JPH066775A - Voice signal transmission system - Google Patents

Abstract

PURPOSE:To make the voice signal transmission system economical by reducing the burden of construction work and maintenance check by superimposing a voice signal in the vertical blanking period of a video signal and transmitting both video and voice signals with one transmission line. CONSTITUTION:The voice signal is time-axis compressed and transmitted by super-posed to the video signal. For example, the voice signal is converted into a digital signal by an A/D converter 2 using sampling frequency 30kHz and the voice signal is converted into the digital signal of 30KB. The video signal is made the signal of 60 fields per second like the normal TV signal and the voice signal of 30KBdivided by 60=500B per field is to send. Thus, 500 samples of voice signals are transmitted in the 1H period of the horizontal scanning line per field. Further, the writing is performed with clock signals of memories 3-30kHz. For the clock signals for reading, the frequency of 4fsc (burst signal as four times as 3.58MHz) is used to read. Thus, the circuits shown in the illustration are provided on both transmission and reception sides.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for time-axis-compressing an audio signal, superimposing it on a video signal, and transmitting it, and a demodulator for time-axis-expanding and demodulating a transmitted time-axis-compressed audio signal. In particular, it is suitable for use as a surveillance system having a plurality of surveillance locations.

[0002]

2. Description of the Related Art In a conventional monitoring system, one bus line can transmit only video signals from one video camera. Therefore, in order to transmit the video signal and the audio signal, a dedicated transmission line is provided for each, and the monitoring place and the monitoring center are connected to monitor the condition of the monitoring place.

[0003]

In the conventional method, two cables are required to transmit a video signal and an audio signal from one monitoring place, and when the number of monitoring places is increased, the monitoring is required. Along with the increase in the number of places, the number of connecting cables also increased, which required a lot of cost for installation work and maintenance and inspection. According to the present invention, the transmitting side is provided with means for transmitting the audio signal by time-axis compression and superimposing it on the video signal, and transmitting the audio signal by superimposing the audio signal on the video signal. By extending the time axis of the audio signal and demodulating it, it is possible to transmit the video signal and audio signal from one monitoring place with one cable, which saves the trouble of installation work and maintenance inspection. An object is to provide an economical audio signal transmission system.

[0004]

FIG. 1 is a block diagram of an electric circuit on the transmitting side of an audio signal transmission system showing an embodiment of the present invention. As shown in FIG. An A / D converter 2 for converting an input into a digital signal and outputting the digital signal; a memory 3 for compressing the digital signal on a time axis;
A / which converts video signal input to digital signal and outputs
A D converter 6, a switch circuit 7 that switches between the input from the memory 3 and the input from the A / D converter 6 and outputs the converted signal, and the output from the switch circuit 7 is converted into an analog signal and output. D / A converter 8 and the A / D converter 2
And 6 to supply a sampling clock signal, a writing / reading clock signal to / from the memory 3, and a synchronization / command discriminating unit 4 for outputting a switching control signal of the switch circuit 7 to a video signal. The audio signal is time-axis compressed and superimposed during the vertical blanking period of
Video and audio signals are transmitted.

FIG. 2 is a block diagram of an electric circuit on the receiving side of a voice signal transmission system showing an embodiment of the present invention. As shown in the figure, the receiving side digital signals the transmitted signals. A / D converter 11 for converting into a digital signal and outputting the same, and a memory 1 for expanding the audio signal in the digital signal on the time axis
2, a D / A converter 13 that converts an input from the memory 12 into an analog signal and outputs the analog signal, and the A / D converter 11
The sampling / clock signal is supplied to the memory 12 and the synchronization / command controller 15 which supplies the clock signal for writing / reading to / from the memory 12 is used to expand the audio signal on the time axis and reproduce it. Furthermore, a command signal is generated and transmitted according to an operation signal input by the synchronization / command control unit 15 on the receiving side, and the command signal is input to the synchronization / command determining unit 4 on the transmitting side,
According to the control signal output from the synchronization / command discrimination unit 4 in response to the command signal, the audio signal can be superimposed on the memory 3 at a predetermined position in the vertical blanking period.

[0006]

According to the present invention, the audio signal is time-axis-compressed and superposed on the video signal and transmitted by the above-mentioned configuration. For example, the audio signal, sampling frequency 30KHz
If the A / D converter 2 is used to convert into a digital signal, the voice signal becomes a 30 KB (kilobyte) digital signal. If a 60-field signal for 1 second is used as a video signal as in the case of an ordinary television signal, it is sufficient to transmit an audio signal of 30 KB ÷ 60 = 500 B (bytes) per field, and a horizontal scanning line of each field can be transmitted. The audio signal of 500 samples is transmitted in the period of 1H, and the frequency of 4fsc (burst signal, about 4 times of 3.58MHz) is used as the clock signal for writing and reading to the memory 3 by using the clock signal of 30KHz. The audio signal is time-axis-compressed and output from the memory 3 by using the.

FIG. 3 is an explanatory diagram of the position of the audio signal superimposed on the video signal. The synchronization / command determination unit 4 is provided with a counter that uses the vertical synchronization signal as a reset signal and the horizontal synchronization signal as a clock signal, and the counter detects the scan line of the scanning line according to the command signal input to the synchronization / command determination unit 4. By identifying a predetermined position, outputting a control signal, and switching the switch circuit 7 so that the input from the memory 3 is output, the audio signal is superimposed immediately after the burst signal of the horizontal scanning line. Therefore, it is possible to output the video signal and the audio signal with one cable by compressing and superimposing the audio signal on the video signal on the time axis.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an electric circuit on the transmission side of a voice signal transmission system showing an embodiment of the present invention. Reference numeral 1 is an audio signal input terminal, and 5 is a video signal input terminal. For example, at the same monitoring location, a video signal picked up by a video camera is input through the input terminal 5, and a sound collected by a microphone is collected. It is assumed that a signal is input via the input terminal 1. Two
Is an A / D converter, which converts a voice signal input into a digital signal by a 30 KHz clock signal input from the synchronization / command discrimination unit 4, outputs the digital signal, and inputs the digital signal into the memory 3. A FIFO (first-in first-out) type memory is used as the memory 3, and the digital signal from the A / D converter 2 is written by the clock signal input from the synchronization / command determination unit 4 and read in order. The audio signal is time-axis-compressed by using 30 KHz as a write clock signal and a frequency of 4 fsc as a read clock signal and input to one of the input terminals of the switch circuit 7.

A video signal input through the input terminal 5 is branched and one of the video signals is input to the synchronization / command determination unit 4, and the synchronization / command determination unit 4 outputs a horizontal synchronization signal or a burst signal in the video signal. To match the timing and phase of the generated clock signal,
The other branched one is input to the A / D converter 6, and the A / D
4fsc input from the synchronization / command discrimination unit 4 in the converter 6
It is converted into a digital signal by a clock signal having a frequency of, and is output to the other input terminal of the switch circuit 7. A control signal from the synchronization / command discrimination unit 4 is input to the control terminal of the switch circuit 7, and normally the A / D
The video signal input from the converter 6 is output, the switch circuit 7 is switched at a predetermined position in the vertical blanking period of the video signal, and the audio signal input from the memory 3 is output. From 7, a video signal on which the audio signal is superimposed is output. The output is converted into an analog signal by the D / A converter 8 and sent to the transmission line via the input / output terminal 9.

FIG. 2 is a block diagram of an electric circuit on the receiving side of the audio signal transmission system, showing an embodiment of the present invention. 14
Is an input / output terminal, and the video signal on which the audio signal transmitted through the transmission line is superimposed is input,
The same input is branched and one of them is input to the synchronization / command control unit 15, and the synchronization / command control unit 15 detects the horizontal synchronization signal or the burst signal in the video signal and determines the timing and phase of the clock signal to be generated. To match and input the other branched into the A / D converter 11,
4f from the sync / command controller 15 in the A / D converter 11
It is converted into a digital signal by the clock signal of the frequency of sc and output, and the output is branched so that one is input to the video signal processing circuit to reproduce the video signal, and the other is input to the memory 12. The memory 12 has a FIFO (fir
st-in first-out) type memory, A / D converter 1
Only the audio signal which is time-axis-compressed and superposed on the digital signal from 1 is extracted and written with the clock signal of the frequency of 4 fsc input from the synchronization / command control unit 15, and similarly the synchronization / command control unit is also written. A 30 KHz clock signal input from 15 is read and output in the order written, and the audio signal is time-axis compressed by the memory 3 on the transmission side to be expanded and restored, and input to the D / A converter 13. is doing. The restored audio signal is converted into an analog signal by the D / A converter 13, output through the output terminal 16, and an audio signal is reproduced by an amplifier or the like based on the output.

Further, the synchronization / command control unit 1 on the receiving side
An analog command signal is generated according to the operation signal input at 5 and transmitted to the transmitting side via the input / output terminal 14, and as shown in FIG. 1, on the transmitting side, via the input / output terminal 9 The transmitted analog command signal is input to the A / D converter 10, converted into a digital signal so that the A / D converter 10 can input the same to the synchronization / command determination unit 4, and then the synchronization / command determination unit 4 is input. Input the command signal,
In response to a control signal from the synchronization / command discrimination unit 4, a voice signal is superimposed and output at a predetermined position in the vertical blanking period in the memory 3, for example, at position 11 of the horizontal scanning line as shown in FIG. I am able to do it. In FIG. 3, two horizontal scanning lines for superimposing the audio signal are used, and one is L
A stereo signal may be transmitted by superimposing the ch audio signal and superimposing the Rch audio signal on the other. In this case, on the transmitting side, Lch and Rc
An A / D converter and a memory are respectively provided for the audio signal of h, and the output of each memory is switched by the switch circuit 7 to be output, whereby the audio signal is compressed on the time axis and in the vertical blanking period. The Lch and Rch audio signals are superimposed and output at a predetermined position, and on the receiving side, after the A / D converter 11, a memory for expanding the Lch and Rch audio signals by time axis expansion and restoring is provided, respectively. The outputs from the memory may be output via the D / A converters and reproduced.

[0012]

As described above, according to the present invention,
It is possible to superimpose an audio signal in the vertical blanking period of the video signal and to transmit the video signal and the audio signal through one transmission path. It is adopted in a surveillance system, etc. If you use a cable to transmit, you can save time and effort for installation work and maintenance,
An audio signal transmission system can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of an electric circuit on a transmitting side of an audio signal transmission system, showing an embodiment of the present invention.

FIG. 2 is a block diagram of an electric circuit on the receiving side of the audio signal transmission system, showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram of positions of audio signals to be superimposed on video signals.

[Explanation of symbols]

 1 Input Terminal 2 A / D Converter 3 Memory 4 Synchronization / Command Discrimination Section 5 Input Terminal 6 A / D Converter 7 Switch Circuit 8 D / A Converter 9 Input / Output Terminal 10 A / D Converter 11 A / D Conversion Device 12 Memory 13 D / A converter 14 Input / output terminal 15 Synchronization / command control unit 16 Output terminal

Claims (3)

[Claims] 1. On the transmitting side, a first A / D converter for converting an audio signal input into a digital signal and outputting the digital signal, a memory for compressing the digital signal on a time axis, and converting a video signal input into a digital signal. A second A / D converter for outputting,
A switch circuit for switching and outputting the input from the memory and the input from the second A / D converter, and a D / circuit for converting the output from the switch circuit into an analog signal and outputting the analog signal.
A converter, the first A / D converter and the second A / D
In addition to supplying a sampling clock signal for the converter, supplying a writing and reading clock signal to the memory, and outputting a switching control signal for the switch circuit, a synchronization / command discrimination unit outputs a vertical video signal. An audio signal transmission method characterized by transmitting a video signal and an audio signal by compressing and superimposing the audio signal on the time axis during the blanking period. 2. On the receiving side, an A / D converter for converting a transmitted signal into a digital signal and outputting the digital signal, a memory for time-axis expanding the voice signal in the digital signal, and an input from the memory D to convert to analog signal and output
A / A converter and a synchronization / command control unit which supplies a sampling clock signal in the A / D converter and a writing / reading clock signal to / from the memory expands the audio signal on the time axis. The audio signal transmission method according to claim 1, wherein the audio signal transmission method is performed by reproducing. 3. A command signal is generated in accordance with an operation signal input by the synchronization / command control unit on the receiving side and transmitted to the transmission side, and the command signal is input to a synchronization / command determining unit on the transmission side. 3. The audio signal is superposed on a predetermined position of the vertical blanking period in the memory by a control signal output from the synchronization / command discrimination unit according to the command signal. Audio signal transmission system.