Script to split Mackie DLZ Creator multi track recording polywave

dlz-creator-polywave-split.sh

#!/bin/bash
#
# This script converts multi-track "polywave" recording files generated by the Mackie DLZ Creator
# to A) combines the 2GB split recording files and B) split the multi-track 14-channel WAV file
# into 9 separate WAV files: inputs 1-4 (mono) and stereo 5/6, 7/8, 9/10, 11/12, and Stereo LR.
#
# It does everything in a single pass and joining the split recording parts is done with the
# concat filter rather than the concat demuxer (or protocol) so that there's no need for temporary
# files and there's less issues with quoting filenames. This script should work on anything that
# runs bash and has 'ffmpeg' somewhere in PATH. Tested on Linux but it should work in cygwin/msys
# for Windows or on a Mac.

set -euo pipefail

usage() {
    cat <<EOF
Usage: $0 OUTPUT_PREFIX INPUT_FILE [INPUT_FILE...]"

This script will use ffmpeg to split a multi-track recording from the Mackie DLZ Creator
into individual wav files for each channel. It can also concatenate split recording files
since the DLZ creates a new file every 2G.
EOF
    exit 1
}

# not enough args
if (( $# < 2 )); then
    usage
fi

prefix="$1"
shift
inputs=("$@")

# output_prefix shouldn't be a file that exists. If all arguments are files that exist
# then the user probably actually forgot the prefix.
if [[ -f "$prefix" ]]; then
    usage
fi

for input in "${inputs[@]}"; do
    if [[ ! -f "$input" ]]; then
        echo "Error: input file '$input' doesn't exist"
        exit 1
    fi
done

# build the concat filtergraph
concat_filter=""
i=0
for input in "${inputs[@]}"; do
    concat_filter+="[${i}:0]"
    i=$((i + 1))
done
concat_filter+="concat=n=${#inputs[@]}:v=0:a=1[merged]; "

# split filter is used to duplicate merged several times, since it doesn't work to use re-use the
# same output label multiple times for different inputs of subsequent filterchains
split_filter="[merged]asplit=9[m0][m1][m2][m3][m4][m5][m6][m7][m8]; "

# ffmpeg filter_complex string to use the pan filter to split a single multi-track input stream
# (which we call [merged_input] as the result of concatenation of the original inputs) into 9
# output streams: 4 mono (inputs 1, 2, 3, and 4) and 5 stereo (inputs 5/6, 7/8, 9/10, 11/12,
# and the stereo master bus). cN channel numbers in the pan filter are 0 indexed, so numbers
# below are one smaller than the actual DLZ input numbers
pan_filter=''
pan_filter+='[m0]pan=mono|c0=c0[out0]; '
pan_filter+='[m1]pan=mono|c0=c1[out1]; '
pan_filter+='[m2]pan=mono|c0=c2[out2]; '
pan_filter+='[m3]pan=mono|c0=c3[out3]; '
pan_filter+='[m4]pan=stereo|c0=c4|c1=c5[out4]; '
pan_filter+='[m5]pan=stereo|c0=c6|c1=c7[out5]; '
pan_filter+='[m6]pan=stereo|c0=c8|c1=c9[out6]; '
pan_filter+='[m7]pan=stereo|c0=c10|c1=c11[out7]; '
pan_filter+='[m8]pan=stereo|c0=c12|c1=c13[out8]; '

# build the ffmpeg command
cmd=(ffmpeg)
for input in "${inputs[@]}"; do
    cmd+=(-i "$input")
done

# add the full filter to the ffmpeg command
cmd+=( -filter_complex "${concat_filter}${split_filter}${pan_filter}" )

# now for the output files. The DLZ records in 24 bit wav and the input files are pcm_s24le, but
# that gets forgotten among our filtergraph, so it has to be re-specified for each output.
# Alternatively, codec and ext could be changed to transcode to FLAC or another codec in one pass
# without needing to waste disk space on intermediate wav files. (TODO: this could be a
# command-line option)
codec='pcm_s24le'
ext='wav'

cmd+=(
    -map "[out0]" -c:a "$codec" "${prefix}_1_ch1.${ext}"
    -map "[out1]" -c:a "$codec" "${prefix}_2_ch2.${ext}"
    -map "[out2]" -c:a "$codec" "${prefix}_3_ch3.${ext}"
    -map "[out3]" -c:a "$codec" "${prefix}_4_ch4.${ext}"
    -map "[out4]" -c:a "$codec" "${prefix}_5_ch5-6.${ext}"
    -map "[out5]" -c:a "$codec" "${prefix}_6_ch7-8.${ext}"
    -map "[out6]" -c:a "$codec" "${prefix}_7_ch9-10.${ext}"
    -map "[out7]" -c:a "$codec" "${prefix}_8_ch11-12.${ext}"
    -map "[out8]" -c:a "$codec" "${prefix}_9_main-LR.${ext}"
)

echo "+ ${cmd[*]}"
"${cmd[@]}"