#!/usr/bin/env python
# filename: m4b-to-many-mp3.py
import os, sys

sheet = sys.argv[1]
file_in = sys.argv[2]
tpl_out = sys.argv[3]

with open(sheet, 'r') as f:
    chapters = f.readlines()

for index, pair in enumerate(chapters, 1):
    template = 'ffmpeg -i %s -sameq -ss %s -t %s %s_%02i.mp3'
    start, end = pair.split()
    skip_seconds = int(float(start))
    duration_seconds = int(float(end) - float(start))
    command = template % (file_in, skip_seconds, duration_seconds,
                          tpl_out, index)
    print command
    os.system(command)

Вот так я получаю таблицу частей: ffmpeg -i english.m4b 2>&1| grep Chapter | awk '{print $4, $6}'|tr -d ',' > chapters.txt

Пример использования скрипта: python ~/bin/m4b-to-many-mp3.py chapters.txt english.m4b english