JPH02150153A - Voice conference system - Google Patents

Abstract

PURPOSE:To make it unnecessary to repeatedly encoding and decoding a signal, and to decrease the deterioration of a tone quality by synchronizing a signal at a point with the signal from the other point at one point, and digitally adding and obtaining the necessary signal out of the synchronized signals. CONSTITUTION:Signals A1 to C1 from respective points A to C timing-regulated by timing regulating circuits 15 and 16 are mutually synchronized, and their phases correspond. Signals A1 and B1 except for a signal C1 at the point C of itself are digitally added by an adder 17, and supplied through a D/A converter 4 to a speaker 2. The signal A1 and B1, and A1 and C1 except for B1 or C1 at sending destinations are respectively digitally added by an adder 18, further encoded by a voice encoder 6, then sent to the respective points B and C. In such a way, since the signals necessary for the respective transmission destinations are added on the basis of the digital signal after the synchronization of the signals of the respective points at one point, decoding is smoothly executed at the respective points, and encoding and decoding and practically required only for once.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an audio conference device that allows participants at three or more locations to hold a conference.

[Prior art] Figure 5 shows, for example, the Journal of the Institute of Electronics, Information and Communication Engineers (°87/1
1Vo1. J70-B No. 11) is a block diagram showing the conventional audio conference device shown in 11). In the figure, A, B, and C are the points where participants of the conference are, and N is each point A, B, and C. It is a voice bridge on the line side that connects the two. At each point A, B, and C, 1 is a microphone used by the participant, 3 is an A/D converter that digitizes the analog audio signal from microphone 1, and 6 is a predetermined output signal of A/D converter 3. 7 is an audio decoder that decodes the digital audio signal sent from the audio bridge N from another point; A D/A converter converts the output signal into an analog audio signal, 2 is a speaker to which the analog audio signal is supplied, and 5 is an echo canceller for preventing howling.

In the audio bridge N, 8 is each point A, B.

An audio decoder 9 decodes the digital audio signal from C to form an analog signal; 9 an adder that adds the analog signals from each audio decoder 8; The subtracter 11 that subtracts the signal is a voice encoder that encodes the output signal of the subtracter 10 and sends it to the destination point.

Next, the operation will be explained. At each point A, B, and C, audio signals spoken by each participant are transmitted to microphone 1. A/
After passing through the D converter 3 and being encoded by the audio encoder 6, it is sent to the audio bridge N. In the audio bridge N, digital audio signals sent from each point are sent to an audio decoder 8.
The adder 9 converts each analog signal into an analog signal.
Synthesize with The combined signals are respectively applied to a subtracter 10, where the signal from the audio decoder 8 corresponding to the signal destination is subtracted. The output signal of each subtractor 10 is encoded again by the audio encoder 11, and then
C, respectively. At each point A, B, and C, after the signal from the audio bridge N is decoded by the audio decoder 7, the D/A
It is supplied to the speaker 2 through the converter 4. Also, the output signal of the audio decoder 7 and the output signal of the A/D converter 3 are applied to the echo canceller 5, which prevents the sound from the speaker 2 from going around to the microphone 1 and causing howling. That's what I do.

[Problems to be Solved by the Invention] Since the conventional audio conference device is configured as described above, the audio signal must go through the encoding and decoding process twice by the audio bridge N, and this Therefore, the sound quality deteriorates. Further, when adding or subtracting audio signals, there are problems such as the need for an equihole type to absorb group delay deviations whose delay times differ depending on the frequency.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain an audio conferencing device that can be constructed entirely of digital circuits and has less deterioration in sound quality.

[Means for Solving the Problems] An audio conference device according to the present invention synchronizes digital audio signals from each location with each other based on a frame synchronization signal included therein, and transmits the synchronized signals according to the destination. A circuit is provided at one point for digitally adding signals and sending the added signals to each point.

[Effect]

In the audio conference device according to the present invention, after the signals from each point are synchronized at one point, the signals necessary for each destination are added as digital signals. Furthermore, the encoding and decoding processes are substantially performed only once.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, the configuration at point C is different from that in FIG. 5, and other parts correspond to those in FIG. 5, so the same reference numerals are given and explanations are omitted. At point C in FIG. 1, 12 is a timing generation circuit, 13 is a timing signal of a predetermined frequency generated by the timing generation circuit 12, and 14 is a timing signal generated by the audio decoder 7.
A frame synchronization signal extracted from digital audio signals sent from other points A and B, 15 synchronizes the signals from the other points A and B with each other based on the timing signal 13 and frame synchronization signal 14. 16 is a timing adjustment circuit that synchronizes the signal from the A/D converter 3 at its own point C with the synchronization of the timing adjustment circuit 15; 17 is each timing adjustment circuit 15;
18 is an adder for digitally adding the synchronized signals from points A and B to obtain a signal to be used at the own point C; This is an adder that digitally adds the signal at a point and the synchronized signal obtained from the timing adjustment circuit 15 corresponding to the destination point. Note that the timing generation circuit 12 and timing adjustment circuits 15 and 16
etc., constitute a synchronization means for synchronizing the digital audio signals from each point A, B, and C with each other.

FIG. 2 shows data obtained when the audio signal 19 is sampled and digitized at times t0 to t+s.

In FIG. 3, a, b, and c indicate the timing of data generated at each point A, B, and C, respectively, using 3-bit data as an example. Also, At, B+.

C1 indicates data obtained by adjusting the timing of data a, b, and c and synchronizing them. In addition, each point A and B.

The data content in C is illustrated as being equal. Further, each data has a frame synchronization signal arranged for each predetermined number of bits, although not shown.

Next, the operation will be explained. The digital audio signals sent from points A and B to point 0 pass through the audio decoder 7 and are supplied to the timing adjustment circuit 15, and the audio decoder 7 extracts the frame synchronization signal 14 and sends it to the timing adjustment circuit 15. send to The timing adjustment circuit 15 adjusts the timing of the signals from points A and B based on the frame synchronization signal 14 and the timing signal 13. At the same time, the timing adjustment circuit 16 adjusts the timing of the signal from the A/D converter 3. FIGS. 3A, 3B, and 3C show signals from points A, B, and C before timing adjustment, and as shown, the data of every three bits are out of phase regardless of each other.

The signals A3. shown in FIG. 3 from each point A, B, C whose timing has been adjusted by the timing adjustment circuit 15.16. B.I.
C+ are synchronized with each other and in phase. Signals A1 and B1, excluding signal C at own point C, are digitally added in an adder 17 and supplied to the speaker 2 through the D/A converter 4. Also, the destination signal B1 or C
Signals A, B, , A, and C5 excluding 1 are sent to adder 1, respectively.
After being digitally added at step 8 and further encoded by an audio encoder 6, the signals are sent to each point B and C.

In addition, in the above embodiment, the timing of each point A, B, and C was adjusted at one place (point C in the above embodiment), but if the timing is not completely synchronized on the line side like NTT's line, In this case, as shown in FIG. 4, the timing adjustment circuits 15 and 16 and the timing generation circuit 12 are unnecessary, and the same effects as in the above embodiment can be obtained. That is, in FIG. 4, digital audio signals from points A and B are input to the audio decoder 7 via the switching network 20. In FIG. At that time,
In the switching network 20, the frame synchronization timings of the digital voice signals are matched as shown in FIG. 3A, B, CI. Therefore, the timing adjustment circuit 15.16 of FIG.
The timing generation circuit 12 is no longer necessary, and the signals are directly input to the adders 17 and 18. Note that the other operations are the same as those in the above embodiment.

〔Effect of the invention〕

As described above, according to the present invention, a signal at a point L is synchronized with a signal from another point, and a necessary signal from among the synchronized signals is digitally added and obtained. Since the system is structured as follows, there is no need to perform signal encoding and decoding processing many times (and since all signal processing is performed digitally, deterioration in sound quality can be reduced and it can be provided at low cost). There is an effect that can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an audio conference device according to an embodiment of the present invention, FIGS. 2 and 3 are timing charts for explaining signal processing, and FIG. 4 is an audio conference device according to another embodiment of the invention. Block Diagram Showing Conference Device FIG. 5 is a block diagram showing a conventional audio conference device. A, B, C are points, 6 is a voice encoder, 7 is a voice edger,
12 is a timing generation circuit, 15.16 is a timing adjustment circuit, and 17.18 is an adder. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent applicant Mitsubishi Electric Corporation ω′ 0100+1 2nd WJ Figure 3 1! 0 change +00 1 10 -〉Time ■

Claims (1)

[Claims] In an audio conferencing device that conducts a conference between three or more points, one point receives a digital audio signal sent from another point and a digital audio signal sent from one's own point. a synchronizing means that synchronizes with each other based on a frame synchronization signal included in the digital audio signals received from the station; and a signal that adds together the synchronized digital audio signals sent from other points to be used at the own point. an adder that adds the digital audio signal sent from the synchronized own point and the digital audio signal sent from other points other than the destination point, and sends the result to the destination point. 1. An audio conferencing device comprising: an adder for obtaining a digital audio signal.