ATRAC

ATRAC (Adaptive TRansform Acoustic Coding) is an audio compression algorithm used to store information on Minidiscs, developed by Sony. It uses quadrature mirror filters[?] and modified discrete cosine transform to represent encoded audio.

Table of contents 1 ATRAC SP 2 ATRAC LP 3 ATRAC-3 LP-2 4 ATRAC-3 LP-4

ATRAC SP

Two stacked QMF split the signal into 3 parts:

• 0 ... 5.5125 kHz
• 5.5125...11.025 kHz
• 11.025...22.05 kHz

No joint stereo encoding.

Data rate is ...

ATRAC LP

Double play time, only mono.

ATRAC-3 LP-2

Three stacked QMF split the signal into 4 parts:

• 0 ... 2.75625 kHz
• 2.75625 ... 5.5125 kHz
• 5.5125...11.025 kHz
• 11.025...22.05 kHz

Joint stereo encoding. 132 kbps (yes, 15% below ATRAC SP/2)

ATRAC-3 LP-4

Similar to ATRAC-3 LP-2, but 66 kbps (half the datarate of ATRAC-3 LP-2). Low quality, similar to MP3 at 80...96 kbps.

see also: Lossy data compression, MP3