Adaptive Transform Acoustic Coding

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Adaptive Transform Acoustic Coding

Adaptive Transform Acoustic Coding (ATRAC) is a lossy audio compression format developed by Sony that uses a psychoacoustic model to remove parts of the audio signal that are less audible to the human ear. It is designed to achieve high compression ratios while maintaining good audio quality.

What does Adaptive Transform Acoustic Coding mean?

Adaptive Transform Acoustic Coding (ATRAC) is a lossy audio data compression technology initially developed by Sony Corporation for use in its MiniDisc (MD) format. ATRAC applies psychoacoustic modeling and transform coding techniques to reduce the size of audio files while preserving perceptual quality.

During the encoding process, ATRAC analyzes the input audio signal to identify audible frequencies and amplitudes. This information is then used to create a compressed representation that retains the essential sound components while discarding less perceptible details. The compression algorithm employs a combination of fixed and adaptive transform techniques, with the transform size varying based on the audio content to optimize compression efficiency.

Applications

ATRAC’s ability to deliver high-quality audio at low bitrates makes it suitable for various applications:

  • Portable Audio: ATRAC was instrumental in the success of Sony’s MiniDisc format, which used ATRAC compression to store up to 80 minutes of audio on a small, rewritable disc.
  • Digital audio Broadcasting (DAB): ATRAC is one of the audio codecs used for DAB radio, which allows for the transmission of high-quality audio over terrestrial radio waves.
  • Internet Audio Streaming: ATRAC is used in some internet audio streaming services, providing a balance between compression efficiency and audio quality.
  • Music Production: ATRAC has been employed in certain music production software for recording and Editing purposes, enabling efficient file management and storage of high-quality audio projects.

History

The development of ATRAC began in the early 1990s as Sony aimed to create a high-quality audio compression technology for its MiniDisc format. The first iteration, ATRAC1, was introduced in 1992, offering a compression ratio of 4:1 to 5:1 while maintaining audio quality comparable to Compact Disc (CD).

Subsequent versions of ATRAC were developed to improve compression efficiency and introduce additional features:

  • ATRAC3 (1995): Increased compression ratio to 10:1, reduced compression artifacts, and added support for multi-channel audio.
  • ATRAC3plus (1999): Further improved compression efficiency while maintaining audio quality, and introduced support for higher sampling rates.
  • ATRAC Advanced Lossless (2005): [Lossless Compression](https://amazingalgorithms.com/definitions/lossless-compression) format with high compression ratios, preserving all of the original audio information.