Trim audio files with fade

trim.sh

#!/bin/sh
# Usage:
#     trim  FILE  START  END  FADE_IN  FADE_OUT
#           1     2      3    4        5
# Trim the file between START and END, with fade in and out, and
# 2 seconds of silence after

dur=`expr "${3%:*}" \* 60 + "${3#*:}" - "${2%:*}" \* 60 - "${2#*:}"`
fo=`expr "$dur" - $5`

ffmpeg \
	-ss "$2" -to "$3" \
	-i "$1" \
	-af "afade=t=in:st=0:d=$4,afade=t=out:st=$fo:d=$5,apad=pad_dur=2" \
	-ab 320k \
	-map_metadata 0 -id3v2_version 3 \
	"${1%flac}mp3"