JPH03136448A - Video telephone system of voice and picture simultaneous communication type - Google Patents

Abstract

PURPOSE:To prevent disturbance due to a voice signal sent simultaneously even when a picture signal level is extremely decreased like a gray picture signal by controlling a voice signal level depending on a picture signal level. CONSTITUTION:A detector 8 detects a transmission picture signal level and inputs the result to a comparator 10, and when an amplitude voltage of a picture signal carrier is smaller than a reference voltage, the voice signal amplified by an amplifier 2 is attenuated by an attenuator 3 and then sent to an opposite video telephone system. A comparator 30 of an opposite receiver side compares the reference voltage with a level of a received picture signal carrier detected by a detector 28 and when the level of the picture signal carrier is smaller than the reference voltage, an amplifier 23 amplifies the voice signal by the attenuation of the sender side to restore the level to the original voice signal level. Thus, even when a low level picture signal is sent, the disturbance of the picture signal by the voice signal sent simultaneously is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a simultaneous voice/image call type video telephone device that simultaneously transmits a video signal and an audio 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.

Fig. 2 shows a conventional video telephone device with 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, (12) is the line, (11) is the line (12)
(24) is a speech network that separates the received signal sent from the network and the transmitted signal sent to the line, and (24) is a band eluminate filter (hereinafter referred to as B and E) that extracts the voice signal by removing a specific frequency band from the received signal. ,
(abbreviated as F), (41) is a converter that converts the audio signal into two wires and four wires, (42) is a telephone set, and (4) is a telephone set (4
B, E, and F limit the transmission signal from 2) to the necessary band to form a transmission audio signal. (26) is a band pass 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).

(abbreviated as P, F), (40) is videophone, (
40a) is the modem of the videophone (40), (40b) is the image processing unit of the videophone (40), and (6) is the modem (40).
B, P which limits the image signal modulated by 0a) to the necessary band to form a transmission image signal.

F (37) is an amplifier that synthesizes the output audio signals of B, E, F (4) and the output image signals of B, P, F (6).

Next, the operation of the circuit configuration shown in FIG. 2 will be explained. The image signals are B and P having the characteristics shown in Fig. 3(a).
, F (6), (26). Furthermore, the band into which the image signal enters the audio signal is removed by B, E, F (4), (24) having the characteristics shown in FIG. 3(b). In this way, the image signal and the audio signal whose frequency bands are divided through the filter can be communicated simultaneously by frequency division multiplexing, and simultaneous voice and image communication 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).
), B, P,
Band-limited by F (6) and amplifier for synthesis (37)
is input. At the same time, the transmitting signal from the telephone (42) is converted into 2-wire and 4-wire by the converter (41).
E, F (4) band-limits the signal and inputs it to the other input side of the amplifier (37). At this time, the amplifier (37
As mentioned above, the image signal and audio signal input to ) are B, P,
By using F(6) and B, E, F(4), it is possible to divide the bands so that they do not overlap, as shown in FIG. For this reason,
Image signals and audio signals can be transmitted simultaneously without interfering with each other.

The output of the amplifier (37) shown in FIG.
2) is output. Also on this line (12), since the image signal and the audio signal are band-divided, the signals do not interfere with each other.

Next, on the receiving side, the received signal sent from the line (12) passes through the speech network (11),
P, F (26) removes out-of-band components that are interfering components, and extracts the image signal. This image signal is reproduced by the receiving section of the modem (40a) of the video telephone (40), and is expressed as an image and received by the image processing section (40b). At the same time, the received signals passing through the speech network (11) 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) and sent to the telephone (42).
) will be accepted. 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.

[Problem to be Solved by Invention C] However, in the conventional video telephone device that allows simultaneous voice and image communication, when the image signal is gray, the image signal level is extremely reduced with the current means. There is a problem in that the audio signal interferes with the image signal in relation to the signal level.

In this way, when the image signal level decreases relatively compared to the audio signal level, the conventional simple method, P,
Interference cannot be prevented simply by dividing the band by F, B, E, or F. 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, with a high-order filter with improved attenuation characteristics, B
, P, F and B.

If E and F are configured, there is a problem that the filter price becomes high and the overall cost increases.

This invention was made with the aim of solving the above-mentioned problems, and even when the image signal level is extremely low, such as when the image signal is gray, the audio signal transmitted at the same time can be In addition to preventing interference caused by B, P, F, B,
It is an object of the present invention to provide a video telephone device for simultaneous voice and image communication, which can reduce costs by configuring E and F with inexpensive filters.

[Means for Solving the Problems] In the video telephone device for simultaneous audio and video communication according to the present invention, on the transmitting side, first, a first detector detects the level of the image signal to be transmitted, and a first comparator detects the level of the image signal. When it is detected that the detected image signal level is lower than a specified level, the attenuator lowers the audio signal level transmitted simultaneously with the image signal by a specified level amount and transmits the lowered level.

Next, on the receiving side, the second detector detects the received image signal level, and when the second comparator detects that the detected image signal level is lower than the specified level, the amplifier At the same time, the transmitted audio signal level is increased by a specified level amount and returned to the original audio signal level.

[Function] In the audio/video simultaneous video telephone device according to the present invention, when the level of the image signal transmitted simultaneously with the audio signal is lower than a specified level, the audio signal level is lowered and transmitted. Then, on the receiving side, the audio signal level is increased by the same amount as the audio signal level decreased on the transmitting side to restore the original audio signal level.

In this way, by controlling the audio signal level depending on the image signal level, it is possible to reduce the relative signal level difference between the image signal and audio signal being transmitted. Interference to the image signal can be removed.

[Embodiment] Hereinafter, a preferred embodiment of the simultaneous audio/video call type videophone device according to the present invention will be described based on the drawings.

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

In Fig. 1, (1) is the microphone of the receiver, (2) is an amplifier that amplifies the audio signal from the microphone (1), and (3) is a first amplifier that attenuates the audio signal amplitude by a specified amount according to the output of the first comparator. Attenuator (4) removes the image signal band from the audio signal of the microphone (1) to prevent interference to the image signal carrier. B, E, F, (5) removes the image signal band from the audio signal of the microphone (1).
A transmitter 40a) generates a carrier modulated with an image signal. (6) are B, P, and F for passing only the modulation component of the image signal carrier; (7) is a mixer for combining the audio signal and the image signal carrier;
8) is the first detector that detects the amplitude of the envelope of the image signal carrier, (9) is the reference voltage source, and (10) is the reference voltage (E r) generated by the reference voltage source (9) and the voltage of the image signal carrier. The first comparator (11), which compares the voltage of the envelope, is a speech network that combines the transmitted and received signals with the line, and has the function of a telephone. (12) is a line for transmitting image signals and audio signals.

On the receiving side (21) is the speaker of the receiver, (22) is an amplifier that amplifies the audio signal from the line, (23) is an amplifier that increases the audio signal amplitude by a specified amount by the output of the second comparator, (24) B, E, F, (25
) is the receiving section of the modem (40a) that demodulates the modulated image signal carrier into an image signal, and (26) is the line (12).
B, E, and F (27) are dividers that divide the received signal from the line (12) into an audio signal side and an image signal side. (
28) - is a second detector for detecting the amplitude of the image signal carrier amplitude-controlled in the receiving section of the modem (40a);
9) is a reference voltage source that generates a reference voltage (Er), (3)
0) is the reference voltage (Er-) of the reference voltage g(29) and the second
This is a second comparator that compares the output voltage with the wave detector (28). (40) is a videophone; (40a) is a modem that modulates and demodulates the image signal of the videophone; and (40b) is an image processing section of the videophone that displays or generates the image signal.

The operation of the simultaneous voice/video call type videophone apparatus of this embodiment having the above configuration will be described next.

First, the image signal generated in the image processing section (40b) of the videophone (40) is sent to the transmitting section (5) of the modem (40a) with an amplitude phase that corresponds the gradation of the pixel of the image to the amplitude and phase of the carrier. Performs modulation and converts it into an image signal carrier. Then, this image signal carrier is transferred to B, P,
F (6) to allow only the modulation component to pass. The audio signals generated by the microphone (1) at the same time as this image signal are shown in B and E.

F(4) to remove the frequency component band in which the modulation component of the image signal carrier is distributed, and pass the other bands. In this way, B, P, F(6) and B,
The image signal and the audio signal band-limited in E and F (4) are combined by a mixer (7) and transmitted via a speech network (11) on a line (12).

At this time, if there is a pixel corresponding to a gray pixel in the image, the amplitude of the image signal carrier of that pixel becomes close to zero, and the signal level drops significantly. In such cases, conventionally, B
, E, F Even if the audio signal has been sufficiently attenuated in (4) to sufficiently attenuate the band component in which the modulation component of the image signal carrier exists, it will still interfere with the image signal whose signal level has been reduced. There was a problem with this.

Therefore, in this embodiment, as shown in FIG.
A first detector (8) detects the amplitude of the envelope of the image signal carrier that has passed through P, F (6). Thereby, the image signal level can be detected.

In addition, the specified level of the first comparator (10) that operates the attenuator (described later) is set to the reference voltage source (9) based on the amplitude voltage (E') of the image signal that is less susceptible to interference from the audio signal. Set the voltage.The reference voltage source (9) that generates this voltage (E') is connected to the first comparator (1
0) and compare it with the amplitude of the envelope of the image signal carrier. If the amplitude voltage of the image signal carrier is smaller than the reference voltage (E'), the image signal may be interfered with by the audio signal, so the amplifier (
The audio signal amplified in step 2) is attenuated by a first attenuator (3) to a specified level that does not interfere with the image signal. As a result, the attenuated audio signal becomes B, E, F (
4), is combined with the image signal carrier in the mixer (7), and is sent to the speech network (11) and the line (1).
2) is transmitted to the receiving side of the other party's videophone device.

On the other hand, the receiving side of the other party's video telephone device has the same configuration as the receiving side shown in FIG. As seen in FIG. 1, on the receiving side, a received signal from a line (12) is received by a speech network (11) and distributed by a distributor (27) into an image signal side and an audio signal side.

Here, the image signal carrier transmits the combined received signal (see FIG. 4) from the line (12) to B and P.

F (26). Furthermore, the audio signal is obtained by passing the received signal through B, E, F (24) and removing only the band in which the modulation component of the image signal carrier exists.

The second detector (28) is a receiving section (of the modem (40a)).
25), the amplitude of the envelope of the image signal carrier whose maximum amplitude is always controlled to a constant value is detected. Thereby, the level of the received image signal can be detected.

Then, the reference voltage source (29) on the receiving side generates a reference voltage (Er-
).

Thereby, the reference voltage (Er=) and the level of the image signal carrier detected by the second detector (28) are compared by the second comparator (30). As a result of this comparison, the level of the image signal carrier is equal to the reference voltage (Er-).
If the attenuation is smaller than that, the amplifier (23) uses the output of the second comparator (30) to amplify the audio signal by the same amount as the amount of attenuation on the transmitting side to restore the original audio signal level.

Therefore, the amplitude relationship between the image signal and the audio signal is the same on the transmitting side and the receiving side. Further, the amplified audio signal is sent to an amplifier (22) that drives a speaker, is amplified to a predetermined level, and is emitted from the speaker (21).

As described above, in this embodiment, when transmitting a low-level image signal, the simultaneously transmitted audio signal level is attenuated and transmitted, and the receiving side restores the original audio signal level to the original audio signal. It is possible to faithfully transmit the image signal and to prevent the image signal from being interfered with by the audio signal.

Therefore, it has become possible to transmit clearer images. Also, B, P, F and B, E.

For F, since the same inexpensive filter as the conventional one can be used as is, an increase in cost can be suppressed.

Note that in the above embodiment, the comparator (10).

Although the voltage to be compared and the attenuation amount of the attenuator were set to one value in (30), the outputs of the detectors (8) and (28) were A/D converted and a digital gain controller corresponding to the attenuator was used. The audio signal level may be appropriately controlled by adding data to the audio signal.

In the above embodiment, an attenuator is provided on the transmitting side and an amplifier is provided on the receiving side, but gain adjusters are provided on both the transmitting side and the receiving side, and the gain adjuster on the transmitting side works as an attenuator. The gain adjuster on the receiving side may also function as an amplifier. Furthermore, since the transmitting side is then switched to the receiving side, the gain adjuster on the transmitting side may be made to work as the gain adjuster on the receiving side.

In addition, in this embodiment, a videophone device that transmits and receives audio and images has been described, but a device that transmits data such as text information using a drawing transmission device, facsimile device, captain system, etc. instead of image information may also be used. The same effect as in the above embodiment can be achieved.

[Effects of the Invention] As explained above, even when transmitting a low-level image signal, the videophone device for simultaneous voice and image communication according to the present invention can suppress the image signal by the simultaneously transmitted audio signal. There will be no more interference. As a result, it is possible to perform suitable simultaneous communication of image signals and audio signals, and since it can be configured with an inexpensive filter, it is possible to reduce costs.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing a conventional example, Figs. 3 (a) and (b) are filter characteristic diagrams, and Fig. 4 is a diagram showing the usage band arrangement of audio signals and image signals. In the figure, (3) is an attenuator, (8) is a first detector,
(10) is the first comparator, (23) is the amplifier, (
28) is a second detector, and (30) is a second comparator. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

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 call type videophone device, the transmitting side of the videophone device includes a first detector that detects the level of the image signal to be transmitted, and a level of the image signal detected by the first detector that is lower than a specified level. a first comparator that detects when the image signal is small; and an attenuator that reduces the audio signal level transmitted simultaneously with the image signal by a specified level based on the detection by the first comparator; a second detector that detects the image signal level detected by the second detector; a second comparator that detects when the image signal level detected by the second detector is lower than a specified level; What is claimed is: 1. A video telephone device for simultaneous audio and video communication, characterized in that it is equipped with an amplifier that increases the level of an audio signal transmitted simultaneously with the image signal by a specified level.