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I would like to take an mp3 file and re-encode it to play faster (perhaps at 1.5x speed). I primarily use avconv in debian linux, but can use any other program if recommended. I can use any operating system if linux isn't the preferred method.

I understand that VLC can play files at faster than normal speed, but I want to re-encode the files so that they can be played faster on devices that do not support VLC (such as my iphone).

Also: I am doing this for 50+ files, so an automated command-line interface would be preferable, if possible.

Any help is appreciated. And as always, thank you for your time.

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Just note that this will change the pitch of the encoded file, as you are effectively discarding samples from the input data (unless you re-encode at a higher sample rate), so you may also want to apply a pitch shift to the audio signal before encoding it. –  Breakthrough Jun 5 '13 at 15:18
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2 Answers

While not a CLI method (and probably not as clean as one), this is possible in Audacity, which does support batch processing.

  1. On the File menu, click Edit Chains

  2. Create a new chain

  3. Insert a ChangeSpeed command with your desired percentage

  4. Insert a ExportMp3 command

  5. Close the dialog box

  6. On the File menu, click Apply Chains

  7. Select the chain you just created and click Apply to files...

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You might look at:

sox original.mp3 faster.mp3 tempo 1.5

The tempo, speed, and pitch parts of the sox man page have other options to possibly create higher quality versions or variations of speed and pitch.

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