Using FFmpeg to split mp3 audiobook file into mp3 parts based on audio volume level

audiobook-split-parts.sh

#!/bin/bash

IN="$1"
MIN_DUR_MINS="${2:-30}"
MIN_PART_DURATION_SECS=$(($MIN_DUR_MINS * 60))

IN_PATH=`realpath "$1"`
DEFAULT_OUTDIR="$(dirname "$IN_PATH")/parts"
OUTDIR="${3:-$DEFAULT_OUTDIR}"
OUTFILE_PATTERN="${OUTDIR}/part-%03d.mp3"

true ${SD_PARAMS:="-55dB:d=0.3"};

export MIN_PART_DURATION_SECS


echo "Determining split points..." >& 2

SPLITS=$(
    ffmpeg  -v warning -i "$IN" -af silencedetect="$SD_PARAMS",ametadata=mode=print:file=-:key=lavfi.silence_start -vn -sn  -f s16le  -y /dev/null \
    | grep lavfi.silence_start= \
    | cut -f 2-2 -d= \
    | perl -ne '
        our $prev;
        INIT { $prev = 0.0; }
        chomp;
        if (($_ - $prev) >= $ENV{MIN_PART_DURATION_SECS}) {
            print "$_,";
            $prev = $_;
        }
    ' \
    | sed 's!,$!!'
)


echo "Splitting points are $SPLITS"

mkdir -p "$OUTDIR"
echo "Saving ${MIN_DUR_MINS} min parts to ${OUTDIR}"

ffmpeg -v warning -i "$IN" -c copy -map 0 -f segment -segment_times "$SPLITS" "$OUTFILE_PATTERN"