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  • Publier sur MédiaSpip

    13 juin 2013

    Puis-je poster des contenus à partir d’une tablette Ipad ?
    Oui, si votre Médiaspip installé est à la version 0.2 ou supérieure. Contacter au besoin l’administrateur de votre MédiaSpip pour le savoir

  • Ajouter des informations spécifiques aux utilisateurs et autres modifications de comportement liées aux auteurs

    12 avril 2011, par

    La manière la plus simple d’ajouter des informations aux auteurs est d’installer le plugin Inscription3. Il permet également de modifier certains comportements liés aux utilisateurs (référez-vous à sa documentation pour plus d’informations).
    Il est également possible d’ajouter des champs aux auteurs en installant les plugins champs extras 2 et Interface pour champs extras.

  • Possibilité de déploiement en ferme

    12 avril 2011, par

    MediaSPIP peut être installé comme une ferme, avec un seul "noyau" hébergé sur un serveur dédié et utilisé par une multitude de sites différents.
    Cela permet, par exemple : de pouvoir partager les frais de mise en œuvre entre plusieurs projets / individus ; de pouvoir déployer rapidement une multitude de sites uniques ; d’éviter d’avoir à mettre l’ensemble des créations dans un fourre-tout numérique comme c’est le cas pour les grandes plate-formes tout public disséminées sur le (...)

Sur d’autres sites (10053)

  • Compressing videos from a smartphone

    9 novembre 2016, par fejesjoco

    I have a Nexus 6p with the stock camera. It’s set to record at 1080p, 30fps. Here’s a 5 second sample (11 MB).

    Videos from this phone come out at about 17 Mbps on average. I tried to compress it with ffmpeg with -c:v libx264 -crf 23 -preset veryslow, the result comes out at about 5.5 MB, which is about 9 Mbps.

    I think this bitrate is a bit too much. When I look at torrent file listings, I can see high quality videos at 3 GB in size on average, and if such a movie is 90 minutes long on average, that is about 4-5 Mbps which sounds okay.

    I’m wondering, why the big difference ? I can notice that my video is noisy/grainy (which is expected from a phone), and that might reduce compressibility. I tried a few ffmpeg filters, like hqdn3d and atadenoise, but the noise mostly remained (maybe I didn’t play with it enough). Then I figured, the video is also shaky (which is also expected), and that might reduce compressibility too (and even makes temporal noise filtering less effective). I tried to stabilize it with the deshake filter, but that didn’t help either.

    I know I could just limit the bandwidth to whatever I like, but there must be a reason why ffmpeg thinks it needs a high bandwidth to maintain a certain quality, and a lower bandwidth would just decrease the quality.

    Why do these videos have such a high bitrate ? What’s the best way to compress them more while keeping or even increasing their quality ?

  • Compressing videos from a smartphone

    21 septembre 2019, par fejesjoco

    I have a Nexus 6p with the stock camera. It’s set to record at 1080p, 30fps. Here’s a 5 second sample (11 MB).

    Videos from this phone come out at about 17 Mbps on average. I tried to compress it with ffmpeg with -c:v libx264 -crf 23 -preset veryslow, the result comes out at about 5.5 MB, which is about 9 Mbps.

    I think this bitrate is a bit too much. When I look at torrent file listings, I can see high quality videos at 3 GB in size on average, and if such a movie is 90 minutes long on average, that is about 4-5 Mbps which sounds okay.

    I’m wondering, why the big difference ? I can notice that my video is noisy/grainy (which is expected from a phone), and that might reduce compressibility. I tried a few ffmpeg filters, like hqdn3d and atadenoise, but the noise mostly remained (maybe I didn’t play with it enough). Then I figured, the video is also shaky (which is also expected), and that might reduce compressibility too (and even makes temporal noise filtering less effective). I tried to stabilize it with the deshake filter, but that didn’t help either.

    I know I could just limit the bandwidth to whatever I like, but there must be a reason why ffmpeg thinks it needs a high bandwidth to maintain a certain quality, and a lower bandwidth would just decrease the quality.

    Why do these videos have such a high bitrate ? What’s the best way to compress them more while keeping or even increasing their quality ?

  • Revision 7eca086707 : Add segmentation map array for current and last frame segmentation. The origina

    17 juillet 2014, par hkuang

    Changed Paths :
     Modify /vp9/common/vp9_alloccommon.c


     Modify /vp9/common/vp9_alloccommon.h


     Modify /vp9/common/vp9_entropymode.c


     Modify /vp9/common/vp9_onyxc_int.h


     Modify /vp9/decoder/vp9_decodemv.c


     Modify /vp9/decoder/vp9_decoder.c



    Add segmentation map array for current and last frame segmentation.

    The original implementation only allocates one segmentation map and this
    works fine for serial decode. But for frame parallel decode, each thread
    need to have its own segmentation map and the last frame segmentation map
    should be provided from last frame decoding thread.

    After finishing decoding a frame, thread need to serve the old segmentation
    map that associate with the previous decoded frame. The thread also need to
    use another segmentation map for decoding the current frame.

    Change-Id : I442ddff36b5de9cb8a7eb59e225744c78f4492d8

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