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• Evolution #3949 (Nouveau) : lang en url dans le privé

  20 mai 2017, par jluc -

  https://www.spip.net/ecrire/?exec=articles liste 3500 articles en différentes langues, de même que https://www.spip.net/ecrire/?exec=articles&lang=fr

  De même, https://www.spip.net/ecrire/?exec=mot&id_mot=497 liste 33 articles en différentes langues, exactement pareil que que https://www.spip.net/ecrire/?exec=mot&id_mot=497&lang=fr

  C’est à dire que l’arg lang=fr n change rien aux listes présentées.

  Il me semble que ce serait bien que la langue spécifiée en url soit prise en compte. Ensuite il pourrait aussi y avoir un sélecteur de langue pour cela dans le privé : non pour la langue de l’UI mais pour les listes présentées.

• Difference of pixel value between MATLAB and OpenCV extracting frames from video

  31 mai 2017, par Andrey Kosmachev

  I’m trying to open a video file encoded with H264 using Matlab. I rip the first frame, analyze the north-western square 9x9, I get the following matrix :

     116   128   126   126   127   126   127   126   130
  
  
  
     125   128   127   131   131   130   131   129   127
  
  
  
     147   150   150   152   157   151   157   152   149
  
  
  
     145   152   158   151   155   158   154   158   156
  
  
  
     145   155   157   155   154   161   152   158   154
  
  
  
     149   154   151   156   158   152   157   152   156
  
  
  
     151   152   155   152   158   151   155   150   151
  
  
  
     148   161   156   157   155   155   152   152   154
  
  
  
     150   157   150   152   151   149   151   156   155

  I try to do the same thing with OpenCV and have the following result :

     116   128   125   125   126   125   126   125   130 
  
  
  
     124   128   126   131   131   130   131   129   126 
  
  
  
     146   150   150   152   157   151   157   152   149 
  
  
  
     145   152   158   151   154   158   153   158   156 
  
  
  
     145   154   157   154   153   160   152   158   153 
  
  
  
     149   153   151   156   158   152   157   152   156 
  
  
  
     151   152   154   152   158   151   154   150   151 
  
  
  
     147   160   156   157   154   154   152   152   153 
  
  
  
     150   157   150   152   151   149   151   156   154 

  It is seen that approximately in 50 percent of cases the brightness value of the pixel in the first matrix is one more than in the second one. For this reason, the results of further processing, respectively, in Matlab and OpenCV are different. Can someone explain to me, what is this effect related to and how to overcome it ?

• ffmpeg is preferring to encode in VP9 but I'm trying to encode in VP8

  1er septembre 2016, par user1689634

  I’m trying to encode webm video files specifically in VP8, but ffmpeg is forcing VP9. I’m using -c:v libvpx, which to my knowledge is supposed to be VP8, but when it encodes I see it’s encoding in VP9 instead :

  ffmpeg -framerate 7 -loop 1 -i "C:\converted\cover.jpg" -c:v libvpx
  
  -i "C:\converted\Image.wav" -b:v 50k -c:a libvorbis -b:a 96k
  
  -vf scale=-1:300 -shortest -metadata title="%artist% - %album%" 
  
  -metadata author="%artist%" -threads 8 -y "C:\converted\%artist% - %album%.webm"
  
  
  
  ffmpeg version N-81489-ga37e6dd Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 5.4.0 (GCC)
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-dx
  
  va2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-lib
  
  ebur128 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --ena
  
  ble-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfree
  
  type --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enab
  
  le-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-lib
  
  openh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschr
  
  oedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheor
  
  a --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvo
  
  rbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --ena
  
  ble-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --e
  
  nable-decklink --enable-zlib
  
    libavutil      55. 29.100 / 55. 29.100
  
    libavcodec     57. 54.101 / 57. 54.101
  
    libavformat    57. 48.101 / 57. 48.101
  
    libavdevice    57.  0.102 / 57.  0.102
  
    libavfilter     6. 57.100 /  6. 57.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  1.100 /  2.  1.100
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, image2, from 'C:\converted\cover.jpg':
  
    Duration: 00:00:00.14, start: 0.000000, bitrate: 3159 kb/s
  
      Stream #0:0: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 500x495 [S
  
  AR 1:1 DAR 100:99], 7 fps, 7 tbr, 7 tbn, 7 tbc
  
  Guessed Channel Layout for Input Stream #1.0 : stereo
  
  Input #1, wav, from 'C:\converted\Image.wav':
  
    Metadata:
  
      artist          : ???????
  
      genre           : Alternative Rock
  
      title           : goodnight, wonderend
  
      date            : 2014
  
    Duration: 00:04:48.00, bitrate: 1421 kb/s
  
      Stream #1:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 2 channels,
  
   s16, 1411 kb/s
  
  [swscaler @ 055f7d60] deprecated pixel format used, make sure you did set range
  
  correctly
  
  [libvpx-vp9 @ 0312d8e0] v1.6.0
  
  [webm @ 0316e380] Using AVStream.codec to pass codec parameters to muxers is dep
  
  recated, use AVStream.codecpar instead.
  
      Last message repeated 1 times
  
  Output #0, webm, to 'C:\converted\カラスヤサボウ - goodnight, wonderend.w
  
  ebm':
  
    Metadata:
  
      title           : カラスヤサボウ - goodnight, wonderend
  
      author          : カラスヤサボウ
  
      encoder         : Lavf57.48.101
  
      Stream #0:0: Video: vp9 (libvpx-vp9), yuv420p, 303x300 [SAR 10000:9999 DAR 1
  
  00:99], q=-1--1, 50 kb/s, 7 fps, 1k tbn, 7 tbc
  
      Metadata:
  
        encoder         : Lavc57.54.101 libvpx-vp9
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
  
      Stream #0:1: Audio: vorbis (libvorbis), 44100 Hz, stereo, fltp, 96 kb/s
  
      Metadata:
  
        encoder         : Lavc57.54.101 libvorbis
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mjpeg (native) -> vp9 (libvpx-vp9))
  
    Stream #1:0 -> #0:1 (pcm_s16le (native) -> vorbis (libvorbis))
  
  Press [q] to stop, [?] for help
  
  frame=   30 fps=0.0 q=0.0 size=      29kB time=00:00:00.71 bitrate= 333.4kbits/s
  
  frame=   37 fps= 36 q=0.0 size=      49kB time=00:00:01.71 bitrate= 233.6kbits/s
  
  frame=   45 fps= 27 q=0.0 size=      60kB time=00:00:02.85 bitrate= 170.6kbits/s
  
  frame=   53 fps= 23 q=0.0 size=      84kB time=00:00:04.00 bitrate= 172.7kbits/s
  
  frame=   57 fps= 21 q=0.0 size=     102kB time=00:00:04.57 bitrate= 183.5kbits/s
  
  frame=   62 fps= 19 q=0.0 size=     112kB time=00:00:05.28 bitrate= 173.4kbits/s
  
  frame=   64 fps= 12 q=0.0 Lsize=     141kB time=00:00:09.00 bitrate= 128.1kbits/
  
  s speed=1.69x
  
  video:87kB audio:47kB subtitle:0kB other streams:0kB global headers:4kB muxing o
  
  verhead: 4.908199%
  
  Exiting normally, received signal 2.

  The build I have does have --enable-libvpx and --enable-libvpx-vp9 flags. It is also the latest default static build, I made no changes, just extracted it : ffmpeg-20160828-a37e6dd-win32-static.zip

  I was using an outdated build for a long time and updated today. I can’t find any documentation online to help me with this problem.