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    26 avril 2011, par

    The table below is the list of Linux distributions compatible with the automated installation script of MediaSPIP. Distribution nameVersion nameVersion number Debian Squeeze 6.x.x Debian Weezy 7.x.x Debian Jessie 8.x.x Ubuntu The Precise Pangolin 12.04 LTS Ubuntu The Trusty Tahr 14.04
    If you want to help us improve this list, you can provide us access to a machine whose distribution is not mentioned above or send the necessary fixes to add (...)

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    La gestion de la ferme passe par l’exécution à intervalle régulier de plusieurs tâches répétitives dites Cron.
    Le super Cron (gestion_mutu_super_cron)
    Cette tâche, planifiée chaque minute, a pour simple effet d’appeler le Cron de l’ensemble des instances de la mutualisation régulièrement. Couplée avec un Cron système sur le site central de la mutualisation, cela permet de simplement générer des visites régulières sur les différents sites et éviter que les tâches des sites peu visités soient trop (...)

  • Personnaliser en ajoutant son logo, sa bannière ou son image de fond

    5 septembre 2013, par

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Sur d’autres sites (7522)

  • 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

  • For lossless video compression, which is better ? crf or qp ?

    19 avril 2020, par Nagabhushan S N

    I have a raw video. I need it to compress it losslessly. There are two ways to do this. Setting the parameters crf or qp to 0. crf achieves constant bitrate while qp has constant quantization. I've two questions :

    



      

    1. Do the options -crf 0 and -qp 0 achieve the same result (lossless compression) ?

      2. 


    2. If not, what is the difference ? Which is recommended to have lossless compression ?

      3. 


    



    This question asks about crf and qp, but doesn't talk about lossless compression.

    


  • How to estimate the file size of a video in a particular resolution ?

    13 octobre 2019, par Habib

    I’m trying to develop a video compressor where I have to estimate the file size before compression based on different resolutions.

    For encoding I am using H264 codec. And I have no idea how it compress the video.

    I'm looking forward to something like this. 
    
1440*720 - estimated file size : 6.2mb - 75%
    
960*480  - estimated file size : 2.9mb - 37%
    
480*240  - estimated file size : 857kb - 25%

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