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I'm looking for a Windows command-line tool that will allow me to increase the playback speed of MP3 files (podcasts and audiobooks). Preferrably free or open source.

Update: I want to be able to listen to a 1 hour podcast in less than 60 minutes, but it would be nice if the pitch wasn't changed.

If necessary, I can convert the MP3 to WAV first and then back again.

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Increase the speed like make them sound chipmunky and have the file shorter? –  MrStatic Jan 2 '10 at 8:46
    
ideally this would be a function built into the player, so you wouldn't have to process audio first, then play it. sadly not all players (software or hardware) include add-on/plugin capabilities. –  quack quixote Jan 2 '10 at 9:06
    
Yes, my MP3 player does support faster playback, but it doesn't always work, and I'd like to fine-tune the speed setting. –  Christian Davén Jan 2 '10 at 9:12
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this free web service may be of interest to you: podshifter.com –  Molly7244 Jan 2 '10 at 16:32
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2 Answers

up vote 5 down vote accepted

SoX, the Swiss Army knife of sound processing programs, can do this without a hitch:

sox --show-progress input.mp3 output.mp3 speed 1.5 pitch -700

specifying a lower pitch will prevent your files from getting the "chipmunk" effect. 700 may not be exact for your file, so you can play around with pitch until it sounds right.

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Thanks, but it removes all ID3 data after re-encoding. –  Christian Davén Jan 2 '10 at 9:35
    
SoX doesn't have support for MP3 by default, but there's a build at CodeProject with Lame and Mad built-in: codeproject.com/KB/aspnet/Compiling_SOX_with_Lame.aspx (or follow the build instructions in README.win32.txt) –  Christian Davén Jan 2 '10 at 16:38
    
Awesome, nice find! –  John T Jan 2 '10 at 16:43
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Use the switch "tempo" instead of "speed" and the pitch won't be changed. I ended up converting my MP3s to WAV, running SoX, encoding back to MP3 and re-insert ID3 tags... –  Christian Davén Jan 2 '10 at 23:12
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SoX works much better if you use "tempo" as Christian said. Use "tempo -s 1.5" for even better quality for podcasts. –  Alexander Kellett Apr 19 '12 at 8:40
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the best: mp3-speed.en.softonic.com/

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Gave it a try and the quality of the output of a 1.75x speed-up seemed quite choppy. I'm used to listening at 2x on an iPod and that was much smoother. –  pettys Apr 12 '12 at 0:21
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