Recherche avancée

Sur d’autres sites (7291)

• FFMpeg amix filter volume changes. Explanation request

  22 janvier 2020, par klodoma

  First, the question :
  IS THERE somewhere documented or explained how ffmpeg amix filter changes the volume in the mixed audio files ? I couldn’t find any good reference.

  There are several threads regarding this "issue" that the amix filter changes the volume of the input files. I played around with these and I just cannot explain what is going on. It makes a difference if you "mix" files like concatenate them at specific times or you overlap audio tracks and volume changes just doesn’t make any sense.

  Firstly, I don’t understand WHY the volumes need to be changed.

  Some related refs :

  • FFMPEG amix filter volume issue with inputs of different duration
  • FFMPEG set volume in amix

• Révision 123057 : icones svg pour le porte plume (!1)

  23 mars 2020, par b b

  Icône svg un peu plus fidèle à l’ancienne

  Tant qu’à faire, une mignonnette icône en svg + les crédits dans paquet.xml

  Changement pour l’italique : i → I. Finitions dans le CSS. On supprime les vieux png, remplacés par les svg.

  Fallback pour les variables CSS

  « G » pour gras, « T » pour intertitres, couleur espace privé en amélioration progressive, handle en svg aussi

  Crédits pour certaines icônes

  Màj icônes et réorganisation du fichier.

  Optimisation svg

  svg avec les textes transformés en chemins

  un premier jet, à affiner

  Co-authored-by : Charles Razack <tcharlss@bravecassine.com>

• Script to cut video by silence part with FFMPEG

  11 février 2020, par fricadelle

  This is a question that is raised here How to split video or audio by silent parts or here How can I split an mp4 video with ffmpeg every time the volume is zero ?

  So I was able to come up with a straightforward bash script that works on my Mac.

  Here it is (only argument is the name of the video to be cut, it will generate a file start_timestamps.txt with the list of silence starts if the file does not exist and reuse it otherwise) :

  #!/bin/bash
  
  
  
  INPUT=$1
  
  
  
  filename=$(basename -- "$INPUT")
  
  extension="${filename##*.}"
  
  filename="${filename%.*}"
  
  
  
  SILENCE_DETECT="silence_detect_logs.txt"
  
  TIMESTAMPS="start_timestamps.txt"
  
  
  
  if [ ! -f $TIMESTAMPS ]; then
  
      echo "Probing start timestamps"
  
      ffmpeg -i "$INPUT" -af "silencedetect=n=-50dB:d=3" -f null - 2> "$SILENCE_DETECT"
  
      cat "$SILENCE_DETECT"| grep "silence_start: [0-9.]*" -o| grep -E '[0-9]+(?:\.[0-9]*)?' -o > "$TIMESTAMPS"
  
  fi
  
  
  
  PREV=0.0
  
  number=0
  
  
  
  cat "$TIMESTAMPS"| ( while read ts
  
  do
  
      printf -v fname -- "$filename-%02d.$extension" "$(( ++number ))"
  
      DURATION=$( bc <<< "$ts - $PREV")
  
      ffmpeg -y -ss "$PREV" -i "$INPUT" -t "$DURATION" -c copy "$fname"
  
      PREV=$ts
  
  done
  
  printf -v fname -- "$filename-%02d.$extension" "$(( ++number ))"
  
  ffmpeg -y -ss "$PREV" -i "$INPUT" -c copy "$fname" )

  Unfortunately it does not seem to work :

  I have a video that is basically a collection of clips, each clip being introduced by a 5 second silence with a static frame with a title on it. So I want to cut the original video so that each chunk is the 5 seconds "introduction" + video until the next introduction. Hope it’s clear.

  Anyway, in my script I first find all silence_start using ffmpeg silencedetect plugin. I get a start_timestamps.txt that read :

  141.126
  
  350.107
  
  1016.07
  
  etc.

  Then for example I would call (I don’t need to transcode again the video), knowing that (1016.07 - 350.107) = 665.963

  ffmpeg -ss 350.107 -i Some_video.mp4 -t 665.963 -c copy "Some_video02.mp4"

  The edge cases being the first chunk that has to go from 0 to 141.126 and the last chunk that has to go from last timestamp to end of the video.

  Anyway the start_timestamps seem legit. But my output chunks are completely wrong. Sometimes the video does not even play anymore in Quicktime. I don’t even have my static frame with the title in any of the videos...

  Hope someone can help. Thanks.

  EDIT Ok as explained in the comments, if I echo $PREV while commenting out the ffmpeg command I get a perfectly legit list of values :

  0.0
  
  141.126
  
  350.107
  
  1016.07
  
  etc.

  With the ffmpeg command I get :

  0.0
  
  141.126
  
  50.107
  
  016.07
  
  etc.

  bash variable changes in loop with ffmpeg shows why.

  I just need to append < /dev/null to the ffmpeg command or add -nostdin argument. Thanks everybody.