The embedded audio coder (EAC) is a fully scalable psychoacoustic audio
coder which uses a novel perceptual audio coding approach termed
"implicit auditory masking" which is intermixed with a scalable entropy
coding process. When encoding and decoding an audio file using the EAC,
auditory masking thresholds are not sent to a decoder. Instead, the
masking thresholds are automatically derived from already coded
coefficients. Furthermore, in one embodiment, rather than quantizing the
audio coefficients according to the auditory masking thresholds, the
masking thresholds are used to control the order that the coefficients
are encoded. In particular, in this embodiment, during the scalable
coding, larger audio coefficients are encoded first, as the larger
components are the coefficients that contribute most to the audio energy
level and lead to a higher auditory masking threshold.