Atrac3plus Technology
Atrac3plus represents a further enhancement of atrac3, featuring a new algorithm for even more precise sound signal analysis. this enables the technology to compress CD data to approximately 1/20 its original size with almost no loss of sound quality.
Main features1. analyzes sound characteristics in sixteen bands
Atrac3 divides the sound signal into four bands to analyze sound characteristics. atrac3plus divides the signal into 16 bands, enabling an even more precise analysis. atrac3plus also uses longer analysis window than atrac3 to convert signals into frequency data, resulting in finer frequency resolution and allowing the technology to analyze the sound signals more precisely than atrac3.
2. uses more rules to replace digital patterns
Atrac3plus replaces patterns in the digital signal just like atrac3, but uses more rules for substitution to enable it to cover a wider variety of patterns. This technique has increased the rate of compression.
From: http://www.sony.net/Products/ATRAC3/tech/atrac3plus.html