ATRAC3

ATRAC3 is a different audio compression from Adaptive Transform Acoustic Coding( ATRAC). It operates in two modes, LP2 and LP4, with compression ratios of 10:1 and 20:1.

In contrast to the standard ATRAC process, ATRAC3 uses three Quadrature Mirror Filters (QMF) to filter the signals into four frequency components: from 0 to 2.75 kHz, from 2.75 kHz to 5.5 kHz, from 5.5 kHz to 11 kHz, and from 11 kHz to 22 kHz. The quality is essentially the same as MP3; however, the sound quality ofOgg Vorbis, Advanced Audio Coding( AAC+ and aacPlus (AAC+) is not achieved. The upper frequency limit of ATRAC3 in LP2 mode is 17.5 kHz. This mode works with a data rate of 132 kbit/s, which results from halving the data rate of 292 kbit/s for stereo, minus 14 kbit/s needed for suppression of interfering signals during playback on older music players.

To increase the recording length of music tracks, LP4 mode halves the data rate to 66 kbit/s, which results in a correspondingly lower sound quality. LP-4 has an upper frequency of 13.5 kHz and is best suited for voice recordings.