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Low bit-rate speech coder using adaptive open-loop subframe pitch lag estimation and vector quantization

  • US 6,345,248 B1
  • Filed: 11/02/1999
  • Issued: 02/05/2002
  • Est. Priority Date: 09/26/1996
  • Status: Expired due to Term
First Claim
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1. A system for coding speech, the speech being represented as plural speech samples segregated into a frame, the frame being formed of a plurality of subframes, wherein linear predictive coding (LPC) analysis and quantization of the speech samples in the frame are performed to determine an LPC residual signal, the system comprising:

  • lag means for estimating an unquantized pitch lag value within a predetermined minimum-allowed pitch lag and a predetermined maximum-allowed pitch lag for each subframe within the frame;

    means for obtaining a pitch lag vector comprising the unquantized pitch lag values for each subframe within the frame;

    a vector quantizer for quantizing the pitch lag vector to generate a quantized pitch lag vector;

    means for determining a pitch contribution vector for a current subframe, the pitch contribution vector being adapted to the quantized pitch lag vector;

    codebook means for generating an excitation signal representative of the speech samples of the current subframe; and

    means for applying the excitation signal of each current subframe to subsequent subframes to provide coded speech for the frame.

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