create an m4b audiobook file from a movie or an mp3 file.

2m4b

#!/usr/bin/env bash
#
# Author:         Kai Xia <xiaket@corp.netease.com/xiaket@gmail.com>
# Filename:       2m4b
# Date created:   2014-02-27 16:52
# Last modified:  2014-02-27 16:52
# Modified by:    Kai Xia <xiaket@corp.netease.com/xiaket@gmail.com>
#
# Description:
# create an m4b audiobook file from a movie or an mp3 file.
# This works only in OSX where afconvert command is found. 
#
# Update of this file can be found in my repo:
#    https://github.com/xiaket/etc/blob/master/bin/2m4b
# Changelog:
# 2014-02-28 11:28: added mp3 support.
# 2014-03-03 15:55: use min function to avoid if-else.

DEFAULT_SAMPLE_RATE=32000
DEFAULT_BIT_RATE=80

fullpath="$1"
filename=`basename "$fullpath"`
suffix=`echo "$filename" | awk -F '.' '{print $NF}'`
basename=`basename "$filename" $suffix`
temp_name="${basename}mp3"
output_name="${basename}m4b"

mediainfo=`mplayer -endpos 0 -vo null -ao null "$fullpath" 2>/dev/null | grep "^AUDIO"`
bit_rate=`python -c "br = '${mediainfo}'.split(',')[3].strip().split()[0]; print min(br, ${DEFAULT_BIT_RATE})"`

if [ $suffix = "mp3" ]
then
    afconvert "${fullpath}" -v -s 3 -o "${output_name}" -q 127 -b "${bit_rate}000" -f m4bf -d aac
else
    ffmpeg -i "$fullpath" "${temp_name}" && afconvert "${temp_name}" -v -s 3 -o "${output_name}" -q 127 -b "${bit_rate}000" -f m4bf -d aac && rm "${temp_name}"
fi