A wideband audio coding concept is presented that provides good audio
quality at bit rates below 3 bits per sample with an algorithmic delay of
less than 10 ms. The concept is based on the principle of Linear
Predictive Coding (LPC) in an analysis-by-synthesis framework. A
spherical codebook is used for quantisation at bit rates which are higher
in comparison to low bit rate speech coding for improved performance for
audio signals. For superior audio quality, noise shaping is employed to
mask the coding noise. In order to reduce the computational complexity of
the encoder, the analysis-by synthesis framework has been adapted for the
spherical codebook to enable a very efficient excitation vector search
procedure. Furthermore, auxiliary information gathered in advance is
employed to reduce a computational encoding and decoding complexity at
run time significantly. This auxiliary information can be considered as
the SCELP codebook. Due to the consideration of the characteristics of
the apple-peeling-code construction principle, this codebook can be
stored very efficiently in a read-only-memory.