2. Audio compression formats

2.1 Principles

Audio data reduction includes :

• reducing the amount of information resulting from the native digital format. For example, we can reduce either the sampling frequency, and therefore the number of coded samples, or the audio frequency band. We can also reduce the coding depth of each sample, from 24 bits to 20 bits, 16 bits or 8 bits;

• compression of the remaining data using specific algorithms.

The elimination of redundancy in audio makes particular use of the phenomenon of frequency masking. When there is more energy in one frequency band, for example at 1 kHz, the ear seems to protect itself from overload by failing to register energy in neighboring bands...