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• Normalizing audio of several wav snippets with ffmpeg

  17 mai 2023, par dick_kickem

  I searched the site and I figured that maybe ffmpeg-normalize could be part of my solution but I'm really not sure.

  


  In my free time me and my friends create quizzes for people to solve. One of these is a music quiz, where you hear audio snippets and have to guess the artist and song title. A few years back I did most of them using Audacity, which means recording snippets from existing videos, inserting fade in and fade out to every snippet, putting announcements like "Number x" before the x-th song and also making sure that all songs are fairly of equal loudeness (-6.0 dB).

  


  The result in Audacity looked like this.

  


  

  


  Lazy as I am, I learned about ffmpeg and wrote a script, which does all these steps for me. The script is mostly written in bash. I use some audio files where I extract the audio in wav-format, add a fade in and fade out and then I try to set the volume to -6.0 dB as with Audacity. The part where this happens looks like this :

  


  ...[some code before]...

# write the audio details of temmp.wav into the "info" file
ffmpeg -i temp.wav -filter:a volumedetect -f null - 2> info

#check out the max volume of temp.wav
max_vol=$(grep "max_volume" info | cut -d ' ' -f5)

# determine the difference between the max volume and -6
vol_diff=$(expr "-6-($max_vol)" | bc -l)

# change temp.wav loudness by the determined difference
ffmpeg -y -i temp.wav -filter:a "volume=$vol_diff$db" $count.wav

...[some code after]...


  


  I do this with all snippets, leaving me with usually ten snippets in the format 1.wav, 2.wav and so on. Lastly, I concatenate them all with announcements in the form nr1.wav, 1.wav, nr2.wav, 2.wav and so on. Overall this works really great for me. Yet, the loudness is not quite as equal as in Audacity. Here is a screenshot of a generated music quiz using the described script (not the same music snippets as the example before) :

  


  

  


  You can see some peaks pointing out. It's not bad and in fact, it works for me in most cases, but it's not like what I used to have with Audacity. Does anyone have any idea how to fix that to make it more equal ?

  


  Thank you in advance and kind regards

  


• avfilter/tinterlace : Properly preserve CEA-708 closed captions

  5 mai 2023, par Devin Heitmueller

  avfilter/tinterlace : Properly preserve CEA-708 closed captions
  Because the interlacing filter halves the effective framerate, we
  
  need to ensure that no CEA-708 data is lost as frames are merged.
  Make use of the new ccfifo mechanism to ensure that caption data
  
  is properly preserved as frames pass through the filter.
  Thanks to Thomas Mundt for review and noticing a couple of
  
  missed codepaths for injection on output.  Thanks to Lance Wang
  
  for pointing out a memory leak.
  Signed-off-by : Devin Heitmueller <dheitmueller@ltnglobal.com>
  
  Signed-off-by : Limin Wang <lance.lmwang@gmail.com>
  

  • [DH] libavfilter/tinterlace.h
  • [DH] libavfilter/vf_tinterlace.c

• avfilter/vf_libplacebo : add flexible crop exprs

  1er mai 2023, par Niklas Haas

  avfilter/vf_libplacebo : add flexible crop exprs
  Motivated by a desire to use vf_libplacebo as a GPU-accelerated
  
  cropping/padding/zooming filter. This commit adds support for setting
  
  the `input/target.crop` fields as dynamic expressions.
  Re-use the same generic variables available to other scale and crop type
  
  filters, and also add some more that we can afford as a result of being
  
  able to set these properties dynamically.
  It's worth pointing out that `out_t/ot` is currently redundant with
  
  `in_t/t` since it will always contain the same PTS values, but I plan on
  
  changing this in the near future.
  I decided to also expose `crop_w/crop_h` and `pos_w/pos_h` as variables
  
  in the expression parser itself, since this enables the fairly common
  
  use case of determining dimensions first and then placing the image
  
  appropriately, such as is done in the default behavior (which centers
  
  the cropped/placed region by default).
  

  • [DH] doc/filters.texi
  • [DH] libavfilter/vf_libplacebo.c