JPH1051807A - Color signal system discrimination circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate the system of a received color signal with high accuracy in a VTR of the PAL or SECAM system. SOLUTION: An output of an oscillation circuit 12 oscillated at a prescribed frequency is frequency-divided into 1/7 by a frequency divider circuit 13 and a frequency conversion carrier A is generated. Upon the receipt of a low frequency conversion chrominance signal, a frequency converter 14 uses the frequency conversion carrier A to convert it into upper and lower side wave chrominance signals. A BPF 15 extracts a color signal of a lower side wave and outputs a DC voltage proportional to an amplitude of the chrominance signal extracted by a detection circuit 16. A comparator circuit 17 compares an output voltage of the detection circuit 16 with a reference voltage to discriminate the PAL or SECAM system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal type discriminating circuit for discriminating color signal types in VTR recording and reproduction.

[0002]

2. Description of the Related Art A recording / reproducing system of a color signal of a VTR differs depending on a television signal system (broadcasting standard).
In particular, the PAL system and the SECAM system are used in adjacent areas, and a VTR that can support both systems is used. Such a VTR is configured to automatically discriminate signals of the respective systems and record and reproduce a program. Conventionally, when discriminating between the PAL system and the SECAM system, the broadcasting system is identified by using the difference in the modulation system of the carrier chrominance signal.

First, a recording / reproducing method of a color signal in a VTR will be briefly described. In the PAL system, the carrier chrominance signal frequency is 4.434 MHz, and at the time of recording, it is converted to a low-band conversion chrominance signal by a conversion carrier having a frequency of 5.061 MHz.

On the other hand, the color signal of the SECAM system is FM-modulated, and its frequency is 4.25 every one horizontal scanning period.
MHz and 4.406 MHz.

There are two types of VTR SECAM systems. The first method is SECAM which divides a color signal by １ ／.
The second method is a frequency division method, and the second method is an SECA using a conversion carrier having a frequency of 5.061 MHz as in the PAL method.
This is an M frequency conversion method. In any of the methods, a method of converting a color signal into a low frequency is used. However, since the frequency of the input signal and the method of low frequency conversion are different, the low frequency conversion color signal is different in three methods.

[0006] In the case of the PAL system, the frequency of the low-frequency conversion color signal is 627 kHz. In the frequency division method of the SECAM method, the frequency of the low-frequency conversion color signal is 1.063 MHz, which is equal to 1.0.
102 MHz. At the time of frequency conversion of the SECAM system, the frequency is 811 kHz and 655 kHz, and recording is performed at those frequencies. It is well known that at the time of reproduction, the opposite process to any of the methods, that is, the frequency conversion method is frequency-converted by a conversion carrier having the same frequency as recording, while the frequency division method is converted to a reproduced color signal by a multiplication circuit.

A conventional color signal type discriminating circuit for detecting a SECAM signal will be described below. FIG. 12 is a block diagram showing a configuration example of a conventional color signal type determination circuit. In this figure, a color signal type discriminating circuit includes an input terminal 1 for a low-frequency-converted color signal (low-frequency converted color signal), an FM demodulator 2, a detection circuit 3, sample-and-hold circuits (S / H) 4, 5, It comprises a differential amplifier 6, an absolute value circuit 7, and an output terminal 8 for system identification.

The operation of the color signal type discriminating circuit having such a configuration will be described. First, an FM demodulator 2 performs FM demodulation of only a burst portion of a low-frequency conversion color signal input from an input terminal 1. Next, this signal is converted into a voltage proportional to the frequency of the low-frequency conversion color signal by the detection circuit 3 and supplied to the S / H circuits 4 and 5. If fH is the horizontal scanning frequency,
The S / H circuits 4 and 5 operate at a switching frequency of 1/2 fH,
The sample hold is performed alternately for each horizontal scan (line).

Therefore, when a signal of the PAL system is applied to the input terminal 1, the frequency of the low-frequency conversion color signal is 627 kHz on any scanning line, so that the output V1 of the S / H circuit 4 and the S / H The output V2 of the circuit 5 becomes equal. That is, in the S / H circuits 4 and 5, the same voltage corresponding to the frequency of 627 kHz is obtained.

When a signal of the SECAM frequency division system is applied to the input terminal 1, the frequency of the low-frequency conversion chrominance signal changes between 1.063 MHz and 1.102 MHz for each line. Therefore, the output V1 of the S / H circuit 4 and the output V2 of the S / H circuit 5 have different voltages corresponding to the respective frequencies.

When a signal of the SECAM frequency conversion method is given to the input terminal 1, the frequency of the low-frequency conversion color signal changes to 655 kHz and 811 kHz for each line.
The output V1 of the / H circuit 4 and the output V2 of the S / H circuit 5 are equal to S
The voltage becomes different as in the case of the ECAM frequency division method.

In any case, the outputs of the S / H circuits 4 and 5 are converted into a differential voltage by a differential amplifier 6 and input to an absolute value circuit 7. In the case of the SECAM system, the input V1 of the differential amplifier
And V2 are different voltages, so that the output of the differential amplifier 6 is higher in the SECAM system than in the PAL system. When the difference voltage is large, S
The ECAM system is determined, and the determination result is output from the output terminal 8.

[0013]

However, in the color signal type discriminating circuit having the above-described configuration, the number of burst cycles of the low-frequency conversion color signal is as small as two to three wavelengths, so that the FM demodulation sensitivity is low. In particular, in the case of the SECAM frequency division method, since the frequency difference of each line of the low-frequency conversion color signal is as small as about 40 kHz, the sensitivity is further reduced. For this reason, it is difficult to design a color signal type discrimination circuit, and there is a drawback that malfunction (erroneous discrimination) occurs during special reproduction or the like.

The present invention has been made in view of such conventional problems, and has as its object to provide a color signal type discriminating circuit capable of accurately detecting a color signal type.

[0015]

In order to solve such a problem, an invention according to claim 1 of the present application is directed to an oscillation circuit that oscillates at a reference frequency of a color signal included in a television signal, and an oscillation circuit of the oscillation circuit. A frequency dividing circuit for dividing the output signal by 1 / N to generate a frequency-converted carrier signal; and a low-frequency converted color signal being input, and using the frequency-converted carrier signal to color the upper and lower side wave components. A frequency converter for converting a frequency into a signal, a band-pass filter for extracting only a component of a specific frequency band from an output of the frequency converter, and a detection circuit for generating a DC voltage proportional to an output amplitude of the band-pass filter And a comparator for comparing an output voltage of the detection circuit with a reference voltage to determine a television broadcasting system.

In the case of the PAL system, the converted lower side wave component is concentrated on the lower frequency components. Therefore, the pass band of the band-pass filter is reduced by removing the signal components of the PAL system and by SECAM.
It is a frequency that allows the signal of the system to pass. This way SE
Only in the case of the CAM system, a large output can be obtained from the detection circuit.

According to a second aspect of the present invention, there is provided an oscillation circuit which oscillates at a reference frequency of a color signal included in a television signal, and a frequency conversion carrier which divides an output signal of the oscillation circuit by 1 / N. A frequency dividing circuit for generating a signal, a high-pass filter for extracting a high-frequency component of the luminance signal, a waveform shaping circuit for shaping an output of the high-pass filter and generating a gate signal, and a gate of the waveform shaping circuit A gate circuit for extracting a low-frequency component of the low-frequency conversion color signal using the signal, and converting the low-frequency conversion color signal extracted by the gate circuit into an upper-wave component and a lower-wave component using the frequency-converted carrier signal. A frequency converter that converts the frequency into a color signal, a band-pass filter that extracts only a component of a specific frequency band from the output of the frequency converter, and a frequency that is proportional to the output amplitude of the band-pass filter. A detection circuit for generating a flow voltage, compares the output voltage with a reference voltage of the detection circuit, is characterized in that it comprises a comparator for discriminating the television broadcasting system.

By removing the chrominance signal of the portion where the luminance signal changes greatly, the chrominance signal passed through the gate circuit becomes a signal of a relatively narrow band. Also, since the band of the output signal of the frequency converter becomes narrower, PAL by the band-pass filter is used.
Signal components can be more accurately removed. The pass band of the band pass filter is the same as that of the first aspect. This makes it possible to accurately determine the presence or absence of the SECAM signal.

According to a third aspect of the present invention, there is provided an oscillation circuit which oscillates at a reference frequency of a color signal included in a television signal, and a frequency conversion carrier which divides an output signal of the oscillation circuit by 1 / N. A frequency divider for generating a signal, a low-frequency conversion color signal, and a frequency converter for frequency-converting the upper-frequency component and lower-frequency component color signals using the frequency-converted carrier signal; and the frequency converter. Out of the output, a band-pass filter that extracts only a component of a specific frequency band, a detection circuit that generates a DC voltage proportional to the output amplitude of the band-pass filter, and a comparison between the output voltage of the detection circuit and a reference voltage. A comparator for judging a television broadcasting system, a dropout detection circuit for detecting a lack of a reproduced FM signal when reproducing a television signal from a recording medium, When the detection circuit detects the loss of signal, and characterized by comprising a latch circuit for holding an output of said comparator before missing.

An FM signal may be lost due to a transition of a track during special reproduction of a VTR or a scratch on a tape. The signal in this case is noise or no signal. Therefore, according to such a configuration, when a dropout occurs, by holding the previous state in the latch circuit, it is possible to prevent a malfunction without delaying the response. The pass band of the band pass filter is the same as that of the first aspect.

According to a fourth aspect of the present invention, there is provided an oscillation circuit which oscillates at a reference frequency of a color signal included in a television signal, and a frequency conversion carrier which divides an output signal of the oscillation circuit by 1 / N. A frequency dividing circuit for generating a signal, a high-pass filter for extracting a high-frequency component of the luminance signal, a waveform shaping circuit for shaping an output of the high-pass filter and generating a gate signal, and an input low-frequency conversion A frequency converter that frequency-converts a color signal into color signals of an upper wave component and a lower wave component using the frequency conversion carrier signal, and extracts only a component of a specific frequency band from the output of the frequency converter. A band-pass filter, a detection circuit that generates a DC voltage proportional to the output amplitude of the band-pass filter, and comparing the output voltage of the detection circuit with a reference voltage to determine a television broadcast system. A comparator, and a latch circuit for holding an output of the comparator compared with a low-frequency component color signal using a gate signal of the waveform shaping circuit. .

If the frequency band of the color signal is wide, the sensitivity of discrimination decreases. Here, a high-frequency component of the luminance signal is detected, and when the luminance signal has changed, the immediately preceding discrimination result of the comparison circuit is held in the latch circuit, thereby preventing a decrease in detection sensitivity. The pass band of the band pass filter is the same as that of the first aspect.

According to a fifth aspect of the present invention, there is provided an oscillation circuit which oscillates at a reference frequency of a color signal included in a television signal, and a frequency conversion carrier which divides an output signal of the oscillation circuit by 1 / N. A frequency divider for generating a signal, a low-frequency conversion color signal, and a frequency converter for frequency-converting the upper-frequency component and lower-frequency component color signals using the frequency-converted carrier signal; and the frequency converter. A first band-pass filter that extracts only the component of the first frequency band from the output of the first frequency band; and a second band-pass filter that extracts only the component of the second frequency band from the output of the frequency converter. A first detection circuit that generates a DC voltage proportional to the output amplitude of the first band-pass filter; a second detection circuit that generates a DC voltage proportional to the output amplitude of the second band-pass filter; The first Comparing the output voltage and a first reference voltage of the detection circuit, a first comparator for determining the single television broadcast system, the output voltage of the second detection circuit and the second
And a second comparator for comparing the reference voltage with a second reference voltage to determine another television broadcasting system.

Here, the first frequency band of the first band-pass filter is a band higher than the converted lower side wave component of the PAL system and including the converted lower side wave component of the SECAM frequency conversion system. The second frequency band of the second band-pass filter is higher than the converted lower side wave component of the PAL system, and
It is assumed that the band includes the converted lower side wave component of the ECAM dividing method.
In this case, a large output can be obtained from the first detection circuit only in the case of the SECAM frequency conversion method. Further, a large output can be obtained from the second detection circuit only in the case of the SECAM frequency division method. As described above, the PAL method, the SECAM frequency division method, and the SE
Three methods of the CAM frequency conversion method can be determined.

According to a sixth aspect of the present invention, there is provided an oscillation circuit which oscillates at a reference frequency of a color signal included in a television signal, and a frequency conversion carrier which divides an output signal of the oscillation circuit by 1 / N. A frequency divider for generating a signal, a low-frequency conversion color signal, and a frequency converter for frequency-converting the upper-frequency component and lower-frequency component color signals using the frequency-converted carrier signal; and the frequency converter. , A low-pass filter that extracts only components below a specific low frequency, a detection circuit that generates a DC voltage proportional to the output amplitude of the low-pass filter, and two horizontal scans of the output of the detection circuit. Two sample-and-hold circuits that alternately sample and hold each time, a differential amplifier that amplifies the output difference between the two sample-and-hold circuits, and an absolute value of the output of the differential amplifier. It is characterized in that it comprises an absolute value circuit for determining a television broadcasting system based on the calculation result.

Here, the cutoff frequency of the low-pass filter is defined as a frequency between two converted lower side wave frequencies which alternately change every line in the SECAM frequency conversion system. In this way, in the case of the SECAM frequency conversion method, a large output and a small output can be obtained for each line. In the PAL system and the SECAM frequency division system, the output from the absolute value circuit is low. Therefore, the SECAM frequency conversion system can be distinguished from other systems. Here, since the voltage difference for each line is used, it is hardly influenced by variations in the filter, the detection circuit, and the reference voltage, and stable determination can be performed.

According to a seventh aspect of the present invention, there is provided an oscillation circuit which oscillates at a reference frequency of a color signal included in a television signal, and a frequency conversion carrier which divides an output signal of the oscillation circuit by 1 / N. A frequency divider for generating a signal, a low-frequency conversion color signal, and a frequency converter for frequency-converting the upper-frequency component and lower-frequency component color signals using the frequency-converted carrier signal; and the frequency converter. , A band-pass filter that extracts only a component of a specific frequency band, a detection circuit that generates a DC voltage proportional to the output amplitude of the band-pass filter, and an output of the detection circuit that alternates every two horizontal scans. Sample and hold circuits, a differential amplifier for amplifying the output difference between the two sample and hold circuits, and an absolute value of the output of the differential amplifier, and the arithmetic operation Is characterized in that it comprises an absolute value circuit for determining a television broadcasting system based on the result, the.

Here, the band-pass filter sets the pass frequency to a band including any one of the converted lower side wave components of the SECAM frequency conversion method. This way SEC
In the case of the AM frequency conversion method, a large output and a small output are obtained for each line. In the PAL method and the SECAM frequency division method, the output from the absolute value circuit is low. Here, since the voltage difference for each line is used, it is hardly influenced by variations in the filter, the detection circuit, and the reference voltage, and stable determination can be performed.

The invention according to claim 8 of the present application provides a burst gate circuit for extracting only a burst signal of a color signal,
The frequency converter is provided before the frequency converter.

Here, since the color signal is detected only by the burst signal, the band of the color signal can be narrowed, and the removal and extraction of the signal component by the filter can be performed accurately.
The pass band of the band pass filter is the same as that of the first aspect. Therefore, the television broadcasting system can be determined stably and accurately.

In the invention according to claim 9 of the present application, the frequency dividing circuit is characterized in that the frequency dividing ratio 1 / N is 1/7.

In the invention according to claim 10 of the present application, the frequency dividing circuit is characterized in that the frequency dividing ratio 1 / N is 1/8.

Here, the configuration of the frequency dividing circuit can be simplified by setting the frequency dividing ratio of the frequency dividing circuit to 1/8 frequency dividing. The pass band of the band pass filter is the same as that of the first aspect.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A color signal type discriminating circuit according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a basic configuration of a color signal type determination circuit according to the first embodiment. In FIG. 1, the color signal type discrimination circuit includes a low-frequency conversion color signal input terminal 11, a crystal oscillation circuit 12, a 1/7 frequency divider 13, a frequency converter 14,
It is configured to include a band-pass filter (BPF) 15, a detection circuit 16, a comparison circuit 17, and an output terminal 18 for the determination result.

The operation of the thus configured color signal type discriminating circuit of this embodiment will be described. First, the crystal oscillation circuit 1
2 is divided by the frequency dividing circuit 13 into 1/7, and the frequency conversion carrier A of the frequency converter 14 is created. The crystal oscillation circuit 12 is generally used for color signal processing of a VTR, and has an oscillation frequency of 4.4336 MHz used for PAL reproduction, for example. Therefore, the frequency of the frequency conversion carrier A of the frequency converter 14 is 633 kHz.
Becomes Next, the low-frequency conversion color signal input from the input terminal 11 is frequency-converted by the frequency converter 14.

When the frequency of the input signal is f1 and the frequency of the frequency conversion carrier A is f2, the frequency converter 14 has an upper wave component having a frequency of (f1 + f2) and a lower wave component having a frequency of | f1-f2 | Outputs two components of the component.
By increasing the gain of the frequency converter 14, only the frequency component can be extracted without depending on the amplitude of the input signal. The signal whose frequency has been converted in this way is a BPF
15 removes the upper wave component.

In the case of the PAL system, the frequency of the low-frequency converted chrominance signal is 627 kHz, so that the frequency components of the output signal of the frequency converter 14 are lower side wave 6 kHz and upper side wave 1.26.
Converted to 0 MHz.

On the other hand, in the case of the SECAM frequency division method, the frequency components of the output of the frequency converter 14 are a lower side wave of 430 kHz and an upper side wave of 1.696 MHz on a certain line, and a lower side wave of 469 kHz and an upper side wave of 1 on the next line. .735MH
z.

In the case of the SECAM frequency conversion method, a certain line has a lower side wave of 178 kHz and an upper side wave of 1.443 MHz.
In the next line, the lower side wave 22 kHz and the upper side wave 1.
287 MHz.

FIG. 2 shows the relationship between the frequency component of the input low-frequency conversion color signal and the lower side wave component at the output of the frequency converter 14. The upper wave component at the output of the frequency converter 14 is 1.25 M in any case.
Hz or higher, and can be easily removed by the BPF 15, so that the illustration is omitted. As shown in FIG.
In the case of the system, since the lower side wave component is concentrated on the lower frequency component, the pass band of the BPF 15 is set to 100 kHz to 800 kHz.
If it is about z, the signal component of the PAL system is removed, and SE
Only in the case of the CAM system, a large output of the BPF 15 can be obtained.

The output signal of the BPF 15 is converted by the detection circuit 16 into a DC voltage VA proportional to the amplitude. Then, in the comparison circuit 17, the DC voltage VA is changed to the reference voltage Vref.
If it is higher, it is determined to be a SECAM signal. Since the output voltage VA of the detection circuit 16 becomes a high voltage only in the case of the SECAM method, the SECAM signal can be reliably detected by setting the reference voltage Vref to an appropriate value.

A color signal type discriminating circuit according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a block diagram showing a basic configuration of a color signal type discriminating circuit according to the second embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 3, the input terminal 11, the crystal oscillation circuit 12, 1/7
In addition to the frequency divider 13, the frequency converter 14, the BPF 15, the detector 16, the comparator 17, and the output terminal 18, a gate circuit 19, a high-pass filter (HPF) 20, and a waveform shaping circuit 21 are provided.

The operation of the color signal type discriminating circuit having such a configuration will be described. First, the HPF 20 receives a luminance signal and extracts its high frequency component. The high-frequency component of the luminance signal is a portion where the signal changes drastically. Generally, where the luminance signal changes, the color signal often changes. This is well known as the correlation between the luminance signal and the chrominance signal. The high-frequency component of the luminance signal extracted by the HPF 20 is shaped by the waveform shaping circuit 21 to generate a gate signal. This gate signal is used as a control signal in the gate circuit 1
9 is output. Gate circuit 19 via input terminal 11
In the low-frequency conversion color signal input to the luminance signal, a portion where the high-frequency portion of the luminance signal exists is removed.

Although the color signal generally has a band of 500 kHz, the band can be narrowed by removing a changing portion. Therefore, by removing the color signal in a portion where the luminance signal changes greatly from the correlation between the luminance signal and the color signal, the color signal passed through the gate circuit 19 becomes a signal of a relatively narrow band. Also, the band of the output signal of the frequency converter 14 is narrower than that shown in FIG.
The accuracy of separation by the PF 15 is improved. That is, BPF
Since the PAL signal component can be more accurately removed according to No. 15, the presence or absence of the SECAM signal can be accurately performed.

A color signal type discriminating circuit according to the third embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a block diagram showing a basic configuration of a color signal type discriminating circuit according to the third embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 4, an input terminal 11, a crystal oscillation circuit 12, 1/7
In addition to the frequency divider 13, the frequency converter 14, the BPF 15, the detection circuit 16, the comparison circuit 17, and the output terminal 18, a latch circuit 22 and a dropout (DO) detection circuit 23 are provided.

The latch circuit 22 is a circuit for temporarily holding the output of the comparison circuit 17 immediately before the FM signal dropout occurs. The DO detection circuit 23 is a circuit that detects a loss (dropout) of the FM signal. For VTR,
An FM signal may be lost due to a transition of a track during special reproduction or a scratch on a tape. Since the signal in this case is noise or no signal, the color signal type determination circuit cannot operate normally. As a means for solving the problem at the time of dropout, a method of increasing the time constant of the detection circuit 16 to make it a unit of several fields can be considered, but in this case, the response of the color signal type determination circuit becomes slow.

Therefore, when a dropout occurs in the FM signal, by holding the previous state in the latch circuit 22, malfunction can be prevented without delaying the response. The dropout detection circuit 23 is provided with a dropout compensation system (DO) for luminance signal processing in the VTR.
The one generally used as part of C) is used.

A color signal type discriminating circuit according to the fourth embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a block diagram showing a basic configuration of a color signal type discriminating circuit according to the fourth embodiment. The same parts as those in the second embodiment are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 5, an input terminal 11, a crystal oscillation circuit 12, 1/7
In addition to the frequency dividing circuit 13, the frequency converter 14, the BPF 15, the detection circuit 16, and the comparing circuit 17, a latch circuit 22 is provided at the subsequent stage of the comparing circuit 17, and the luminance signal is passed through the HPF 20 and the waveform shaping circuit 21. The output of the comparison circuit 17 is held.

As in the above-described embodiment, a high-frequency component of the luminance signal exists in a portion where the color signal changes largely. If the frequency band of the color signal is wide, the sensitivity of the determination is reduced. Therefore, in the present embodiment, the detection sensitivity is prevented from lowering by detecting the high-frequency component of the luminance signal and, when the luminance signal has changed, retaining the immediately preceding discrimination result of the comparison circuit 17 in the latch circuit 22. Things.

A color signal type discriminating circuit according to a fifth embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a block diagram showing a basic configuration of a color signal type discriminating circuit according to the fifth embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 6, the color signal type determination circuit includes an input terminal 11, a crystal oscillation circuit 12, a 1/7 frequency divider 13, a frequency converter 1
4, in addition to the BPF 15, the detection circuit 16, the comparison circuit 17, and the output terminal 18, another BPF 24 and the detection circuit 2
5, a comparison circuit 26, and an output terminal 27 are provided.

The first BPF 15 is 100 kHz to 300 kHz.
This is a bandpass filter having a pass band at kHz. The second BPF 24 is a band-pass filter having a pass band at 300 kHz to 800 kHz. The first detection circuit 16 is a circuit for obtaining a DC voltage proportional to the output amplitude of the BPF 15. The second detection circuit 25 is a circuit that obtains a DC voltage proportional to the output amplitude of the BPF 24. The comparison circuit 17 is a circuit that compares the output voltage of the detection circuit 16 with the reference voltage Vref1 and outputs a discrimination output 1 from an output terminal 18. The comparison circuit 26 compares the output voltage of the detection circuit 25 with the reference voltage Vref2, and outputs the discrimination output 2 from the output terminal 27.
Is a circuit that outputs.

As shown in FIG. 2, the lower side wave component of the output signal of the frequency converter 14 is 6 kHz and SE in the PAL system.
430kHz and 469kHz in CAM frequency division method, SE
In the CAM frequency conversion method, they are 22 kHz and 178 kHz. Therefore, the signal passes through the BPF 15 and passes through the first detection circuit 16.
Becomes a large voltage only in the SECAM frequency conversion method. The signal VB output from the second detection circuit 25 after passing through the BPF 24 is
The voltage becomes large only in the AM frequency division method. Therefore, the SECAM frequency conversion method is detected from the output terminal 18, and the SECAM frequency division method is detected from the output terminal 27.

Of course, in the case of the PAL system, two B
Since the outputs of the PFs 15 and 24 are small, the detection circuits 16 and 2
5, the output voltages VA and VB do not increase. FIG.
3 shows an example having three types of discrimination ability. In this color signal type discriminating circuit, a NOR circuit 28 is added to that shown in FIG. 6 so that the PAL system can be detected from an output terminal 29 thereof. That is, the output of the comparison circuit 17 is SECAM
Since the output level of the comparison circuit 26 becomes H level in the frequency system and the output of the comparison circuit 26 becomes H level in the SECAM frequency division system, the NOR circuit 28 inverts the logical sum (NO
If R) is taken, a result at the H level in the PAL system is obtained from the output terminal 29. In this way, three types of determination results are obtained.

A color signal type discriminating circuit according to a sixth embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a block diagram showing a basic configuration of a color signal type discriminating circuit according to the sixth embodiment. The same parts as those in the first to fifth embodiments are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 8, the color signal type determination circuit of the sixth embodiment includes an input terminal 11, a crystal oscillation circuit 12, a 1/7 frequency divider 13, a frequency converter 14, a low-pass filter (LP
F) In addition to 35, the detection circuit 16, and the output terminal 18, sample and hold circuits (S / H circuits) 30, 31, a differential amplifier 32, an absolute value circuit 33, and an inverter 34 are provided.

From the frequency components of each system shown in FIG.
If the cut-off frequency of No. 5 is about 100 kHz, P
In the AL system, a high voltage is obtained from the detection circuit 16 and SE
In the CAM frequency division method, a low voltage can be obtained.

In the case of the SECAM frequency conversion method, the frequency for each horizontal scan (line) is 22 kHz and 178 kHz.
Therefore, only the 178 kHz component is attenuated by the LPF 35. Therefore, the output of the detection circuit 16 has a small voltage when the frequency is 178 kHz, and has a high voltage when the frequency is 22 kHz. That is, SECA
In the M frequency conversion method, a high voltage and a low voltage are obtained for each line.

The S / H circuits 30 and 31 operate at a repetition frequency of 1/2 fH (fH is a horizontal scanning frequency).
Sample hold is performed alternately for each line. Therefore, P
In the AL system, the output VC of the S / H circuit 30 is equal to the output VD of the S / H circuit 31. In the case of the SECAM frequency division method, the outputs VC and VD of the S / H circuits 30 and 31 are both small. In the SECAM frequency conversion method, a different voltage is obtained for each line. When the voltage difference between the lines is larger than a predetermined value, the differential amplifier 32 and the absolute value circuit 33 determine the SECAM frequency conversion method, and output the determination result to the output terminal 18.

In the sixth embodiment, since the voltage difference for each line is used, it is hardly influenced by variations in the filter, the detection circuit, and the reference voltage, and stable determination can be made. In the case of a general VTR, the SECAM frequency conversion method is also used for signal processing of the PAL method.
It is often sufficient to be able to determine the M frequency conversion method. When it is necessary to determine the SECAM frequency division method, it can be determined using the other embodiments described above. In the sixth embodiment, a low-pass filter (LPF)
However, a similar discrimination output can be obtained by using a band-pass filter (BPF) for only one of the two frequencies of the SECAM frequency conversion method.

A color signal type discriminating circuit according to a seventh embodiment of the present invention will be described with reference to FIG.
FIG. 9 is a block diagram showing a basic configuration of a color signal type discriminating circuit according to the seventh embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 9, the color signal type determination circuit according to the seventh embodiment includes an input terminal 11, a crystal oscillation circuit 12, a 1/7 frequency divider 13, a frequency converter 14, a BPF 15, a detection circuit 16,
In addition to the comparison circuit 17 and the output terminal 18, the frequency converter 1
4, a burst gate circuit 36 is provided.

The burst gate circuit 36 is a circuit for extracting only a burst signal from the input low-frequency conversion color signal. The frequency converter 14 converts the frequency of the burst signal. The burst signal is a reference signal for the color signal,
In the case of the L system, it becomes a reference for amplitude and phase. Also SECA
In the case of the M system, since it is used as a frequency reference, it can be used as a stable signal in the case of color broadcasting.

Also, since the color signal is subjected to various modulations (for example, phase modulation and amplitude modulation in the PAL system,
The frequency band is about 500 kHz in the SECAM system. Generally, the frequency band is about 500 kHz. However, in the case of a signal including only a burst, the bandwidth is about 200 kHz because a single frequency is output in a burst form. Therefore, by narrowing the bandwidth of the color signal, the band-pass filter (B
The accuracy of separation by PF) is improved. That is, since the PAL signal can be accurately removed, the detection accuracy of the SECAM signal is improved. In this embodiment, the burst gate circuit 3
6 is provided before the frequency converter 14, but the frequency converter 1
4 may be provided at the subsequent stage.

A color signal type discriminating circuit according to the eighth embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a block diagram showing a basic configuration of a color signal type discriminating circuit according to the eighth embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 10, the color signal type determination circuit includes an input terminal 11, a crystal oscillation circuit 12, a 1/8 frequency divider 13A,
It includes a frequency converter 14, a BPF 15, a detection circuit 16, a comparison circuit 17, and an output terminal 18.

In the eighth embodiment, the 1/8 frequency dividing circuit 13
The frequency division ratio of A is set to 1/8, and the conversion carrier A
Is 554 kHz. Therefore, as shown in FIG. 11, the lower side wave component output from the frequency converter 14 is PA PA
73 kHz in the L system, 509 kHz and 548 kHz in the SECAM frequency division system, and 100 kHz and 256 kHz in the SECAM frequency conversion system. B
By setting the pass band of the PF 15 to about 200 kHz to 800 kHz, the same operation as in the first embodiment can be performed. However, in the case of the eighth embodiment, the bandwidth of the BPF 15 must be narrowed as compared with the first embodiment, but since the frequency division ratio of the frequency divider is 1/8, the circuit configuration of the frequency divider is Will be very easy.

[0064]

As described above, according to the first aspect of the present invention, the presence or absence of a signal of the SCAM system can be accurately detected.

According to the second aspect of the present invention, the band of the color signal can be narrowed, the signal component can be accurately extracted by the band-pass filter, and the discrimination of the system can be stabilized.

According to the third aspect of the present invention, the reproduction F
When a loss occurs in the M signal, by holding the output before the loss occurs in the latch circuit, it is possible to prevent noise or malfunction in a no-signal state.

According to the fourth aspect of the present invention, the output immediately before the change of the luminance signal is held in the latch circuit, thereby ignoring the discrimination result of the portion where the color signal fluctuates greatly, and stabilizing the broadcasting system. Can be identified.

According to the fifth aspect of the present invention, by providing two sets of the band-pass filter, the detection circuit, and the comparator, it is possible to determine which of the PAL system, the SECAM frequency division system, and the SECAM frequency conversion system. it can.

According to the sixth and seventh aspects of the present invention, the output of the detection circuit is sampled and held for every two horizontal scanning lines, and discrimination is made based on the difference between the two sampled values, whereby the phase of the color signal is obtained. And the SECAM frequency conversion method can be identified without being affected by the variation of the reference voltage.

According to the eighth aspect of the present invention, since the color signal is detected only by the burst signal, the band of the color signal can be narrowed, and the signal component can be accurately extracted by the filter.

According to the tenth aspect of the present invention, by setting the frequency dividing ratio to 1/8, the configuration of the frequency dividing circuit can be simplified.

In any case, according to the present invention, particularly when a television cassette broadcast program is recorded on one tape cassette, the program is immediately identified when the program is reproduced by the VTR, A good reproduction state can be entered.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a color signal type determination circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation principle of the first embodiment,
FIG. 7 is a frequency characteristic diagram of a low-frequency conversion color signal in the system, the SECAM frequency conversion system, and the SECAM frequency division system.

FIG. 3 is a block diagram illustrating a configuration of a color signal type determination circuit according to a second embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a color signal type determination circuit according to a third embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a color signal type determination circuit according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration of a color signal type determination circuit according to a fifth embodiment (part 1) of the present invention.

FIG. 7 is a block diagram illustrating a configuration of a color signal type determination circuit according to a fifth embodiment (part 2).

FIG. 8 is a block diagram illustrating a configuration of a color signal type determination circuit according to a sixth embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration of a color signal type determination circuit according to a seventh embodiment of the present invention.

FIG. 10 is a block diagram illustrating a configuration of a color signal type determination circuit according to an eighth embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating an operation of a color signal type determination circuit according to an eighth embodiment.

FIG. 12 is a block diagram illustrating a configuration example of a conventional color signal type determination circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Input terminal 12 Crystal oscillator 13, 13A frequency divider 14 Frequency converter 15, 24 Band-pass filter (BPF) 16, 25 Detection circuit 17, 26 Comparison circuit 18, 27, 29 Output terminal 19, 35 Gate circuit 20 High Bandpass filter (HPF) 21 Waveform shaping circuit 22 Latch circuit 23 Dropout detection circuit 28 NOR circuit 30, 31 Sample hold circuit (S / H circuit) 32 Differential amplifier 33 Absolute value circuit 34 Inverter 35 Low-pass filter (LPF) ) 36 Burst Gate

Claims (10)

[Claims] An oscillation circuit that oscillates at a reference frequency of a color signal included in a television signal; a frequency divider circuit that divides an output signal of the oscillation circuit by 1 / N to generate a frequency-converted carrier signal; A frequency converter that receives a low-frequency conversion color signal and converts the frequency into a color signal of an upper-side component and a lower-side component using the frequency-converted carrier signal, and a specific frequency band among the outputs of the frequency converter. A band-pass filter that extracts only the components of the above, a detection circuit that generates a DC voltage proportional to the output amplitude of the band-pass filter, and compares the output voltage of the detection circuit with a reference voltage to determine a television broadcast system. And a comparator. 2. An oscillation circuit that oscillates at a reference frequency of a color signal included in a television signal; a frequency divider that divides an output signal of the oscillation circuit by 1 / N to generate a frequency-converted carrier signal; A high-pass filter that extracts a high-frequency component of the luminance signal; a waveform shaping circuit that shapes an output of the high-pass filter to generate a gate signal; and a low-frequency conversion color signal using the gate signal of the waveform shaping circuit. A gate circuit for extracting a low-frequency component of the frequency conversion; and A band-pass filter that extracts only a component of a specific frequency band from the output of the frequency converter; and a detection circuit that generates a DC voltage proportional to the output amplitude of the band-pass filter. Compares the output voltage with a reference voltage of the detector circuit, a color signal system discrimination circuit characterized by comprising a comparator for discriminating the television broadcasting system. 3. An oscillation circuit that oscillates at a reference frequency of a color signal included in a television signal, a frequency divider that divides an output signal of the oscillation circuit by 1 / N to generate a frequency-converted carrier signal, A frequency converter that receives a low-frequency conversion color signal and converts the frequency into a color signal of an upper-side component and a lower-side component using the frequency-converted carrier signal, and a specific frequency band among the outputs of the frequency converter. A band-pass filter that extracts only the components of the above, a detection circuit that generates a DC voltage proportional to the output amplitude of the band-pass filter, and compares the output voltage of the detection circuit with a reference voltage to determine a television broadcast system. When a television signal is reproduced from the recording medium, the reproduction F
A dropout detection circuit for detecting a loss of the M signal; and a latch circuit for holding an output of the comparator before the loss when the dropout detection circuit detects a loss of the signal. Color signal type determination circuit. 4. An oscillation circuit that oscillates at a reference frequency of a color signal included in a television signal, a frequency divider circuit that divides an output signal of the oscillation circuit by 1 / N to generate a frequency-converted carrier signal, A high-pass filter that extracts a high-frequency component of the luminance signal; a waveform shaping circuit that shapes an output of the high-pass filter to generate a gate signal; A frequency converter that performs frequency conversion into color signals of an upper wave component and a lower wave component using: a band-pass filter that extracts only a component of a specific frequency band from an output of the frequency converter; and the band-pass filter. A detection circuit that generates a DC voltage proportional to the output amplitude of the detection circuit; a comparator that compares an output voltage of the detection circuit with a reference voltage to determine a television broadcast system; and the waveform shaping circuit. Using the gate signal, the color signal system discrimination circuit characterized by comprising a latch circuit for holding an output of the comparator is compared against the low-frequency component color signals. 5. An oscillation circuit that oscillates at a reference frequency of a color signal included in a television signal, a frequency divider circuit that divides an output signal of the oscillation circuit by 1 / N to generate a frequency-converted carrier signal, A frequency converter for inputting a low-frequency conversion color signal and frequency-converting the upper-frequency component and lower-color component color signals using the frequency-converted carrier signal; and a first frequency output from the frequency converter. A first band-pass filter that extracts only a band component; a second band-pass filter that extracts only a second frequency band component from the output of the frequency converter; and an output of the first band-pass filter. A first detection circuit for generating a DC voltage proportional to the amplitude, a second detection circuit for generating a DC voltage proportional to the output amplitude of the second band-pass filter, and an output voltage of the first detection circuit And the first A first comparator for comparing with a reference voltage to determine one television broadcasting system; and comparing an output voltage of the second detection circuit with a second reference voltage to determine another television broadcasting system. A second comparator for determining the color signal type. 6. An oscillation circuit that oscillates at a reference frequency of a color signal included in a television signal, a frequency divider that divides an output signal of the oscillation circuit by 1 / N to generate a frequency-converted carrier signal, A frequency converter that receives a low-frequency conversion color signal and converts the frequency into a color signal of an upper-side component and a lower-side component using the frequency-converted carrier signal, and a specific low-frequency output from the frequency converter. A low-pass filter that extracts only the following components; a detection circuit that generates a DC voltage proportional to the output amplitude of the low-pass filter; and two samples that alternately sample and hold the output of the detection circuit every two horizontal scans. A sample-and-hold circuit, a differential amplifier for amplifying an output difference between the two sample-and-hold circuits, an absolute value of an output of the differential amplifier, and a television set based on the operation result. Color signal system discrimination circuit characterized by comprising an absolute value circuit for determining the emission broadcast system, the. 7. An oscillation circuit that oscillates at a reference frequency of a color signal included in a television signal, a frequency divider that divides an output signal of the oscillation circuit by 1 / N to generate a frequency-converted carrier signal, A frequency converter that receives a low-frequency conversion color signal and converts the frequency into a color signal of an upper-side component and a lower-side component using the frequency-converted carrier signal, and a specific frequency band among the outputs of the frequency converter. A band-pass filter that extracts only the component of the band-pass filter; a detection circuit that generates a DC voltage proportional to the output amplitude of the band-pass filter; and two sample-hold circuits that alternately sample and hold the output of the detection circuit every two horizontal scans A differential amplifier for amplifying the difference between the outputs of the two sample and hold circuits; and a television for calculating the absolute value of the output of the differential amplifier, based on the calculation result. Color signal system discrimination circuit characterized by comprising an absolute value circuit for determining a transmission scheme, the. 8. The apparatus according to claim 1, wherein a burst gate circuit for extracting only a burst signal of a color signal is provided in a preceding stage of the frequency converter. The color signal type determination circuit described in the item. 9. The dividing circuit according to claim 1, wherein a dividing ratio 1 / N is 1/7.
9. The color signal type discrimination circuit according to claim 1, wherein: 10. The frequency dividing circuit has a frequency dividing ratio 1 / N of 1 / N.
9. The color signal type discriminating circuit according to claim 1, wherein the color signal type is eight.