Method and apparatus for reproducing speech signals and method for transmitting same

• US 5,926,788 A
• Filed: 06/17/1996
• Issued: 07/20/1999
• Est. Priority Date: 06/20/1995
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Nishiguchi, Masayuki
• Primary Examiner(s): Dorvil, Richemond
• Application Number:
  US08/664,512
• Time in Patent Office: 1,128 Days
• Field of Search: 395/2.74, 395/2.16, 395/2.31, 395/2.32, 395/2.28, 395/2.67, 395/2.77, 704/265, 704/266, 704/258, 704/268, 704/207, 704/208, 704/222, 704/223, 704/219, 704/220, 704/211, 704/205, 704/206, 704/262, 704/200, 704/214
• US Class Current: 704/265
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/10 the excitation function being a multipulse excitation
• CPC Class Codes: G10L 2019/0012 Smoothing of parameters of the decoder interpolation
• CPC Class Codes: G10L 21/04 Time compression or expansion

Abstract

An encoding unit 2 divides speech signals provided to an input terminal 10 into frames and encodes the divided signals on the frame basis to output encoding parameters such as line spectral pair (LSP) parameters, pitch, voiced(V)/unvoiced (UV) or spectral amplitude A_m. The modified encoding parameter calculating unit 3 interpolates the encoding parameters for calculating modified encoding parameters associated with desired time points. A decoding unit 6 synthesizes sine waves and the noise based upon the modified encoding parameters and outputs the synthesized speech signals at an output terminal 37. Speed control can be achieved easily at an arbitrary rate over a wide range with high sound quality with the phoneme and the pitch remaining unchanged.

Claims

1. A method for reproducing an input speech signal based on first encoded parameters produced by dividing the input speech signal into frames having a predetermined length on a time axis and by encoding the input speech signal on a frame by frame basis, said first encoded parameters being spaced by a first interval, comprising the steps of:

producing second encoded parameters by interpolating said first encoded parameters, said second encoded parameters being spaced by a second interval different from said first interval; and

generating a modified speech signal different in time scale from the input speech signal by using said second encoded parameters.

2. The method for reproducing an input speech signal as claimed in claim 1 wherein the modified speech signal is produced by at least synthesizing sine waves in accordance with the second encoded parameters.

3. The method for reproducing an input speech signal as claimed in claim 2 wherein a parameter period is changed by one of compressing and expanding the first encoded parameters respectively before or after the step of interpolating said first encoded parameters.

4. The method for reproducing an input speech signal as claimed in claim 1 wherein the step of interpolating said first encoded parameters is performed by linear interpolation of linear spectral pair parameters, pitch, and a residual spectral envelope contained in said first encoded parameters.

5. The method for reproducing an input speech signal as claimed in claim 1 wherein said first encoded parameters used are determined by representing short-term prediction residuals of the input speech signal as a synthesized sine wave and noise and by encoding frequency spectral information of each of the synthesized sine wave and the noise.

6. An apparatus for reproducing a speech signal in which an input speech signal is regenerated based on first encoded parameters determined by dividing the input speech signal into frames having predetermined length on a time axis and by encoding the input speech signal on a frame by frame basis, said first encoded parameters being spaced by a first interval, comprising:

interpolation means for producing second encoded parameters by interpolating said first encoded parameters, said second encoded parameters being spaced by a second interval different from said first interval; and

speech signal generating means for generating a modified speech signal different in time scale from the input speech signal by using said second encoded parameters.

7. The speech signal generating apparatus as claimed in claim 6 wherein said speech signal generating means generates said modified speech single by at least synthesizing a sine wave in accordance with said second encoded parameters.

8. The speech signal generating apparatus as claimed in claim 7 further comprising period changing means at one of upstream and downstream of said interpolating means for respectively compressing and expanding said first encoded parameters to change encoded parameter periods.

9. The speech signal generating apparatus as claimed in claim 6 wherein said interpolating means perform linear interpolation on linear spectral pair parameters, pitch, and residual spectral envelope contained in said first encoded parameters.

10. The speech signal generating apparatus as claimed in claim 6 wherein said first encoded parameters used are determined by representing short-term prediction residuals of the input speech signal as a synthesized sine wave and noise and by encoding frequency spectral information of each of the synthesized sine wave and the noise.

11. A method for transmitting a speech signal comprising the steps of:

producing first encoded parameters by dividing an input speech signal into frames having predetermined length on a time axis and by encoding the input speech signal on a frame by frame basis, said first encoded parameters being spaced by a first interval;

producing second encoded parameters by interpolating said first encoded parameters, said second encoded parameters being spaced by a second interval different from said first interval; and

transmitting said second encoded parameters.

12. The method for transmitting the input speech signal as claimed in claim 11 wherein said first encoded parameters used are determined by representing short-term prediction residuals of the input speech signal as a synthesized sine wave and noise and by encoding frequency spectral information of each of the synthesized sine wave and the noise.