reproduce the depth and cant mask things using the depth buffer where as with the png I can.

  


  How is it possible for a linear float range to turn out so different to a linear integer range in an image ?

  


  UPDATE :

  


  I now write 3 channels to the ffmpeg with this code

  


  float f2 = this.linearizeDepth(depth);

buffer.putFloat(f2);
buffer.putFloat(0);
buffer.putFloat(0);


  


  the byte buffer is of the size width * height * 3 * 4 -> 3 channels with each 4 bytes. The command is now -f rawvideo -pix_fmt gbrpf32be -s %WIDTH%x%HEIGHT% -r %FPS% -i - -vf %DEFVF% -preset ultrafast -tune zerolatency -qp 6 -compression zip1 -pix_fmt gbrpf32le %NAME%_depth_%d.exr which should mean that the input (byte buffer) is expecting 32 bit floats with 3 channels.

  


  FFmpeg is somehow splitting up channels or whatever... could be a bug, could be my fault ?

  


• Revision 122868 : Toujours sur ces vues de saisies fieldset. Champ extra se base sur le ...

  7 mars 2020, par Maïeul Rouquette — Log

  Toujours sur ces vues de saisies fieldset.
  Champ extra se base sur le classe vide pour ne pas afficher les saisies
  sans réponse. Le masquage est en css, contrairement à ce que je pensais
  (suis-je bête !)
  On ajoute donc la classe vide à la vie d’une saisie si l’ensemble de ses
  sous saisies sont vide.
  Permet d’éviter avec champ extra d’avoir un titre de fieldset qui se
  balade sans aucune réponse en dessous.

• Evolution #2040 (Nouveau) : Accueil inistial sur un site nouvellement installé

  1er mai 2011, par Suske -

  Première arrivée dans le privé : contenu/accueil.html est vide => il y a mieux que le vide :-)

  un lien vers la config du site

  une phrase "Créez maintenant une rubrique puis publiez-y un premier article... bla."

  ... Un page "premiers pas en quelques sortes (...)