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Autres articles (91)

  • MediaSPIP en mode privé (Intranet)

    17 septembre 2013, par

    À partir de la version 0.3, un canal de MediaSPIP peut devenir privé, bloqué à toute personne non identifiée grâce au plugin "Intranet/extranet".
    Le plugin Intranet/extranet, lorsqu’il est activé, permet de bloquer l’accès au canal à tout visiteur non identifié, l’empêchant d’accéder au contenu en le redirigeant systématiquement vers le formulaire d’identification.
    Ce système peut être particulièrement utile pour certaines utilisations comme : Atelier de travail avec des enfants dont le contenu ne doit pas (...)

  • Multilang : améliorer l’interface pour les blocs multilingues

    18 février 2011, par

    Multilang est un plugin supplémentaire qui n’est pas activé par défaut lors de l’initialisation de MediaSPIP.
    Après son activation, une préconfiguration est mise en place automatiquement par MediaSPIP init permettant à la nouvelle fonctionnalité d’être automatiquement opérationnelle. Il n’est donc pas obligatoire de passer par une étape de configuration pour cela.

  • Automated installation script of MediaSPIP

    25 avril 2011, par

    To overcome the difficulties mainly due to the installation of server side software dependencies, an "all-in-one" installation script written in bash was created to facilitate this step on a server with a compatible Linux distribution.
    You must have access to your server via SSH and a root account to use it, which will install the dependencies. Contact your provider if you do not have that.
    The documentation of the use of this installation script is available here.
    The code of this (...)

Sur d’autres sites (7443)

  • avformat/movenc : remove mvex from final mp4 in hybrid_fragmented mode

    1er septembre, par Zhao Zhili
    avformat/movenc : remove mvex from final mp4 in hybrid_fragmented mode

    In hybrid_fragmented mode, the first moov at start should contain
    
mvex tag, since it's fmp4. When writing the moov at the second time,
    
it's not fmp4 any more, so mvex should be skipped.
    • [DH] libavformat/movenc.c
    • [DH] tests/fate/mov.mak
    • [DH] tests/ref/lavf/mov_hybrid_frag

  • When compressing a set of images with libx264, why does frame rate affect final output size ?

    3 avril 2018, par jd20

    I’m using ffmpeg to encode a set of images as a short timelapse video, using libx264 codec. My first attempt, I encoded it at 30 FPS, using :

    ffmpeg -r 30 -pattern_type glob -i "*.jpg" -vcodec libx264 -crf 30 -pix_fmt yuv420p output.mp4

    With 60 frames, that gives me a 163 KB file that’s 2 seconds long. Then I realized I needed it to be slower, so I re-ran the same command, but changed -r to 2. Now I have a file that’s 30 seconds long, but the size jumped to 891 KB ! The video quality looks perceptually the same.

    How do I encode at a slower frame rate, without the final file size ballooning ?

    Notes : Some theories I had, and things I checked. First, to make sure ffmpeg wasn’t duplicating frames in the longer verison, I check the I/P/B counts. The 30 FPS file had :

    [libx264 @ 0x7f9b26001c00] frame I:1     Avg QP:30.67  size: 44649
    
[libx264 @ 0x7f9b26001c00] frame P:15    Avg QP:31.19  size:  5471
    
[libx264 @ 0x7f9b26001c00] frame B:44    Avg QP:31.45  size:   767

    The 2 FPS file had :

    [libx264 @ 0x7fcd32842200] frame I:1     Avg QP:21.29  size: 90138
    
[libx264 @ 0x7fcd32842200] frame P:15    Avg QP:22.48  size: 33686
    
[libx264 @ 0x7fcd32842200] frame B:44    Avg QP:26.29  size:  6674

    So, the I/P/B counts are identical, but the QP is much lower for the 2 FPS file. To offset, I tried increasing -crf for the 2 FPS file, to get about the same target size, but that just gave me a very blurry video (had to go to crf=40). I tried messing with -minrate, -maxrate, -bt, none helped. I’m guessing there is some x264 codec setting which is frame rate dependent, but I’m at a loss trying to figure out which one (from what I understand, constant bitrate is affected by frame rate but CRF should not be, but maybe I’m misunderstanding it.

  • When compressing a set of images with libx264, why does frame rate affect final output size ?

    3 avril 2018, par jd20

    I’m using ffmpeg to encode a set of images as a short timelapse video, using libx264 codec. My first attempt, I encoded it at 30 FPS, using :

    ffmpeg -r 30 -pattern_type glob -i "*.jpg" -vcodec libx264 -crf 30 -pix_fmt yuv420p output.mp4

    With 60 frames, that gives me a 163 KB file that’s 2 seconds long. Then I realized I needed it to be slower, so I re-ran the same command, but changed -r to 2. Now I have a file that’s 30 seconds long, but the size jumped to 891 KB ! The video quality looks perceptually the same.

    How do I encode at a slower frame rate, without the final file size ballooning ?

    Notes : Some theories I had, and things I checked. First, to make sure ffmpeg wasn’t duplicating frames in the longer verison, I check the I/P/B counts. The 30 FPS file had :

    [libx264 @ 0x7f9b26001c00] frame I:1     Avg QP:30.67  size: 44649
    
[libx264 @ 0x7f9b26001c00] frame P:15    Avg QP:31.19  size:  5471
    
[libx264 @ 0x7f9b26001c00] frame B:44    Avg QP:31.45  size:   767

    The 2 FPS file had :

    [libx264 @ 0x7fcd32842200] frame I:1     Avg QP:21.29  size: 90138
    
[libx264 @ 0x7fcd32842200] frame P:15    Avg QP:22.48  size: 33686
    
[libx264 @ 0x7fcd32842200] frame B:44    Avg QP:26.29  size:  6674

    So, the I/P/B counts are identical, but the QP is much lower for the 2 FPS file. To offset, I tried increasing -crf for the 2 FPS file, to get about the same target size, but that just gave me a very blurry video (had to go to crf=40). I tried messing with -minrate, -maxrate, -bt, none helped. I’m guessing there is some x264 codec setting which is frame rate dependent, but I’m at a loss trying to figure out which one (from what I understand, constant bitrate is affected by frame rate but CRF should not be, but maybe I’m misunderstanding it.

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