How does MPEG-1 and MPEG-2 Audio work?
The MPEG Audio coders, aimed for generic audio, i.e. all types of speech and music signals, are perceptual audio coders, rather than so-called ‘waveform coders’. In a perceptual audio coder, the codec does not attempt to retain the input signal exactly after encoding and decoding, rather its goal is to ensure that the output signal sounds the same to a human listener. The primary psychoacoustic effect that the perceptual audio coder uses is called ‘auditory masking’, where parts of a signal are not audible due to the function of the human auditory system. The parts of the signal that are masked are commonly called ‘irrelevant’, as opposed to parts of the signal that are removed by a source coder (lossless or lossy), which are termed ‘redundant’. In order to remove this irrelevancy, the encoder contains a psychoacoustic model. This psychoacoustic model analyses the input signals within consecutive time blocks and determines for each block the spectral components of the input audio signa
