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  • La sauvegarde automatique de canaux SPIP

    1 April 2010, by

    Dans le cadre de la mise en place d’une plateforme ouverte, il est important pour les hébergeurs de pouvoir disposer de sauvegardes assez régulières pour parer à tout problème éventuel.
    Pour réaliser cette tâche on se base sur deux plugins SPIP : Saveauto qui permet une sauvegarde régulière de la base de donnée sous la forme d’un dump mysql (utilisable dans phpmyadmin) mes_fichiers_2 qui permet de réaliser une archive au format zip des données importantes du site (les documents, les éléments (...)

  • HTML5 audio and video support

    13 April 2011, by

    MediaSPIP uses HTML5 video and audio tags to play multimedia files, taking advantage of the latest W3C innovations supported by modern browsers.
    The MediaSPIP player used has been created specifically for MediaSPIP and can be easily adapted to fit in with a specific theme.
    For older browsers the Flowplayer flash fallback is used.
    MediaSPIP allows for media playback on major mobile platforms with the above (...)

  • De l’upload à la vidéo finale [version standalone]

    31 January 2010, by

    Le chemin d’un document audio ou vidéo dans SPIPMotion est divisé en trois étapes distinctes.
    Upload et récupération d’informations de la vidéo source
    Dans un premier temps, il est nécessaire de créer un article SPIP et de lui joindre le document vidéo "source".
    Au moment où ce document est joint à l’article, deux actions supplémentaires au comportement normal sont exécutées : La récupération des informations techniques des flux audio et video du fichier; La génération d’une vignette : extraction d’une (...)

On other websites (3565)

  • Revision a9a1eac6c7: tests: fix Continue() signatures they're const member functions, they need to m

    8 August 2012, by James Zern

    Changed Paths: Modify /test/config_test.cc Modify /test/keyframe_test.cc tests: fix Continue() signatures they're const member functions, they need to match the base class to be called Change-Id: Id0580c5078b5876ead6731d95d8b86fef4029c40

  • Color Correcting MP4/Webm videos

    2 October 2014, by sottenad

    I have a large video that features some animations too complex/long for other methods of embedding (gif, png sequence, etc.) and we are running into an issue with the colors in the video. Essentially we are including the background of the web page as part of the video in order to prevent the appearance of any edges on the video when it plays. We are trying to get the gradient background on the video to match that on the webpage, but the colors are WAY off.

    Are there any recommendations on how to color correct an MP4 video? Or any html5-safe ways to do video with an alpha channel?

  • How does mp4 block matching work

    19 June 2019, by YAHsaves

    I’ve been working on a video encoder that uses block matching to find similar blocks on previous frames.

    For the sake of simplicity I’ll leave out most of the details, but I’m wondering if I got the block matching algorithm right.

    In order to find a block on a previous frame my encoder uses the mean squared algorithm for the Y channel in YUV color space.

    This works by comparing each pixel of the block we want to match, with the block on the previous frame. It takes the difference of each pixel and squares it.

    After all the pixels are compared the block that has the least average difference is chosen as the desired block.

    Now this is where I need help. My encoder looks at every possible block in a 256x256 area and uses half pixel searches as well. The smallest block size it can use is 4x4.

    From what I’ve read online this is the same things mp4 uses.

    However I can’t find nearly as many blocks as mp4 appears to be able to find.

    For example here are 2 frames I want to compress. The first will be the I frame and the second is the P frame:

    enter image description here

    Now after my encoder has run it is able to reduce the second frame by 80% and, what it can’t match close enough it saves as "difference" blocks. Which are grey blocks only recording the difference. They look like this:

    enter image description here

    Now what I don’t get is to save these "difference" blocks as a jpg takes roughly 90kb to be accurate enough.

    Multiply that by 24 (24 frames per second) you get 2070kb per second. That’s not including how much space the actual motion vectors take up or anything else.

    However somehow mp4 is able to compress the video of the images above into a mere 700kb per second and still look better than my encoder at much larger data amounts.

    Why is this? Is there something I’m doing wrong when looking for blocks? Any help would be much appreciated.

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