An Audio File Validator for LibriVox Contributions

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Installation Help
Ways You Can Help Out
Version History (What's Changed)
Source Code


Checker is an open source tool that looks for common problems with recordings for LibriVox, a site where volunteers collaborate to make audio books of public domain texts. The Checker tool can save you time by checking your file for common issues before you go to the trouble of uploading it.

To use Checker, drag and drop one or more MP3 files (or a folder or ZIP archive that contains them) onto the Checker window and allow it to analyze them. Once it is done, click on any file to see a report of any issues that were detected. The report will either state that the file "passed" (no problems were detected), or it may list a number of errors or warnings. Errors generally indicate more serious problems that should be fixed before uploading the file. A warning is a less serious problem, or in some cases a potential problem that Checker is not sure about.

What does Checker Check?

The program checks many technical features about your file. It can find problems with file name conventions, metadata (ID3 tags), audio format and MP3 encoding options, volume, and more. Checker has also been designed with extensibility in mind, so other programmers can easily add new tests (or modify the existing ones) in the future.

It does not check the content of the recording: it won't tell you if you've read a word incorrectly or criticize your performance.


Once you have Java 6 or newer installed, you can download Checker and run it by double clicking the downloaded file.

Current Release—0.96 January 28, 2014
Windows (32-bit Java) checker-windows-0.96.exe (1.6 MiB)
Windows (64-bit Java) checker-windows-x64-0.96.exe (1.5 MiB)
Linux/Solaris checker-unix-0.96.tar.gz (1.6 MiB)
Mac OS X checker-macos-0.96.dmg (1.8 MiB)
Important: See Installation Help below.

Installation Help

To use Checker you will need to have Java 6 or newer installed. See below for more information.

Windows: Download and run the installer as you would any other Windows software. Download either the 32-bit or 64-bit version, depending on whether you have the 32-bit or 64-bit version of Java installed. If in doubt, try the 64-bit installer. If that doesn't work, try the 32-bit installer.

OS X: Download the disk image (.dmg) file. To open the installer under OS X 10.8 (Mountain Lion) or newer, you must control-click (or right click) the file and choose Open from the displayed popup menu. Then, click the Open button again in the displayed dialog box. When the disk image opens, double click the enclosed installer and follow the prompts.

Linux/Solaris: Download and unzip the file, then run the checker script to start the application.

Java Help

Checker was written in the Java language, so it will run on all of the most popular platforms, including Windows, Linux and OS X. It requires Java version 6, or newer. If you don't have Java installed, then the Checker installer for Windows or OS X will attempt to download and install Java for you. If that fails, you can install Java from the Java update site.

Ways You Can Help Out

Things you can do to help out:

  1. Throw a lot of MP3s at it so that the decoding and analysis system can be made as stable and reliable as possible.
  2. Report any bugs (or submit fixes).
  3. Suggest help language that will be friendly to novice LV volunteers.
  4. Provide feedback about the results and/or sensitivities for the various tests.

Things that will be possible later:

  1. Translate the default English localization files into other languages, as demand dictates.


January 28 2014 (0.96)

May 23 2013 (0.95)

May 20 2013 (0.94)

May 11 2012 (alpha 0.93)

April 1 2012 (alpha 0.9)

January 6 2009 (alpha 0.2)

October 29 2008 (prototype 1)

Source Code

checker-0.96-src.7z (498 kB)

This program uses the JavaLayer library for decoding MP3 audio and the Jaudiotagger library for parsing ID3 metadata. Both of these are made available under an LGPL license. Source code to both of these libraries is included with the source for Checker.

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October 29, 2008  Updated January 28, 2014