JPH0457587A - Signal transmitter - Google Patents

Abstract

PURPOSE:To transmit an audio signal by using a signal whose frequency is equal to that of a vertical synchronizing signal or a horizontal synchronizing signal of a component video signal as a luminance signal of the component video signal when no component video signal exists. CONSTITUTION:A signal detector 100 detects the presence of a luminance Y signal and when the luminance Y signal exists, a high level Hi is outputted and when no luminance Y signal exists, a low level Lo is outputted, a Y signal 200 is outputted from a switch 101 when an output 201 of a monostable multivibrator is at a high level Hi and a signal 201 inputted from a signal generator 102 is outputted from the switch 101 when the output 201 of the monostable multivibrator is at a low level Lo. A pulse frequency width (PFWM) modulator applies pulse frequency (PFM) modulation to the Y signal included in the output of the switch 101 and applies pulse width modulation to the obtained signal alternately by using color difference signals PR, PB. Moreover, a digital audio signal subjected to time axis compression and an identification signal representing the position are used to apply PFM binary pulse width modulation for part of a horizontal blanking period or vertical blanking period. Thus, even when no Y signal 200 exists, since the reference signal exists, the transmission of the audio signal is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a signal transmission device for transmitting component video signals, audio signals and data signals, especially over a -core optical fiber.

Conventional technology Conventionally, when transmitting a component video signal through a single optical fiber, one transmission method is to pulse frequency modulate (hereinafter referred to as PFM) a luminance signal (hereinafter referred to as Y signal) and generate the PFM signal. There is a method of alternately pulse width modulating (hereinafter referred to as PWM) using two color difference signals and transmitting a component video signal as one pulse train (Japanese Patent Application Nos. 177428/1982 and 13885/1982).

This is a signal transmission method that efficiently transmits one pulse train without greatly expanding the transmission band. Therefore, the device scale is small and low-cost transmission can be performed.

This method (hereinafter referred to as PFWM transmission method) will be briefly explained. In FIG. 10, Y of the component video signal
The signal is converted into a PFM signal 700 in which the pulse width is constant and the pulse interval T varies depending on the signal amplitude of the Y signal.

The Pb and Pr signals are alternately subjected to pulseless width change gllTPB and TPR, respectively, using the rising edge of the PFM signal 700 as a reference.

Furthermore, the time-axis compressed digital audio signal and the identification signal indicating the position of the audio signal are subjected to binary pulse width modulation instead of the color difference signal during the horizontal synchronization period or the vertical synchronization period.

The digital signals "0" and "1" are each subjected to pulse width modulation TO1T1 of 0" and 1" using the rising edge of the PFM signal 700 as a reference, and become a multiplexed signal 701.

In this way, the component video signal, the time-base compressed digital audio signal, and the identification signal indicating the position of the audio signal are transmitted as one pulse train.

Problem to be Solved by the Invention By the way, when audio is transmitted using the above-mentioned PFWM transmission method, the audio signal is transmitted based on the horizontal synchronization signal or vertical synchronization signal of the video signal, so that the component video signal is If there was no reference signal, there would be no reference signal, and the time-base compressed digital audio signal could not be transmitted.

In this case, there is no problem if the audio signal does not need to be transmitted when there is no component video signal, but in practice there is a requirement to transmit the audio signal independently of the video signal, so if there is no component video signal, the audio signal The problem is that it cannot be transmitted.

The present invention has been made in view of this point, and an object of the present invention is to provide a signal transmission device that can transmit audio even when there is no component video signal.

Means for Solving the Problems In order to achieve the above object, the first invention performs pulse frequency modulation on the luminance signal of a component video signal having a luminance signal and two color difference signals, and sequentially modulates the pulse frequency modulated signal as described above. Alternately pulse width modulated with two color difference signals,
A part of the horizontal blanking period or the vertical blanking period of the component video signal is divided into two pulse frequency modulated signals using a time-axis compressed digital audio signal and an identification signal indicating the position of the digital audio signal. A signal transmission device that performs value pulse width modulation to generate one pulse train signal, comprising: a signal generation circuit that generates a signal having a repetition frequency equal to a horizontal synchronization signal or a vertical synchronization signal of the component video signal; a signal detection circuit for detecting; and an output circuit for outputting a signal having a repetition frequency equivalent to a horizontal synchronization signal or a vertical synchronization signal of the component video signal to a modulation section as a luminance signal of the component video signal when there is no component video signal; It is characterized by having the following.

Further, in the second invention, the luminance signal of the component video signal having a luminance signal and two color difference signals is subjected to pulse frequency modulation, and the pulse frequency modulated signal is sequentially and alternately pulse width modulated with the two color difference signals. , during a part of the horizontal blanking period or vertical blanking period of the component video signal, the pulse frequency modulated signal is converted into two signals using a time-axis compressed digital audio signal and an identification signal indicating the position of the digital audio signal. A signal transmission device that performs value pulse width modulation to generate one pulse train signal, comprising: a synchronization signal generation circuit that generates a synchronization signal synchronized with a horizontal synchronization signal or a vertical synchronization signal of a component video signal; It is characterized by comprising a signal detection circuit that detects the presence or absence of a signal, and an output circuit that outputs the synchronization signal as a luminance signal of the component video signal to a modulation section when there is no component video signal.

Further, in the second invention, the signal detector detects the presence or absence of the component video signal, and waits for synchronization establishment time when the component video signal changes from presence to absence or vice versa. The configuration may be such that the output circuit is notified that the signal has changed.

The first invention detects the presence or absence of a component video signal,
If there is no component video signal, by using a signal with the same repetition frequency as the horizontal synchronization signal or vertical synchronization signal of the component video signal as the luminance signal of the component video signal, the time axis can be compressed even when there is no component video signal. Digital audio signals can be transmitted.

The second invention generates a synchronization signal that is synchronized with the horizontal synchronization signal or vertical synchronization signal of the component video signal, detects the presence or absence of the component video signal, and if there is no component video signal, the synchronization signal is transmitted to the luminance of the component video signal. By converting it into a signal, even if the component video signal is suddenly interrupted, the time-axis compressed digital audio signal can be continuously transmitted.

Embodiment FIG. 1 is a diagram showing the overall configuration of a signal transmission device as an embodiment of the present invention. Further, FIG. 4 is a diagram showing waveforms of various parts of the apparatus shown in FIG. 1.

The signal generator 102 generates a Y signal 20 of the component signals.
A signal 203 having the same repetition frequency as the horizontal synchronizing signal of 0 (see FIG. 4(a)) is output. Although the specific configuration of the signal generator 102 is not shown, for example, it includes a pulse generator with the same repetition frequency as the horizontal synchronizing signal of the Y signal, and a differentiation circuit that performs second-order differentiation of the falling waveform of the pulse generated by this generator. It can be configured with a circuit that shapes the waveform of this differential output.

A Y signal 200 of the component video signal is input to a signal detector 100 and a switch 101.

The signal detector 100 detects the "presence/absence" of the Y signal, and outputs a Hi level when the Y signal is "presence" and "absence".

In this case, Lo level is output. As the signal detector 100, for example, a comparator 1000 as shown in FIG.
and a monostable multi-bi break 1001.

Since the comparator 1000 has a threshold level as shown by the dashed line in FIG. 4(a), the luminance signal 2
When 00 is input, a detection pulse synchronized with the synchronization signal is output as shown in FIG. 4(b). Since the multi-by-break has a time constant slightly longer than the repetition frequency of this pulse, when a synchronization signal detection pulse is given from the comparator 1000, it emits a Hi level output, and when the detection pulse is no longer given, it emits a Lo level output. (See Figure 4(c)).

The output 201 of this multi-high break is the switch 10
1 is input.

The switch 101 outputs the Y signal 200 when the multi-high break output 201 is at Hi level, and outputs the signal 201 input from the signal generator 102 when it is at Lo level. FIG. 3 shows an example of the switch 101. A signal is applied to the AND circuit A1, and an output 202 of the signal generator 102 is applied to the AND circuit A2. The former AND circuit A1 opens the gate when the output 201 of the multivibrator 1001 is at Hi level, and the latter AND circuit A1 opens the gate when the output 201 is at the LO level. The outputs from both AND circuits Al and A2 are output to the subsequent stage as an output 203 through an OR circuit OR.

FIG. 4(e) shows the waveform output from the switch 101. As can be understood from this waveform diagram, the output 203 of the switch 101 outputs a signal having the same repetition frequency as the synchronization signal of the component video signal even when the Y signal 200 is "absent". A PFWM modulator 110 is provided after the switch 101.

The PFWM modulator 110 pulse frequency (PFM) modulates the Y signal included in the output of the switch 101, and converts the obtained signal into two color difference signals P.

Pulse width (PWM) modulation is performed alternately by pulse width (PWM) and PR, and furthermore, during a part of the horizontal blanking period or vertical blanking period, the PFM signal is binary-valued using a time-axis compressed digital audio signal and an identification signal indicating its position. Pulse width modulation. PFWM modulator 1
The output waveform of 10 is the same as that shown in FIG.

It should be noted that the configuration of the PFWM modulator 110 is well known and is not shown because it is not directly related to the subject matter of the present invention.

By the way, if the method of transmitting the output 203 of the switch 101 as the Y signal of the component video signal to the PFWM modulator 110 as described above is performed, the time-axis compressed digital audio signal will be Since there is also a reference signal, transmission is possible.

FIG. 5 is a diagram showing another embodiment of the present invention.

Moreover, FIG. 6 is a diagram showing waveforms of each part. Figure 5 is the first
This is not an overall view as shown in the figure, but a view of the main parts.

The output 403 of the switch 101 in FIG.
Provided to the FWM modulator instead of the Y signal.

In FIG. 5, Y signal 40 of the component video signal
0 is input to the signal detector 100, switch 101, and synchronous comparison circuit 300. The synchronization comparison circuit 300 controls the repetition frequency of the synchronization signal generator 301 so that the Y signal 400 of the component video signal and the synchronization signal 402 can be synchronized. Both the synchronization comparison circuit 300 and the synchronization signal generator 301 use, for example, PLL (Phase
(Locked Loop) circuit.

The signal detector 100 detects the "presence" of the Y signal 400, and outputs a Hi level when the Y signal 400 is "present", and outputs a Lo level when it is "absent". The output 401 of the signal detector 100 is input to the switch 10.

The switch 101 causes the output 401 of the signal detector 100 to be set to H.
A Y signal 400 is output when the level is I, and a synchronization signal 402 input from the synchronization signal generator 301 when the level is Lo.
Output. In addition, the signal detector 100 and the switch 101
has the same configuration as that shown in FIG. 1, so a description of the configuration will be omitted.

In this way, the output 403 of the switch 101 always outputs a signal to which a synchronization signal is added, regardless of the presence or absence of the Y signal 400.

Therefore, if a method is used in which the output 403 of the switch 101 is transmitted to the PFWM modulator as the Y signal of the component video signal, the time-axis compressed digital audio signal will always be output from the switch 101 regardless of the presence or absence of the Y signal 400. This means that it is synchronized with 403. Therefore, Y
Regardless of the presence or absence of the signal 400, time-base compressed audio transmission is possible.

Furthermore, if the video signal is suddenly interrupted during transmission of the video signal and the time-axis compressed digital audio signal, the synchronization signal 402 that is synchronized with the video signal is transmitted as the Y signal of the video signal, so Synchronization of axially compressed digital audio signals allows audio signals to be transmitted continuously without distortion.

FIG. 7 is a circuit showing still another embodiment of the present invention,
FIG. 8 is a diagram showing waveforms at various parts in FIG. 7. Except for the operation of the signal detector 500, this embodiment is the same as the second embodiment. The signal detector 500 detects the “presence or absence” of the Y signal and determines whether the Y signal is “
When the state changes from “absent” to “present”, the high level is set after a delay of the synchronization establishment time of the synchronization comparator circuit 3゜O.
When the state changes from "present" to "absent", the Lo level is output with a delay of the synchronization establishment time.The configuration of such a signal detector 500 includes a comparator 510, a first , second multi-by-break 511
, 512 and an OR circuit 513.

Comparator 510 and first multi-high break 511
has the same configuration as the signal detector 100 shown in FIG.

Therefore, the signal detector 500 in FIG. 9 corresponds to a configuration in which the signal detector 100 in FIG. 2 is combined with a second multivibrator 512 and an OR circuit 513.

The time constant of the second multi-by-break 512 defines the synchronization establishment time.

With the above configuration, when the video signal changes from the "absent" state to the "present" state while transmitting the video signal and the time-axis compressed digital audio signal, the video signal and the synchronization signal generator 301 Since the video signal is transmitted after synchronization is established, the synchronization of the time-axis compressed digital audio signal is
Audio signals can be transmitted continuously without being distorted.

Therefore, even if a momentary interruption of the video signal occurs, the time-base compressed digital audio signal can always be transmitted continuously.

In the embodiment, only the horizontal synchronizing signal of the component video signal is described, but it goes without saying that the present invention can also be applied to the vertical synchronizing signal.

As described above in detail, according to the first aspect of the invention, audio can be transmitted even when the component video signal is "absent", which has great practical effects.

Furthermore, according to the second invention, audio can be transmitted regardless of the presence or absence of component video signals. moreover,
Even if there is a sudden interruption of the video signal, the audio signal can be continuously transmitted, which has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of a signal transmission device as an embodiment of the present invention, FIG. 2 is a diagram showing a specific configuration of a signal detector, FIG. 3 is a diagram showing a specific configuration of a switch, and FIG. 4 is a waveform diagram of each part in FIG. 1, FIG. 5 is a block diagram showing another embodiment of the present invention, FIG. 6 is a waveform diagram of each part in FIG. 5, and FIG.
FIG. 8 is a block diagram showing still another embodiment of the present invention.
The figure is a waveform diagram of each part of FIG. 7, FIG. 9 is a diagram showing an example of the configuration of the signal generator of FIG. 7, and FIG. 10 is a waveform diagram for explaining the operation of the conventional signal transmission device. . 100.500...Signal detector, 101...Switch, 102...Signal generator, 300...Synchronization comparison circuit, 301...Synchronization signal generator. Figure 3

Claims (3)

[Claims] (1) Among component video signals having a luminance signal and two color difference signals, the luminance signal is subjected to pulse frequency modulation, and the pulse frequency modulated signal is sequentially and alternately pulse width modulated with the two color difference signals, and the component video signal is Part of the horizontal blanking period or vertical blanking period of the signal is
In a signal transmission device that binary pulse width modulates the pulse frequency modulated signal using a time-axis compressed digital audio signal and an identification signal indicating the position of the digital audio signal to generate one pulse train signal, A signal generation circuit that generates a signal with the same repetition frequency as a horizontal synchronization signal or a vertical synchronization signal, a signal detection circuit that detects the presence or absence of a component video signal, and a signal detection circuit that detects the presence or absence of a component video signal. A signal transmission device comprising: an output circuit that outputs a signal having the same repetition frequency as a vertical synchronization signal to a modulation section as a luminance signal of the component video signal. (2) Among the component video signals having a luminance signal and two color difference signals, the luminance signal is subjected to pulse frequency modulation, and the pulse frequency modulated signal is sequentially and alternately pulse width modulated with the two color difference signals, and the component video A part of the horizontal blanking period or vertical blanking period of the signal is binary pulse width modulated on the pulse frequency modulated signal using a time-base compressed digital audio signal and an identification signal indicating the position of the digital audio signal. A signal transmission device that generates one pulse train signal, comprising: a synchronization signal generation circuit that generates a synchronization signal that is synchronized with a horizontal synchronization signal or a vertical synchronization signal of a component video signal; and a signal that detects the presence or absence of the component video signal. A signal transmission device comprising: a detection circuit; and an output circuit that outputs the synchronization signal as a luminance signal of the component video signal to a modulation section when there is no component video signal. (3) The signal detection circuit detects the presence or absence of the component video signal, and waits for synchronization establishment time when the component video signal changes from presence to absence or from absence to presence, and then changes the component video signal. 3. The signal transmission device according to claim 2, wherein the signal transmission device is configured to notify the output circuit of the fact that the signal has been transmitted.