AAC, the abbreviation of Advanced Audio Coding, is a technique for compressing digital audio files. It is conceptually similar to the existing MP3 format but officially it is the part of the MPEG-4 standard.
For compressing the audio files, AAC discards the unnecessary digital sound bits and keep only the necessary and loud sound bits that can be easily to listen and asses. It follow the formula of auditory masking. In auditory masking system the quite sounds are masked in such a way that it does not feel something odd or missing. So this technique allows to discard the data with minimal loss of fidelity.
AAC has a similar disadvantage like MP3 and that is unable to recreate the original digital audio from the compressed bits alone. Though there is no loss of data if the compressed file is properly encoded. Here it is superior to MP3. For getting transparency MP3 requires a bit rate of approximately 256 kilobits per second (kbps) while ACC needs 128 bits per second for the same quality. So ACC file is almost half of the MP3 files and one-tenth the size of CD digital data.
AAC is quite capable of handling very higher and lower frequencies of sound that allows for Digital Rights Management, or DRM, which can be used to control how the audio file is used. ACC is also be able to handle the audio books and the free version of encoding/ decoding is available at free of cost. AAC is most widely used in Apple Computer's line of iPod portable music players as well as in the next-generation of DVD.
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