sync/scripts/transcode_opus.sh

#!/usr/bin/env bash
set -euo pipefail

# evaluate options through given arguments
file_suffix=
map=
while [[ $# > 0 ]]; do
   case $1 in
      -t | --type) file_suffix=$2; shift 2;;
      -map       ) map='-map 0:0'; shift;;
      *          )                 break ;; # Anything else stops command line processing.
   esac
done

# ensure existence of destination folder
dir="$(pwd)"
dest=${dir%/*}/${dir##*/}_ogg
if [[ !(-d $dest) ]]; then
   mkdir "$dest"
fi

for file in ./*.$file_suffix; do
   # `-vbr on -application audio` should be default, but let's be sure
   echo "ffmpeg -i '$file' -c:a libopus -b:a 64k -vbr on -application audio $map '$dest/${file%$file_suffix}ogg'";
   ffmpeg -i "$file" -c:a libopus -b:a 64k -vbr on -application audio $map "$dest/${file%$file_suffix}ogg";
done