Pitch period estimation for use with audio coders
AssigneeLucent Technologies Inc.
InventorJuin-Hwey Chen
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Abstract
A highly efficient, low delay pitch parameter derivation and quantization permits overall delay which is a fraction of prior coding delays for equivalent speech quality at low bitrates. In distinguishing between pitch period information for voiced and non-voiced frames of input signals, non-voiced frames are assigned a non-zero "bias" value, while voiced frames have associated with them generated pitch information based on an analysis of signals in a present frame and comparison with signals relating to the pitch in a prior frame. Transitions from non-voiced to voiced input frames are efficiently accomplished using a non-uniform quantization method based on an analysis of a sequence of frames. Typical uses include low delay, low-bitrate coders such as Code Excited Linear Prediction (CELP).
Claims4
A method of quantizing a pitch period signal relating to the pitch period for one of a sequence of frames of sampled input speech signals to one of a plurality, N, of quantizing values comprising the steps of
- determining whether said one frame of input speech signals corresponds to voiced speech or to other than voiced speech,
- when said one frame of input speech signals corresponds to other than voiced speech
- assigning a particular non-zero one of said N quantizing values to said pitch period signal, said non-zero quantizing value comprising a bias value for said pitch period,
- when said one frame of input speech signals corresponds to a voiced speech signal,
- extracting from said one frame of input speech signals a first signal representative of the pitch period for said one frame of input speech signals,
- generating a prediction signal corresponding to a prediction of the pitch period for said one frame based on the value of the pitch period signal for at least one preceding frame of sampled input speech signals,
- comparing the value of said first signal with the value of said prediction signal to form a difference signal, and
- assigning a value, other than the bias value, to said pitch period signal for said one frame based on said difference signal.
Dependencies are inferred from the claim text.