Adjusting Audio Volume Levels with MacMP3Gain
MacMP3Gain is an AppleScript Studio application which brings an Aqua GUI to the command line version of mp3gain, a utility that performs statistical analysis to determine how loud the MP3 file actually sounds to the human ear and performs lossless volume adjustments. And so if you want to make automatic equalizer adjustments to your mp3 sound files, but are not confident with using the command line interface, this is the tool for you.
The great thing about MacMP3Gain is that it is a FREE and open source application available for download online as an application or project containing the entire source code. It also runs in OSX on everything from 10.1 and up, and has been recently ported so that it can run natively on Intel-based Macs.
As described in the initial reading of the MacMP3Gain web site, the application is designed to "modify MP3 and unprotected AAC files with no provision provided to undo the changes made". It therefore makes copmplete sense to make a full backup of your MP3 library prior to running mp3gain on it. At the very least you should run some tests to see that the results of the process are as desired.
Also, as a word of caution, the new "iTunes Plus" files may be corrupted by the current version of aacgain (the underlying program included in MacMP3Gain). Again, it would be advisable to make a full backup copy of your music library before running MacMP3Gain.
Alas the application, as with all great little open source projects, lacks any decent documentation, and so hopefully this article and how-to will go some of the way to helping people understand MacMP3Gain a little better.
Getting Started with Adjusting Volume Levels
To get started, simply download the .dmg file containing the software from the MacMP3Gain web site, open it up and drag and drop the application to your Applications folder. Once copied just open up the folder and double click the application icon to proceed. This will bring the options window to the fore.
This panel provides you with a slew of available options, of anything from reducing the level of CPU time used by the application to a target decibel level and more. Click on the "Choose Folder" button and navigation to and select the respective folder containing the MP3 or AAC files in the "Choose A Folder" dialog that comes to the front. If you prefer to use the contents of a pre-selected playlist in iTunes, then click the "Choose Playlist" button and select the correct playlist with which to adjust the volume of the audio files within it.
Once done you need to go through the other options:
- Album Gain Mode - This option sets MacMP3Gain to normalize the volume levels amongst the songs of a single album, rather than taking the levels of songs collectively within the entire library or playlist. This may lead to variations in the volume from one album to another within the library.
- Radio Gain Mode - As opposed to "Abum Gain" mode, this option forces ALL the audio files in the selected playlist or folder to be normalized at the same level of volume. Thus, if you want to listen to the entire list of audio files and not have any difference in volume level, then you need to select the "Radio Gain" option.
- Allow Clipping - The term "Clipping" refers to situation when music hits maximum volume and, as a results, gets distorted. It would therefore be preferable to leave this option unchecked, so that songs do not become distorted and therefore unpalatable to listen to.
- Process Sub-Folders - When processing a directory structure like the iTunes Music folder, in which audio files tend to be organized in a "Artist" > "Album" fashion, you need to set this option on, so that MacMP3Gain will recursively search through the contents of the entire directory and pick up each and every mp3 or aac file available.
- Target MP3 Gain Value (dB) - If you wish to set a specific target volume for your files, then you can, rather than to allow MacMP3Gain to nomalise the volume level. This setting is of course measured in decibels.
- Be Nice (Reduce CPU priority) - If you don't want to give the script full use of the CPU and to force it to play nice so that you can use the computer at the same time without it being bogged down, then check this option. The downside, however, is that theprocess will take longer.
Having completed all of this checklist you are ready to rock and roll, as they say! So click "Start".
But wait ... "Are there any basic system requirements?" I hear you ask. Well, MacMP3Gain now runs on any version of Mac OSX from 10.1 and up, and it has been recently ported so that it runs natively on both intel and powerpc based apple macintosh computers. Thereafter it's just a matter of the more RAM and the faster CPU the better.
Conclusion: Normalising Volume Levels
On a 1ghz G4 Mac PowerBook, the application took about 30 or so seconds per song to process and then change the levels of each file, so all in all the procedure can be relatively quick, but certainly don't expect it to fly by. It is a CPU intesnive task and with a huge volume of files, the length of time it would take to complete could easily be considerable. Having said that, MacMP3Gain works great as a cover for mp3gain and aacgain and is a very handy addition to the armory of any Mac audiophile, and is exceedingly easy to use, even for a novice.
Find out more about the application by visiting the MacMP3Gain Home Page.