摘要:
Apparatus is described for digitally encoding an input audio signal for storage or transmission. A distinguishing parameter is measure from the input signal. It is determined from the measured distinguishing parameter whether the input signal contains an audio signal of a first type or a second type. First and second coders are provided for digitally encoding the input signal using first and second coding methods respectively and a switching arrangement directs, at any particular time, the generation of an output signal by encoding the input signal using either the first or second coders according to whether the input signal contains an audio signal of the first type or the second type at that time. A method for adaptively switching between transform audio coder and CELP coder, is presented. In a preferred embodiment, the method makes use of the superior performance of CELP coders for speech signal coding, while enjoying the benefits of transform coder for other audio signals. The combined coder is designed to handle both speech and music and achieve an improved quality.
摘要:
Apparatus is disclosed for digitally encoding an input audio signal, for storage or transmission, comprising: a pitch detector for determining at least a dominant time-domain periodicity in the input signal; a generator for generating a prediction signal based on the dominant time domain periodicity of the input signal; a first discrete frequency domain transform generator for generating a frequency domain representation of the input signal; a second discrete frequency domain transform generator for generating a frequency domain representation of the prediction signal; a subtractor to subtract at least a portion of the frequency domain representation of the prediction signal from the frequency domain representation of the input signal to generate an error signal; and a generator to generate an output signal from the error signal and parameters defining the prediction signal. A corresponding decoder is also described.