Recherche avancée

Médias (1)

Mot : - Tags -/école

Autres articles (83)

  • 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

  • Personnaliser les catégories

    21 juin 2013, par

    Formulaire de création d’une catégorie
    Pour ceux qui connaissent bien SPIP, une catégorie peut être assimilée à une rubrique.
    Dans le cas d’un document de type catégorie, les champs proposés par défaut sont : Texte
    On peut modifier ce formulaire dans la partie :
    Administration > Configuration des masques de formulaire.
    Dans le cas d’un document de type média, les champs non affichés par défaut sont : Descriptif rapide
    Par ailleurs, c’est dans cette partie configuration qu’on peut indiquer le (...)

  • Encoding and processing into web-friendly formats

    13 avril 2011, par

    MediaSPIP automatically converts uploaded files to internet-compatible formats.
    Video files are encoded in MP4, Ogv and WebM (supported by HTML5) and MP4 (supported by Flash).
    Audio files are encoded in MP3 and Ogg (supported by HTML5) and MP3 (supported by Flash).
    Where possible, text is analyzed in order to retrieve the data needed for search engine detection, and then exported as a series of image files.
    All uploaded files are stored online in their original format, so you can (...)

Sur d’autres sites (10049)

  • How to calculate ffmpeg output file size ?

    25 septembre 2011, par poundifdef

    I am using ffmpeg to convert home videos to DVD format and want to calculate the output file size before doing the conversion.

    My input file has a bit rate of 7700 kbps and is 114 seconds long. The audio bitrate is 256 kbit (per second ?) The input file is 77MB. To get this information I ran :

    mplayer -vo null -ao null -frames 0 -identify input.MOD

    So in theory, the input file should have (roughly) a file size of :

    ((7700 / 8) * 114) / 1024

    That is, (7700 / 8) is kilobytes/second, multiplied by 114 seconds, and then converted to megabytes. This gives me 107MB, which is way beyond my 77. Thus I am skeptical of his formula.

    That said, after converting the video :

    ffmpeg -i input.MOD -y -target ntsc-dvd -sameq -aspect 4:3 output.mpg

    The numbers seem to make more sense. Bitrate is 9000 kbps, and applying the above formula, I get 125MB, and my actual output file size is 126MB.

    So, two questions :

    1. How do I factor the audio bitrate into this calculation ? Is it additive (video file size + audio file size) ?

    2. Do DVDs always have a 9000 kilobit/second rate ? Is that the definition of a DVD ? Or might that change depending on video quality of my input video ? What does "-target ntsc-dvd" guarantee about my video ?

    3. Why does my input file not "match" the calculation, but the output file does ? Is there some other variable I'm not accounting for ?

    What is the correct way to calculate filesize ?

  • AVCodecContext settings for H264 (1080i)

    23 septembre 2013, par moose

    I'm trying to configure x264 for 1080i capturing. Most of these settings below are found in different examples. However, compiled together they don't work. ffmpeg API reports no error, but avcodec_encode_video() always returns zero.

    Some of the numbers are strange to me... for example, gop_size. Isn't 250 too high ?

    Event you can't offer the final answer, I'm still interested in any kind of comment on this subject.

    pCodecContext->codec_type              = AVMEDIA_TYPE_VIDEO;
    
pCodecContext->codec_id                = CODEC_ID_H264;
    

    
pCodecContext->coder_type              = FF_CODER_TYPE_AC;
    
pCodecContext->flags                  |= CODEC_FLAG_LOOP_FILTER | CODEC_FLAG_INTERLACED_ME | CODEC_FLAG_INTERLACED_DCT;
    
pCodecContext->me_cmp                 |= 1;
    
pCodecContext->partitions             |= X264_PART_I8X8 | X264_PART_I4X4 | X264_PART_P8X8 | X264_PART_B8X8;
    
pCodecContext->me_method               = ME_UMH;
    
pCodecContext->me_subpel_quality       = 8;
    
pCodecContext->me_range                = 16;
    

    
pCodecContext->bit_rate                = 10 * 1024 * 1024; // 10 Mbps??
    
pCodecContext->width                   = 1920;
    
pCodecContext->height                  = 1080;
    

    
pCodecContext->time_base.num           = 1;    // 25 fps
    
pCodecContext->time_base.den           = 25;   // 25 fps
    

    
pCodecContext->gop_size                = 250; // 250
    
pCodecContext->keyint_min              = 25;
    
pCodecContext->scenechange_threshold   = 40;
    
pCodecContext->i_quant_factor          = 0.71f;
    
pCodecContext->b_frame_strategy        = 1;
    
pCodecContext->qcompress               = 0.6f;
    
pCodecContext->qmin                    = 10;
    
pCodecContext->qmax                    = 51;
    
pCodecContext->max_qdiff               = 4;
    
pCodecContext->max_b_frames            = 3;
    
pCodecContext->refs                    = 4;
    
pCodecContext->directpred              = 3;
    
pCodecContext->trellis                 = 1;
    
pCodecContext->flags2                 |= CODEC_FLAG2_WPRED | CODEC_FLAG2_MIXED_REFS | CODEC_FLAG2_8X8DCT | CODEC_FLAG2_FASTPSKIP;  // wpred+mixed_refs+dct8x8+fastpskip
    
pCodecContext->weighted_p_pred         = 2; // not implemented with interlaced ??
    
pCodecContext->crf                     = 22;
    

    
pCodecContext->pix_fmt                 = PIX_FMT_YUV420P;
    

    
pCodecContext->thread_count            = 0;

  • What is the meaning of the hexadecimal value that follows the avc1 in an m3u8 variant playlist

    16 février 2013, par Anand

    From this apple's sample variant playlist

    https://devimages.apple.com.edgekey.net/resources/http-streaming/examples/bipbop_4x3/bipbop_4x3_variant.m3u8

    i see hexadecimal numbers follow the av1 like avc1.4d4015,avc1.4d401e,avc1.4d401e,avc1.4d401f can anybody know what is the meaning of them

Navigation