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• Use bash script with yt-download and ffmpeg to extract OR covert depending on format

  7 juin 2018, par Keyslinger

  I have a batch of files I uploaded to YouTube which I now wish to backup on my MacBook. When I download and extract the audio, I get either *.m4a or *. opus :

  #!/bin/sh
  
  ID="$1"
  
  
  
  youtube-dl -f bestaudio -x -i --audio-format best -o '%(playlist)s/%(playlist_index)s %(uploader)s - %(title)s.%(ext)s' https://www.youtube.com/playlist?list="$ID"

  When the file extension is m4a, I need to leave it that way and perform no conversion, when the extension is opus, I need to convert it to m4a.

  If I want to convert every file, I can do something like this :

  youtube-dl -f bestaudio -x -i --audio-format m4a -o '%(playlist)s/%(playlist_index)s %(uploader)s - %(title)s.%(ext)s' https://www.youtube.com/playlist?list="$ID"

  But then the conversion is performed no matter what.

  How can I extract and only convert when the file extension is not m4a ?

• ffmpeg shell script to squeeze videos for twitter

  12 juin 2018, par André Levy

  Here’s a pretty rookie attempt at creating a shell script to squeeze videos into twitter’s 140s limitation :

  for f in "$@"
  
  do
  
      /Applications/ffmpeg -i $f -filter_complex "[0:v]setpts=140 / \ 
  
    $(/Applications/ffprobe -i $f -show_entries format=duration -v quiet -of csv="p=0") \
  
    * PTS[v];[0:a]atempo= \
  
    $(/Applications/ffprobe -i $f -show_entries format=duration -v quiet -of csv="p=0") \
  
    / 140[a]" -map "[v]" -map "[a]"  "${f%.*}_twitter.mp4"
  
  done

  It works, but it’s pretty badly written. Can you help me improve it ?

  1. How can I run ffprobe only once ?
  2. Do I need ffprobe at all, or does ffmpeg have the duration of the input amongst its arguments ?
  3. Will it encode faster with other settings (e.g. HW acceleration) ?
  4. Any twitter upload scripts out there to pipe this into ?

  Needless to say, I looked for this answers all around, to no avail.

  Cheers.

• set variable and call result during FOR loop ; batch script windows

  19 juin 2018, par Doons

  I have read several posts here on Stackoverflow about binding a variable during a FOR loop. While I figure most of the help provided here has been for Linux/Unix, I’m reaching out for help with batch scripting in Windows. My main goal is to extract the "date created" from a mp4-file and "overlay the date on my video" using ffmpeg (and or ffprobe).

  I have experimented a lot, but my latest attempt has been trying to bind the result from ffprobe onto a variable, and use the variable later. My latest and simplest attempt looks like this :

  SETLOCAL ENABLEDELAYEDEXPANSION
  
  for %%a in ("*.mp4") do (
  
  for /F "tokens=*" %%G in ('ffprobe -v quiet %%a -print_format compact -show_entries format_tags=creation_time') do (
  
  set DateC=%%G
  
  echo !DateC!)
  
  )

  I was hoping to be able to print the tag result from ffprobe using that code, but apparently not. So helping me bind that variable, and how to call it again later inside the following code snippet in Windows, would be deeply appreciated :

   ffmpeg -i %%a -filter_complex "drawtext=fontfile=/Windows/Fonts/Arial.ttf:x=28:y=650:fontsize=45:fontcolor=white:box=1:boxcolor=black@0.4:text='!DateC!'" -c:a copy output.mp4

  I must also mention I’ve seen the following code on StackOverflow :

   ffmpeg -i %%a -filter_complex "drawtext=fontfile=/Windows/Fonts/Arial.ttf:x=28:y=650:fontsize=45:fontcolor=white:box=1:boxcolor=black@0.4:text='%{metadata\:creation_time}'" -c:a copy output.mp4

  But I have the same problem making Windows recognize and print the metadata.

  I am certain the file in question contains this metadata.