ATRAC
Adaptive Transform Acoustic Coding

It is adoptedfor MD and the like, the speech compression technology which SONY developed.Withthe appearance of MD it is used from 1992.If as for the data quantity after the compressing,the sound quality like CD it becomes1 of 5 parts of CD. Because of this, capacity it is possibleto recordthe musicequivalent to CD 1 even with MD of approximately 140MB.Same as MP3, improvement is added tocompressedplayback system attendant upon technological nnovation, but compatibility of the data is kept, (when playing back sound quality falls depending upon combinationwhensomewhat, it is).With ATRAC, the aural signal is divided into four frequency zones withthe bandwidth division filter. After that, fromthe time based data string it converts to the frequency based data string with Modified, DCT (deformation dispersion cosinconversion) it compresses encodes. ... The continuation is read At that time, making use of the quality of hearing of the human, the quantity of the data which is encoded without impairing

the sound quality by between pulling the data of front and back of the componentandthe big sound which are difficult to be audible, is decreased. The foundation of these principles after that is the sameasthe speech compressionof MP3and the like which appears. As for ATRAC3 which is used for the SONY and the like music transmissionit is the technology which improves ATRAC, but there is no compatibility in the data.