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 mp4 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! THIS IS EXPERIMENTAL SOFTWARE. THERE HAVE BEEN BUGS IN PAST RELEASES THAT CORRUPTED MUSIC FILES. I AM NOT RESPONSIBLE FOR DAMAGED FILES.

AACGain was implemented using

• mpeg4ip's mp4v2 library to parse the files and to read and write metadata, and
• FAAD2 to decode the audio samples.

AACGain is released under GPL I am distributing AACGain in source code form only

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

Version 1.7 is now available

It fixes 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 this directory.

Contact me if you want to contribute to its development.

Unix

Prakash Punnoor has set up a build system for Linux. It is checked into cvs as unix_build_system.tar.bz2.

Miguel Angel Alvarez has used this to package the build for aacgain 1.7. You can download aacgain-1.7.tar.bz2, aacgain-1.7-1.i586.rpm, or aacgain-1.7-1.src.rpm.