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• Evolution #3892 (Nouveau) : Différence de tri entre {id_patate IN ...} et {id_patate ?}

  24 janvier 2017, par tcharlss (*´_ゝ｀)

  Avec un critère {id_patate IN ...}, le compilateur ajoute un ORDER BY FIELD(id_patate,...) à la requête, du coup les résultats sont triés dans l’ordre du IN : joie.
  En revanche, avec un critère optionnel {id_patate?} et un array dans l’environnement, ça fait bien un IN dans la requête par contre il n’y a pas ORDER BY et on perd l’ordre de tri : tristesse.

  Dans les 2 cas, on devrait avoir cet ORDER BY FIELD fort pratique.

  Exemples :

  
  

  SELECT articles.id_article, articles.lang, articles.titre
  FROM spip_articles AS `articles`
  WHERE (articles.statut = ’publie’)
      AND ((articles.id_article  IN (3,1,2)))
  ORDER BY FIELD(articles.id_article,3,1,2)
  

  SELECT articles.id_article, articles.lang, articles.titre
  FROM spip_articles AS `articles`
  WHERE (articles.statut = ’publie’)
      AND ((articles.id_article  IN (3,1,2)))
  

  Testé en SPIP 3.1.3

• multichannel (dolby digital, DTS, ecc.) delay difference on original master

  17 janvier 2017, par esposito

  I have different flac files with 6/8 channels (this is the audio of movie) and I need to mix with ffmpeg part of rear channels with front channels and sometimes viceversa.

  There is no problem do it the operation work with an automate software.

  But I’am sure there is a phase difference beetween front channels and rear channels and I like to add a delay to compensate this difference (when I listen it is clear there is a phase offset and this degrade the result).

  I don’t have an idea about how many milliseconds I need to add to compensate and what channel and if the difference is negative or positive.

  Someone can help me please to understand approximately what are the range of delay for each channel (a table is very useful) ?

  Thank you !!

• What's the difference with crf and qp in ffmpeg ?

  18 novembre 2016, par Nova

  After browsing around Google, I’ve came across this page about h264 encoding and discovered about qp. https://trac.ffmpeg.org/wiki/Encode/H.264

  My questions are : What are the differences with crf and qp ? Is it better to use qp over crf overall, or is it only if for using qp 0 for best lossless ? Does qp have a known sensible setting if it’s preferred ? So far, I know crf has the default value of 23 while 18 is a sensible preferred increase in quality, although I don’t understand why 18 wouldn’t be default if better sensible lossless. Lastly, would changing either of them cause incompatibility with non-ffmpeg players or just qp ?

  I’m converting from webm to mp4 by the way.

  I was going to test crf 23 and 18 and pick which is best but I can’t seem to find any concrete information on this comparison or about qp.