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• ffmpeg error : Unable to find a suitable output format for 'scale=1500:1000'

  13 février 2021, par Tomáš Zato - Reinstate Monica

  I am trying to convert a bunch of images into a video. The original image resolution is 6000x4000, but if I use ffmpeg to create a video with that resolution, no player can even play it because it's way to huge.

  


  I tried to set the output resolution as such, dividing the input resolution by 4 :

  


  ffmpeg -r 60 -s 1500x1000 -start_number 3790 -i DSC_%04d.jpg -vcodec libx264 -crf 25  -pix_fmt yuv420p ../video_lowres.mp4


  


  This had no effect and still produced 6000x4000 video. So instead, I tried this parameter : scale=1500:1000 The full command I ran :

  


  ffmpeg -r 60 scale=1500:1000 -start_number 3790 -i DSC_%04d.jpg -vcodec libx264 -crf 25  -pix_fmt yuv420p ../video_lowres.mp4


  


  But I got this error :

  


  [NULL @ 000002ad897bd9c0] Unable to find a suitable output format for 'scale=1500:1000'
scale=1500:1000: Invalid argument


  


  How can I create a downscaled video from photos using ffmpeg ?

  


• Anomalie #4342 (Fermé) : Erreur 1071 de mysql : Specified key was too long ; max key length is 1000 ...

  26 mai 2019

  Bonjour,

  Après avoir configuré MariaDB pour être en UTF8MB4, je n’ai pas pu installer un plugin (comme il y a aussi un bug SVP, je vais faire un autre ticket spécifique).
  Pour être précis, un table du plugin n’a pas été créée et sql.log contient :
  

  2019-05-25 16:23:59 78.205.175.37 (pid 16091) :Pri:ERREUR : Erreur 1071 de mysql : Specified key was too long ; max key length is 1000 bytes
  in ecrire/base/create.php L73 [sql_create(),creer_ou_upgrader_table(),alterer_base(),maj_tables(),serie_alter(),maj_while(),maj_plugin(),referer_spam_upgrade(),spip_plugin_install(),plugins_installer_dist(),installer_plugin(),do_install(),do_action(),one_action(),action_actionner_dist(),traiter_appels_actions()]
  CREATE  TABLE IF NOT EXISTS `mutu_pro2spipf126`.spip_referer_spam (
          date DATE NOT NULL,
          referer VARCHAR (255) ,
          PRIMARY KEY (referer)) ENGINE=MyISAM
  

  La documentation sur ce sujet est abondante.
  Ceci m’a semblé un bon résumé du problème : https://stackoverflow.com/questions/6172798/mysql-varchar255-utf8-is-too-long-for-key-but-max-length-is-1000-bytes
  Et la solution générale consiste à faire un index de seulement 191 : https://dev.mysql.com/doc/refman/5.7/en/charset-unicode-conversion.html :
  

  In an InnoDB table that uses COMPACT or REDUNDANT row format, these column and index definitions are legal :
  col1 VARCHAR(500) CHARACTER SET utf8, INDEX (col1(255))
  To use utf8mb4 instead, the index must be smaller :
  
  col1 VARCHAR(500) CHARACTER SET utf8mb4, INDEX (col1(191))
  

• Split a movie into 1000+ shots using PyAV in a single pass ?

  3 mai 2019, par Andrew Klaassen

  I need to split a 44 minute MP4 into 1000 shots (i.e. separate MP4s) with ffmpeg. I want to do it quickly (i.e. in a single pass rather than 1000 passes), I need perfect frame accuracy, and I need to do it in Windows.

  The Windows command-line length limit is stopping me from doing this, and I’m wondering if someone could show me an example of how to do this using a library like PyAV or Avpy. (Libraries like ffmpeg-python and ffmpy won’t help, since they simply construct an ffmpeg command line and run it, leading to the same Windows command-line length issue that I already have.)

  After much testing and gnashing of teeth, I’ve learned that the only way to get perfect frame accuracy from ffmpeg, 100% of the time, is to use the "select" filter. ("-ss" in the newest versions of ffmpeg is frame accurate 99% of the time ; unfortunately, that’s not good enough for this application.)

  There are two ways to use "select" for this. There’s the slow way, which I’m doing now, and which requires having ffmpeg open the file 1000 times :

  for (start, end, name) in shots:
  
      audio_start = start / frame_rate
  
      audio_end = end + 1 / frame_rate
  
      cmd = [
  
          path_to_ffmpeg,
  
          '-y',
  
          '-i', input_movie,
  
          '-vf', r'select=between(n\,%s\,%s),setpts=PTS-STARTPTS' % (start, end),
  
          '-af', 'atrim=%s:%s,asetpts=PTS-STARTPTS' % (audio_start, audio_end),
  
          '-c:v', 'libx264',
  
          '-c:a', 'aac',
  
          '-write_tmcd', '0',
  
          '-g', '1',
  
          '-r', str(frame_rate),
  
          name + '.mp4',
  
          '-af', 'atrim=%s:%s' % (audio_start, audio_end),
  
          name + '.wav',
  
      ]
  
      subprocess.call(cmd)

  And there’s the fast way, which causes the Windows command line to explode when there are too many shots. The long command line leads to a failure to run :

  cmd = [
  
      path_to_ffmpeg,
  
      '-y',
  
      '-i',
  
      input_movie,
  
  ]
  
  for (start, end, name) in shots:
  
      audio_start = start / frame_rate
  
      audio_end = end + 1 / frame_rate
  
      cmd.extend([
  
          '-vf', r'select=between(n\,%s\,%s),setpts=PTS-STARTPTS' % (start, end),
  
          '-af', 'atrim=%s:%s,asetpts=PTS-STARTPTS' % (audio_start, audio_end),
  
          '-c:v', 'libx264',
  
          '-c:a', 'aac',
  
          '-write_tmcd', '0',
  
          '-g', '1',
  
          '-r', str(frame_rate),
  
          name + '.mp4',
  
          '-af', 'atrim=%s:%s' % (audio_start, audio_end),
  
          name + '.wav',
  
      ]
  
  subprocess.call(cmd)

  I’ve looked through the documentation of PyAV and Avpy, but I haven’t been able to figure out whether the second form of my function is something I could do there, or how I’d go about doing it. If it is possible, would someone be able to write a function equivalent to my second function, using either library ?