Abstract: There is described a method of encoding a signal (s(n)) in a coder (400) to generate a corresponding encoded bit-stream (x(n); STP). The method comprises steps of: (a) processing the signal (s(n)) to determine main sinusoidal components and transient components thereof to generate corresponding component parameters; (b) processing the signal (s(n)) by removing the sinusoidal and transient components therefrom to generate a residual signal (r(n)); (c) processing the residual signal (r(n)) to determine a spectral representation (PSD) and determining therefrom a spectral broadening measure (SBM); (d) determining from the residual signal (r(n)) spectral envelope parameters by linear prediction; and (e) combining the components parameters together with the spectral envelope parameters and the spectral broadening measure to generate the encoded bit-stream. The method is capable of reducing noise that would otherwise arise were the bitstream to be decoded not subjected to such spectral broadening.

Abstract: An audio encoding device (100) comprises first encoding means (101, 111) for encoding transient signal components and/or sinusoidal signal components of an audio signal (x(n)) and producing a residual signal (z(n)), and second encoding means for encoding the residual signal. The second encoding means comprise filter means (122) for selecting at least two frequency bands of the residual signal. The selected frequency bands (LF, HF) of the residual signal (z(n)) are encoded by a first encoding unit (123) and a second encoding unit (124) respectively. The first encoding unit (123) may comprise a waveform encoder, such as a time-domain encoder, while the second encoding unit (124) may comprise a noise encoder.

Abstract: A hybrid sinusoidal/pulse excitation encoder has been recently proposed for constructing a scalable audio encoder The base layer consisting of data supplied by the sinusoidal encoder retains the main features of the input signal achieving medium to high quality audio at a very low bit rate. Quality can be further enhanced by adding excitation signal layers associated with a decreasing decimation that increasingly model more subtle aspects of the original signal. The invention provides a method of mixing the different excitation signal layers so that the full concept of scalability is realised without compromising the quality of the encoded signals. The mixing is controlled via a quality parameter that weights the significance of previous layers when constructing a new higher layer.

Abstract: A method of encoding a digital audio signal, wherein for each time segment the signal is spectrally flattened to obtain a spectrally flattened signal (r) and possibly spectral flattening parameters (LPP). The spectrally flattened signal is modelled by an excitation signal comprising a first partial excitation signal (px) conforming to an excitation signal generated by an RPE or CELP technique, and a second partial excitation signal (PEp) being a set of extra pulses with arbitrary positions and amplitudes. An audio bit stream as comprising the first and second partial excitation signals is generated. The extra pulses can be added to the excitation signal at positions in time that correspond to the time of occurrence of the spike, or preferably at positions in time of an RPE time grid.