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  • Use, discuss, criticize

    13 avril 2011, par

    Talk to people directly involved in MediaSPIP’s development, or to people around you who could use MediaSPIP to share, enhance or develop their creative projects.
    The bigger the community, the more MediaSPIP’s potential will be explored and the faster the software will evolve.
    A discussion list is available for all exchanges between users.

  • Le profil des utilisateurs

    12 avril 2011, par

    Chaque utilisateur dispose d’une page de profil lui permettant de modifier ses informations personnelle. Dans le menu de haut de page par défaut, un élément de menu est automatiquement créé à l’initialisation de MediaSPIP, visible uniquement si le visiteur est identifié sur le site.
    L’utilisateur a accès à la modification de profil depuis sa page auteur, un lien dans la navigation "Modifier votre profil" est (...)

  • Les tâches Cron régulières de la ferme

    1er décembre 2010, par

    La gestion de la ferme passe par l’exécution à intervalle régulier de plusieurs tâches répétitives dites Cron.
    Le super Cron (gestion_mutu_super_cron)
    Cette tâche, planifiée chaque minute, a pour simple effet d’appeler le Cron de l’ensemble des instances de la mutualisation régulièrement. Couplée avec un Cron système sur le site central de la mutualisation, cela permet de simplement générer des visites régulières sur les différents sites et éviter que les tâches des sites peu visités soient trop (...)

Sur d’autres sites (10433)

  • Convert mp3 to AAC with mpeg-2 container (FFMPEG)

    18 mars 2016, par jsurf

    I’m trying to convert an mp3 audio file to an AAC file with FFMPEG, and I need the audio to be wrapped in an MPEG-2 container.
    The resulting AAC file needs to be AAC-LC (Low Complexity), 1-channel, CBR mode, 44100 sample rate, and 48kb/s bitrate, so I use this command :

    ffmpeg -y -i input.mp3 -ar 44100 -ab 48k -acodec libfdk_aac -ac 1 output.aac

    But when I examine the ADTS headers, the audio file is always being wrapped in an MPEG-4 container. I have tried all the codecs listed here but I still end up with an mpeg-4 container wrapped around the audio : http://trac.ffmpeg.org/wiki/AACEncodingGuide.

    Here are the headers I get when examining the AAC output file :

    mpeg_type : ’MPEG4’,
    profile : 2,
    profile_name : ’AAC LC’,
    sample_freq : 44100,
    channel_config : 1,
    channels : 1,
    frame_length : 139,
    buffer_fullness : 157,
    number_of_frames : 1,
    frames_per_sec : 43.06640625

    Any ideas as to why ffmpeg wraps an mp4 container around the audio ? Can I get around this somehow ? Are there any other encoders I can try aside from FFMPEG ? I was giving FAAC encoder a shot and it gives me the proper encoding and ADTS headers, but alas it does not support mp3, only WAV.

  • Setting qscale programmatically when using MPEG4 encoder ( for constant quality / VBR)

    14 février 2019, par Dennis

    i implemented the possibility to encode various self-rendered video-frames with MPEG4 codec and create an .mp4 video file. This works fine. Now i want to add the possibility to define a quality slider (0-100%) to parameterize a factor for constant quality (VBR). I don’t know how to do that.

    I found out that -qscale seems to do what i want, so i looked in ffmpeg_opt.c what happens there and tried the same :

    config.codecContext->flags |= AV_CODEC_FLAG_QSCALE;
    
config.codecContext->global_quality = FF_QP2LAMBDA * QualityLvl;

    with :

    • "config.codecContext" being the code context
    • "FF_QP2LAMBDA" being 118
    • "QualityLvl" is the "factor for constant quality" (has to be an int between 1 and 31 according to this :
      https://trac.ffmpeg.org/wiki/Encode/MPEG-4)

    The problem is, that it actually doesn’t matter if "QualityLvl" is 1,2 or 30 it always results in the same file size and a visually same(?) video file. I would have expected file size and quality differences ?!

  • Does 'keyint infinite' improve overall compression with crf and mb-tree ?

    23 avril 2012, par HitomiTenshi

    After reading what intra-refresh does, I kinda got confused. I'm encoding for YouTube and YouTube will re-encode the video-file anyways, so I thought "why not removing all these heavy IDR-frames ?" I just want to compress my video as hard as possible, enabling everything that could help me getting a lower filesize, but still maintaining a high quality.

    I used to test around stuff with lossless QP encoding, but the only thing I could max out was the merange. Here is a paste of my x264 settings : Pastebin.

    I want to achieve highest compression while maintaining visually lossless quality. (using crf values around 10 - 13, and merange 32)

    Could anyone give me advice on how to compress my video super hard (without touching the crf value !). I also want to know if it's true, that keyint infinite reduces overall compression.

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