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Checker: An Audio File Validator for LibriVox Contributions

Download from here

There are earlier versions but Current Release—0.95 posted May 23, 2013 is the recommended version.

N.B. The Experimental version is the only version that displays the volume in decibels (on the Information tab).

Here is a video on Using the Checker Program to see the decibel level of your MP3: Click Here to see Video


Checker is a 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 installed, you can download Checker and run it by double clicking the downloaded file. Please use the experimental version, which shows volume in decibels on the Information tab.

Current Release—0.95 May 23, 2013 Windows (32-bit Java) checker-windows-0.95.exe (1.6 MiB) Windows (64-bit Java) checker-windows-x64-0.95.exe (1.5 MiB) Mac OS X checker-macos-0.95.dmg (1.8 MiB) Linux/Solaris checker-unix-0.95.tar.gz (1.6 MiB)

Getting Started

Windows: Download and run the installer as you would any other Windows software. If you get an error message when you try to run the program, you probably don't have Java installed. See below for help. Note that you must 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 version 6 of Java, or newer.

If the button does not work (for example, if you have disabled JavaScript in your browser), use one of the following links instead:

Ways You Can Help Out

Things you can do to help now:

  • Writing additional "mini help" files to accompany the various tests.
  • Suggesting language that will be friendly to novice LV volunteers.
  • Throw a lot of MP3s at it so that the decoding and analysis system can be made as stable and reliable as possible.
  • Report any bugs (or submit fixes).
  • Provide feedback about the results and/or sensitivities for the various tests.

Things that will be possible later:

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