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• Anomalie #3894 : Jointures (erronées ?) avec les boucles documents et leurs critères

  27 janvier 2017, par marcimat ☺☮☯♫

  Les cas objet / id_objet¶

  En appelant page=test&objet=rubrique&id_objet=1 :

  - (DOCUMENTS){objet?}{id_objet?}
  - (DOCUMENTS){id_objet?}{objet?}
  - (DOCUMENTS){objet?}{id_objet?}{vu=non}
  - (DOCUMENTS){id_objet?}{objet?}{vu=non}
  - (DOCUMENTS){vu=non}{id_objet?}{objet?}
  Jointures correctes : 1 seule jointure L1 sur spip_documents_liens

  - (DOCUMENTS){id_article?}{objet?}{id_objet?}
  Jointure incorrecte : il y a 2 jointures différentes pour objet & id_objet
  

  SELECT documents.fichier
  FROM spip_documents AS `documents`  
  INNER JOIN spip_documents_liens AS L3 ON ( L3.id_document = documents.id_document ) 
  INNER JOIN spip_documents_liens AS L2 ON ( L2.id_document = documents.id_document )
  WHERE (documents.statut = ’publie’)
      AND (documents.mode IN (’image’,’document’))
      AND (documents.taille > 0 OR documents.distant=’oui’)
      AND (L2.objet = ’rubrique’)
      AND (L3.id_objet = 1)
  GROUP BY documents.id_document
  

  - (DOCUMENTS){id_article?}{objet?}{id_objet?}{vu=non}
  Même comportement erroné, avec vu sur L1 et 2 jointures pour objet & id_objet :
  

  SELECT documents.fichier
  FROM spip_documents AS `documents`  
  INNER JOIN spip_documents_liens AS L3 ON ( L3.id_document = documents.id_document ) 
  INNER JOIN spip_documents_liens AS L2 ON ( L2.id_document = documents.id_document ) 
  INNER JOIN spip_documents_liens AS L1 ON ( L1.id_document = documents.id_document )
  WHERE (documents.statut = ’publie’)
      AND (documents.mode IN (’image’,’document’))
      AND (documents.taille > 0 OR documents.distant=’oui’)
      AND (L2.objet = ’rubrique’)
      AND (L3.id_objet = 1)
      AND (L1.vu = ’non’)
  GROUP BY documents.id_document
  

  Il me semble que les jointures objet / id_objet ne fonctionnent que s’ils sont les premiers critères optionnels créant possiblement une jointure de la boucle.
  Cependant (DOCUMENTS){vu?}{objet?}{id_objet?} fonctionne aussi avec vu optionnel (1 seule jointure).

• OpenCV not finding libavcodec installed in centos

  18 juillet 2016, par Ras

  ffmpeg is installed in /usr/local as shared libraries in Cent OS 6.8, but while compiling opencv 2.4.10, it couldn’t find these libraries, configuration output is

  -- Looking for linux/videodev.h
  
  -- Looking for linux/videodev.h - found
  
  -- Looking for linux/videodev2.h
  
  -- Looking for linux/videodev2.h - found
  
  -- Looking for sys/videoio.h
  
  -- Looking for sys/videoio.h - not found
  
  -- checking for module 'libavcodec'
  
  --   package 'libavcodec' not found
  
  -- checking for module 'libavformat'
  
  --   package 'libavformat' not found
  
  -- checking for module 'libavutil'
  
  --   package 'libavutil' not found
  
  -- checking for module 'libswscale'
  
  --   package 'libswscale' not found
  
  -- Looking for libavformat/avformat.h
  
  -- Looking for libavformat/avformat.h - found
  
  -- Looking for ffmpeg/avformat.h
  
  -- Looking for ffmpeg/avformat.h - not found

  To run ffmpeg, I added /usr/local/lib to /etc/ld.so.conf file, should I need to add each library separately into directory /etc/ld.so.conf.d/ instead ?

• Transcode HLS Segments individually using FFMPEG

  27 mai 2013, par rayh

  I am recording a continuous, live stream to a high-bitrate HLS stream. I then want to asynchronously transcode this to different formats/bitrates. I have this working, mostly, except audio artefacts are appearing between each segment (gaps and pops).

  Here is an example ffmpeg command line :

  ffmpeg -threads 1 -nostdin -loglevel verbose \
  
     -nostdin -y -i input.ts -c:a libfdk_aac \
  
     -ac 2 -b:a 64k -y -metadata -vn output.ts

  Inspecting an example sound file shows that there is a gap at the end of the audio :

  

  And the start of the file looks suspiciously attenuated (although this may not be an issue) :

  

  My suspicion is that these artefacts are happening because transcoding are occurring without the context of the stream as a whole.

  Any ideas on how to convince FFMPEG to produce audio that will fit back into a HLS stream ?

  ** UPDATE 1 **

  Here are the start/end of the original segment. As you can see, the start still appears the same, but the end is cleanly ended at 30s. I expect some degree of padding with lossy encoding, but I there is some way that HLS manages to do gapless playback (is this related to iTunes method with custom metadata ?)

  
  

  ** UPDATED 2 **

  So, I converted both the original (128k aac in MPEG2 TS) and the transcoded (64k aac in aac/adts container) to WAV and put the two side-by-side. This is the result :

  
  

  I'm not sure if this is representative of how a client will play it back, but it seems a bit odd that decoding the transcoded one introduces a gap at the start and makes the segment longer. Given they are both lossy encoding, I would have expected padding to be equally present in both (if at all).

  ** UPDATE 3 **

  According to http://en.wikipedia.org/wiki/Gapless_playback - Only a handful of encoders support gapless - for MP3, I've switched to lame in ffmpeg, and the problem, so far, appears to have gone.

  For AAC (see http://en.wikipedia.org/wiki/FAAC), I have tried libfaac (as opposed to libfdk_aac) and it also seems to produce gapless audio. However, the quality of the latter isn't that great and I'd rather use libfdk_aac is possible.