JP2597026B2 - Audio / video transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to simultaneous transmission of image data and audio signals using a low-speed and narrow-band transmission line such as a general telephone line or a wireless communication line. The present invention relates to a video / audio transmission device suitable for use.

[Prior Art] As a low-speed and narrow-band transmission line, there are, for example, a general telephone line, a wireless communication line, and the like. Hereinafter, a general telephone line will be described as an example.

In recent years, ISDN (Integrated Services Digital Network) lines that have been operated as services are called digital lines,
Since the general telephone line is called an analog line, this name will be used hereinafter.

As a device for transmitting data other than audio signals, for example, still image data by an analog line, a still image transmission device,
Monochrome still picture telephones (videophones) are already known.

In any of these devices, the method of a modem (modem) for converting image data at a low speed and transmitting the image data occupies almost all of the band of 30 to 3400 Hz which is the analog line band. Therefore, it has not been possible to transmit the audio signal by frequency division multiplexing.

FIG. 6 shows a carrier waveform diagram of a commercially available videophone.

In this case, an AM-PM (amplitude / phase modulation) system is adopted as a modem system, and as shown in FIG.
Is assigned to the maximum amplitude of the first phase, “white” is assigned to the maximum amplitude of the second phase, and the halftone between them is assigned to the amplitude equally divided into eight. That is, modulation corresponding to 16 gradations of the luminance signal is performed by a combination of two phases and eight amplitude values.

Here, when the AM-PM method is expressed by a mathematical formula, E AM-PM = A ｛1 + maV (t)｝ cos ｛2πfct + 2πmpV (t) +
θ｝ V (t) = Vcos (2πfmt); modulation signal ma; AM modulation factor mp; PM modulation factor, and the energy distribution of the AM-PM system is spread over the entire band of the analog line.

Therefore, it is impossible to simultaneously put the image data and the audio signal modulated by the modem in the band of 300 to 3400 Hz.

As one method, a method has been considered in which image data and an audio signal are digitally encoded and simultaneously transmitted by time-division multiplexing. However, according to this method, it is possible to avoid a large system and high cost. Absent.

On the other hand, this type of apparatus that handles small-capacity image data, not large-capacity image data, has already been put to practical use.

This is because FSK (Frequency Shift Ke
A system that can transmit handwritten figures and the like even during a call by multiplexing image data converted to a signal, and has been internationally standardized as a telewriting standard. However, FSK has a low baud rate of about 300 bps, which is not suitable for transmitting image data.

[Problems to be Solved by the Invention] In this telewriting standard, image data can be transmitted at the same time during a telephone call. However, FSK has a low baud rate of about 300 bps and has a large capacity such as image data. Not suitable for data transmission.

For example, if the luminance signal is 64 gradations and 256 × 240 dots of still image data, the capacity is 256 × 240 × 8 bits. When transmitting this at 300 bps, 256 × 240 × 8 {300} That is, 1638 seconds divided by 28 minutes, which means that it takes nearly 30 minutes to transmit one image.

On the other hand, as a modulation method, as described above, the AM-PM method,
Alternatively, if a QAM (Quadrature AM) system or the like is used, its frequency components occupy almost all of the frequency band of the analog line, so that simultaneous transmission with an audio signal is impossible.

When transmitting an image and a sound, it is necessary to first perform an operation of capturing a video and then perform an operation of transmitting an image, as in the related art. Therefore, even when a conversation is being performed by transmitting voice, the video capturing operation and the image transmitting operation must be performed as needed, which is very troublesome.

In view of the above, the present invention provides an image and sound transmission apparatus capable of simultaneously transmitting image data and an audio signal, increasing the baud rate of data transmission, and improving transmission operability.

[Means for Solving the Problems] The present invention provides a multi-frequency value modulating means for converting an image signal into an audio area signal, and a component of a used frequency band of the audio band signal from the multi-frequency value modulating means from the audio signal. A band removing filter for removing, a signal combining means for combining a voice band signal from the multi-frequency value modulating means with a voice signal from the band removing filter to obtain a transmission signal, and sending of a transmission start signal for an image and a voice Means, signal separation means for separating an audio signal and an audio band signal carrying image data from the frequency division multiplexed transmission signal transmitted from the transmission side, and converting the audio band signal from the signal separation means into image data. Multi-frequency value demodulation means for conversion, transmission means for a reception ready signal corresponding to the transmission start signal transmitted from the transmission side, and transmission from the reception side. Means for executing a processing operation for transmitting and receiving so that reception and transmission are alternately repeated in response to the reception preparation completion signal.

[Operation] In the above configuration, since the image data is converted into the audio band signal and frequency-division multiplexed to the audio signal and transmitted, the image data and the audio signal can be transmitted simultaneously.

Further, since the image data is converted into the audio band signal by the multi-frequency value modulation, it is possible to increase the baud rate of the data transmission.

Prior to the transmission of the video, the selection switch for automatic transmission and manual transmission is operated to switch to automatic transmission. Then,
On the transmitting side, data representing the transmission start signal is read from the control data storage means and transmitted to the receiving side.

On the receiving side, upon receiving this transmission start signal, the CPU determines whether the receiving side is in a reception ready state when the snooping switch is switched to the automatic transmission mode. Data representing the reception preparation completion signal is read from the control data storage means and transmitted. After receiving this, the CPU takes in the image and then enters the transmission start mode.

Images and sounds captured under such a handshake are simultaneously transmitted, and similarly transmitted images and sounds are received. Transmission and reception are automatically repeated in a predetermined cycle.

Embodiment An embodiment of the present invention will be described below with reference to FIG. This example is an example of transmission using an analog line, and is an example in which image data is frequency division multiplexed in a band of 2000 to 2400 Hz.

In the figure, 100A and 100B are transmission / reception sets as terminal devices connected to an analog line (general telephone line) 200.

 The transmission / reception set 100A is configured as follows.

103 is an image memory. A video signal from the video camera 101 is converted into a digital signal of, for example, 6 bits per sample by the A / D converter 102 and supplied to the image memory 103, and image data for one screen is written.

The image data read from the image memory 103 is D
Monitor TV 1
Supplied to 05.

The image data read from the image memory 103 is sent to a modem 106 constituting a multi-frequency modulation / demodulation unit via a data bus 115. This modem 106 is configured, for example, as shown in FIG.

At the same time, a modulation counter 106a is supplied with 6-bit image data indicating 64 steps (gradations) from the image memory 103 to the counter 106a. The counter 106a counts down from a predetermined value corresponding to the image data. The counter 106a outputs a one-cycle square wave signal having a cycle corresponding to the value (step) of the image data. In other words, the period of the square wave corresponding to each step is given a time difference at equal intervals.

In this case, the cycle corresponding to the first step is 1/2000 Hz,
The cycle corresponding to the 64th step is set to 1/2400 Hz. In other words, the frequency of the square wave in the first step is 20
00Hz, the frequency of the second step square wave is 2005Hz, ...
The frequency of the square wave at the 63rd step is 2393 Hz, and the frequency of the square wave at the 64th step is 2400 Hz (illustrated in FIG. 4A).

Reference numeral 106c denotes a waveform shaping circuit.
An audio band signal supplied from the transmitting side via the analog line 200 is supplied to 106c. This audio band signal
As described later, the above-described square wave signal is a sine wave signal that has passed through a band-pass filter having a pass band of 2000 to 2400 Hz. In the waveform shaping circuit 106c, the original square wave signal is reproduced based on the zero cross point of the sine wave signal.

Then, the square wave signal from the waveform shaping circuit 106c is supplied to a demodulation counter 106b. As described above, the square wave signal has a cycle corresponding to the value (step) of the image data. The counter 106b performs a counting operation in each one cycle period of the square wave signal, and calculates a cycle of each one cycle of the square wave signal from the count value. The counter 106b outputs 6-bit image data having a value corresponding to the cycle. The 6-bit image data is supplied to the image memory 103.

Returning to FIG. 1, the square wave signal output from the counter 106a of the modem 106 is supplied as a voice band signal to a two-wire / four-wire switching unit 108 via a band-pass filter 107 having a pass band of 2000 to 2400 Hz. You. This voice band signal is
It becomes a sine wave signal as shown in FIG.

The audio signal from the handset 109 is supplied to the conversion unit 108 via a band elimination filter 110 for removing a band of 2000 to 2400 Hz.

The conversion unit 108 is configured, for example, as shown in FIG.

In the figure, reference numeral 108a denotes a synthesizing circuit.
At 108a, the audio band signal from the band-pass filter 107 and the band-limited audio signal from the band elimination filter 110 are combined to form a transmission signal. This transmission signal is the fifth
As shown in the drawing, the audio band signal and the audio signal are frequency division multiplexed.

The transmission signal from the combining circuit 108a is transmitted to the hybrid circuit 108b.
The signal is supplied to the analog line 200 via the line transformer 108c.

Further, a transmission signal supplied from the transmission side via the analog line 200 is supplied to buffers 108d and 108e via a line transformer 108c and a hybrid circuit 108b.

Returning to FIG. 1, the transmission signal from the buffer 108d of the conversion unit 108 is supplied to a band-pass filter 107 to extract an audio band signal, and this audio band signal is supplied to a modem 106. Then, as described above, the image data is demodulated by the audio band signal, and this is supplied to the image memory 103 via the data bus 115.

Further, the transmission signal from the buffer 108e of the conversion unit 108 is supplied to a band elimination filter 110 to extract an audio signal, and the audio signal is supplied to a handset 109.

112 is a CPU for controlling the transmission mode. Reference numeral 113 denotes a selection switch for selecting an automatic transmission mode or a manual transmission mode. 114 is control data storage means, which includes data (code signal) indicating a transmission start signal,
Data indicating a reception preparation completion signal is stored. Therefore, the CPU 112, the selection switch 113, and the control data storage unit 114 constitute a transmission start signal transmission unit.

When the manual transmission mode is selected, it is necessary to execute a transmission processing operation similar to the conventional one. Therefore, operation keys (a key for imaging, a key for transmission, etc.) necessary for the transmission mode are provided. Have been. However, it is not shown.

The transmission / reception set 100A is configured as described above,
The transmission / reception set 100B is configured similarly to the transmission / reception set 100A. Therefore, the CPU 11 provided in the transmission / reception set (set 100B as described below) functioning as the reception side
2, the selection switch 113 and the control data storage means 114
It will function as a means for sending a reception preparation completion signal.

In the above configuration, for example, an operation in the case where the transmission / reception set 100A is the transmission side and the transmission / reception set 100b is the reception side will be described. It is assumed that the selection key 113 has been switched to the automatic transmission mode.

Before transmitting the video, first, the transmission key 11
3 is operated. Then, the CPU 112 determines this, and the necessary data, that is, the transmission start signal, is read from the storage means 114, and is supplied to the modem 106 via the data bus 115 and transmitted.

On the receiving side, by receiving the transmission start signal,
The CPU 112 determines the state of the receiving side, and only when the preparation for reception is completed, a `` reception preparation completion signal '' is read from the storage means 114 and sent to the modem 106 via the data bus 115, and Sent.

On the transmission side, the reception of the reception preparation completion signal causes the capture of the image and the transmission and reception of the captured image and sound to be repeated at a predetermined timing. Therefore, when the automatic transmission mode is selected, transmission and reception are alternately repeated in a predetermined cycle. On the other hand, the automatic transmission mode is selected only on the transmission side. When the manual transmission mode is selected on the receiving side, the transmitting side performs only the transmitting operation, and the receiving side performs only the receiving operation.

As described above, after the handshake in the transmission / reception mode is performed, the image capturing processing is performed, and the apparatus enters the transmission mode of the captured image and sound.

Therefore, the video signal from the video camera 101 is converted into a 6-bit digital signal by the A / D converter 102, and then supplied to the image memory 103. The image memory 103 stores one screen, for example, 256 × 240 bits. Minute image data is written.

Then, 6-bit image data of each dot is sequentially read from the image memory 103 and supplied to the modem 106 via the data bus 115. The modem 106 outputs a cycle corresponding to the value (step) of the image data. The one-cycle square wave signal is output.

The square wave signal output from the modem 106 is converted into a sine wave signal in a frequency band of 2000 to 2400 Hz,
Supplied to

The audio signal output from the handset 109 is supplied to the conversion unit 108 after the components in the frequency band of 2000 to 2400 Hz are removed by the band removal filter 110.

Then, the conversion unit 108 performs frequency division multiplexing of the audio band signal and the audio signal to form a transmission signal, and this transmission signal is supplied to the analog line 200 and transmitted and received by the transmission / reception set
Is transmitted to

 Next, the operation of the transmission / reception set 100B will be described.

The transmission signal transmitted from the transmission / reception set 100A via the analog line 200 is supplied to the band elimination filter 110 via the conversion unit 108, and the audio signal extracted by the band elimination filter 110 is supplied to the handset 109, A sound based on the sound signal is output.

In this case, since the audio band signal of 2000 to 2400 Hz is removed by the band elimination filter 110, an unpleasant sound (squeezing sound) due to the audio band signal is not output from the handset 109.

A transmission signal transmitted from the transmission / reception set 100A via the analog line 200 is supplied to a band-pass filter 107 via a conversion unit 108, and a voice band signal extracted by the band-pass filter 107 is supplied to a modem 106. Is done.

Then, the modem 106 demodulates 6-bit image data from the audio band signal. In this case, the bandpass filter 107 removes audio signals outside the frequency band of 2000 to 2400 Hz, so that the modem 106 does not malfunction due to the audio signals.

Then, the 6-bit image data demodulated by the modem 106 is supplied to the image memory 103 via the data bus 115 and written therein.

Then, 6-bit image data of each dot is sequentially read from the image memory 103, converted into an analog signal by the D / A converter 104, and supplied to the monitor television 105,
An image based on the image data is displayed.

As described above, according to this example, since the audio band signal obtained by multi-frequency-modulating the image data and the band-controlled audio signal are frequency-division multiplexed and transmitted, the image data and the audio signal are transmitted simultaneously. Can be.

In addition, according to this example, since the audio band signal is formed by modulating the image data with multi-frequency values, the baud rate of data transmission can be increased, and the image transmission time can be greatly reduced.

That is, the frequency band used for the voice band signal is 2000
The baud rate when using ~ 2400Hz is as follows on average.

Baud rate = 2200 × 6 = 13200 bps Therefore, if the luminance signal is 64 gradations and 256 × 240 dots of still image data, the capacity is 256 × 240 × 8 bits, so the transmission time is 256 × 240 × 8 ÷ 13200 ≒ 37 seconds. That is, one image can be transmitted in about 1/40 of the time required for telewriting using FSK of 300 baud (assuming that the image is transmitted even in the telewriting standard).

In the above-described embodiment, the image data has 6 bits. However, an image data having an arbitrary number of bits can be similarly configured. The frequency band used for the audio band signal is 2000 to 2400 Hz, but the frequency and range are not limited to this.

Further, in the above-described embodiment, two sets of transmission / reception sets are shown. However, those in which more transmission / reception sets are provided can be similarly configured.

Further, in the above-described embodiment, the transmission using an analog line has been described. However, the present invention can be similarly applied to a system for simultaneously transmitting image data and an audio signal using another transmission medium. For example, the present invention can be applied to a system that handles image data and an audio signal, such as an amateur band wireless communication, a transmission period of a home appliance and a remote controller, a security information system using a household power line (100 V), and the like. .

[Effects of the Invention] As described above, according to the present invention, since an audio band signal and an audio signal obtained by modulating image data are frequency-division multiplexed and transmitted, the image data and the audio signal are transmitted simultaneously. Thus, the broadcast of the image and the voice can be secured.

Thereby, it is possible to talk while watching the image.
Also, even if you transmit the image, the story will not be interrupted,
Conventionally, the image transmission by manual operation can be automatically repeated alternately by image transmission-reception-transmission-reception-..., Thereby simplifying the operation.

Also, since the audio band signal is formed by modulating the image data with multi-frequency values, the baud rate in data transmission can be increased, the image transmission time can be greatly reduced, and the waiting time is cumbersome. Can be reduced.

Furthermore, according to the present invention, since an automatic transmission function is added, if this function is used, the image capturing operation and the image transmitting operation are automated, so that the image capturing operation and the image transmitting operation are not required as in the related art. Has the feature that it can be greatly improved

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram of a modem, FIG. 3 is a block diagram of a two-wire / four-wire converter, FIG.
FIG. 5 is an explanatory diagram of multi-frequency value modulation, FIG. 5 is a diagram showing a configuration of a transmission signal, and FIG. 6 is a diagram showing a relationship between gradation and carrier waveform in a conventional videophone. 100A, 100B: Transmission / reception set 101 Video camera 102 A / D converter 103 Image memory 104 D / A converter 105 Monitor TV 106 Modem 107 Bandpass filter 108 ... 2-wire 4-wire conversion unit 109... Handset 110... Band removal filter 112... CPU 113... Selection switch 114.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Inoue 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Takeshi Yanome 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-1-238262 (JP, A) JP-A-1-300689 (JP, A) Payton Z, Peebles, Jr. Written, translated by Nobuo Hirano, "Digital Communication System" 1989, published by HBJ Publishing Bureau, p. 402 to 403

Claims (1)

(57) [Claims] 1. A multi-frequency value modulation means for converting image data into an audio band signal, a band elimination filter for removing a component of a used frequency band of the audio band signal from the multi-frequency value modulation means from the audio signal, A signal synthesizing unit for synthesizing an audio band signal from the multi-frequency value modulation unit and an audio signal from the band elimination filter to obtain a transmission signal; a transmission unit for transmitting a transmission start signal for images and audio; Signal separation means for separating an audio signal and an audio band signal carrying image data from an incoming frequency division multiplexed transmission signal; and a multi-frequency value demodulation means for converting the audio band signal from the signal separation means into image data. Means for transmitting a reception preparation completion signal corresponding to the transmission start signal transmitted from the transmission side, and responding to the reception preparation completion signal transmitted from the reception side. Image and audio transmission apparatus characterized by transmit and receive and a means for performing a processing operation of transmitting and receiving as repeated alternately.