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• How to use ffmpeg / x264 2-Pass encoding for multiple bitrate output files

  2 décembre 2014, par Jonesy

  While performing a 2-Pass encode to multiple output files I was receiving the error

  ratecontrol_init: can't open stats file 1 ffmpeg2pass-2.log

  My setup is to do a single first pass and then multiple second pass encodes to output files with different target bitrates using the same first pass results.

  ffmpeg -y -i $INPUT_FILE -an -vcodec libx264 -pass 1 -b:v 700k -f rawvideo /dev/null
  
  
  
  ffmpeg -y -i $INPUT_FILE -i out-aud.mp4 \
  
  $AUDIO_OPTIONS_P2 -vcodec libx264 -pass 2 -b:v 250k -f mp4 out-250.mp4 \
  
  $AUDIO_OPTIONS_P2 -vcodec libx264 -pass 2 -b:v 500k -f mp4 out-500.mp4 \
  
  $AUDIO_OPTIONS_P2 -vcodec libx264 -pass 2 -b:v 700k -f mp4 out-700.mp4

  This sequence resulted in the error listed above. What I discovered thru code-inspection is that ffmpeg/x264 looks for a different set of first-pass files for each second-pass encoding path. The first encoding path uses the set of files originally created

  ffmpeg2pass-0.log
  
  ffmpeg2pass-0.log.mbtree

  The second encoding path requires first-pass files with the names

  ffmpeg2pass-2.log
  
  ffmpeg2pass-2.log.mbtree

  The third encoding path requires first-pass files with the names starting with ffmpeg2pass-4*, etc.

  My solution was to create soft-links to the originally created set of files with the new names that were required for each pass before running the second-pass command.

  ln -s ffmpeg2pass-0.log ffmpeg2pass-2.log
  
  ln -s ffmpeg2pass-0.log.mbtree ffmpeg2pass-2.log.mbtree
  
  ln -s ffmpeg2pass-0.log ffmpeg2pass-4.log
  
  ln -s ffmpeg2pass-0.log.mbtree ffmpeg2pass-4.log.mbtree

  This seems to work as it results in the output encodes that I needed. However, I don’t know if this method is legitimate. Am I getting sub-optimal encoding results by using a first-pass output for one bitrate (700k) as the input to second-pass encodings for other bitrates ?

• ffmpeg - very slow conversion

  25 juillet 2015, par karoluch

  I create web app in JavaEE which displays many video formats. I use ffmpeg solution to convert videos to formats which is supported natively by main browsers.

  According to : http://www.jwplayer.com/html5/formats/
  I convert to WEBM container (VP8/VORBIS or VP9/OPUS). But conversion is very slow, bit rate equals to 200kbits/s. To convert I execute following command

  ffmpeg -i file.mov -c:v libvpx -preset ultrafast result.webm

  How to speed up conversion to natively supported formats by main browsers ?

• Evolution #3000 (Nouveau) : box-sizing et mediabox

  13 mai 2013, par Valéry -

  Je signale un problème que j’ai rencontré à deux reprises. Certains intégrateurs ou frameworks css (knacss par ex.) choisissent dans le reset box-sizing:border-box ; or ceci casse l’affichage du plugin mediabox.

  On peut naturellement dans le css surcharger les styles de mediabox mais ne serais-ce pas plutôt aux plugins SPIP de préciser systématiquement le modèle de boîte qu’ils utilisent pour que les utilisateurs n’aient pas à rechercher la solution (sachant que seuls les utilisateurs avancés vont la trouver).