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Wednesday, January 11, 2012

Microcontroller based audio volume level compressor - The Great [Volume] Leveler (AVR Audio Compressor) | Non-Lexical Vocables

The AVR Audio Compressor (Volume Leveler)

Video Link...
http://www.youtube.com/watch?v=YaEc6_wQ9FM&w=470

The Great [Volume] Leveler (AVR Audio Compressor)

Posted on January 8, 2012 by Mike

Like many people, I have fairly diverse taste in music. My media library holds tracks from Bach, Beethoven, Billy Joel, Bonobo, Brent Lamb, Brahms, Brian Hughes, and the Bee Gees (to name just the “B” section). I love variety. The trouble is, all of these different genres tend to require slightly different volume settings. Worse still, in the case of some classical music, you can get quite a wide range of volumes within a single piece (e.g. O Fortuna). So if I hook up my BlackBerry and set it to shuffle, I find myself having to continually adjust the volume knob – either because I can hardly hear the current track, or because my neighbors are about to come banging on my door.

Well, I’m not the first one to have this problem. Nor am I the only one to attempt to solve it. In fact, it’s already been solved. As you may know, there are plenty of software solutions out there for so-called volume leveling. But before the advent of the BlackBerry, or the personal computer, there was the analog compressor.

The sole purpose of such a device is to compress the dynamic range of an incoming audio signal: amplifying the soft parts and reducing the volume of the loud parts (thus decreasing, or compressing, the range of the track’s volume). It’s quite a simple thing, really. And you can buy one of these units for between $100 and $200. But why buy something when you can build it from spare parts?

Now for all of you comp-sci majors out there who are planning on commenting on any one of a million different audio leveling programs out there, don’t worry, I know they exist. The trouble is, even if I leveled every single MP3 I possess, what about internet radio? Specifically, the Pandora app for my BlackBerry? Alright, maybe there’s a software-only solution for that too (although I haven’t found it), but you know what? Just for the fun of it, I’m going with hardware this time. Well, mostly. Actually, it’s going to be a mix of analog hardware and an 8-bit Atmel AVR running some embedded C code. Sound good? Alright, then let’s get started!