Adaptive Transform Acoustic Coding

ATRAC stands for Adaptive Transform Acoustic Coding ( German about: Adaptable Tonumwandlungskodierung ) and represents an audio data compression method

  • 3.1 versions


ATRAC is based on psychoacoustic principles and compressed audio files to a fraction of the original data volume. The ATRAC codec was introduced by Sony with the introduction of MiniDisc in 1992 and continuously developed. Few other manufacturers own ATRAC versions are, for example, Sharp or Panasonic, but which put less emphasis on the development of ATRAC than Sony. The reason for the lack of interest from other manufacturers to ATRAC high license fees are suspected. Because of the sound characteristics of "foreign " ATRAC versions (which roughly on par with Sony's ATRAC 4.5 are ) is recommended to include DSP Type-R or Type-S in order to achieve the greatest possible transparency.


The ATRAC codec uses three frequency bands from 0 to 5.5 kHz, 5.5 kHz to 11 kHz and from 11 kHz to 22 kHz, which are each subdivided by means of MDCT in 128 bands. There is a block mode of 11.6 ms and a mode consisting of three short blocks of 2.9 ms, 2.9 ms and 1.45 ms. All versions of ATRAC ( 1.0 to DSP Type - S) with 292 kbit / s encoded, including the mono record "LP" (which includes only one instead of two stereo channels and thus occupies only half the storage space. ) ATRAC3, however, as quality levels 132 kbit / s " LP2 " and 66 kbit / s " LP4 " by Sonic days later, 105 kbit / s ( also referred to as " LP2 .") is striking here is that LP2 only 132 kbit / s instead of 146 kbit / s used. This is due to the fact that the remaining 14 kbit / s can be used to older MiniDisc devices which are not MDLP capable, feign an ordinary SP file that can be played back without sound.


The advantage of the codecs over other formats is the possibility of uninterrupted playback and relatively low cost decoding the compressed data, so that with portable devices a longer battery life is possible. When playing can at a given bit rate about 20 % longer battery life than MP3 files are reached, although ATRAC3 was rated worse than MP3 in an independent test and one would therefore use a higher bit rate to arrive at a similar quality ( however was not documented what version of ATRAC used for this purpose ). Another disadvantage of ATRAC is that you can hardly find music in this format. Converts one from an already lossy compressed source (such as MP3) in ATRAC, the quality suffers especially. A special feature of ATRAC is that the codec is not explicitly a bit depth is allocated, causing some MiniDisc playback and recording devices (mainly decks of various manufacturers and portable devices from Sharp) playback and recording in true 20 - or 24-bit allow quality. Was made If an analog or digital recording of a playback source to the CD standard with 16-bit (for analog recordings, an A / D converter with 20 - or 24-bit function requires ), this can be reproduced in correspondingly high quality (if the player also controls the D / A conversion 16 -bit. )

Copy protection measures

The codec includes various copy protection mechanisms, since ATRAC3 and digital rights management. So copyright infringement should be prevented, but also the possibilities of using ATRAC be restricted at the same time. Here Sony has remedied in 2006 with the release of the software SonicStage 3.4. The copy can now be switched off at will, and has thus become ineffective. Only when you buy music from Sony's Connect online store he remains.


In addition to the MiniDisc support other players from Sony ATRAC, such as the PlayStation 3, PlayStation Portable, audio player with flash memory, portable ATRAC CD player and all the latest Walkman products. Moreover, it is in the professional Filmtonformat SDDS (Sony Dynamic Digital Sound) used to compress the data. The time available for various MP3 players alternative Rockbox firmware also provides the ability to play files compressed with ATRAC.

August 30, 2007 Sony announced to discontinue its online music store Connect and convert all Walkman products in 2008 to the format of WMA. Since then, no ATRAC compatible devices appeared more. Thus, the development of ATRAC was obviously set.


Support older devices from Sony ATRAC only, newer devices but also MP3, AAC and other formats, is regarded as indication that Sony has given up the attempt to establish its own format in addition to more common formats in the market. ATRAC should as a proprietary format inseparable from the hitherto successful Walkmans have a dominant position ( a similar approach is also observed for other companies such as Apple, which is also a closed system operates with the iPod and iTunes).

The result of this strategy was a strong decline in sales of portable audio players that support ATRAC only, because from a consumer perspective, the necessary conversion of MP3 files into the ATRAC format was too cumbersome. Only in 2004 relented and brought Sony NW -HD3 with the first MP3 -enabled Walkman on the market. Meanwhile, support all digital audio player by Sony several file formats.


The following versions of the ATRAC codecs have been published: