#!/bin/bash
#
# convert-song - Convert an mp3 file to m4a format with reduced bitrate
#
# Converts an mp3 to an m4a (AAC) and reduces the bitrate to 128 kbps.
# Drops video streams (useful for mp3s with embedded artwork).
#
# Usage: convert-song <input.mp3>
#
# Requirements: ffmpeg

set -euo pipefail

input="$1"
if ! [ -r "$input" ]; then
  if ! [ -z "$input" ]; then
    echo "[error] File not found: $input"
  else
    echo "usage: $0 <input mp3>"
    echo
    echo "Converts an mp3 to an m4a (AAC) and reduces the bitrate to 128 kbps."
  fi
  exit 1
fi

# -vn drops video on the floor, required for source mp3s with artwork
ffmpeg -i "$input" -vn -c:a aac -b:a 128k "${input%.mp3}.m4a"