AACGAIN

aacgain is a modification to Glen Sawyer's excellent mp3gain program. It supports AAC (mp4/m4a/QuickTime) audio files in addtion to mp3 files. If you are not familiar with mp3gain, stop reading this, and go to http://mp3gain.sourceforge.net.

aacgain normalizes the volume of digital music files using the Replay Gain algorithm. It works by modifying the global_gain fields in the aac samples. Free-form metadata tags are added to the file to save undo information, making the normalization process reversable.

aacgain uses the same command-line user interface as mp3gain, and is compatible with the mp3gain Visual Basic GUI.

It also integrates with iTunes using my iGain GUI.

BACK UP YOUR MUSIC FILES BEFORE USING AACGAIN! UNLIKE MP3GAIN, AACGAIN IS NOT COMPLETELY REVERSABLE. THE UNDO OPTION IS INTENDED TO RESTORE A MUSIC FILE TO BE FUNCTIONALLY EQUIVALENT TO ITS ORIGINAL STATE, BUT IT WILL NOT BE BIT-FOR-BIT IDENTICAL TO THE ORIGINAL FILE. IT IS POSSIBLE FOR APPLE TO CHANGE THE ITUNES MUSIC FILE FORMAT IN WAYS THAT ARE INCOMPATIBLE WITH AACGAIN, RESULTING TO CORRUPTED MUSIC FILES THAT CANNOT BE RESTORED TO THEIR ORIGINAL STATE. I AM NOT RESPONSIBLE FOR DAMAGED FILES.

aacgain was implemented using

• mp4v2 to parse mp4 files, and to read and write metadata, and
• FAAD2 to decode the audio samples.

aacgain is released under the GPL V2 license. I distribute AACGain in source code form only

• to avoid any MPEG royalty issues, and
• to ensure that users have the knowledge to fix whatever bugs they find :-)

Source code can be found in the mp3gain cvs repository on Sourceforge. The module name is aacgain.

A compiled binary for Microsoft Windows® is hosted at rarewares.org.

Pre-built Unix packages are available for Arch, Debian, Mac OS X, Slackware, and Ubuntu.

What's new in Version 1.9

• Fixed a bug in mp4v2 which caused iTunes music video files to fail with "not a valid mp4/m4a file" error.
• Gives a more meaningful error message when attempting to process Apple Lossless files.
• Built with updated mp4v2 from Google Code, which should build error-free on modern Windows, Mac and Linux systems.
• Built with updated faad2 code, which should build error-free on modern Windows, Mac and Linux systems.
• Built with latest mp3gain version 1.5.2 source checked into CVS, which includes id3v2 tag support.
• MSVC++ solution and project files have been converted to Visual C++ 2010 Express Edition.

Version 1.8 fixed the following issues:

• Built with mpeg4ip/mp4v2 version 1.6.1. Aacgain 1.7.1 was built with
  version 1.5.20. Mp4v2 version 1.6.1 corrects problems that corrupted
  video files containing Quicktime chapter markers.
• Built with latest mp3gain version 1.4.7 sources checked into CVS.
  The mp3gain changes made since 1.7.1 support sample rates up to 96000.
  Previous versions had a maxmimum sample rate of 48000.
• Ignores faad2 "scalefactor out of range" errors. These errors resulted
  in "invalid file format" errors on apparently good files.

Version 1.7.1 fixed the following issue:

• MSVC++ solution and project files have been converted to Visual
  C++ 2005 Express Edition. Other than the version number, no other
  source code changes have been made.

Version 1.7 fixed the following issue:

• If the total length of the directory plus file name path exceeded 64 bytes, memory corruption would occur. This has been corrected.

Version 1.6 fixed the following issue:

• Files with a 'cprt' (copyright) tag are now processed correctly. Previous versions of aacgain corrupted the metadata of files with a copyright tag.
• AACGain now works on video or other files where the first audio track has a track number of other than 1. Previous versions required the audio track to have a number of 1. AACGain will still only process the first audio track found on a file. Thanks to Arthur Yarwood at Sony Computer Entertainment Europe for this fix.

Version 1.5 fixed the following issue:

• Running AACGain on Apple lossless or other unsupported file format resulted in a crash with an unhandled exception.

Version 1.4 fixed the following issues:

• Temporary files are created in the same directory as the input file. Formerly they were created in the same directory that the program was run in. This solves a problem only seen on Unix systems where the temporary file could not be renamed back to the original input filename, if the input file was located on a different filesystem from where the program was run. Windows users are unaffected by this problem and can continue to use 1.3.

Version 1.3 fixed the following issues:

• Always uses the /t (use temp file) option, even if it is not specified on the command line. This resolves issues where processed files would not play on the iPod Shuffle.
• Preserves original values of MP4 properties bufferSizeDB, maxBitrate and avgBitrate. Without this change, mpeg4ip/mp4vs was recalulating the actual values of these parameters. This caused bitrate as displayed by iTunes to change slightly, i.e. songs ripped at 320KB would display as 319KB.
• Incorporates recent changes to mp3gain which prevent crashes when working with 48KB files on Linux.
• Source code directory structure was reorganized to be compatible with mp3gain CVS on sourceforge. Thanks to Glen Sawyer, the AACGain source code is now hosted on sourceforge's CVS repository as part of the mp3gain project.

Version 1.2 fixed the following issues:

• Compatibility issue with MP3GainGUI version 1.2.5 or 1.3.4.
• All temporary files created are erased.

Version 1.1 fixed the following issues:

• Multi-channel and mono files now work.
• Fixes compatibility issues with MP3GainGUI: the /o option always outputs Album gain.
• The /f option is ignored for AAC files. If a file starts with a 'ftyp' atom, it is assumed to be AAC, even if /f was specified. This prevents the /f option from corrupting valid AAC files.
• Uses portable versions of all library functions, and has been successfully compiled under Linux. Thanks to Prakash Punoor for his help with this.

Thanks to Glen Sawyer, source code for AACGain is hosted in the sourceforge cvs repository as part of the mp3gain project, in the aacgain module.

Contact me if you want to contribute to aacgain's development.

Unix

As of aacgain version 1.9, I have access to Linux and Mac systems, and I am now supporting the Linux build environment originally developed by Prakash Punnoor. See the source code "linux" subdirectory for details. The file "unix_build_system.tar.bz2" remains in the CVS repository for historical reasons, but is not being maintained, and is not compatible with the current source code.