JP3122679B2 - Error correction method and apparatus for speech code - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention employs a voice coding method for coding using spectrum information in a band compression technique of a voice signal, and corrects an error due to a transmission path when transmitting via a transmission path (line). To a method and apparatus.

[0002]

2. Description of the Related Art Conventionally, in digital transmission using a speech encoding method, as a method of correcting an error due to a line, data obtained by encoding a speech signal is used as information bits.
In general, an error-correctable code having a parity bit added thereto is used.

[0003]

In the above conventional example, a hole length bit is added to add a parity bit in addition to the audio information bit, and the number of bits to be transmitted increases. Increasing the bits requires an increase in transmission capacity per unit time, that is, an increase in transmission speed, and there is a problem that transmission cannot be performed at the original transmission speed.

[0004]

According to the method of the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, on the transmitting side, a voice signal is subjected to spectrum analysis for each unit time, and the magnitude of power for each frequency is digitally determined. In the audio encoding method of encoding and transmitting, the receiving side reproduces the audio signal by returning the digital code to the original power distribution by spectrum synthesis.
The magnitudes a, b, c, and d with respect to the temporal transitions t _n , t _{n + 1} , t _{n + 2} , and t _{n + 3} of the power at each frequency f _{1 to} fn in the continuous sampling are defined as first to first. 4 registers 6a-
6d, and the power value Cex of the third register 6c at time t _{n + 2} is calculated from the power values a and b of the first and second registers 6a and 6b at time t _n and t _{n + 1} by extrapolation. And the second and fourth registers 6 at times t _{n + 1} and t _{n + 3} .
The power value Cin of the third register 6c at the time t _{n + 2} is calculated from the power values b and d of b and 6d by the interpolation method, and the intermediate value Cca is calculated from the power values Cex and Cin. At time t _{n + 2,} the power value C ′ of the third register 6c and the power value obtained from the power value Cex and the power value Cin are within the estimated range, and C ′ when the power value is outside the range. Is used to correct the error.

In order to solve the same problem, the apparatus of the present invention performs spectrum analysis of a voice signal on a transmission side every unit time by a spectrum analyzer 1 as shown in FIG.
The magnitude of power for each of _{1 to} fn is digitally encoded, the data is converted from parallel to serial by a parallel-to-serial converter 2 and transmitted through a transmission line 3, and the serial data is converted to a serial-to-parallel converter 4 on the receiving side. , And the parallel data is converted by the spectrum synthesizer 5 to each of the frequencies f ₁ to f ₁ .
In a speech encoding apparatus for reproducing an audio signal by reproducing a spectrum distribution from the magnitude of power for each fn and synthesizing the spectrum, the spectrum synthesizer 5
Are the frequencies f _{1 to} f _n in the continuous sampling.
Time transition of power for each time t _n , t _{n + 1} , t _{n + 2} , t _{n + 3}
From the first to fourth registers 6a to 6d for accumulating the magnitudes a, b, c, and d with respect to the first and fourth registers at times t _n and t _{n +} 1, respectively.
A first computing unit 7 for calculating the power value Cex of the third register 6c from the power values a and b of the second registers 6a to 6d by an extrapolation method; and a second computing unit 7 at times t _{n + 1} and t _{n + 3} . Time t from the power values b and d of the four registers 6b and 6d by interpolation.
a second computing unit 8 for calculating the power value Cin of the third register 6c at _{n + 2,} and a power value C of the first and second computing units 7, 8
ex, Cin, and a third computing unit 9 for calculating the intermediate value Cca, and | C′−Cex from the power value C ′ of the third register 6c and the power value Cex of the first computing unit 7 at time t _{n + 2} .
| ≦ A is calculated from the power value C ′ of the third register 6c and the power value Cin of the second computing unit 8 at time t _{n + 2 by} | C−Cin
| ≦ A, and an operation / judgment unit 10 for judging whether or not this condition is satisfied, and C ′ when the condition is satisfied.
Is not satisfied, the switch 11 is used by switching Cca.

[0006]

[Operation] On the transmitting side, the audio signal is spectrum-analyzed by the spectrum analyzer 1 every unit time, and the frequency f ₁
The magnitude of the power for each .about.f _n is digitally encoded, and the data is converted from parallel to serial by the parallel-serial converter 2 and transmitted through the transmission path 3. On the receiving side, the serial data is converted into parallel data by the serial-parallel converter 4, and the spectrum data is reproduced by the spectrum synthesizer 5 from the magnitude of the power at each of the frequencies f _{1 to} f _n .

That is, a temporal transition t _n , t _{n + 1} , of power at each frequency f _{1 to} f _n in continuous sampling.
The sizes a, b, c, and d for t _{n + 2} and t _{n + 3} are the first to the first.
The data is accumulated by the fourth registers 6a to 6d. At time t _n ,
The voltage value Ce of the third register 6c is extrapolated from the power values a and b of the first and second registers 6a and 6b at t _{n + 1} .
x is calculated by the first computing unit 7 and at times t _{n + 1} , t
_From the power values b and d of the second and fourth registers 6b and 6d at _{n +} 3, the power value Cin of the third register 6c at time t _{n + 2} is calculated by the second computing unit 8 by interpolation.

The power values Ce of the first and second computing units 7 and 8 are Ce.
The third arithmetic unit 9 calculates the intermediate value Cca from x and Cin. Based on the power value C 'of the third register 6c at time t _{n + 2} , the power value Cex of the first computing unit 7 and the power value Cin of the second computing unit 8, it is determined by the computing / judging unit 10 that it is within the estimation range. If it is determined, C 'is adopted, and if it is determined that it is out of the range, Cca is adopted. These processes are performed for each frequency f ₁ ~f _n.

In other words, | C'-Cex | ≤A, | C '
If the condition of −Cin | ≦ A is satisfied, it is determined that C ′ is correct and is adopted as it is through the switch 11. If not, it is determined that an error is caused by the transmission path, and Cca is determined by the switch 1.
1, the error is corrected and the decrease in clarity due to a rapid change in the temporal spectrum due to an error in the transmission path is relieved. Thus, the spectrum distribution in which the error in the transmission path has been corrected, that is, the original power distribution, is reproduced, and the audio signal is reproduced.

[0010]

FIG. 1A is a block diagram showing the configuration of an embodiment of the method and apparatus of the present invention, FIG. 1B is a diagram for explaining the operation of the present invention, and FIG. 2 is an explanation of the temporal transition of spectrum information. FIG. 1 spectrum analyzer for digitally encoding the magnitude of the power at each frequency f ₁ ~f _n spectrally analyzing an audio signal for each unit time to be transmitted from the transmission side in FIG. 1, the second series the data from the parallel And a parallel-to-serial converter for transmission through the transmission path 3.

4 is a serial-parallel converter for converting serial data transmitted from the transmission line 3 into parallel data on the receiving side;
Reference numeral 5 denotes a spectrum synthesizer that reproduces an audio signal by reproducing the spectrum distribution of the parallel data from the magnitude of power at each of the frequencies f _{1 to} f _{n and} performing spectrum synthesis.

The spectrum synthesizer 5 has magnitudes a and b with respect to time transitions t _n , t _{n + 1} , t _{n + 2} , and t _{n + 3} of power at each frequency f _{1 to} f _n in continuous sampling. , C, d for storing the first to fourth registers 6a to 6
d and the first and second registers 6 at times t _n and t _{n + 1} .
a first calculator 7 for calculating the power value Cex of the third register 6c from the power values a and b of the third register 6c by the extrapolation method;
_From the power values b and d of the second and fourth registers 6b and 6d at _{n + 1} and t _{n + 3} , the _third values at time t _{n + 2} are obtained by interpolation.
A second calculator 8 for calculating the power value Cin of the register 6c is provided.

A third computing unit 9 for calculating an intermediate value Cca from the power values Cex and Cin of the first and second computing units 7 and 8, and a third register 6c at time t _{n + 2}
From the power value C 'of the first computing unit 7 and the power value Cex of the first computing unit 7 | C'
−Cex | ≦ A is set to the third register 6 at time t _{n + 2} .
from the power value C ′ of c and the power value Cin of the second computing unit 8 |
A computation / determination unit 10 that computes C'-Cin | ≤A and determines whether or not this condition is satisfied, and switches C 'if the condition is satisfied, and switches Cca if not satisfied. And a switching device 11 for performing the switching.

In the above configuration, on the transmitting side, the audio signal is spectrum-analyzed by the spectrum analyzer 1 at every unit time t _n , t _{n + 1} , t _{n + 2} , t _{n + 3} , and the frequency f ₁ to
The magnitude of the power for each f _n is digitally coded. FIG.
FIG. 4 is a diagram illustrating a spectrum analysis of an audio signal for each unit time, and a graph showing how a power distribution for each frequency component changes over time, where the f-axis is frequency, the t-axis is time, and the Z-axis is power magnitude. Is shown. The t-axis is subjected to spectrum analysis every 20 to 30 msec. As shown in FIG. 2, in the case of the frequency f ₁ , the magnitude of the electric power is the time t ₁ , t ₂ , t ₃ , t ₄ ,
In _{t 5 a, b, c,} d, has a gradual change as represented by e, is the gentle likewise its temporal changes in other f _2, ··· f _n .

The digitally encoded parallel data is converted from parallel to serial by the parallel-serial converter 2 and transmitted through the transmission line 3. On the receiving side, the serial data is converted into parallel data by the serial-to-parallel converter 4, and the parallel data is converted by the spectrum synthesizer 5 to each of the frequencies f _{1 to} fn.
The spectrum distribution is reproduced from the magnitude of each power.

That is, the temporal transitions t ₁ , t ₂ , and t of the power for each of the frequencies f _{1 to} f _n in the continuous sampling.
_The magnitudes a, b, c, d for ₃ and t ₄ are stored by the first to fourth registers 6a to 6d. FIG. 1 (B) is FIG.
Time transitions t ₁ , t ₂ , t of the power distribution of only the frequency f _1
3 is a diagram illustrating a t _4, t _5. At time t _3,
As shown in FIG. 2, what should be the value of C has changed to the level of C 'due to an error in the transmission path.

The power value Cex of the third register 6c is calculated by the first computing unit 7 by extrapolation from the power values a and b of the first and second registers 6a and 6b at times t ₁ and t ₂ . _Second and fourth registers 6 at t ₂ and t ₄
The power value Cin of the third register 6c at time t ₃ is calculated by the second computing unit 8 from the power values b and d of b and 6d by the interpolation method.

The power value Ce of the first and second computing units 7 and 8
The intermediate value Cca is calculated from x and Cin by the third computing unit 9, the power value C ′ of the third register 6 c at time t ₃ , the power value Cex of the first computing unit 7 and the second computing unit 8
From the power value Cin of each of the frequencies f
_When the level range of ₁ is estimated and the received power value is determined to be within the estimated range, C 'is adopted, and when it is determined to be outside the range, Cca is adopted.

In other words, | C'-Cex | ≤A, | C '
If the condition of −Cin | ≦ A is satisfied, it is determined that C ′ is correct and is adopted as it is through the switch 11. If not, it is determined that an error is caused by the transmission path, and Cca is determined by the switch 1.
1, the error is corrected as shown by a, b, c, and d in FIG. 1 (B), and a decrease in clarity due to a rapid change in the spectrum due to an error in the transmission path is relieved. Thus, the spectrum distribution in which the error in the transmission path has been corrected, that is, the original power distribution, is reproduced, and the audio signal is reproduced.

Although the above description has been made with respect to only one frequency f ₁ , the same can be said with respect to other frequencies f _{2 to} f _n . The contents of the first register 6a to the fourth register 6d are actually constituted by the number of bits necessary for the quantization level.

[0021]

As described above, according to the present invention, a sharp change in spectrum information due to an error in a transmission line (line) is corrected, so that deterioration of intelligibility after voice decoding can be suppressed. Since there is no increase in information due to error control (correction), the transmission rate does not change using the method and apparatus. Since the amount of information on the transmitting side (encoding) does not change and can be implemented only on the receiving side (decoding), transmission is possible even when the method and apparatus are used.
It can be implemented relatively easily.

[Brief description of the drawings]

FIG. 1A is a block diagram showing a configuration of an embodiment of a method and an apparatus of the present invention, and FIG. 1B is an explanatory view of an operation of the present invention.

FIG. 2 is an explanatory diagram of a temporal transition of spectrum information.

[Explanation of symbols]

 Reference Signs List 1 spectrum analyzer 2 parallel-serial converter 3 transmission line 4 serial-parallel converter 5 spectrum synthesizer 6a first register 6b second register 6c third register 6d fourth register 7 first computing unit 8 second computing unit 9 3rd arithmetic unit 10 arithmetic / judgment unit 11 switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G10L 19/00-19/14 H03M 7/30 H04L 1/00 H04B 14/00-14/06

Claims (2)

(57) [Claims] 1. A transmitter analyzes the spectrum of a voice signal for each unit time, digitally encodes the magnitude of power for each frequency and transmits the digital signal, and the receiver returns the digital code to the original power distribution by spectrum synthesis. Te in the audio coding method for reproducing audio signals, the temporal transition of the power of each frequency in the sampling successive _{(f 1 ~f n) (t} n, t n + 1, t n + 2, t n + ₃ ), the size (a, b, c, d) is set in the first to fourth registers (6a to 6).
d), and extrapolates from the power values (a, b) of the first and second registers (6a, 6b) at time (t _n , t _{n + 1} ) at time (t _{n + 2} ). 3 registers (6c)
At the time (t _{n + 1} , t _{n + 3} )
, The power value (Cin) of the third register (6c) at the time (t _{n + 2} ) is calculated from the power values (b, d) of the second and fourth registers (6b, 6d) by interpolation. The intermediate value (Cca) is calculated from the values (Cex, Cin), and the power value (C ′) of the third register (6c) at the time (t _{n + 2} ) is calculated as the power value (Cex) and the power value (Ci).
(C ') if it is within the level range obtained from n),
An error correction method for a speech code, wherein the error is corrected using (Cca) when the error is outside the range. 2. A digitally coded frequency (f ₁ ~f _n) for each of the size of the power spectrum analyzed by the spectrum analyzer (1) an audio signal for each unit time on the transmission side, parallel data - The data is converted from parallel to serial by the serial converter (2) and transmitted through the transmission line (3). At the receiving side, the serial data is converted to parallel data by the serial-parallel converter (4), and the parallel data is spectrum-synthesized. An audio encoding device for reproducing an audio signal by reproducing the spectrum distribution from the magnitude of the power for each frequency (f _{1 to} f _n ) by the unit (5) and synthesizing the spectrum; Are magnitudes (a, b, b) with respect to a temporal transition (t _n , t _{n + 1} , t _{n + 2} , t _{n + 3} ) of power for each frequency (f _{1 to} f _n ) in continuous sampling. c, d) From the first to fourth registers (6a to 6d) for accumulating the data and the power values (a, b) of the first and second registers (6a to 6b) at the time (t _n , t _{n + 1} ). The power value (Ce) of the third register (6c)
x), a first computing unit (7) for calculating the time (t _{n + 1} , t
_{n + 3} ), the power value (Cin) of the third register (6c) at time (t _{n + 2} ) is calculated from the power values (b, d) of the second and fourth registers (6b, 6d) by interpolation. A second computing unit (8) for calculating, a third computing unit (9) for computing an intermediate value (Cca) from the power values (Cex, Cin) of the first and second computing units (7, 8), From the power value (C ′) of the third register (6c) and the power value (Cex) of the first computing unit (7) at time (t _{n + 2} ), (| C′−Cex | ≦
A) is stored in the third register (6c) at time (t _{n + 2} ).
(C ') and the power value (Ci) of the second computing unit (8).
(| C′−Cin | ≦ A) from (n) and an arithmetic / judgment unit (10) for judging whether or not this condition is satisfied
And (Cca) when the condition is satisfied, and a switch (11) that switches and uses (Cca) when the condition is not satisfied.