This is an update to the How-to article, “How to speed up podcasts for free with Audacity.”
In Audacity 1.3.2 (Beta), configuring the batch script is easier. The developers moved the location, though, so you might be lost if you recently updated to this version.
First, setup the chain: File > Edit Chains
In the left pane of the window that pops up, you’ll need to add a new chain. Title it “Speedup,” or whatever you like. With it selected, the right pane should have only one parameter: END.
Select that command, then at the bottom of the window, click Insert. Another window will pop up, and you’ll want to choose Change Tempo. Change the parameter to 25.000000, then click OK. (Later, you can increase the tempo if you’re comfortable.) Again, click Insert, select the ExportMP3 command, then click OK. Finally, OK out of the Edit Chains window.
Then, if you want to run the script, go to File > Apply Chain. Select the chain you just created, click Apply to Files, then browse to the folder where the podcasts are stored. Like I mentioned in the previous How-to, I copy the MP3s to the root podcast folder, so I’m not limited to one show (folder) at a time.
Conclusion
This’ll empower you to listen to podcasts, or any other supported audio files in a shorter amount of time, and you can convert multiple files at once. In addition to podcasts, I also speed up class lectures. 80-minute classes reduced to 64 minutes — awesome!
All Narfed Up 
This works but there are no editable parameters for the export command so everything get bumped up to Stereo 128kbps. Any idea how to “preserve” the channel count and bitrate on export?
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@dom: I’m not sure. (I can’t check because I don’t have it installed here at work.) You might have to change the setting in the main preferences.
Sorry for the late response.
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Bryan:
Great tip!
I am like Dom and would like to find a way to keep the “chain” from saving at 128k.
This doubles the size of a 48k file.
Tom
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@Tom: I can’t find the documentation for parameters within editing chains. The only alternative is to edit that setting in the main preferences.
Edit > Preferences > File Formats > MP3 Export Setup
So sorry… 😦
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I am using 1.3.4 -beta and there is no “File Formats” setting under preferences.
Have to keep looking.
Tom
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@Tom: Grr, they made it harder! I was using 1.3.2, but I just upgraded.
With a file loaded, go to File > Export. “Save as type” needs to be set to MP3 Files, then click Options.
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Bryan:
Tried that and it did not seem to work.
In desperation I downgraded to 1.3.3.
It did not work the first time.
I then viewed the cfg file and saw MP3Bitrate=48
Somewhere along the way it was saved!
It now works!
Not sure how stable this is but I can peak in the cfg file to make sure.
Thanks – I love it!
Tom
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Hey Tom, I’m stoked that you figured it out. Nice job!
Looks like I need to update this guide again to keep up with the UI changes, huh? 😦
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doesn’t seem to be an option for mono export? my podcasts generally are 64kbs mp3 mono:( its trying to save it all as 128stereo.
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well it finally worked, i guess audacity had to be restarted. doubled checked the cfg file as well.
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btw a tip, gom player lets one run mp3/video on a pc from 1x-3x+ real time time stretching
windvd lets you crank dvds to 2x as well
gomplayer is of course free. so this time stretching is pretty useful in other things as well. say you donwload a flv flash file of a lecture, you can speed through it even if its a video. i think gomplayers algorithm for tempo/time stretch is better, it sounds better.
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@freddy:
Wow, thanks for letting me know that! I’ll definitely try GOM Player, especially if you’ll listen to the audio/video off your computer.
I haven’t been listening to podcasts lately (except for Kevin and Bean on KROQ), but if I do and I’m too lazy to convert, this sounds pretty cool!
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yea time stretching should be a more common feature:)
its especially good for dvd special features/commentary which generally do not merit normal speed playback. especially commentaries where you just want them to talk a bit faster.
as far as i know gom can’t do the dvd playback at speed, which is its only fault, it does everything else with time stretching. the hotkeys let you increase or decrease speed in 10% increments. gomplayer also has nice hotkeys for fast forwarding and jumping around a file very conveniently, seeking by dragging also works with a real time display of where you are. its very good with such interface/control usability features.
so far i find audacity with a 75% boost in tempo is decent for podcasts, i may up it later. the major gripe with audacity is that its pretty damn slow. its not optimized i guess because it can’t be that hard to stretch audio since gomplayer does it so well on the fly with so little cpu usage. longer audio files take up massive chunks of temporary disk space with audacity during processing so make sure you got gigs free.
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ok audacity is behaving pretty bad. if you actually batch a decent amount of files..a couple hours for instance, the temp directory grows to tens of gigs, its like it doesn’t clean up after each file, but keeps piling on!!
the older versions also botched things in the same way
http://thoughtrush.com/blog/2008/03/17/time-stretching-mp3-and-other-audio/
foobar with the soundtouch dsp plugin seems to do it rather quickly. dozens of times faster. and much easier to setup. audacity in its current state is a waste of time.
it even spawns two processes of lame.exe for my dual core:)
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@freddy:
I usually don’t process more than a handful of podcasts, but still it stinks that Audacity had to cache that much space while it works.
But dude, awesome find with that blog article! I’ll just have to link to that. Thanks!
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🙂 i banged my head on the desk trying to get every recent version of audacity to work right:( 🙂
conversion with foobar is drag and drop simplicity!
definetly a must for audio book lovers!
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alternate link to the sound touch dsp, the above link might be down.
http://acropolis.lokalen.org/2006/10/foobar2000/my-foobar2000-components/
its there.
thread on it
http://www.hydrogenaudio.org/forums/index.php?showtopic=46000
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