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• Extract multiple thumbnails in a batch with ffmpeg ?

  15 mai 2016, par JulianJ

  I have a text file of frame numbers. Is there a way using ffmpeg to extract a batch load of thumbnails from a video file using the text file all at once.

  The code below extracts a single frame( frame 100 in this case) from a video file

  ffmpeg -i in_video.avi -vf "select=gte(n\,100)" -vframes 1 out_img.png

• Why isn't my bash script working ?

  15 mai 2016, par JulianJ

  I’m trying to get this bash script to work but am at a loss. I have a text file that contains a list of frame numbers line by line. ffmpeg reports the error :

  Undefined constant or missing '(' in '$name)'

  The script

  #!/bin/bash
  
  source text.txt
  
  while read name
  
  do
  
   ffmpeg -i result.mp4 -vf "setpts=N+1,select='eq(n,\$name)'" -vframes 1 frame-$i.jpg
  
  done code>

• Why is my bash script halting with ffmpeg ?

  16 mai 2016, par JulianJ

  I have a text file that contains frame numbers line by line and I am using a bash script and ffmpeg to cycle through each line and attempt to print out a thumbnail of each frame.

  Each time I run the bash script in my terminal it halts with an error having created the first thumbnail. It seems it is not given the thumbnail a unique name. What am I doing wrong ?

  My bash script :

  #!/bin/bash
  
  source text.txt
  
  while read name
  
  do
  
  ffmpeg -i result.mp4 -vf "setpts=N+1,select='eq(n,$name)'" -vframes 1 frames-$i.jpg
  
  done code>

  The error :

  File 'frames-.jpg' already exists. Overwrite ? [y/N] Not overwriting - exiting