초록 ▼

A speech coder employs vector quantization of LPC parameters, interpolation, and trellis coding for improved speech coding at low bit rates (400 bps). The speech coder has an LPC analysis module for converting input speech to LPC parameters, an LSP conversion module for converting LPC parameters int

A speech coder employs vector quantization of LPC parameters, interpolation, and trellis coding for improved speech coding at low bit rates (400 bps). The speech coder has an LPC analysis module for converting input speech to LPC parameters, an LSP conversion module for converting LPC parameters into line spectrum frequencies (LSP) data, and a vector quantization and interpolation (VQ/I) module for encoding the LSP data into vector indexes for transmission by applying LPC spectral amplitude as weighting coefficients to the LSP data. The VQ/I module outputs one vector index for every two LPC frames in order to reduce the transmission bit rate, and the omitted frames are interpolated on the receiving end. A decoder correspondingly decodes incoming indexes to LPC parameters and synthesizes them into output speech. Trellis coders with an adaptive tracking function encode the pitch and gain parameters of the LPC frames. A universal codebook stores codewords according to a plurality of accents. The speech coder automatically identifies a speaker\s accent and selects the corresponding vocabulary of codewords in order to more intelligibly encode and decode the speaker\s speech.

대표청구항 ▼

A speech coder system comprising an encoder for encoding input speech signals for transmission over a communication channel at a low bit rate, said encoder including: an LPC analysis module for converting input speech to linear predictive coding (LPC) parameters for each of a sequence of LPC frames;

A speech coder system comprising an encoder for encoding input speech signals for transmission over a communication channel at a low bit rate, said encoder including: an LPC analysis module for converting input speech to linear predictive coding (LPC) parameters for each of a sequence of LPC frames; an LSP conversion module for converting the LPC parameters to corresponding line spectrum frequencies (LSP) data, and a vector quantization and interpolation (VQ/I) encoder module for encoding the LSP data into vector indexes for transmission, wherein said VQ/I encoder module includes vector quantizing means for computing weighting coefficients for the LSP data, each of which is the product of LPC spectral amplitude and a predetermined factor, and means for applying said weighting coefficients to said LSP data.