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Autres articles (35)

  • Les autorisations surchargées par les plugins

    27 avril 2010, par

    Mediaspip core
    autoriser_auteur_modifier() afin que les visiteurs soient capables de modifier leurs informations sur la page d’auteurs

  • HTML5 audio and video support

    13 avril 2011, par

    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 janvier 2010, par

    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 (...)

Sur d’autres sites (3549)

  • avcodec/x86/videodsp : Properly mark sse2 instructions in emulated_edge_mc x86 simd...

    24 octobre 2013, par Ronald S. Bultje
    avcodec/x86/videodsp : Properly mark sse2 instructions in emulated_edge_mc x86 simd as such.
    

    Should fix crashes or corrupt output on pre-SSE2 CPUs when they were
    using SSE2-code (e.g. AMD Athlon XP 2400+ or Intel Pentium III) in
    hfix or hvar single-edge (left/right) extension functions.

    Tested-by : Ingo Brückl <ib@wupperonline.de>
    Signed-off-by : Michael Niedermayer <michaelni@gmx.at>

    • [DH] libavcodec/x86/videodsp.asm
    • [DH] libavcodec/x86/videodsp_init.c
  • Encoding with FFMPEG stretches frames

    24 août 2017, par micropro.cz

    I am trying to encode video with FFMPEG into H.265, but I have a problem with a weird stretching. Input video is 1920x1080 and output has the same resolution, but when I compare both images on same timestamp, encoded video seems to be stretched by few pixels (it is visibly wider on both sizes despite the fact resolution is same). It seems that this stretching introduces ugly bluriness in whole video. It seems like FFMPEG crop few pixels from left and right (probably black pixels at the edge of video) and stretches content to fill those missing pixels and preserve same resolution.

    I did not find any way how to disable this behavior. I tried to change encoder from x265 to x264 to see if that is the problem, but result was still stretched.

    I used this command line parameters :

    ffmpeg -i input.mkv -c:v libx265 -preset medium -crf 23 -t 30 output.mp4

    -t 30 is there to test result visual quality on small sample of length 30 seconds.

    Does anyone have any idea why this happens and how to fix it ? Most visual quality is lost because of this deformation and not because of recompression, which I proved by encoding with -crf 0, which is basically lossless and result was still blurred.

    EDIT : Link to full console output : https://pastebin.com/gpMD5Qec

  • WebRTC predictions for 2016

    17 février 2016, par silvia

    I wrote these predictions in the first week of January and meant to publish them as encouragement to think about where WebRTC still needs some work. I’d like to be able to compare the state of WebRTC in the browser a year from now. Therefore, without further ado, here are my thoughts.

    WebRTC Browser support

    I’m quite optimistic when it comes to browser support for WebRTC. We have seen Edge bring in initial support last year and Apple looking to hire engineers to implement WebRTC. My prediction is that we will see the following developments in 2016 :

    • Edge will become interoperable with Chrome and Firefox, i.e. it will publish VP8/VP9 and H.264/H.265 support
    • Firefox of course continues to support both VP8/VP9 and H.264/H.265
    • Chrome will follow the spec and implement H.264/H.265 support (to add to their already existing VP8/VP9 support)
    • Safari will enter the WebRTC space but only with H.264/H.265 support

    Codec Observations

    With Edge and Safari entering the WebRTC space, there will be a larger focus on H.264/H.265. It will help with creating interoperability between the browsers.

    However, since there are so many flavours of H.264/H.265, I expect that when different browsers are used at different endpoints, we will get poor quality video calls because of having to negotiate a common denominator. Certainly, baseline will work interoperably, but better encoding quality and lower bandwidth will only be achieved if all endpoints use the same browser.

    Thus, we will get to the funny situation where we buy ourselves interoperability at the cost of video quality and bandwidth. I’d call that a “degree of interoperability” and not the best possible outcome.

    I’m going to go out on a limb and say that at this stage, Google is going to consider strongly to improve the case of VP8/VP9 by improving its bandwidth adaptability : I think they will buy themselves some SVC capability and make VP9 the best quality codec for live video conferencing. Thus, when Safari eventually follows the standard and also implements VP8/VP9 support, the interoperability win of H.264/H.265 will become only temporary overshadowed by a vastly better video quality when using VP9.

    The Enterprise Boundary

    Like all video conferencing technology, WebRTC is having a hard time dealing with the corporate boundary : firewalls and proxies get in the way of setting up video connections from within an enterprise to people outside.

    The telco world has come up with the concept of SBCs (session border controller). SBCs come packed with functionality to deal with security, signalling protocol translation, Quality of Service policing, regulatory requirements, statistics, billing, and even media service like transcoding.

    SBCs are a total overkill for a world where a large number of Web applications simply want to add a WebRTC feature – probably mostly to provide a video or audio customer support service, but it could be a live training session with call-in, or an interest group conference all.

    We cannot install a custom SBC solution for every WebRTC service provider in every enterprise. That’s like saying we need a custom Web proxy for every Web server. It doesn’t scale.

    Cloud services thrive on their ability to sell directly to an individual in an organisation on their credit card without that individual having to ask their IT department to put special rules in place. WebRTC will not make progress in the corporate environment unless this is fixed.

    We need a solution that allows all WebRTC services to get through an enterprise firewall and enterprise proxy. I think the WebRTC standards have done pretty well with firewalls and connecting to a TURN server on port 443 will do the trick most of the time. But enterprise proxies are the next frontier.

    What it takes is some kind of media packet forwarding service that sits on the firewall or in a proxy and allows WebRTC media packets through – maybe with some configuration that is necessary in the browsers or the Web app to add this service as another type of TURN server.

    I don’t have a full understanding of the problems involved, but I think such a solution is vital before WebRTC can go mainstream. I expect that this year we will see some clever people coming up with a solution for this and a new type of product will be born and rolled out to enterprises around the world.

    Summary

    So these are my predictions. In summary, they address the key areas where I think WebRTC still has to make progress : interoperability between browsers, video quality at low bitrates, and the enterprise boundary. I’m really curious to see where we stand with these a year from now.

    It’s worth mentioning Philipp Hancke’s tweet reply to my post :

    — we saw some clever people come up with a solution already. Now it needs to be implemented 🙂

    The post WebRTC predictions for 2016 first appeared on ginger’s thoughts.