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  • Des sites réalisés avec MediaSPIP

    2 mai 2011, par

    Cette page présente quelques-uns des sites fonctionnant sous MediaSPIP.
    Vous pouvez bien entendu ajouter le votre grâce au formulaire en bas de page.

  • 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

  • XMP PHP

    13 mai 2011, par

    Dixit Wikipedia, XMP signifie :
    Extensible Metadata Platform ou XMP est un format de métadonnées basé sur XML utilisé dans les applications PDF, de photographie et de graphisme. Il a été lancé par Adobe Systems en avril 2001 en étant intégré à la version 5.0 d’Adobe Acrobat.
    Étant basé sur XML, il gère un ensemble de tags dynamiques pour l’utilisation dans le cadre du Web sémantique.
    XMP permet d’enregistrer sous forme d’un document XML des informations relatives à un fichier : titre, auteur, historique (...)

Sur d’autres sites (5000)

  • Need help on handling MPEG4V1 data

    14 septembre 2011, par Gediminas

    I'm in situation where I need to get a chunk of MPEG4V1 (Microsoft MPEG-4 VKI
    Codec V1    ) data located in the beginning of a packet (that was sent by some DVR unit).

    Packet structure looks something like this :

    • Compressed MPEG4 data.
    • Long integer - Number of events and tripwires.
    • Long integer - Number of events.
    • Event - Event's sequence.
    • Long integer - Number of tripwires.
    • Tripwire - Tripwires sequence.
    • Long integer - Cyclical redundant code (CRC).

    So there is no indication of how to know where does the MPEG4 data ends (Or is there ?),
    and from where should I start reading this additional data like "Number of events and tripwires" and etc...

    I uploaded two packet's so you could see how the actual data looks like :
    recvData1.txt,
    recvData2.txt.

    I've tried to decode those packets using FFmpeg library with avcodec_decode_video function and by removing byte by byte from the end of my recvData buffer in a hope for any results,
    but FFmpeg just allways returned with an error messages like this :

    "[msmpeg4v1 @ 038865a0] invalid startcode",
    "[msmpeg4v1 @ 038865a0] header damaged".

    I'm not that good specialist on knowing of how does the MPEG4 works from the inside,
    but judging by the error messages it's clearly seen that I'm missing some data for decoding at the start of the buffer.

    So I'm not sure of what part / kind of MPEG data I'm getting here..
    Maybe it's some kind of MPEG's "frame" data with it's "end" indication or something ?

    I've even compared the start of my recvData buffer to some of MPEG4V1 encoded video files I found on the net "http://www.trekmania.net/clips/video_clips4.htm" to check if the start of my buffer really contains the MPEG data ..and not some kind of DVR vendor specific stuff..

    And I noticed that there are about 20bytes of data
    (at the start of my packet data, and in .avi files right after about 180bytes..)
    that looks like some kind of header or something..

    Please check this image : "http://ggodis.gamedev.lt/stackOverflow/recvData.jpg"

    Maybe someone knows what this part of MPEG4V1 data represents ?

    P.S. ..I've checked the CRC values for my received packets and they were correct..

  • avformat/riffenc : don't force WAVEFORMATEXTENSIBLE for flt/dbl LPCM

    21 décembre 2023, par Gyan Doshi
    avformat/riffenc : don't force WAVEFORMATEXTENSIBLE for flt/dbl LPCM

    2c2a167ca7 forced WAVEFORMATEXTENSIBLE for all LPCM streams with greater
    
than 16 bits per sample. However, WAVEFORMATEX allows IEEE Float samples
    
or any depth where raw depth == coded depth, see Remarks section at
    
https://learn.microsoft.com/en-us/windows/win32/api/mmreg/ns-mmreg-waveformatex
    
and samples M1F1-float32-AFsp, M1F1-float64-AFsp at
    
https://www.mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Samples.html
    

    There are hardware devices and likely software players requiring float samples
    
that fail to qualify files with WAVEFORMATEXTENSIBLE headers.
    • [DH] libavformat/riffenc.c
    • [DH] tests/ref/acodec/pcm-f32le
    • [DH] tests/ref/acodec/pcm-f64le
    • [DH] tests/ref/seek/acodec-pcm-f32le
    • [DH] tests/ref/seek/acodec-pcm-f64le

  • lavc/rawdec : Use AV_PIX_FMT_PAL8 for raw 1 bpp video in AVI

    28 janvier 2016, par Mats Peterson
    lavc/rawdec : Use AV_PIX_FMT_PAL8 for raw 1 bpp video in AVI

     From
    
https://msdn.microsoft.com/en-us/library/windows/desktop/dd318229%28v=vs.85%29.aspx:
    

    "If biCompression equals BI_RGB and the bitmap uses 8 bpp or less, the
    
bitmap has a color table immediatelly following the BITMAPINFOHEADER
    
structure. The color table consists of an array of RGBQUAD values. The
    
size of the array is given by the biClrUsed member. If biClrUsed is
    
zero, the array contains the maximum number of colors for the given
    
bitdepth ; that is, 2^biBitCount colors."
    

    Nothing about "monochrome" here. Unfortunately, pal8 to monow conversion
    
seems a bit flaky, but that’s another story.
    

    Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
    • [DH] libavcodec/raw.c
    • [DH] tests/ref/vsynth/vsynth1-bpp1
    • [DH] tests/ref/vsynth/vsynth2-bpp1
    • [DH] tests/ref/vsynth/vsynth3-bpp1
    • [DH] tests/ref/vsynth/vsynth_lena-bpp1

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