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Autres articles (7)

  • Submit bugs and patches

    13 avril 2011

    Unfortunately a software is never perfect.
    If you think you have found a bug, report it using our ticket system. Please to help us to fix it by providing the following information : the browser you are using, including the exact version as precise an explanation as possible of the problem if possible, the steps taken resulting in the problem a link to the site / page in question
    If you think you have solved the bug, fill in a ticket and attach to it a corrective patch.
    You may also (...)

  • Contribute to translation

    13 avril 2011

    You can help us to improve the language used in the software interface to make MediaSPIP more accessible and user-friendly. You can also translate the interface into any language that allows it to spread to new linguistic communities.
    To do this, we use the translation interface of SPIP where the all the language modules of MediaSPIP are available. Just subscribe to the mailing list and request further informantion on translation.
    MediaSPIP is currently available in French and English (...)

  • Initialisation de MediaSPIP (préconfiguration)

    20 février 2010, par

    Lors de l’installation de MediaSPIP, celui-ci est préconfiguré pour les usages les plus fréquents.
    Cette préconfiguration est réalisée par un plugin activé par défaut et non désactivable appelé MediaSPIP Init.
    Ce plugin sert à préconfigurer de manière correcte chaque instance de MediaSPIP. Il doit donc être placé dans le dossier plugins-dist/ du site ou de la ferme pour être installé par défaut avant de pouvoir utiliser le site.
    Dans un premier temps il active ou désactive des options de SPIP qui ne le (...)

Sur d’autres sites (786)

  • SNES Hardware Compression

    16 juin 2011, par Multimedia Mike — Game Hacking

    I was browsing the source code for some Super Nintendo Entertainment System (SNES) emulators recently. I learned some interesting things about compression hardware. I had previously uncovered one compression algorithm used in an SNES title but that was implemented in software.

    SNES game cartridges — being all hardware — were at liberty to expand the hardware capabilities of the base system by adding new processors. The most well-known of these processors was the Super FX which allows for basic polygon graphical rendering, powering such games as Star Fox. It was by no means the only such add-on processor, though. Here is a Wikipedia page of all the enhancement chips used in assorted SNES games. A number of them mention compression and so I delved into the emulators to find the details :

    • The Super FX is listed in Wikipedia vaguely as being able to decompress graphics. I see no reference to decompression in emulator source code.
    • DSP-3 emulation source code makes reference to LZ-type compression as well as tree/symbol decoding. I’m not sure if the latter is a component of the former. Wikipedia lists the chip as supporting "Shannon-Fano bitstream decompression."
    • Similar to Super FX, the SA-1 chip is listed in Wikipedia as having some compression capabilities. Again, either that’s not true or none of the games that use the chip (notably Super Mario RPG) make use of the feature.
    • The S-DD1 chip uses arithmetic and Golomb encoding for compressing graphics. Wikipedia refers to this as the ABS Lossless Entropy Algorithm. Googling for further details on that algorithm name yields no results, but I suspect it’s unrelated to anti-lock brakes. The algorithm is alleged to allow Star Ocean to smash 13 MB of graphics into a 4 MB cartridge ROM (largest size of an SNES cartridge).
    • The SPC7110 can decompress data using a combination of arithmetic coding and Z-curve/Morton curve reordering.

    No, I don’t plan to implement codecs for these schemes. But it’s always comforting to know that I could.

    Not directly a compression scheme, but still a curious item is the MSU1 concept put forth by the bsnes emulator. This is a hypothetical coprocessor implemented by bsnes that gives an emulated cartridge access to a 4 GB address space. What to do with all this space ? Allow for the playback of uncompressed PCM audio as well as uncompressed video at 240x144x256 colors @ 30 fps. According to the docs and the source code, the latter feature doesn’t appear to be implemented, though ; only the raw PCM playback.

  • Internecine Legal Threats

    1er juin 2011, par Multimedia Mike — Legal/Ethical

    FFmpeg and associated open source multimedia projects such as xine, MPlayer, and VLC have long had a rebel mystique about them ; a bunch of hackers playing fast and loose with IP law in order to give the world the free multimedia experience it deserved. We figured out the algorithms using any tools available, including the feared technique of binary reverse engineering. When I gave a presentation about FFmpeg at Linuxtag in 2007, I created this image illustrating said mystique :



    It garnered laughs. But I made the point that we multimedia hackers just press on, doing our thing while ignoring legal threats. The policy has historically worked out famously for us– to date, I seem to be the only person on the receiving end of a sort-of legal threat from the outside world.

    Who would have thought that the most credible legal threat to an open source multimedia project would emanate from a fork of that very project ? Because that’s exactly what has transpired :



    Click for full threat

    So it came to pass that Michael Niedermayer — the leader of the FFmpeg project — received a bona fide legal nastygram from Mans Rullgard, a representative of the FFmpeg-forked Libav project. The subject of dispute is a scorched-earth matter involving the somewhat iconic FFmpeg zigzag logo :

     
    Original 2D logo enhanced 3D logo

    To think of all those years we spent worrying about legal threats from organizations outside the community. I’m reminded of that time-honored horror trope/urban legend staple : Get out ! The legal threats are coming from inside the house !

    I’m interested to see how this all plays out, particularly regarding jurisdiction, as we have a U.K. resident engaging an Italian lawyer outfit to deliver a legal threat to an Austrian citizen regarding an image hosted on a server in Hungary. I suspect I know why that law firm was chosen, but it’s still a curious jurisdictional setup.

    People often used to ask me if we multimedia hackers would get sued to death for doing what we do. My response was always, “There’s only one way to know for sure,” by which I meant that we would just have to engage in said shady activities and determine empirically if lawsuits resulted. So I’m a strong advocate for experimentation to push the limits. Kudos to Michael and Mans for volunteering to push the legal limits.

  • Revision 32594 : plugins en minuscules, et alias pour les noms de sites

    1er novembre 2009, par fil@… — Log

    plugins en minuscules, et alias pour les noms de sites