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• FFMPEG convert 100 FPS to 30 FPS without jitters

  22 avril 2021, par Michael Joseph Aubry

  I have a rendering mechanism that uses the browser to extract frames and makes a new video. I've found getting frames from the browser while keeping the original frame rate intact with other moving parts to be a hard problem. So my solution is to take a frame every 0.1s resulting in 100 FPS.

  


  So now I have 100 screenshots per 1s of video on the local disk. Then I run this command to encode the frames into a video.

  


  const childProcess = spawn(ffmpeg, [
  "-f",
  "image2",
  "-r",
  "100",
  "-i",
  `/tmp/local-%d.jpg`,
  "-c:v",
  "libx264",
  "-vf",
  "fps=30",
  "-pix_fmt",
  "yuv420p",
  output
]);


  


  I'd like to make the output a normal frame rate like 30 in this case. The problem with this is the video will end up having some jitters because the FFMPEG algorithm is having a hard time dropping the frames correctly because the new video has an overlay on top of it.

  


  Here is an example of a video I rendered at 100 FPS https://s3.us-west-2.amazonaws.com/storycreator.v2.rendered/cknkxtfcw0016spuuem4dfmut?t=1619125309589 if you reduce the FPS to 30 you will see that some parts are not very smooth.

  


  I am wondering if I can add some flags to my command to improve the smoothness or if this is something I am going to need to solve in my screen capturing technique.

  


• Evolution #3958 : Mise à jour de la liste des types mines

  12 juin 2017, par nico d_

  Hop, pour information ce sont les type MIME, pas mines :)
  Type mine c’est pour les voitures ^^
  https://fr.wikipedia.org/wiki/Type_MIME

  Et sinon, ils sont indiqués ici dans le tableau apparemment :
  https://en.wikipedia.org/wiki/High_Efficiency_Image_File_Format#Brands_and_MIME_types

• Perspective transformations

  9 juin 2010, par Mikko Koppanen — Imagick, PHP stuff

  Finally (after a long break) I managed to force myself to update the PHP documentation and this time it was distortImage code example. Things have been hectic lately but that does not quite explain the 6 months(?) break between this and the previous post. As a matter of a fact there is no excuse for such a long silence so I will try to update this blog a bit more often from now on.

  Back in the day I used to blog the examples and update the documentation if I remembered but I am trying to fix this bad habit. Most of the latest examples have been updated in to the manual. In the case of the two last examples I updated the documentation first and then blogged on the subject.

  I took some time to actually understand the perspective transformations properly using the excellent ImageMagick examples (mainly created by Anthony Thyssen) as a reference. The basic idea of perspective distortion seems simple : to distort the control points to new locations. Grabbing the syntax for Imagick was easy, an array of control point pairs in the form of :

  php

  < view plain text >

  1. array(source_x, source_y, dest_x, dest_y ... )

  The following example uses the built-in checkerboard pattern to demonstrate perspective distortion :

  php

  < view plain text >

  1. < ?php
  2. /* Create new object */
  3. $im = new Imagick() ;
  4.  
  5. /* Create new checkerboard pattern */
  6. $im->newPseudoImage(100, 100, "pattern:checkerboard") ;
  7.  
  8. /* Set the image format to png */
  9. $im->setImageFormat(’png’) ;
  10.  
  11. /* Fill background area with transparent */
  12. $im->setImageVirtualPixelMethod(Imagick: :VIRTUALPIXELMETHOD_TRANSPARENT) ;
  13.  
  14. /* Activate matte */
  15. $im->setImageMatte(true) ;
  16.  
  17. /* Control points for the distortion */
  18. $controlPoints = array( 10, 10,
  19.             10, 5,
  20.  
  21.             10, $im->getImageHeight() - 20,
  22.             10, $im->getImageHeight() - 5,
  23.  
  24.             $im->getImageWidth() - 10, 10,
  25.             $im->getImageWidth() - 10, 20,
  26.  
  27.             $im->getImageWidth() - 10, $im->getImageHeight() - 10,
  28.             $im->getImageWidth() - 10, $im->getImageHeight() - 30) ;
  29.  
  30. /* Perform the distortion */ 
  31. $im->distortImage(Imagick: :DISTORTION_PERSPECTIVE, $controlPoints, true) ;
  32.  
  33. /* Ouput the image */ 
  34. header("Content-Type : image/png") ;
  35. echo $im ;
  36.  ?>

  Here is the source image :
  

  And the result :