MUX shell script for Zaireeka

zaireeka-mux.sh

#!/usr/bin/env bash
#
# Script to mix multiple CDs (< 10) into all combinations (order considered unimportant).
# Mixing to a set of 2 channel mixes where all lefts are combined to the final left
# channel and all right channels are combined to the final right.
#
# While I've tried to make it reasonably forgiving failure to follow these rules
# may have unexpected results.
#
# CD Directory rules:
#  - each ripped CD Directory must share a single parent dir.
#  - only one disc number in each CD Directory name.
#  - disc number can be any number above zero (64bit int limit?)
#  - CD Directory names must consistently start OR end with their disc number
#    NO digits in the middle, no mix and matching
#  - NO duplicate disc numbers
#
# Track file rules:
#  - all track files must share the same CD Diretory parent
#  - files are mixed across all combinations of CD
#  - NO duplicate track numbers
#  - to be mixable track files must have the same sample rate, and format
#    formats could vary between different tracks, but not across copies of the
#    same track (matched by track number)
#  - if mixed track files have different duration, result will truncate at the shortest
#

combine() {
  # Create the combinations for mixing the discs
  # Thanks to 'Nominal Animal' on Linux Questions
  # Taken from https://www.linuxquestions.org/questions/programming-9/strings-combinations-945160/
  local limit=$[ 1 << $# ]
  local args=("$@")
  for ((value = 1; value < limit; value++)); do
      local parts=()
      for ((i = 0; i < $#; i++)); do
          [ $[(1<<i) & value] -ne 0 ] && parts[${#parts[@]}]="${args[i]}"
      done
      # If we have combinations then mix the discs
      if [ "${#parts[@]}" -gt 1 ]; then
        mix_discs "${parts[@]}"
      fi
  done
}

mix_discs() {
  # Perform the mixing from the combos
  local args=("$@")
  # Create combo disk number from the array parts
  discno=`quick_join '' "$@"`
  # Get the pre/post fix info and create the ouput directory name
  discindex="${args[0]} - 1"
  [[ "${fixtype[$discindex]}" =~ post ]] && primesrc=`echo "${args[0]}""${fixes[$discindex]}"` || primesrc=`echo "${fixes[$discindex]}""${args[0]}"`
  [[ "${fixtype[$discindex]}" =~ post ]] && destdir=`echo "MUXED""${discno}""${fixes[$discindex]}"` || destdir=`echo "MUXED""${fixes[$discindex]}""${discno}"`
  # Make the output dir if it doesn't exist
  [[ -d $destdir ]] || mkdir "$destdir"
  # Loop through the tracks and grab the track number
  find "${primesrc}" -type f -print0 | while IFS= read -r -d '' track; do
    # Grap the track number
    trackname=${track##*/}
    if [[ ${trackname} =~ ^[0-9] ]]; then
      # Assume it's a track (it starts with a number
      # Start building the ffmpeg command
      local ffmpegcmd=(ffmpeg -i "${track}")
      # grab the track number
      trackno=`grep -o '^[0-9]\+' <<< ${trackname}`
      for (( i=1; i<${#args[@]}; i++ ));
      # Loop through the to be muxed directory entries
      do
        supdiscidx="${args[$i]} - 1"
        [[ "${fixtype[$supdiscidx]}" =~ post ]] && suppsrc=`echo "${args[$i]}""${fixes[$supdiscidx]}"` || suppsrc=`echo "${fixes[$supdiscidx]}""${args[$i]}"`
        suptrack=`ls ${suppsrc}/${trackno}*`
        # If we find the track add the input file
        ffmpegcmd+=(-i "${suptrack}")
      done
      # add input and filter stuff, keep it stereo for now
      ffmpegcmd+=(-filter_complex amerge=inputs=${#args[@]} -ac 2 "${destdir}/${trackname}")
      echo "${ffmpegcmd[@]}"
      # Execute the ffmpeg command for this MUX
      "${ffmpegcmd[@]}" < /dev/null
    fi
  done
}

# Quick efficient array join
# Courtesy of https://dev.to/meleu/how-to-join-array-elements-in-a-bash-script-303a
quick_join () { local IFS="$1"; shift; echo "$*"; }

# EXECUTION STARTS HERE
# Use param as root dir or use current directory if no param
rootdir="."
[[ ! -z "$1" ]] && rootdir=$1
# Go to root, bail if it doesn't exist
cd $rootdir || exit
# Get the directory listing, looking for the individual disc dirs
dirs=(*)
for (( i=0; i<${#dirs[@]}; i++ ));
# Loop through directory entries
do
  if [[ -d ${dirs[$i]} ]] && [[ ! ${dirs[$i]} =~ ^MUXED ]] && ([[ ${dirs[$i]} =~ ^[0-9] ]] || [[ ${dirs[$i]} =~ [0-9]$ ]]); then
    # if it's a directory, it doesn't start with MUXED (previous output) and
    # it's name starts or ends with a number, work out the prefix/postfix type
    [[ ${dirs[$i]} =~ ^[0-9] ]] && fixtype[$i]="post" || fixtype[$i]="pre"
    # Get the Disc number
    cdnums[$i]=`grep -o '[0-9]\+' <<< ${dirs[$i]}`
    # grab the pre/post fix value
    fixes[$i]=`grep -o '[^0-9]\+' <<< ${dirs[$i]}`
  fi
done
# Let the combination fun begin...
combine "${cdnums[@]}"