concat-audio

#!/bin/bash
set -e

out="${1}"
shift 1

if [ -z "${out}" ]
then
    1>&2 echo "usage:"
    1>&2 echo "  ${0} <output_filename.wav> [wav1.wav wav2.wav...] [ffmpeg-options]"
    exit 1
fi

set -x

# Get the list of files as arguments
files=("$@")
n=${#files[@]}

# Generate the args
args=()
for file in "${files[@]}"; do
  args+=('-i')
  args+=("$file")
done

# Generate the format string
fmt=""
for ((i = 0; i < n; i++)); do
    fmt+="[${i}:0]"
done
fmt+="concat=n=${n}:v=0:a=1[out]"

exec ffmpeg "${args[@]}" -filter_complex "$fmt" -map '[out]' "$out"