JP2002290989A - Color signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color signal processing circuit, with which copy prevention is operated by surely sensing a signal added with the copy guard signal of a color stripe system in a recording system and a color signal can be normally displayed in monitor output without being affected by the copy guard signal. SOLUTION: When a difference between a second phase angle detected during a second burst gate pulse period and a third phase angle detected during a third burst gate pulse period is smaller than a prescribed value, burst lock operation is performed with the first phase angle detected during the first burst gate pulse period and in the other case, the burst lock operation is stopped or burst lock operation is performed with the second phase angle or third phase angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal processing apparatus for handling a copy guard signal of a macro vision system, particularly a copy guard signal called a color stripe system for a color signal.

[0002]

2. Description of the Related Art As a copy guard signal for protecting the copyright of video software or the like, a system called a so-called pseudo sync pulse and a color stripe by Macrovision, for example, is known.

A method called a pseudo sync pulse will be described with reference to FIG. FIG. 4 is a schematic diagram of a pseudo guard pulse type copy guard signal. A pseudo sync pulse as shown in FIG. 4 is inserted in the vertical blanking period of the video signal. Insertion of the pseudo-sync pulse causes malfunction of an automatic gain control (AGC) circuit in a video recording device, and compresses the amplitude level of the luminance signal to a normal level to make the recording signal unusable. It deteriorates.

On the other hand, a method called a color stripe will be described with reference to FIG. FIG. 5 is a schematic diagram of a copy guard signal of the color stripe system. FIG. 5 (a), FIG.
As shown in FIG. 5B, for the color burst of 4 lines for every 21 lines of the video signal or 2 lines for every 17 lines, the phase of the first half is set to the normal phase as shown in FIG. On the other hand, the phase is reversed. The burst having the opposite phase part is called a split burst. The line to which the split burst is added causes a malfunction of an automatic phase control (APC) circuit in a video recording device, so that the phase cannot be drawn. The screen is distorted in color.

Hereinafter, a conventional color signal processing device will be described.

FIG. 6 is a block diagram showing the configuration of a conventional color signal processing device. In the figure, 1 is a color signal input terminal, 2 is a color signal demodulation circuit, 3 is a low-pass filter, 1
04 is a burst gate pulse generation circuit, 51 is an averaging circuit, 7 is an angle detection circuit, 12 is a subtractor, 13 is a pulse width modulation (PWM) circuit, 14 is a low-pass filter, 15 is a voltage controlled crystal oscillator (VCXO), Reference numeral 116 denotes a color signal recording processing circuit, 17 denotes an output terminal of a recording color signal, 18 denotes a color signal modulation circuit, and 19 denotes an output terminal of a carrier color signal output to a monitor or the like.

The operation of the conventional color signal processing device configured as described above will be described below with reference to FIG. FIG. 7 is a schematic diagram for explaining the operation of the conventional color signal processing device. First, a carrier color signal is input to the color signal input terminal 1. For example, in the case of the NTSC system, about 3.5
A carrier chrominance signal modulated by an 8 MHz subcarrier, and a carrier chrominance signal modulated by an approximately 4.43 MHz subcarrier in the case of the PAL system, are input. The input carrier color signal is demodulated by the color signal demodulation circuit 2 into baseband color difference signals Pr and Pb. The two color difference signals Pr and Pb are multiplexed on the time axis, and Pr and Pb are transmitted alternately at a predetermined clock cycle. The low-pass filter 3 attenuates high-frequency components to extract only the baseband color difference signal from the output of the color signal demodulation circuit 2. The burst gate pulse generation circuit 104 generates a timing pulse indicating the timing of the color burst portion in the color signal as shown in FIG. 7B and supplies it to the averaging circuit 51. The averaging circuit 51 outputs a signal during a period in which the burst gate pulse is active (Hi in the pulse of FIG. 7B).
gh), the respective components of Pr and Pb of the color burst portion are averaged and output to the angle detection circuit 7. The angle detection circuit 7 detects the phase of the color burst portion from the average values of Pr and Pb during the burst gate period. Specifically, assuming that the average values of Pr and Pb during the burst gate period are Mpr and Mpb, respectively, the phase θ1 of the burst portion is θ1
= Atan (Mpr / Mpb). Where A
tan is the arc tangent. In the subtractor 12, θ
The difference between 1 and a predetermined reference burst phase value is obtained and output. This output is a phase error signal between the burst phase of the input color signal and the reference burst phase. In the pulse width modulation (PWM) circuit 13, the value of the phase error signal is pulse width modulated and output to the low-pass filter 14. The low-pass filter 14 passes only the low-frequency component of the output of the pulse width modulation (PWM) circuit 13 and outputs it to the voltage controlled crystal oscillator 15. The voltage controlled crystal oscillator 15 is a low-pass filter 1
The reference clock is generated by controlling the oscillating frequency according to the output level of No. 4. The generated reference clock is multiplied or divided as necessary and used as a processing clock for the digital circuit. Also, a color signal recording processing circuit 1
Reference numeral 16 receives the color difference signals Pr and Pb output from the low-pass filter 3, performs necessary processing when recording a color signal in a recording device, and outputs the processed signal to a recording color signal output terminal 17. For example, V
In the HS video tape recorder, processing such as conversion to a low-frequency conversion color signal of about 630 KHz is performed. The color signal modulation circuit 18 outputs a color difference signal P output from the low-pass filter 3.
r and Pb are modulated into a carrier color signal and a carrier color signal output terminal 19
Output to This output signal is thereafter connected to a TV monitor or the like. In the above configuration, the output of the voltage controlled crystal oscillator 15 is controlled so that the phase error output from the subtractor 12 becomes zero. The above configuration is called automatic phase control (AP
C) A loop is formed, and a clock locked to the color burst phase of the color signal is generated from the voltage controlled crystal oscillator 15.

[0008]

However, in the above-mentioned conventional configuration, when a copy guard signal of the color stripe type is inputted, the phase error detection is disturbed on the line to which the split burst is added, so that the recording color signal is disturbed. In addition to the above, there is a problem in that interference is also caused with respect to the carrier chrominance signal output to be output to the monitor.

The present invention solves the above-mentioned conventional problems. In a recording system, a copy guard signal of a color stripe type is reliably responded to, and copy prevention is performed. In a monitor output, the copy guard signal is used. It is an object of the present invention to provide a color signal processing circuit that can display normally without being affected.

[0010]

In order to achieve this object, a chrominance signal processing apparatus according to the present invention uses a chrominance signal P
r and a color demodulation circuit for demodulating the color difference signal Pb, a low-pass filter for limiting the band of the output of the color demodulation circuit, a first burst gate pulse and a burst period that are active during a roughly burst period of the output of the low-pass filter. A burst gate pulse generating circuit for generating a second burst gate pulse that is active for a predetermined period in the first half of the burst period and a third burst gate pulse that is active for a predetermined period in the second half of the burst period; and an output of the low-pass filter. An averaging circuit for averaging the Pr component and the Pb component for each period of the first burst gate pulse, the second burst gate pulse, and the third burst gate pulse; a Pr component of the output of the averaging circuit; An angle detection circuit that converts a value of the Pb component into a value of a phase angle between the Pr component and the Pb component, If the difference between the second phase angle detected during the second burst gate pulse period and the third phase angle detected during the third burst gate pulse period is equal to or less than a predetermined value, the first burst gate The burst lock operation is performed by the first phase angle detected during the pulse period, and otherwise, the burst lock operation is stopped, or
The burst lock operation is performed by the second phase angle or the third phase angle.

According to this configuration, the recording system reliably responds to the copy guard signal of the color stripe system to prevent the copy, and the monitor signal can be displayed normally without being affected by the copy guard signal. A processing circuit is obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a color demodulation circuit for demodulating a carrier chrominance signal into a color difference signal Pr and a color difference signal Pb, A filter, a first burst gate pulse that is active during an approximate burst period of the output of the low-pass filter, a second burst gate pulse that is active for a predetermined period in the first half of the burst period, and an active period for a predetermined period in the second half of the burst period A burst gate pulse generation circuit for generating a third burst gate pulse, and a first burst gate pulse, a second burst gate pulse, and a third burst pulse for outputting the Pr component and the Pb component of the output of the low-pass filter. An averaging circuit for averaging for each period of the gate pulse, and Pr components and Pb of the output of the averaging circuit. The minutes value and a angle detection circuit for converting the value of the phase angle between the Pr component and Pb component, the second
The second phase angle detected during the burst gate pulse period and the second phase angle detected during the third burst gate pulse period.
If the difference between the three phase angles is equal to or smaller than a predetermined value, the burst lock operation is performed based on the first phase angle detected during the first burst gate pulse period. Otherwise, the burst lock operation is stopped, or , The second phase angle or the third phase angle to perform a burst lock operation, whereby the burst lock operation is performed even for a signal to which a color stripe copy guard signal is added. A normal signal which is not disturbed and therefore is not affected by the monitor output is output. On the other hand, a color stripe is detected by detecting the second and third phase angles for the signal to be recorded. It is possible to determine whether a copy guard signal has been added or not, and if it is determined that a copy guard signal has been added, stop the recording operation. By performing such processing as described above, the copy protection operation can be reliably performed.

According to a second aspect of the present invention, the averaging circuit performs averaging of the first burst gate pulse period, and averaging of the second burst gate pulse period. And a second averaging circuit for multiplexing and averaging the third burst gate pulse period in the time axis direction for processing.
The averaging of the second burst gate pulse period and the averaging during the third burst gate pulse period can be performed on a single averaging circuit separately on the time axis. Have.

According to the third aspect of the present invention,
By multiplexing the color difference signals averaged during the various burst gate periods in the time axis direction, the phase angle of each burst signal is detected by one angle processing detection circuit. This has the effect that it can be configured with a simple circuit with a small circuit scale.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a color signal processing apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes an input terminal of a color signal, and 2 denotes a carrier color signal demodulated into a color difference signal. Demodulation circuit, 3 is a low-pass filter, 4 is a burst gate pulse generation circuit, and 51 and 52 are output color difference signals Pr and Pb of the low-pass filter 3 for the burst gate pulse period output from the burst gate pulse generation circuit 4, respectively. Averaging circuit, and 6 is an averaging circuit 5
A multiplexer that switches and multiplexes the outputs of 1 and 52 in a time-division manner, 7 is an angle detection circuit, 8 is a register that stores the three phase information detected by the angle detection circuit and the output phase information of the switching circuit 11, and 9 is A comparator 10 for comparing the phase information stored in the register 8, a control circuit 10 for controlling the operation of the switching circuit 11 and the color signal recording processing circuit 16 using the comparison result of the comparator 9, and 11 being stored in the register 8 A switching circuit for selecting and outputting four phase information to be output, 12 a subtractor for subtracting a reference burst phase value from an output of the switching circuit 11, 13 a pulse width for pulse width modulation of an APC phase error signal output from the subtractor A modulation (PWM) circuit, 14 is a low-pass filter, 15 is a voltage controlled crystal oscillator, 16 is a color signal recording processing circuit, and 17 is a recording color signal output terminal. , The modulation circuit of the color signal 18, 19
Is an output terminal for the modulated carrier chrominance signal. In the figure, the same components as those of the conventional example are denoted by the same reference numerals, and description thereof is omitted.

The operation of the color signal processing apparatus configured as described above will be described with reference to FIGS. 1, 2, and 3, focusing on the differences from the conventional example. FIG. 2 is a schematic diagram for explaining the operation of the color signal processing device according to the first embodiment of the present invention,
FIG. 3 is a block diagram showing a detailed configuration of the color signal processing device according to the first embodiment of the present invention. In FIG. 1, a carrier color signal input to a color signal input terminal 1 is demodulated by a color signal demodulation circuit 2 into baseband color difference signals Pr and Pb.
The signal passes through the low-pass filter 3 and is supplied to the averaging circuits 51 and 52, the color signal recording processing circuit 16, and the color signal modulation circuit 18. The above operation is the same as that of the conventional example, and the supplied color signals are obtained by multiplexing Pr and Pb on the time axis. The burst gate pulse generation circuit 4 generates burst gate pulses as shown in FIGS. 2B and 2C and supplies them to the averaging circuits 51 and 52, respectively. FIG.
The burst gate pulse shown in (b) is a pulse having a substantially normal burst width or a slightly narrower width than the burst pulse generated by the conventional burst gate pulse generation circuit 104 (hereinafter, this pulse is referred to as BGP1). Abbreviated). The timing pulse shown in FIG. 2C is active in the first half and the second half of the burst (High in the figure).
(Hereinafter, the pulse that becomes active in the first half is B
GP2, and the pulse that becomes active in the latter half is abbreviated as BGP3). The averaging circuit 51 performs processing for averaging the color difference signals Pr and Pb multiplexed on the time axis during the period in which BGP1 is active. Averaging circuit 52
Averages the components of the color difference signals Pr and Pb in a similar manner during the period when BGP2 and BGP3 are active. Therefore, BGP1, BGP2, and BGP3 change from high to L
When it changes to ow, averaged data of Pr and Pb in each burst gate period is obtained. BGP1
Are averaged data of Pr and Pb during the active period are Mpr1 and Mpb1, respectively, and the averaged data is expressed as Φ1 = (Mpr1, Mpb1) as a pair.
Similarly, the averaged data during the period when BGP2 and BGP3 are active are also Φ2 = (Mpr2, Mpb
2), when Φ3 = (Mpr3, Mpb3), the outputs of the averaging circuits 51 and 52 are represented as (d) and (e) in FIG. 2 (actually, during the period when BGP is active). The average value Mpr of Pr and the average value Mpb of Pb are multiplexed on the time axis and transmitted alternately). Multiplexer 6
Is the output of the averaging circuit 51 (FIG. 2D) and the averaging circuit 5
The output of FIG. 2 (FIG. 2 (e)) is further switched in time and multiplexed. For example, using the pulse of BGP1 (FIG. 2B), the output of the averaging circuit 51 is selected and output when BGP1 is Low, and the averaging circuit 52 is output when BGP1 is High.
2 is switched by the multiplexer 6 to select and output the output of FIG. The angle detection circuit 7 converts each of the multiplexed Pr and Pb averaged data into a phase angle signal. Specifically, the phase θ1 during the period when BGP1 is active is θ1 = Atan (Mpr1 /
Mpb1), phase θ2 during the period when BGP2 is active
Is θ2 = Atan (Mpr2 / Mpb2), BGP3
Is active, the phase θ3 is θ3 = Atan (M
pr3 / Mpb3), a converted output is obtained, and FIG.
The signal is output as shown in FIG. The register 8 is composed of four registers (register A, register B, register C, and register D) as shown in FIG. FIG. 3 is a configuration diagram showing a detailed configuration around the register 8. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals. The registers A to D correspond to T1, T2, T shown in FIG.
By storing (latching) the input signals at the timings of T3 and T4, the values of θ1, θ2, and θ3 are respectively stored in the registers A, B, and C, and the value of 1 is stored in the register D.
The output of the switching circuit 11 before the line is stored. The comparison circuit 9 compares the values of θ1, θ2, and θ3, and based on the result, the control circuit 10 switches the switching circuit 11 as follows.
And the color signal recording processing circuit 16. First, when the difference between θ2 and θ3 is smaller than a predetermined value, the switching circuit 11
Is switched to selectively output θ1. In other cases (that is, when the difference between θ2 and θ3 is large), the switching circuit 11 switches so as to selectively output any one of the following (1) to (3). (1) Output θ3. (2) Output the output result (register D output) of the switching circuit 11 one line before (that is, hold the same output as one line before). (3) Output θ2. When any one of the above (1) and (2) is output, the phase error of the APC is not greatly disturbed even in the line to which the split burst is added. A normal signal whose phase is not disturbed is also output to the terminal 17. (3) corresponds to a special case. In the case of a normal split burst in which the first half of the color burst has an opposite phase, if (3) is output, the phase error is disturbed and has no meaning. Is one of the options for preventing a phase error from being disturbed even in the case of a signal to which a split burst in which the first half has a normal phase and the second half has an opposite phase. Which of the above (1) to (3) is to be selected and output may be uniquely determined, but may be switched in accordance with use conditions or the like by control of a microcomputer or the like. As described above, the control circuit 10
Based on the comparison result of 1 to θ3, the switching circuit 11 is controlled so that the APC is not disturbed (the monitor output screen is not disturbed) even for the line to which the split burst is added. On the other hand, the control circuit 11 has a color signal recording processing circuit 16.
Is controlled so that the signal to which the split burst is added cannot be normally recorded (copied). Specifically, if the difference between θ2 and θ3 is equal to or more than a predetermined value, it is determined that the signal has a split burst added thereto, and therefore processing may be performed to degrade the recording color signal for that line, or It is determined whether the line to which the split burst is added appears at a period as shown in FIG. 5A or FIG. 5B. Control may be performed so as to prohibit this.

As described above, according to the present embodiment, the recording system surely responds to the copy guard signal of the color stripe system to prevent the copy, and the monitor output is affected by the copy guard signal. It can be displayed normally without receiving it.

In the above description, the angle detection circuit 7 detects the burst phase during the period in which the burst gate pulse is active, and the subtractor 12 subtracts the reference burst phase value to determine the phase error. However, a configuration may be used in which the result obtained by previously subtracting the reference burst phase value in the angle detection circuit 7 is output and the subtractor 12 is omitted.

In the above description, the color difference signal P
Although the method of calculating the burst phase using both information of r and Pb has been described, a simple method of calculating the phase error using only one of Pr and Pb may be used.

[0021]

As described above, according to the present invention, the copy guard signal of the color stripe system is reliably sensed in the recording system to prevent the copy, and the monitor output is not affected by the copy guard signal. An excellent effect that normal display can be achieved is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a color signal processing device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining an operation of the color signal processing device according to the first embodiment of the present invention;

FIG. 3 is a block diagram showing a detailed configuration of a color signal processing device according to the first embodiment of the present invention;

FIG. 4 is a schematic diagram of a copy guard signal of a pseudo-synchronous pulse method.

FIG. 5 is a schematic diagram of a color stripe type copy guard signal.

FIG. 6 is a block diagram showing a configuration of a conventional color signal processing device.

FIG. 7 is a schematic diagram for explaining the operation of a conventional color signal processing device.

[Explanation of symbols]

 Reference Signs List 1 color signal input terminal 2 color signal demodulation circuit 3 low-pass filter 4 burst gate pulse generation circuit 6 multiplexer 7 angle detection circuit 8 register 9 comparison circuit 10 control circuit 11 signal switching circuit 12 subtracter 13 pulse width modulation circuit 14 low-pass filter 15 voltage Control oscillator 16 Color signal recording processing circuit 17 Color signal recording output terminal 18 Color signal modulation circuit 19 Color signal monitor output terminal 51 Averaging circuit 52 Averaging circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C053 FA13 HA06 JA27 KA06 KA07 KA08 KA12 KA18 LA06 5C055 AA01 CA15 DA01 DA02 EA01 EA04 EA08 EA19 GA39 HA02 HA03 HA08

Claims (3)

[Claims] 1. A color demodulation circuit for demodulating a carrier chrominance signal into a color difference signal Pr and a color difference signal Pb; a low-pass filter for limiting a band of an output of the color demodulation circuit; First
A burst gate pulse generating circuit for generating a burst gate pulse, a second burst gate pulse that is active for a predetermined period in the first half of the burst period, and a third burst gate pulse that is active for a predetermined period in the second half of the burst period; , The Pr component and the Pb component of the output of the low-pass filter by the first burst gate pulse, the second
Averaging circuit for averaging each period of the burst gate pulse and the third burst gate pulse, and the Pr component and Pb component values of the output of the averaging circuit are represented by Pr component and P
an angle detection circuit that converts the phase angle into a value of a phase angle with the b component, wherein a second phase angle detected during the second burst gate pulse period and a third phase angle detected during the third burst gate pulse period are detected. When the difference between the phase angles is less than or equal to a predetermined value, the burst lock operation is performed by the first phase angle detected during the first burst gate pulse period. Otherwise, the burst lock operation is stopped, or A color signal processing device for performing a burst lock operation at a second phase angle or a third phase angle. 2. An averaging circuit, comprising: a first averaging circuit for averaging the first burst gate pulse period; averaging of the second burst gate pulse period; and averaging the third burst gate pulse period. 2. The color signal processing apparatus according to claim 1, further comprising a second averaging circuit that multiplexes the averaging in the time axis direction for processing. 3. The phase angle of each burst signal is detected by one angle processing detection circuit by multiplexing color difference signals averaged during three types of burst gate pulse periods in the time axis direction. The color signal processing device according to claim 1, wherein