Extract audio from every Powerpoint file in a folder.

pptx-audio.sh

#!/bin/sh

# === PPTX Audio ===
# Extract audio from every Powerpoint file in a folder, and concatenates into one file.
# Requires `ffmpeg` to be installed. 
# See config below for directories configuration.
# Only compatible with `m4a` MPEG format for output, as that is what Powerpoint uses
# Biggest speed loss is using the `unzip` command

# =============== CONFIG =================
  # Directory of inputs pptx files
  in='pptx'
  # Output file for audio
  # Must be m4a, unless ffmpeg command changed
  out='audio.m4a'
  # Temporary file directory
  temp='/tmp/pptx-audio'
# ========================================

# Clean temp dir
[ -d "$temp" ] && rm -r "$temp"
mkdir "$temp"
mkdir "$temp/pptx"  # Extracted pptx data
mkdir "$temp/audio" # All audio files

# Unzip files, save audio paths to file for ffmpeg to read
echo 'Extracting audio from all pptx files...'
inputlist=""
for pptx in $in/*.pptx; do
  # Get name, without path or file extension, replaced spaces with underscores
  name=$(basename -- "$pptx")
  name=${name%.*}
  name=${name// /_}
  
  # Unzip pptx to temp folder
  echo 'Unzipping pptx file...'
  unzip "$pptx" -d "$temp/pptx" \
    || break

  echo 'Moving out all audio files.'
  # Find all audio files (m4a)
  for audio in $temp/pptx/ppt/media/*.m4a; do
    # Move audio file to temporary folder
    id=$(basename -- "$audio")
    mv "$audio" "$temp/audio/${name}_$id"
  done

  # Delete extracted folder, to save disk space during process
  rm -r "$temp/pptx"
done

# Create audio inputs file for ffmpeg
echo 'Including all audio files as inputs.'
inputlist=""
for audio in $temp/audio/*; do
  # Set path relative to audio.txt file
  audio=${audio#$temp/}
  echo "including: $audio"
  # Add to list of inputs
  inputlist+="file '$audio'\n"
done
echo -e "$inputlist" > "$temp/audio.txt"

# Run ffmpeg command, with audio inputs from text file
# `-c copy` tells ffmpeg to copy data, without re-encoding (same codec) (very fast!)
echo 'Concatenating audio files...'
ffmpeg -y \
  -f concat \
  -i "$temp/audio.txt" \
  -c copy \
  "$out" \
  && echo "Saved to $out"

# Remove temp dir
rm -r "$temp"