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• ffmpeg, /dev/video0, -f decklink

  20 mars 2019, par Camille Goudeseune

  I’m trying to capture video from a PCI card, the Blackmagic DeckLink Mini Recorder, via ffmpeg, on a headless host running Ubuntu 18.04.2 LTS, hopefully with a command like

  ffmpeg -f decklink -i /dev/video0 ...

  How can I make that work ? I have two obstacles.

  No /dev/video0

  ffmpeg -i /dev/video0 ... fails : /dev/video0: No such device or address.
  v4l2-ctl --list-devices fails with the same error message.

  I built /dev/video0, and it looks okay :

  mknod /dev/video0 c 81 0
  
  chown root.video /dev/video0
  
  chmod g+rw /dev/video0

  To compare this file with a working one, I ran strace cat /dev/video0 on this host, and on another host (Ubuntu 14) with a working /dev/video0. The outputs began to differ here (good, then bad) :

  fstat(1, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
  
  open("/dev/video0", O_RDONLY)           = 3  
  
  fstat(3, {st_mode=S_IFCHR|0660, st_rdev=makedev(81, 0), ...}) = 0
  
  fadvise64(3, 0, 0, POSIX_FADV_SEQUENTIAL) = 0
  
  ----
  
  
  
  fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0
  
  openat(AT_FDCWD, "/dev/video0", O_RDONLY) = -1 ENXIO (No such device or address)

  So /dev/video0 is broken at a level lower than ffmpeg or v4l2 or even cat.

  On Ubuntu 14, man 8 MAKEDEV suggests that the error message means that "the kernel does not have the driver configured or loaded."

  This Ubuntu 18 host lacks that manpage, but it does have a few /snap/core/*/sbin/MAKEDEV, all the same, so I tried

  /snap/core/6350/sbin/MAKEDEV -n -v video

  It would have created over a hundred devices videoXX, radioXX, vtxXX, vbiXX. Those devices didn’t exist yet, so it seemed harmless to try it.

  rm /dev/video0; /snap/core/6350/sbin/MAKEDEV video

  That rebuilt /dev/video0, but "No such device" remains, from cat or ffmpeg.

  No decklink

  ffmpeg -f decklink ... fails with Unknown input format: 'decklink'.

  Neither black nor deck nor link is mentioned by ffmpeg -devices (fbdev, lavfi, oss, v4l2) and ffmpeg -formats (about 350), either for Ubuntu’s own version 3.4.4-0ubuntu0.18.04.1, or for version N-93330-g7ff89574c7 compiled from source on 2019 Mar 13 :

  git clone https://git.ffmpeg.org/ffmpeg.git ffmpeg
  
  cd ffmpeg
  
  ./configure --enable-nonfree --disable-doc --disable-w32threads --enable-pthreads

  (Although ./configure --help mentions --enable-decklink, using that yielded "ERROR : DeckLinkAPI.h not found." updatedb && locate DeckLinkAPI.h finds no file with that name, either.)

  The DeckLink PCI card is recognized by hwinfo and lspci.

  lsmod reports the loaded modules blackmagic and blackmagic_io.

  Maybe the PCI card is installed ok, but ffmpeg just can’t reach it because I can’t configure it for that.

  Edit : Rebooting didn’t fix anything.

• Anomalie #4495 (Nouveau) : migration 3.2.7 vers 3.3.0

  24 mai 2020, par josiane aletto

  test 1-
  j’ai installée en local un site qui était en SPIP 3.2.7 [24473] pour le migrer en SPIP 3.3.0-dev [24578].
  fichier mesoptions.php avec
  

  <span class="CodeRay"><span class="predefined">define</span>(<span class="string"><span class="delimiter">'</span><span class="content">_IMG_MAX_HEIGHT</span><span class="delimiter">'</span></span>,<span class="integer">1200</span>); <span class="comment">// largeur en pixels</span>
  <span class="predefined">define</span>(<span class="string"><span class="delimiter">'</span><span class="content">_IMG_MAX_WIDTH</span><span class="delimiter">'</span></span>, <span class="integer">1024</span>);  <span class="comment">// hauteur en pixels</span>
  <span class="predefined">define</span>(<span class="string"><span class="delimiter">'</span><span class="content">_IMG_MAX_SIZE</span><span class="delimiter">'</span></span>,  <span class="integer">650</span>);   <span class="comment">// taille en kilo-octets</span>
  </span>
  Télécharger

  
  Des logos de taille superieure a _IMG_MAX_SIZE’, 650 ne sont plus dans IMG Pas non plus dans logo_erreur non plus.
  par exemple rubon3 : 1630 × 648 pixels
  Plugins :
  Adaptive Images 1.9.2 -
  Agenda 3.26.0 -
  API de vérification 1.8.1 - stable
  Centre image 0.10.4 - dev
  Couleur de rubrique 2.3.8
  Facteur 3.6.2 - stable
  Formidable 3.34.3 - stable
  Insérer Modèles 1.3.3 - stable
  Massicot 0.8.1 -
  Mini Calendrier 2.4.1 - stable
  oEmbed 2.0.10 - stable
  Owl Carousel 1.0.18
  Carousel responsive avec support du multi-touch.
  Palette 4.0.7
  pdf.js 0.6.3
  Picto mod avec FontAwesome 2.1.0
  Saisies pour formulaires 3.11.1
  SPIP Bonux 3.4.6
  YAML 2.0.10
  test2
  Pour mieux voir J’ai recommencé installation /migration en désinstallant le plugin massicot et en le supprimant du repertoire plugin et en mettant dans mes_options.php
  define(’_IMG_MAX_HEIGHT’,800) ; // largeur en pixels
  define(’_IMG_MAX_WIDTH’, 500) ; // hauteur en pixels
  define(’_IMG_MAX_SIZE’, 400) ; // taille en kilo-octets

  je constate ; que les logos de taille >400Ko sont présent mais retaillé, rubon3 qui avait 1630 × 648 pixels a maintenant à 500 × 199 pixels 221 ko dans logo/IMG alors qu’il n’ y a pas massicot.
  si je supprime ce rubon3 par logo de la rubrique et télécharge l’image originale j’obtiens une image retaillé avec du noir en plus. mais si je clique dessus l’image est retaillée mais ok et elle est bien en 500*199 dans IMG sans le noir.

  • les images migrées ont bien gardées leurs dimensions*.

  test3
  je telecharge le logo rubon3 de 1630 × 648 pixels comme un document d’un article —> il est enregistré directement en 500 × 199 pixels 221 ko . Ce mécanisme a changé, en mieux, car dans la version 3.2 j’avais un message "Les images doivent obligatoirement faire moins de 650 ko (ce fichier fait 847.5 ko)".

• Using libavcodec to read .mkv video file

  10 mars 2020, par Slav

  Trying to read .mkv file and write it to .bmp, but resulting .bmp is black-and-white and consists of multiple mini-images of what supposed to be written :

  int main()
  
  {
  
      av_register_all();
  
      avformat_network_init();
  
      avfilter_register_all();
  
  
  
      //crashes on -Ofast without =NULL initialization:
  
      AVFormatContext * format = NULL;
  
      if ( avformat_open_input( & format, VIDEO_FILE, NULL, NULL ) != 0 ) {
  
          cerr << "Could not open file " << VIDEO_FILE << endl;
  
          return -1;
  
      }
  
  
  
      // Retrieve stream information
  
      if ( avformat_find_stream_info( format, NULL ) < 0) {
  
          cerr << "avformat_find_stream_info() failed." << endl;
  
          return -1;
  
      }
  
      av_dump_format( format, 0, VIDEO_FILE, false );
  
  
  
      AVCodec * video_dec = (AVCodec*)1;
  
      AVCodec * audio_dec = (AVCodec*)1;
  
      const auto video_stream_index = av_find_best_stream( format, AVMEDIA_TYPE_VIDEO, -1, -1, & video_dec, 0 );
  
      const auto audio_stream_index = av_find_best_stream( format, AVMEDIA_TYPE_AUDIO, -1, -1, & audio_dec, 0 );
  
      if ( video_stream_index < 0 ) {
  
          cerr << "Failed to find video stream." << endl;
  
          return -1;
  
      }
  
      if ( audio_stream_index < 0 ) {
  
          cerr << "Failed to find audio stream." << endl;
  
          return -1;
  
      }
  
  
  
      AVCodecParameters * videoParams = format->streams[ video_stream_index ]->codecpar;
  
      cout << "Having " << videoParams->width << " | " << videoParams->height << " video." << endl;
  
  
  
      av_read_play( format );
  
  
  
      // create decoding context
  
      AVCodecContext * video_ctx = avcodec_alloc_context3( video_dec );
  
      AVCodecContext * audio_ctx = avcodec_alloc_context3( audio_dec );
  
      if ( ! video_ctx || ! audio_ctx ) {
  
          cerr << "Failed to avcodec_alloc_context3()" << endl;
  
          return -1;
  
      }
  
      if ( video_dec->capabilities & AV_CODEC_CAP_TRUNCATED ) video_ctx->flags |= AV_CODEC_FLAG_TRUNCATED; // we do not send complete frames
  
  
  
      /* For some codecs, such as msmpeg4 and mpeg4, width and height
  
         MUST be initialized there because this information is not
  
         available in the bitstream. */
  
  
  
      avcodec_parameters_to_context( video_ctx, format->streams[ video_stream_index ]->codecpar );
  
      avcodec_parameters_to_context( audio_ctx, format->streams[ audio_stream_index ]->codecpar );
  
      if ( avcodec_open2( video_ctx, video_dec, NULL ) < 0 ) {
  
          cout << "Failed to open video decoder." << endl;
  
          return -1;
  
      }
  
      if ( avcodec_open2( audio_ctx, audio_dec, NULL ) < 0 ) {
  
          cout << "Failed to open audio decoder." << endl;
  
          return -1;
  
      }
  
  
  
      uint8_t* picture_buffer = (uint8_t*) (av_malloc( avpicture_get_size( AV_PIX_FMT_RGB24 , videoParams->width, videoParams->height ) ));
  
      AVFrame* picture = av_frame_alloc();
  
      avpicture_fill( (AVPicture *) picture, picture_buffer, AV_PIX_FMT_RGB24, video_ctx->width, video_ctx->height );
  
  
  
      AVPacket packet;
  
      av_init_packet( & packet );
  
  
  
      int cnt = 0;
  
      while ( av_read_frame( format, & packet ) >= 0 && cnt < 10 ) {
  
          if ( packet.stream_index == video_stream_index ) {
  
              int check;
  
              const auto result = avcodec_decode_video2( video_ctx, picture, & check, & packet );
  
              cout << "Bytes decoded " << result << " check " << check << endl;
  
  
  
              std::string name = "debug/av/";
  
              name += std::to_string( cnt ) + ".bmp";
  
              cout << "Writing frame " << name << " with linesize " << picture->linesize[0] << " ..." << endl;
  
              write_bmp( (uint8_t*) picture->data, videoParams->width, videoParams->height, name.c_str() );
  
  
  
              av_frame_unref( picture );
  
  
  
              ++ cnt;
  
          }
  
          else if ( packet.stream_index == audio_stream_index ) {
  
              cout << "Sound packet" << endl;
  
          }
  
          av_free_packet( & packet );
  
          av_init_packet( & packet );
  
      }
  
  }

  How can I fix it ?