JP2001007932A - Voice encoding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voice encoding device which enables a user to normally hear a ring-back tone. SOLUTION: Two efficient voice encoding devices 11' and 12' which have trunk lines 31 and 32 stored in an exchange 2 and face each other with a trunk path between them insert a prescribed synchronizing signal and a control signal to the output signal to each other through the exchange by a synchronous control insertion part 104, and a synchronous detection part 105 turns on the control signal upon detecting the synchronizing signal. Meanwhile, a first rate conversion part 103 adds an ineffective signal, which increases the bit rate to allow intra-exchange transparent transmission, to an efficiently encoded voice signal from trunk lines, and a second rate conversion part 106 deletes this ineffective signal. When the synchronizing signal is detected and the control signal is turned on, selectors 107 and 108 bypass an encoding part 101 and a decoding part 102 through these rate conversion parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice coding apparatus, and more particularly to a voice coding apparatus for a digital switching system using voice compression technology in a relay transmission path between PBXs.

[0002]

2. Description of the Related Art A conventional high-efficiency voice coding / decoding digital one-link relay switching system in a tone dial network using a high-efficiency voice coding apparatus uses a high-speed digital dedicated line service or the like to perform high-efficiency voice coding. And transmit the audio information. At this time, a base station for performing inter-station relay of a digital trunk line by a digital exchange for exchanging with an intra-office extension is provided with a digital exchange, for example, 64 Kbps PC.
In order to match the transmission bit rate of the M coded signal to the transmission bit rate of the 16 kbps high efficiency voice coded signal transmitted in this digital trunk line, for example, a high efficiency voice signal is transmitted between the digital exchange and the digital trunk line. Coding,
A high-efficiency speech encoding device for performing a decoding conversion process is provided.

A plurality of digital trunk lines are accommodated in a digital exchange by using this high-efficiency speech decoding apparatus, and digital exchanges between these digital trunk lines and other digital trunk lines or between internal extensions of the local station. A conventional example of a high-efficiency voice encoding / decoding digital one-link relay switching system for converting voice signals is disclosed in Japanese Patent Application Laid-Open No. 4-1357 / 1992, entitled "Digital One-Link Relay Switching System for Voice Encoding Devices". In this transit switching system, a dedicated exchange having a control function for a high-efficiency speech coding apparatus is used. When performing inter-station relay, a control signal different from the main signal for communication is sent from this exchange to the high-efficiency speech coding apparatus, and the coding and decoding sections in the high-efficiency coding apparatus are speed-converted. By repeating through a circuit or the like, repetition of encoding and decoding is prevented.

Another conventional technique is disclosed in Japanese Patent Laid-Open No. 7-1.
No. 0705, “High-efficiency speech coding apparatus and transit switching system using the same”. This prior art is shown in the block diagram of FIG. This prior art is housed in a switchboard,
A predetermined synchronizing signal is inserted into two high-efficiency encoders facing each other via a relay path, in an output signal to a partner via an exchange. On the receiving side, upon detecting this synchronization signal, the encoding and decoding sections are bypassed to prevent repetition of encoding and decoding. This will be described in more detail below with reference to FIG.

The prior art shown in FIG. 4, that is, the transit switching system, comprises a plurality (three) of high-efficiency speech encoders 10, 11,.
12, 40, 41, 42, exchanges 20, 50, 51, 5
It consists of two. A plurality of telephones (TEL) 210, 510 to 512 are connected to the exchanges 20, 50 to 52, respectively. The exchange 20 has a subscriber circuit 202 and a plurality of trunks 200, 201, 204. In addition, each of the high-efficiency encoding devices 10, 11, 12 includes an encoding unit 101,
Decoding section 102, first rate exchange section 103, synchronization control insertion section 104, synchronization detection section 105, second rate exchange section 106,
It has selectors 107 and 108 and a synchronization signal creation unit 111. In addition, 10-40 between corresponding high-efficiency encoding devices,
11-41 and 12-42 are the trunk lines 30 and 3 respectively.
1, 32.

In the transit switching system shown in FIG. 4, when the call setting for setting the relay between the trunks 203 and 204 of the exchange performing the relay operation is fast up and slow down, the ringback tone may be missing or inaudible. A phenomenon occurs. When a communication channel is set only for the uplink, the synchronization signal inserted by the high-efficiency speech encoding device 12 is detected by the synchronization detecting unit 105 of the high-efficiency encoding device 11 and the selector 1
07 and 108 output the speed conversion units 103 and 106 to S1
And S2. Since one communication channel is not set, the synchronization detection unit 105 of the high-efficiency speech encoding device 12
Does not detect the synchronization signal. Therefore, the selector 107
Outputs the encoded signal to S2,
Outputs the decoded signal to S1. Therefore, the encoding unit 101 of the high-efficiency speech encoding device 41 and the encoding unit 106 of the high-efficiency speech encoding unit 12 face each other via the speed exchange unit 106, and a call cannot be made during this time.
People dialing from 12 may not hear the normal ringback tone.

[0007]

In the above-mentioned prior art, the digital exchange for inter-station relay uses an encoder and a decoder other than a speech signal as a main signal for a high-efficiency speech encoder. It is necessary to transmit a switching control signal for passing through. Therefore, an interface for transmitting a switching control signal is required in the digital exchange, and it cannot be connected to an exchange that does not have this interface, and a dedicated exchange is required.

In the latter conventional system described above,
Although a dedicated exchange is not required, there is a problem in that if the uplink / downlink path connection timing of the digital exchange that performs intra-office relaying is different, the ringback tone is missing or inaudible, so that the model of the exchange is selected.

An object of the present invention is to provide a digital one-ring relay switching system that can normally hear a ringback tone even when the uplink / downlink path connection timing of a digital exchange performing inter-office relay is different without using a dedicated exchange.
More specifically, it is to provide the speech encoding device.

[0010]

In order to solve the above-mentioned problems, the speech encoding apparatus according to the present invention employs the following characteristic configuration.

(1) It is provided between a digital exchange for performing intra-office and inter-office relay exchange of digital voice signals and a digital trunk line encoded at a bit rate lower than that of the digital exchange. A coding unit for converting a voice signal into a low-speed coded voice signal, a decoding unit for performing reverse code conversion on the coded voice signal from the trunk line, and a pseudo-code by adding an invalid signal to the coded voice signal from the trunk line A first speed conversion unit for obtaining a high-speed audio signal, a synchronization control insertion unit for selecting an output of the first speed conversion unit or the decoding unit and outputting the selected signal to the exchange, and converting the invalid signal from the audio signal from the exchange. A second rate exchange section to be removed, a selector for selecting an output of the second rate conversion section or the encoding section and outputting the output to the trunk line, a synchronization detection section for detecting a synchronization signal from an audio signal of the exchange A speech signal encoding apparatus, comprising: a control signal separation unit connected to the synchronization detection unit and the exchange for separating a control signal; and a logical product of an output of the control signal separation unit and the synchronization detection unit to switch the selector. Do A
An audio encoding device having an ND unit.

(2) The speech coding apparatus according to (1), wherein a synchronization signal from a synchronization signal generation unit is inserted into the synchronization control insertion unit, and is controlled by an output of the synchronization detection unit.

(3) The speech coding apparatus according to the above (1) or (2), wherein m-sequence data having a specific bit length is used for the synchronization signal and one bit is allocated to the control signal.

(4) The voice encoding apparatus according to (1), wherein the digital voice signal from the exchange is a 64 Kbps PCM signal, and the voice signal of the trunk line is 16 Kbps.

(5) The voice coding apparatus according to (1), wherein the digital voice signal from the exchange is a 64 Kbps PCM signal, and the voice signal of the trunk line is 8 Kbps.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a preferred embodiment of a speech coding apparatus according to the present invention.

FIG. 1 is a block diagram or a system configuration diagram of a transit switching system using a preferred embodiment of a speech coding apparatus according to the present invention. Many of the components of the switching system of FIG. 1 are the same as those of the switching system of FIG. 4 described above. Accordingly, for convenience, corresponding reference numerals are used for corresponding components.

In FIG. 1, a high-efficiency speech coding apparatus (hereinafter simply referred to as a speech coding apparatus) 10 ', 11', 12 '.
Is a speech coding apparatus to which the present invention is applied, and is connected to the exchange 20 and connected to the exchanges 50 to 52 via the speech coding apparatuses 40 to 42, similarly to the case of FIG. . The telephones 210, 510 to 512 are connected to the exchanges 20, 50 to 52, respectively.

Each of the speech encoding devices 10 to 12 includes an encoding unit 101, a decoding unit 102, a first speed conversion unit 103, a synchronization control insertion unit 104, a synchronization detection unit 105, a second speed conversion unit 106, and a selector 107. , 108 and the synchronizing signal generator 1
11 in that the conventional speech coding apparatuses 10-1 to 10-1 shown in FIG.
Same as 2. However, the speech encoding devices 10 ′ to 12 ′ according to the present invention further include the control signal separating unit 109 and the AN.
It has a D section 110.

The encoding unit 101 receives the 64 from the exchange 20.
Kbps PCM audio signal S1 is converted to ADPCM (adaptive difference P
CM) or the like to perform code conversion to a 16 Kbps encoded audio signal S2.

The decoding section 102 converts the 16 Kbps encoded audio signal S2 from the trunk lines 30 to 32 into a 64 Kbps
It performs inverse code conversion (decoding) on the CM audio signal S1.

The first speed conversion unit 103 includes
A pseudo 64 Kbps by adding an invalid code (for example, all 1 bits) having no meaning as 6-bit communication information for every 2 bits of the 16 Kbps encoded voice signal S2 from 32
Output as PCM audio signal S3.

The synchronization control insertion unit 104 adds an output signal from either the decoding unit 102 or the first speed conversion unit 103 to the output signal.
The synchronization signal of the predetermined bit pattern generated by the synchronization signal creation unit 111 and the detection result of the synchronization signal detection unit 105 are replaced and inserted (see FIGS. 2 and 3) and transmitted to the exchange 20.

The synchronization detecting section 105 receives the 64 Kbps PCM old voice signal S 1 received from the exchange 20 and the pseudo 64
The above-mentioned synchronization signal is detected from the Kbps PCM audio signal S3. Further, control signal separating section 109 separates the control signal.

The AND section 110 performs an AND operation on the output of the synchronization detecting section 105 and the output of the control signal separating section 109.

The second speed converter 106 removes the invalid signal including the above-mentioned synchronization signal from the pseudo 64 Kbps PCM voice signal S3 received from the exchange 20.

When the synchronization signal is not detected according to the detection output from the AND unit 110, the selector 107
Is output from the second speed converter 10 when the synchronization signal is detected.
6 are transmitted to the trunk lines 30 to 32, respectively. Similarly, when the synchronization signal is not detected, the selector 108
When the synchronization signal is detected, the output signal of the first speed conversion unit 103 is sent to the synchronization control insertion unit 104.

The exchange 20 picks up a telephone (telephone terminal) 210 via an internal subscriber circuit 202, and the speech coding apparatus 1 via trunk circuits 201, 203 and 204.
Trunk lines 30 to 32 via 0 ', 11', and 12 'are accommodated, respectively, and a 64 Kbps digital audio signal exchange process is performed. Each of the trunk lines 30 to 32 transmits an encoded digital audio signal of 16 Kbps, and can be multiplexed by a multiplexer (not shown) together with a signal of another audio encoder (not shown). Each trunk line 30 ~
32 are respectively connected to the encoding unit 101 and the decoding unit 1
02 and 64 Kbp
It is connected to telephones 510 to 512 via exchanges 50 to 52 that exchange sPCM voice signals. It should be noted that these other audio encoding devices 40 to 42 are connected to the audio encoding device 10 '.
12 to 12 ', the relay can be further relayed to other exchanges via the exchanges 40 to 42.

Next, the operation of the transit switching system of FIG. 1 will be described. The exchange 20 receives connection information such as a dial signal by a signal receiving device (not shown), and connects the subscriber line 202 and the trunk 201 when connecting the telephone 210 of the local extension and the trunk line 30. Connecting. In the voice encoding device 10 ′, the 64K
In order to input the bps PCM audio signal S1, the synchronization detection unit 105 is not detected, and the selectors 107 and 108 select the encoding unit 101 and the decoding unit 102, respectively. On the other hand, the synchronization control insertion unit 104
P for every 6 samples for 4Kbps PCM audio signal S1
One bit of the least significant digit (LSB) of the CN code data is replaced with one bit of a synchronization signal and a control signal of a predetermined bit pattern (bit stealing). The bit pattern of the synchronization signal uses an m-sequence sequence pattern.

FIG. 2 shows a PC in which the above-mentioned synchronization signal is inserted.
4 shows an example of a data format of an M audio signal. In this example, the synchronization signal S is inserted every six samples.
The synchronization detection unit 105 has a sufficient number of rear protection stages to prevent false synchronization detection. The number of forward protection stages may be several or less because there is almost no line error.

The PCM audio signal S1 as the synchronization signal output from the audio encoding device 10 ′ is output as audio from the telephone 210 via the subscriber circuit 202. However, since the insertion frequency of the synchronization signal is low and only the LSB of the PCM code is replaced, the quality of the output voice is hardly affected. As described above, transmission and reception of audio information between the telephones 210 and 510 are performed using the encoding unit 101 and the decoding unit 102 of the audio encoding devices 10 ′ and 40.

Next, the exchange 20 is connected to the trunk lines 31 and 32.
When relaying between the trunks, the trunks 203 and 204 are connected. Synchronization control insertion unit 1 of speech encoding devices 11 and 12
04 is 64 Kbp from the decoding unit 102 in the initial state.
The synchronization signal generated by the synchronization signal creation unit 111 and the detection result (here, OFF) of the synchronization signal detection unit 105 are replaced and inserted into the sPCM audio signal (see FIGS. 2 and 3), and synchronization control is inserted and output. I do. These signals pass through the exchange 20 transparently (transparently), and are input to the synchronization detection unit 105 and the control signal separation unit 109 of the speech encoding devices 12 and 11 facing each other. Each synchronization detection unit 105 sends a detection result (here, ON) to a synchronization control insertion unit 104 that detects a synchronization signal from an input signal.

The detection result of the synchronization detection unit 105 and the detection result of the control signal separation unit 109 are ANDed by the AND unit 110. When the logical product of the synchronization detection AND control signal (ON) is obtained, the selectors 107 and 108 are switched to the second speed converter 106 and the first speed converter 103, respectively. Each first speed conversion unit 103 is connected to the trunk line 3
The bit data of the invalid signal is added to the 16 Kbps coded voice code signal S2 received from 1, 32 to 64 Kb.
The synchronization control insertion unit 104 replaces some bits of the invalid signal with bits of the synchronization signal, as a pseudo PCM audio signal S3 of ps.

FIG. 3 shows an example of the data format of the audio signal. In this example, a total of 6 bits of 5 bits on the upper side and 1 bit on the lower side are added as an invalid signal to 2 bits of the encoded data D for each sample as an invalid signal. Further, the synchronization signal S is inserted by bit stealing of the lower invalid signal portion for every six samples. 64 output from each of the speech encoding devices 11 'and 12'
The Kbps audio signal S3 also passes through the exchange 20 transparently, and is manually input to the other party. Each second rate conversion unit 106 deletes the bit data of the invalid signal including the synchronization signal from the 64 Kbps audio signal S3 received from the exchange 20, and returns to the 16 Kbps encoded audio signal S2. When the exchange 20 functions as a transit exchange in this manner, each of the voice encoding devices 11 ', 1
Since the encoding unit 101 and the decoding unit 102 of 2 ′ are bypassed, the transmission and reception of voice information between the telephones 511 and 512 requires only one time of old voice coding and decoding, respectively, and the voice quality of the call deteriorates. Does not occur. Further, when the exchange 20 functions as a transit exchange, even if there is a time difference between the uplink and downlink call settings, the encoding unit 101 and the encoding unit are not detected until the synchronization signal is detected and the control signal is turned on. By bypassing 102, the phenomenon of missing or inaudible ringback tone does not occur.

After the end of the call, the exchange 20
In order to cut off the relay path between 3, 3 and 204, a silent PCM audio signal is manually input to the audio encoding devices 11 'and 12', and the synchronization detection units 105 no longer detect the synchronization signal.
Each of the selectors 107 and 108 returns to the initial state.

The preferred embodiment of the speech coding apparatus according to the present invention has been described above in detail. However, the present invention should not be limited to only such specific examples, and those skilled in the art can easily understand that various modifications can be made without departing from the gist of the present invention. For example, the present invention can support not only 16 Kbps but also other data rates. For example, in the case of 8 Kbps encoding, the pseudo 64K of FIG.
Bits 0 and 2 to 7 of the bps PCM audio signal are all set to 1, an encoded signal is assigned to bit 1, and a control signal C is assigned to bit 0. The configuration and operation are the same as those described above except that the encoding unit 101 and the decoding unit 102 in FIG. 1 become the 8 Kbps encoding unit and the decoding unit, and the speed conversion units 106 and 103 become operations corresponding to the above-mentioned bit allocation. The same is true.

[0037]

As can be understood from the above description, according to the voice coding apparatus of the present invention, the transmission and reception of voice information between the telephones 511 and 512 requires only one voice coding and one decoding, and the call There is no degradation in voice quality. Also, when the exchange 20 functions as a relay exchange, even if there is a time difference between the uplink and downlink communication path settings, the encoder 101 and the decoder 102 are not activated until the synchronization signal is detected and the control signal is turned on. Since the bypass is performed, there is a practically remarkable effect that a phenomenon such as a missing or inaudible link back tone does not occur.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a transit switching system using a preferred embodiment of a speech coding apparatus according to the present invention.

FIG. 2 shows an example of a data format of a PCM audio signal into which a synchronization signal is inserted.

FIG. 3 shows an example of a format of an encoded audio signal to which an invalid signal is added and a synchronization signal is inserted.

FIG. 4 is a system configuration diagram of a conventional transit switching system.

[Explanation of symbols]

10, 11, 12, 10 ', 11', 12 'Speech coding device 20 Switching device 30, 31, 32 Trunk line 101 Coding unit 102 Decoding unit 103 First rate conversion unit 104 Synchronization control insertion unit 105 Synchronization detection unit 106 second speed conversion unit 107, 108 selector 109 control signal separation unit 110 AND unit 111 synchronization signal creation unit

Claims (5)

[Claims] 1. A digital switch provided between a digital exchange for performing intra-station and inter-station relay exchange of digital voice signals and a digital trunk line encoded at a bit rate lower than that of the digital exchange. A coding unit for converting a signal into a low-speed coded voice signal, a decoding unit for performing reverse code conversion on the coded voice signal from the trunk line, and a pseudo high speed by adding an invalid signal to the coded voice signal from the trunk line. A first speed conversion unit for obtaining an audio signal, a synchronization control insertion unit for selecting an output of the first speed conversion unit or the decoding unit and outputting the output to the exchange, and removing the invalid signal from the audio signal from the exchange And a selector for selecting an output of the second rate converter or the encoder and outputting the output to the trunk line, and a synchronization detector for detecting a synchronization signal from a voice signal of the switch. In the voice encoding device, a control signal separation unit connected to the synchronization detection unit and the exchange for separating a control signal, and performs a logical product of an output of the control signal separation unit and the synchronization detection unit to switch the selector. An audio encoding device comprising: an AND unit. 2. A speech coding apparatus according to claim 1, wherein a synchronization signal from a synchronization signal generation section is inserted into said synchronization control insertion section, and is controlled by an output of said synchronization detection section. . 3. The speech encoding apparatus according to claim 1, wherein m bits of a specific bit length are used for the synchronization signal, and one bit is assigned to the control signal. 4. The digital audio signal from the exchange is 6
2. The speech encoding apparatus according to claim 1, wherein the speech encoding signal is a 4 Kbps PCM signal, and the speech signal of the trunk line is 16 Kbps. 5. The digital audio signal from the exchange is 6
The speech encoding apparatus according to claim 1, wherein the speech encoding signal is a 4Kbps PCM signal, and the speech signal of the trunk line is 8Kbps.