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• 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.

• Problem with streamcopy of a part of av1 video in ffmpeg

  22 avril 2020, par vorrom

  I'm trying to cut part of a video from av1-mp4 file with FFMmpeg command and I want do it withuout recompressing. But there is no result.&#xA;I try method with -ss -t or -to parameters with different combinations.

  &#xA;&#xA;

  ffmpeg -ss 10 -i D:\in_av1.mp4 -t 5 -vcodec copy -acodec copy D:\out_av1.mp4


  &#xA;&#xA;

  -ss from input file get me 15 seconds video from beginning instead 5 seconds from 10

  &#xA;&#xA;

  ffmpeg -i D:\in_av1.mp4 -ss 10 -t 5 -vcodec copy -acodec copy D:\out_av1.mp4


  &#xA;&#xA;

  this way get 5 seconds audio file without video data.&#xA;It seems to me that coder can not find start point for operation.

  &#xA;&#xA;

  I make an av1.mp4 example file, you can find it here. https://pixeldrain.com/u/c8fbQgYK I understand that AV1 is new format and have experimental flag while converting with it. But nevertheless FFmpeg carrectly change result when I change -t parameter. If I use

  &#xA;&#xA;

  ffmpeg -ss 10 -i D:\in_av1.mp4 -t 7 -vcodec copy -acodec copy D:\out_av1.mp4


  &#xA;&#xA;

  it give me 17 seconds. So -t part working. Whats why I hope there is way to solve my problem.

  &#xA;&#xA;

  I use ffmpeg-20200417-889ad93-win64-static for Windows.

  &#xA;

• All audios should be played after combing using ffmpeg. But there is only audio for the first part

  6 mai 2020, par Eric Z

  This code is combining 3 mp4 files using ffmpeg command. Each file has audio. &#xA;After combining, I can listen audio for only first part. &#xA;How can I solve this problem ?

  &#xA;&#xA;

  ===========================================================================

  &#xA;&#xA;

  ffmpeg -y -i "tmp/titled-0c33a83dc70534c67f66.mp4" -i "tmp/titled-1c2fc9a95e644ab135a3.mp4" -i "tmp/titled-73c3fb1a3ea435cacdd2.mp4" -i "logo/logo.png"  -filter_complex "
nullsrc=s=1280x720[bg];
[0:v]setpts=PTS-STARTPTS+0/TB[v0];
[1:v]setpts=PTS-STARTPTS+4.039/TB[v1];
[2:v]setpts=PTS-STARTPTS+8.078/TB[v2];
[bg][v0]overlay=x='if(lte(t,4.039),0,min(0,-w*min(1,max(0,0.98*(t-4.039)^2))))':y=0,trim=duration=13.145[bg];
[bg][v1]overlay=x='if(gte(t,8.078),-w*min(1,max(0,0.98*(t-8.078)^2)),max(0,1280*(1-min(1,max(0,0.69*(atan(8*(t-4.039)^2.7)))))))':y=0[bg];
[bg][v2]overlay=x='max(0,1280*(1-min(1,max(0,0.69*(atan(8*(t-8.078)^2.7))))))':y=0"
-y -vcodec h264 -crf 13 -acodec aac -strict -2 "out.mp4"


  &#xA;