The invention relates to an audio
encoder and decoder and methods for audio encoding and decoding. In a preferred
encoder embodiment an
audio signal is encoded by deterministic
encoder means to form a first encoded
signal part. A spectrum of the
audio signal is determined and represented by an
excitation pattern, i.e. spectral values corresponding to human auditory filters, as a second encoded
signal part. A masking curve is also extracted based on the
excitation pattern, thus improving encoding efficiency in terms of
bit rate. In a preferred decoder the first encoded
signal part is decoded by deterministic decoder means. A
noise generator uses the decoded first signal part together with the second signal part, i.e. the
excitation pattern for the original
audio signal, to generate a
noise signal. The
noise signal is then added to the first decoded signal part to form an output audio signal. At the decoder side the masking curve is also extracted based on the second encoded signal part, i.e. the excitation pattern. The noise signal is generated so that the output audio signal exhibits an excitation pattern nearly identical to the original audio signal. Thus, a perceived high quality audio is obtained while the encoded signal is scalable since a possible deviation between encoding and decoding of the first signal part is compensated by the
noise generator at the decoder side. In preferred embodiments the coding means comprises a sinusoidal coder.