JPH04183083A - Simultaneous voice/image communication type video telephone system - Google Patents

Abstract

PURPOSE:To enable the satisfactory and simultaneous speaking of voices and images by lowering a transmission signal level when the S/N of a picture signal is lower than a rated level. CONSTITUTION:An S/N detector 28 is connected to the demodulated output of a MODEM reception part 25 and when the S/N is lowered rather than a reference value 29, a comparator 30 is operated. Then, an attenuator 3 is driven, the transmission signal level is lowered and as the result, the S/N of the received picture signal is increased so as to remove interference from voice signals. Since a line transmission loss is large, the interference from a picture transmission side transmission signal does not become a problem. Thus, the picture signal is not interrupted by the voice signal to be simultaneously transmitted, and the picture signal and the voice signal can be satisfactorily communicated at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video telephone device of simultaneous voice and image communication type that simultaneously transmits a video signal and a voice signal via a public telephone line or the like.

[Prior Art] In recent years, videophones have been developed that allow users to send and receive audio signals and image signals from telephones that use only audio to communicate while viewing the other party's video while having a conversation. Such videophone calls require a technology that allows audio signals and image signals to be transmitted simultaneously over a line without interfering with each other.

Figure 2 shows a conventional video telephone device for simultaneous voice and image communication, which is the same circuit as the conventional circuit shown in, for example, Japanese Patent Application Laid-Open No. 62-216462, but with a still image video telephone connected instead of the modem circuit. FIG.

In the figure, (121 is a line, (111 is a speech network that separates the received signal sent from the line (12) and the transmitted signal sent to the line, +2
4) is a band eluminator filter (hereinafter referred to as B) that extracts the audio signal by removing a specific frequency band from the received signal.
, E, F), +41+ is a 2-wire 4
The converter 142) for line conversion is a telephone set, and (4) (B, E, F) limits the transmission signal from the telephone set (42) to the necessary band to form an output voice signal.

(26) is a band bus filter (hereinafter referred to as B) that extracts an image signal by passing a specific frequency band from the received signal sent via the speech network (11).
, P, F), +40) is a videophone, f
40a) is the videophone (40) modem, +40bj
is the image processing unit of the videophone (40), and (6) is the modem [
B, P, F, which limits the image signal modulated in step 40a) to the necessary band to form a transmission image signal, (37) is B.
, E.

The output audio signal of F, (4) and the output audio signal of B, P, F, (6
] is an amplifier that synthesizes the output image signals.

Next, the operation of the circuit configuration shown in FIG. 2 will be explained. The image signals are B, P, and F having the characteristics shown in Figure 3(a).
, (6), +26).

Furthermore, the audio signal has a band in which the image signal is included is removed by B, E, F, , (4), (24) having the characteristics shown in FIG. 3 fbl. In this way, the image signal and the audio signal whose frequency bands are divided through the filter can be communicated simultaneously by single frequency division multiplexing, and simultaneous communication of audio and images is possible.

Therefore, first, on the transmitting side, the image signal created by the image processing unit (40b) of the videophone (40) is sent to the modem (40a).
), band-limited by B-P, F, (6), and input to a synthesis amplifier (37). At the same time, the transmitted signal from the telephone (42) is transferred to the converter (41).
The signals B, E, F, (4+) are band-limited and input to the input terminal of the amplifier (37) and added to the image signal. At this time, the image signal input to the amplifier (37) and the audio signal are shown in FIG. 3 (al(b
B, P, F, +6+ and B, E with the characteristics shown in +
. be able to.

The output of the amplifier (37) shown in FIG. 2 is transmitted through the speech network 1) and the line 2).
is output to. Also on this line (12), one image signal and an audio signal are band-divided, so the signals do not interfere with each other.

Next, on the receiving side, the received signal sent from line 9 (12) passes through the speech network (11) and is sent to B.

P, F, +261 removes out-of-band components, which are interfering components, and extracts one image signal. This image signal is reproduced by the receiving section of the modem (4(lal) of the videophone (40), expressed as an image by the image processing section (40bl), and received.At the same time, the speech network (II) is The received signals that passed through are B, E, F.
.

(24) removes the image signal component and extracts the audio signal, which is converted into 2-wire and 4-wire by a converter (41) to set the telephone (
The call is received at 42). As described above, in the conventional videophone device shown in FIG. 2, the band-divided image signal and audio signal can be simultaneously communicated without interfering with each other.

[Problems to be Solved by the Invention] However, in the conventional video telephone device for simultaneous voice and image communication, when the received image signal level is low.

There is a problem in that the audio signal level increases relatively and the audio signal interferes with the image signal.

In this way, when the level of one image signal is relatively lower than that of the audio signal, the conventional simple method, P,
For F, B, E, and F, interference cannot be prevented simply by dividing the band. Therefore, it may be possible to improve the attenuation characteristics of the filter to remove interference between the image signal and the audio signal. However, if B, P, F, and B, E, F are configured with high-order filters with improved attenuation characteristics,
There is a problem that the filter becomes expensive and the overall cost increases.

The present invention has been made to solve the above-mentioned problems, and even when the level of one image signal is extremely low, it is possible to prevent interference caused by simultaneously transmitted audio signals.

B, P, F, and B used in videophone equipment
It is an object of the present invention to provide a video telephone device for simultaneous voice and image communication that can reduce costs by configuring E and F with inexpensive filters.

[Means for Solving 5 Problems] The audio-image simultaneous communication type videophone device according to the present invention is provided with a signal-to-noise ratio detector for the image signal received on the receiving side, and the signal-to-noise ratio is at a specified level. It is equipped with a comparator that detects when the signal is smaller, and an amplifier that lowers the transmitting level on the receiving side to a specified level based on the detection by the comparator.

[Operation] In the simultaneous voice/image communication type video telephone device according to the present invention, when the S/c ratio of one image signal is smaller than a specified level, the transmitting signal level is lowered. Then, the interference of the audio signal with the image signal can be removed.

[Embodiment] A preferred embodiment of the simultaneous voice/image communication type videophone device according to the present invention will be described below based on seven drawings.

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

In Figure 1, (1) is a microphone, (2) is a microphone (1
), (3) is an attenuator that attenuates the amplification degree of the sound flux signal by a specified amount according to the S ratio output of the modem receiver (25), and (4) is the audio signal of microphone (1). B, PF, which removes the image signal band from the image signal carrier and prevents it from interfering with the image signal carrier, (5) is the modem 1.
A carrier modulated with one image signal is created in the 40al transmitter. (6) (B, P, Fl that passes only the modulation component of the image signal carrier; (7) is a mixer for combining the transmitting signal and the image signal carrier; (1)
1) is a speech network that combines transmitted and received signals with lines. (12) is.

This is a line that transmits image signals and audio signals.

On the receiving side, (21) is a speaker, +22) is an amplifier that amplifies the received signal from 3 lines, +23+ is an amplifier that increases the received signal amplification degree by a specified amount by the output of the modem receiver, (241 is 2 for 9 lines) B, E, and F, which band-limits the received signal from and extracts the audio signal.

(25) is the receiving section of the modem (40a) that demodulates the image signal from the modulated image signal carrier, +26) is the B, E, F that limits the band of the received signal from the line (12) and extracts the image signal carrier. ,, (27) is line 2
) is a distributor that separates the received signal from the audio signal side and the image signal side. (28) is an S/N ratio detector that detects the S/N ratio from the image signal demodulated by the receiving section of the modem (40a), and +29) is a standard that generates a reference voltage corresponding to the S/N ratio reference value. Voltage source, (30) is the basis! 1! This is a comparator that compares the output of the voltage source (29) and the output of the S/N ratio detector. (40) is a videophone, (4
0a) is a modem that modulates and demodulates the image signal of the videophone (40), and (40b) is an image processing section of the videophone (40) that displays or generates the image signal.

The operation of the simultaneous audio/video communication type videophone device of this embodiment having the above configuration will be explained.

First, on the image signal transmission side, the image signal generated by the image processing section (40b) of the videophone (40) is sent to the modem 140a.
) is modulated and converted into two image signal carriers at the transmitter (5). Then, these image signal carriers are
, F, (6) to pass only the modulation component. A transmission signal generated by the microphone (1) at the same time as this image signal is passed through B, E, F, and (4) to remove the frequency band in which the modulation component of the image signal carrier is distributed, and to remove the frequency band in which the modulation component of the image signal carrier is distributed. pass the band. In this way, B, P, F, +
61 and B, E, F, f4], the image signal and the audio signal band-limited are synthesized by a mixer (7).

It is transmitted on a line (12) via a speech network (11). Also, for one line, the reception signal from the other party is received via the speech network (11) via 2).

A received signal is manually input to B, E, F, +24) via a distributor (27). The received signal passes through the amplifier +23+ and the amplifier (22), and is generated by the speaker.

On the other hand, the receiving side of the other party's video telephone device has the same configuration as the receiving side of the device shown in FIG. On the receiving side, the received signal from the 5th line (12) is sent to the speech network (11
), the signal is distributed into an image signal and an audio signal by a receiver 1 distributor (27). Here, one image signal carrier has 7 lines (12
) from B, P,
F, +26). Also 9
The audio signal received from the line (12) is
E, F, +24] and remove only the band in which the modulation component of one image signal carrier exists. The audio signal generated by the microphone (1) on the image receiving side is passed through B, E, F, (4) to remove the frequency band where the modulation component of the image signal carrier is distributed, and pass the other bands. , mixer (7), speaker network (
11) to the line (12). At this time, noise N in the received image signal is expressed by the following equation.

N=Nt+La/L+La/Lb, e, f.

[dBm) Nt2 Noise mixed from the line (dBm) La: Sending signal level on the image transmitting side (dBm) L2 Line transmission loss (dB) Lb, e, f,: B, E, F, stopband attenuation (d
B) What is the received image signal level S (dBm)?

5=Lv/L (dBm) Lv/image signal transmission level ldB+n). At this time, the 7 line transmission loss fL) is large,
When the transmitting signal level (fLa) is high, the S/N ratio decreases and there is a problem that interference with the audio signal appears in the image signal.

Therefore, in this embodiment, as shown in FIG. 1, an S-ratio detector (28) is connected to the demodulated output of the modem receiver (25), so that the S-ratio decreases and becomes lower than the reference value (29). When it drops, the comparator (30) operates to drive the attenuator (3) to lower the transmit signal level, thereby increasing the S/N ratio of the received image signal and removing interference from the audio signal.

Interference from the transmitting signal on the image transmitting side is 1 line transmission loss (L)
is large, so this is not a problem.

In addition, prior to 1-image communication, handshaking is performed between the 1-communication side and the receiving side, and the 9-image sending side is notified that the audio output level of the image receiving side has been lowered by a specified amount. ) can be increased by a specified amount to faithfully transmit the original audio level.

Therefore, even when the single-line transmission loss is large, it is possible to transmit a clearer image signal without interference from the audio signal. Also, B, P-F, and B, E, F.

：Since the same inexpensive filter as before can be used as is, it is possible to prevent cost increases.

In the above embodiment, the voltage compared by the comparator (30) and the attenuation of the attenuator and amplifier were fixed to one value, but the output of the S/N ratio detector (28) was A/D converted, Data may be added to a digital gain controller corresponding to an attenuator or amplifier to appropriately control the audio output level and audio amplification degree.

In addition, in this embodiment, a videophone device that transmits and receives audio and images has been described, but it is also possible to use a device that transmits data such as text information using a drawing transmission device, facsimile device, captain system, etc. instead of image information. It's okay.

The same effects as in the above embodiment are achieved.

[Effects of the Invention] As explained above, the simultaneous audio/video communication type video telephone device according to the present invention has a large transmission loss on seven lines, even when the audio level is high.

The image signal is no longer interfered with by the audio signal transmitted at the same time, and as a result, it is possible to simultaneously communicate the image signal and the audio signal, and it can be configured with an inexpensive filter, reducing costs. be able to.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing a conventional example, Fig. 3 (a) (bl is a filter characteristic diagram, and Fig. 4 is a block diagram showing the use of audio signals and image signals. This is a band allocation diagram. In the figure, (3) is an attenuator, (2) is an amplifier, (28) is an S/N ratio detector, and (301 is a comparator). In the two figures, the same symbols are the same or A considerable portion is shown.

Claims (1)

[Claims of Claims] A sound/image system in which a modulated image signal and a voice signal from a telephone call are each passed through a filter that divides the frequency band of an analog line to divide the band, and the image signal and voice signal are simultaneously transmitted by frequency division multiplexing. In the simultaneous communication type videophone device, the receiving side of the videophone device includes a signal-to-noise ratio detector for detecting the signal-to-noise ratio of the received image signal, and a signal-to-noise ratio detector for detecting the signal-to-noise ratio of the received image signal. What is claimed is: 1. A video telephone device for simultaneous audio and video communication, comprising: a comparator that detects when the detection ratio is smaller than a specified level; and an amplifier that lowers the receiving side audio output level to a specified level upon detection by the comparator.