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• Evolution #3071 : Performance boucle DATA sur CSV

  15 octobre 2013, par esj -

  De l’utilité de faire "svn cp" et non une copie dans éditeur perso pour que l’historique d’un code soit facile à retrouver.

  Ce code est apparu en 2007 dans r10948 qui répondait à une difficulté signalée dans Spip-contrib, à laquelle il fut répondu par un code, documenté sur spipnet comme il se doit :
  http://contrib.spip.net/Creer-de-grands-tableaux-dans-SPIP,9#forum401060

  Cette fonction faisait alors 3 lignes, c’était plus rapide à écrire que de regarder si PHP avait l’équivalent en magasin.
  Ensuite, il y a eu quantités de signalements de problèmes, ce format propriétaire à l’origine ayant un RFC tardif et imprécis dont tout le monde se fout,
  d’où un code qui n’a pas cessé de croître avec les années (r11111, r11113, r13859, r14013 surtout). Au vu du commentaire dans la doc PHP de fgetcsv, ce code semble toujours d’actualité. En tout cas il y a intérêt à vérifier que les cas signalés dans les logs des commit ci-dessous sont bien pris en compte par cette fonction avant de mettre le code des autres à la poubelle sans chercher à comprendre, marque de fabrique de SPIP3.

• ffmpeg drop frames on purpose to lower filesize

  20 octobre 2014, par max

  Our security system records and archives our IP cameras streams with ffmpeg -use_wallclock_as_timestamps 1 -i rtsp://192.168.x.x:554/mpeg4 -c copy -t 60 my_input_video.avi

  I run it with crontab every minute so it creates videos of 60 seconds ( 15Mb) for each camera every minute. When an intrusion occurs, the camera sends a picture through FTP and a script called by incrontab :

  1- forwards immediately the picture by email

  2- selects the video covering the minute the intrusion occured, compress it with h264 (to 2,6Mb) and sends it by email

  It is working really well but if a thief crosses the path of various cameras, the connection to the SMTP server is not fast enough so video emails are delayed. I’d like to compress the videos even more to avoid that. I could lower the resolution (640x480 to 320x240 for example) but sometimes 640x480 is handy to zoom on something which looks to be moving...

  So my idea is to drop frames in the video in order to lower the filesize. I don’t care if the thief is walking like a "stop motion Lego" on the video, the most important is I know there is someone so I can act.

  mediainfo my_input_video.avi says Frame rate = 600.000 fps but it is of course wrong. FPS sent by IP cameras are always false because it varies with the network quality ; this is why i use "-use_wallclock_as_timestamps 1" in my command to record the streams.

  with ffmpeg -i  my_input_video.avi -vcodec h264 -preset ultrafast -crf 28 -acodec mp3 -q:a 5 -r 8 output.avi the video is OK but filesize is higher (3Mb)

  with ffmpeg -i  my_input_video.avi -vcodec h264 -preset ultrafast -crf 28 -acodec mp3 -q:a 5 -r 2 output.avi the filesize is lower (2,2Mb) but the video doesn’t work (it is blocked at the first frame).

  Creating a mjpeg video (mjpeg = not interlaced frames) in the middle of the process (first exporting to mjpeg with less frames and then exporting to h264) creates same results.

  Do you know how I can get my thief to walk like a "stop motion Lego" to lower the filesize to a minimum ?

  Thanks for any help

• Why is this ffmpeg conversion turning up trash ?

  12 octobre 2015, par DigitalJedi805

  So, the company I work for still archives some of our data in Windows Media format.

  I’ve written a C# application that loops through all of our WMVs, and in the event that a corresponding MP4 doesn’t exist, it fires off ffmpeg to convert the file.

  What I’m running into, is a combination of problems.

  When I run the following into ffmpeg ( rough C# ) :

  "-i " + File.FullName + " -vf scale=720:480 -b:v 512k -bufsize 512k -vcodec libx264 -acodec aac -strict experimental " + OutputPath

  I end up with a file that cannot play in our browser based player ( JWPlayer ), and cannot play on my local system in Windows Media Player.

  Additionally, the file is larger than my WMV, and is larger than the file I output with [roughly] the same parameters in AVS Video Converter.

  Furthermore, the file details don’t show any values for the video properties - as in, when I right click and go to properties->details, under ’video’, there is a list of length, height, width, frame rate, and bitrate - they are all empty - when I would very much expect some data normally.

  Does anyone have any idea how I can make the conversion more straightforward, or what might be creating the problem in the first place ?

  I’ve tried running this without scaling or bitrate parameters, and added them as an attempt to resolve the more core problem - obviously to no avail.

  For everyone’s appeasement...

  FFMPEG Output :

  video:537604kB audio:158748kB subtitle:0kB other streams:0kB global headers:0kB
  
  muxing overhead: 1.159483%
  
  [libx264 @ 0453d000] frame I:1234  Avg QP:19.98  size: 33645
  
  [libx264 @ 0453d000] frame P:94430 Avg QP:22.92  size:  3984
  
  [libx264 @ 0453d000] frame B:208152 Avg QP:30.67  size:   638
  
  [libx264 @ 0453d000] consecutive B-frames:  7.6%  1.8%  4.0% 86.6%
  
  [libx264 @ 0453d000] mb I  I16..4: 10.5% 61.2% 28.2%
  
  [libx264 @ 0453d000] mb P  I16..4:  0.4%  1.4%  0.3%  P16..4: 26.8%  9.3%  4.8%
  
   0.0%  0.0%    skip:57.0%
  
  [libx264 @ 0453d000] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8: 21.6%  1.1%  0.2%
  
   direct: 0.4%  skip:76.6%  L0:42.6% L1:55.1% BI: 2.3%
  
  [libx264 @ 0453d000] 8x8 transform intra:65.1% inter:71.9%
  
  [libx264 @ 0453d000] coded y,uvDC,uvAC intra: 61.6% 59.3% 30.9% inter: 6.0% 6.7%
  
   1.7%
  
  [libx264 @ 0453d000] i16 v,h,dc,p: 34% 52%  7%  7%
  
  [libx264 @ 0453d000] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 23% 27% 24%  3%  4%  4%  5%
  
   4%  7%
  
  [libx264 @ 0453d000] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 27% 38% 10%  3%  5%  4%  6%
  
   3%  5%
  
  [libx264 @ 0453d000] i8c dc,h,v,p: 47% 35% 14%  4%
  
  [libx264 @ 0453d000] Weighted P-Frames: Y:0.2% UV:0.1%
  
  [libx264 @ 0453d000] ref P L0: 67.8% 12.3% 14.3%  5.6%  0.0%
  
  [libx264 @ 0453d000] ref B L0: 88.7%  9.7%  1.6%
  
  [libx264 @ 0453d000] ref B L1: 92.6%  7.4%
  
  [libx264 @ 0453d000] kb/s:434.44

  I’ll make the video files available shortly.