JPH0787032A - Band compression processing unit, band expansion processing unit and voice communication equipment - Google Patents

Abstract

PURPOSE:To attain voice communication using a signal whose frequency is over a frequency band width of an analog communication line in use. CONSTITUTION:The communication system is provided with a band compression processing unit and a band expansion processing unit. The band compression processing unit has a FFT arithmetic circuit 2 transforming a time series broad band voice signal into a signal on a frequency axis, a band compression circuit 3 applying interleaving to a high frequency component of the transformed signal, and an inverse FFT arithmetic circuit 4 transforming the frequency component signal compressed by the band compression circuit 3 into the time series signal. The band expansion processing unit has a pitch detection circuit 10 detecting a pitch frequency from the time series compression voice signal, a FFT arithmetic circuit 9 transforming the compression voice signal into a signal on a frequency axis, a band expansion circuit 11 arranging the frequency component of the signal from the FFT arithmetic circuit 9 to a position of the frequency axis being an integral multiple of the pitch frequency detected by the pitch detection circuit 10, and an inverse FFT arithmetic circuit 12 transforming the expanded frequency component signal thereby into the time series signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band compression processor, a band expansion processor, and a voice communication device for analog transmission of voice signals.

[0002]

2. Description of the Related Art Conventionally, as a voice communication device, Japanese Patent Laid-Open No.
-175452 and JP-A-61-21095
Some are described in Japanese Patent Publication. In the conventional voice communication device, since the frequency bandwidth of the analog communication line used is limited, high frequency components outside the transmission band are removed, and voice communication is realized only with the low frequency components within the transmission band. There is.

[0003]

In the conventional voice communication device, since the high frequency component outside the transmission band cannot be transmitted due to the limitation of the frequency bandwidth of the analog communication line to be used, the communication with the sound quality close to the real voice is not possible. It is impossible.

An object of the present invention is to provide a band compression processor, a band expansion processor, and a voice communication device that enable voice communication with a frequency bandwidth exceeding the analog communication line used.

[0005]

According to the present invention, means for converting a time-series wideband speech signal into a signal on the frequency axis, and thinning out the high frequency components of the signal converted by this means. A band compression processor having a band compression unit for performing the conversion and a unit for converting the frequency component signal compressed by the band compression unit into a time series signal can be obtained.

Further, according to the present invention, a pitch frequency detecting means for detecting a pitch frequency from a time-series compressed voice signal, a signal converting means for converting the compressed voice signal into a signal on a frequency axis, and the pitch frequency. Band expansion means for arranging the frequency component of the signal from the signal conversion means at a position where the frequency is an integer multiple of the pitch frequency detected by the detection means, and the frequency component signal expanded by the band expansion means is converted into a time series signal. A band expansion processor having means for converting is obtained.

Further, according to the present invention, it is provided with a band compression processor and a band expansion processor, and the band compression processor converts the time-series wideband speech signal into a signal on a frequency axis, The band expansion unit has band compression means for thinning out high frequency components of the signal converted by this means, and means for converting the frequency component signal compressed by the band compression means into a time series signal. The processor includes a pitch frequency detecting means for detecting a pitch frequency from a time-series compressed audio signal, a signal converting means for converting the compressed audio signal into a signal on a frequency axis, and a pitch detected by the pitch frequency detecting means. Band expansion means for arranging the frequency component of the signal from the signal conversion means at a position where the frequency is an integral multiple of the frequency, and the frequency component signal expanded by the band expansion means is time-series. Voice communication device is obtained, characterized in that it comprises a means for converting the items.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

First, on the transmitting side, a wideband voice signal is converted to A /
The D converter 1 converts the signal into a time-series digital signal, and the FFT operation circuit 2 converts the signal into a signal on the frequency axis. The spectrum of the signal at this point is shown in FIG.

Of these frequency components, frequencies are thinned out for high frequency components. The frequency thinning section is shown in Fig. 2.
As in (a), the thinning rate is increased as the frequency increases from the 2: 1 section to the 4: 1 section. In selecting the frequency component to be left as the effective component, the maximum power in the thinning section is selected. The frequency components shown in black in the figure are components to be left as effective components, and the frequency components shown in white are components to be reduced by thinning. Next, the component remaining as the effective component is moved into the transmission path band as shown in FIG. 2B to perform band compression. It is assumed that these are performed by the band compression circuit 3.

Further, after the frequency signal compressed by the band compression circuit 3 is returned to the time series signal by the inverse FFT operation circuit 4, it is converted into an analog signal by the D / A converter 5 and converted into an analog compressed audio signal. To send as.

Next, on the receiving side, the compressed audio signal is converted into a time-series digital signal by the A / D converter 7, and then the transmission path loss compensation filter 8 compensates for the frequency characteristic lost in the transmission path. Then, the FFT calculation circuit 9 converts the signal into a signal on the frequency axis. The spectrum of the signal at this point is shown in FIG.
It is shown by (b). The pitch detector 10 receives the signal from the transmission line loss compensation filter 8 and obtains the fundamental frequency of the compressed audio signal. Usually, the pitch detector 10 is composed of a low-pass filter set to a cutoff frequency of 500 Hz or less and an autocorrelation calculator.

Next, the frequency components in the compression section are rearranged in the frequency range in the thinning section at a position close to an integer multiple of the pitch frequency obtained by the pitch detector 10.
FIG. 2C shows the situation. These are performed by the band expansion circuit 11.

Further, the frequency signal expanded by the band expansion circuit 11 is returned to a time series signal by the inverse FFT operation circuit 12, and then converted into an analog signal by the D / A converter 13 to be a expanded audio signal. Is played.

[0016]

As described above, the present invention enables voice communication exceeding the frequency bandwidth of the analog communication line used.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining band compression and band expansion by frequency thinning according to the present invention.

[Explanation of symbols]

 1,7 A / D converter 2,9 FFT operation circuit 3 Band compression circuit 4,12 Inverse FFT operation circuit 5,13 D / A converter 8 Transmission line frequency loss compensation filter 10 Pitch detector 11 Band expansion circuit

Claims (3)

[Claims] 1. A means for converting a time-series wideband speech signal into a signal on a frequency axis, a band compression means for thinning out high frequency components of the signal converted by this means, and this band compression means. Band compression processor having means for converting the frequency component signal compressed by the above into a time series signal. 2. A pitch frequency detecting means for detecting a pitch frequency from a time-series compressed audio signal, a signal converting means for converting the compressed audio signal into a signal on a frequency axis, and the pitch frequency detecting means. It has band expansion means for arranging the frequency component of the signal from the signal conversion means at a position where the frequency is an integral multiple of the pitch frequency, and means for converting the frequency component signal expanded by the band expansion means into a time series signal. Band extension processor. 3. A band compression processor and a band expansion processor, wherein the band compression processor converts the time-series wideband audio signal into a signal on the frequency axis, and the means converts the means. The band expansion processor has band compression means for thinning out high frequency components of the signal, and means for converting the frequency component signal compressed by the band compression means into a time series signal. Pitch frequency detecting means for detecting a pitch frequency from the compressed audio signal, and signal converting means for converting the compressed audio signal into a signal on a frequency axis,
A band expansion unit for arranging the frequency component of the signal from the signal conversion unit at a position where the frequency is an integer multiple of the pitch frequency detected by the pitch frequency detection unit, and a frequency component signal expanded by the band expansion unit And a means for converting to a sequence signal.