Sony ATRAC3 Audio Codec was developed by Sony for its portable audio players. The highest bit rate supported by Atrac3 is 132 kbps (which they say is superior to MP3 128 kbps) and supplies a decent quality.
For the best quality ATRAC3 files, you must convert the tracks directly from the audio CD. ATRAC3 is a compression technology based on Sony’s ATRAC (Adaptive TRansform Acoustic Coding) technology that originated with and is supported by MiniDisc. ATRAC3 achieves twice the data compression rate of ATRAC with virtually no loss in sound quality and reduces the size of audio data to 1/10 of the original audio CD source.