#define private public - Claus Brod on stuff (22 Apr 2009)

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---+++ [[DefinePrivatePublic20090422SpeedingThroughTheCrisis][Speeding through the crisis]] (22 Apr 2009)

<summary>
That darn ol' MP3 player. Five years old, but still looks cute. 
Stubbornly refuses to break, too, so no excuse to go out
and buy a new one. Which, of course, I wouldn't do anyway these days.
You know, the <i>crisis</i> and all - who has the guts
to make investments like this now. I mean, a new player could easily
cost me as much as <i>30 euros</i>! ;-)
</crisis>

So I'm sticking to the old hardware, and it works great, except for one
thing: It cannot set bookmarks. Sure, it remembers which file I was playing
most recently, but it doesn't know where I was within that file. Without 
bookmarks, resuming to listen to that podcast of 40 minutes length which 
I started into the other day is an awkward, painstakingly slow and daunting task.

But then, those years at university studying computer science needed to 
finally amortize themselves anyway, and so I set out to look for a software solution!

The idea was to preprocess podcasts as follows:
   * Split podcasts into five-minute chunks. This way, I can easily
     resume from where I left off without a lot of hassle.
   * While I'm at it, speed up the podcast by 15%. Most podcasts
     have more than enough verbal fluff and uhms and pauses in them,
     so listening to them in their original speed is, in fact, a waste
     of time. Of course, I don't want all my podcasts to sound like
     Mickey Mouse cartoons, of course, so I need to preserve the original pitch.
   * Most of the time, I listen to technical podcasts over el-cheapo
     headphones in noisy environments like commuter trains, so I don't
     need no steenkin' 320kbps bitrates, thank you very much.
   * And the whole thing needs to run from the command line so that I
     can process podcasts in batches.

I found it surprisingly difficult to find the single right tool for the 
purpose, so after experimenting for a while, I wrote the following
<tt>bash</tt> script which does the job.

<pre>
#! /bin/bash
#
# Hacked by Claus Brod, 
#   http://www.clausbrod.de/Blog/DefinePrivatePublic20090422SpeedingThroughTheCrisis
#
# prepare podcast for mp3 player:
#  - speed up by 15%
#  - split into small chunks of 5 minutes each
#  - recode in low bitrate
#
# requires:
#  - lame
#  - soundstretch
#  - mp3splt

if [ $# -ne 1 ]
then
  echo Usage: $0 mp3file >&2
  exit 2
fi

bn=`basename "$1"`
bn="${bn%.*}"

lame --priority 0 -S --decode "$1" - | \ 
  soundstretch stdin stdout -tempo=15 | \ 
  lame --priority 0 -S --vbr-new -V 9 - temp.mp3

mp3splt -q -f -t 05.00 -o "${bn}_@n" temp.mp3
rm temp.mp3
</pre>


The script uses [[http://lame.sourceforge.net/][lame]], 
[[http://www.surina.net/soundtouch/soundstretch.html][soundstretch]] and 
[[http://mp3splt.sourceforge.net/][mp3splt]] for the job, so you'll have to download
and install those packages first. On Windows, =lame.exe=, =soundstretch.exe= and
=mp3splt.exe= also need to be accessible through =PATH=.

The script is, of course, absurdly _lame_ with all its hardcoded filenames and parameters
and all, and it works for MP3 files only - but it does the job for me, 
and hopefully it's useful to someone out there as well. Enjoy!

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TBD: Review http://wiki.gpodder.org/wiki/Time_stretching

TBD: Review http://www.hackerpublicradio.org/eps.php?id=0185
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