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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.
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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
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