JP4724934B2 - Color signal processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color signal processing apparatus that handles a macrovision copy guard signal, particularly a copy guard signal called a color stripe method for a color signal.
[0002]
[Prior art]
As a copy guard signal for protecting the copyright of video software or the like, for example, a so-called pseudo-synchronization pulse and color stripe method by Macrovision Corporation is known.
[0003]
A method called a pseudo synchronization 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. By inserting this pseudo-synchronization pulse, an automatic gain control (AGC) circuit malfunctions in the video recording device, and the amplitude level of the luminance signal is compressed to be smaller than the normal level so that the recorded signal cannot be put into practical use. Deteriorate.
[0004]
On the other hand, a method called color stripe will be described with reference to FIG. FIG. 5 is a schematic diagram of a color stripe type copy guard signal. As shown in FIG. 5C, the first half of the color burst for 4 lines for every 21 lines of video signals or 2 lines for every 17 lines as shown in FIG. The phase of the part is made opposite to the normal phase. A burst having this antiphase 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, and the phase cannot be pulled in. Therefore, even if this signal is recorded / reproduced, the color is not colored normally but becomes a stripe shape. The screen is distorted.
[0005]
Hereinafter, a conventional color signal processing apparatus will be described.
[0006]
FIG. 6 is a block diagram showing the configuration of a conventional color signal processing apparatus. In the figure, 1 is a color signal input terminal, 2 is a color signal demodulation circuit, 3 is a low-pass filter, 104 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), 116 is a color signal recording processing circuit, 17 is an output terminal for recording color signals, 18 is a color signal modulation circuit, 19 Is an output terminal for a carrier color signal output to a monitor or the like.
[0007]
The operation of the conventional color signal processing apparatus configured as described above will be described below with reference to FIG. FIG. 7 is a schematic diagram for explaining the operation of a conventional color signal processing apparatus. First, a carrier color signal is input to the color signal input terminal 1. For example, in the case of the NTSC system, a carrier color signal modulated by a subcarrier of about 3.58 MHz is inputted, and in the case of the PAL system, a carrier color signal modulated by a subcarrier of about 4.43 MHz is inputted. The input carrier color signal is demodulated into baseband color difference signals Pr and Pb by the color signal demodulation circuit 2. The two color difference signals Pr and Pb are multiplexed on the time axis, and Pr and Pb are alternately transmitted at a predetermined clock cycle. Since the low-pass filter 3 extracts only the baseband color difference signal from the output of the color signal demodulation circuit 2, the high-pass component is attenuated. 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 averages the Pr and Pb components of the color burst portion and outputs the result to the angle detection circuit 7 during the period when the burst gate pulse is active (the period of FIG. 7B is high). The angle detection circuit 7 detects the phase of the color burst part from the average values of Pr and Pb in 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 obtained by θ1 = Atan (Mpr / Mpb). Here, Atan is an arctangent. The subtracter 12 calculates and outputs the difference between θ1 and a predetermined reference burst phase value. That is, 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 pulse width modulation (PWM) circuit 13 output and outputs it to the voltage controlled crystal oscillator 15. The voltage controlled crystal oscillator 15 controls the oscillation frequency according to the output level of the low pass filter 14 and generates a reference clock. The generated reference clock is used as a processing clock for the digital circuit by multiplying or dividing as necessary. The color signal recording processing circuit 116 receives the color difference signals Pr and Pb output from the low-pass filter 3, performs necessary processing when recording the color signal on the recording device, and outputs the processed signal to the recording color signal output terminal 17. For example, in a VHS 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 modulates the color difference signals Pr and Pb output from the low-pass filter 3 into a carrier color signal and outputs the carrier color signal to the carrier color signal output terminal 19. This output signal is then 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 constitutes a so-called automatic phase control (APC) loop, and the voltage controlled crystal oscillator 15 generates a clock locked to the color burst phase of the color signal.
[0008]
[Problems to be solved by the invention]
However, in the conventional configuration described above, when a color stripe type copy guard signal is input, the phase error detection is disturbed at the line to which the split burst is added, thereby disturbing the recording color signal and monitoring. There is also a problem in that it interferes with the output of the carrier color signal.
[0009]
The present invention solves the above-mentioned conventional problems. The color stripe type copy guard signal is surely sensitive in the recording system to prevent copy, and the monitor output is affected by the copy guard signal. It is an object of the present invention to provide a color signal processing circuit that can display normally.
[0010]
[Means for Solving the Problems]
In order to achieve this object, the color signal processing apparatus of the present invention provides:
A color demodulation circuit that demodulates the carrier color signal into a color difference signal Pr and a color difference signal Pb, a low-pass filter that limits the band of the output of the color demodulation circuit, and a first active that is active during a general burst period of the output of the low-pass filter A burst gate pulse generating circuit that generates 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; An averaging circuit that averages the Pr component and the Pb component of the output of the low-pass filter for each period of the first burst gate pulse, the second burst gate pulse, and the third burst gate pulse, and the averaging circuit Output Pr component and Pb component values are converted into phase angle values of the Pr and Pb components. A difference between 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 is less than or equal to a predetermined value. Performs a burst lock operation according to the first phase angle detected during the first burst gate pulse period, otherwise the burst lock operation is stopped, the second phase angle, or the third phase angle The burst lock operation is performed according to the phase angle.
[0011]
With this configuration, a color signal processing circuit that reliably responds to the color stripe type copy guard signal and prevents copy in the recording system and can be displayed normally without being affected by the copy guard signal in the monitor output. can get.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
According to the first aspect of the present invention, a color demodulation circuit that demodulates a carrier color signal into a color difference signal Pr and a color difference signal Pb, a low-pass filter that limits a band of an output of the color demodulation circuit, and the low-pass filter The first burst gate pulse that is active during the burst period of the output, the second burst gate pulse that is active for a predetermined period in the first half of the burst period, and the third burst gate that is active for the predetermined period in the second half of the burst period A burst gate pulse generation circuit for generating a pulse, and an average of Pr and Pb components of the output of the low-pass filter for each period of the first burst gate pulse, the second burst gate pulse, and the third burst gate pulse. An averaging circuit for performing averaging, and Pr component and Pb component values of the output of the averaging circuit as Pr components and an angle detection circuit for converting the phase angle to a value of the b component, and a second phase angle detected during the second burst gate pulse period and a third phase detected during the third burst gate pulse period. If the phase angle difference is equal to or less than a predetermined value, the burst lock operation is performed according to the first phase angle detected during the first burst gate pulse period, otherwise, the burst lock operation is stopped, or The burst lock operation is performed according to the second phase angle or the third phase angle, so that the burst lock operation can be performed even in a signal to which a color stripe type copy guard signal is added. A normal signal that is not disturbed and is therefore not affected by the monitor output is output. On the other hand, the second phase angle and the third phase angle are detected for the recorded signal. Thus, it is possible to determine whether or not a color stripe type copy guard signal is added, so that when the copy guard signal is determined to be added, processing such as stopping the recording operation is performed. The copy prevention operation can be performed reliably.
[0013]
According to a second aspect of the present invention, the averaging circuit includes: a first averaging circuit that performs the first burst gate pulse period averaging; the averaging of the second burst gate pulse period; The second burst gate pulse period is characterized by comprising a second averaging circuit that multiplexes and processes the averaging of the third burst gate pulse period in the time axis direction. And the averaging during the third burst gate pulse period can be performed on a single time by dividing it on the time axis, so that it can be configured with a simple circuit with a small circuit scale.
[0014]
The invention according to claim 3 of the present invention multiplexes the color difference signals averaged in each of the three types of burst gate periods in the time axis direction, so that the phase angle of each burst signal is obtained by one angle processing detection circuit. This is also characterized in that it can be configured with a simple circuit having a small circuit scale.
[0015]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.
[0016]
(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of a color signal processing apparatus according to the present invention. In FIG. 1, 1 is an input terminal for a color signal, 2 is a demodulation circuit for demodulating a carrier color signal into a color difference signal, 3 is a low-pass filter, 4 is a burst gate pulse generation circuit, 51 and 52 are averaging circuits that average the output color difference signals Pr and Pb of the low-pass filter 3 with respect to the burst gate pulse period output from the burst gate pulse generation circuit 4, 6 Is a multiplexer that switches and multiplexes the outputs of the averaging circuits 51 and 52 in a time division manner, 7 is an angle detection circuit, 8 is three phase information detected by the angle detection circuit, and output phase information of the switching circuit 11 is stored. A register, 9 is a comparator for comparing the phase information stored in the register 8, and 10 is a switching circuit 11 and a color signal recording process using the comparison result of the comparator 9. A control circuit for controlling the operation of the circuit 16, 11 a switching circuit for selectively outputting the four phase information stored and output in the register 8, 12 a subtractor for subtracting the reference burst phase value from the output of the switching circuit 11, and 13 A pulse width modulation (PWM) circuit that performs pulse width modulation on the APC phase error signal that is the output of the subtractor, 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. An output terminal, 18 is a color signal modulation circuit, and 19 is an output terminal of a modulated carrier color signal. In the figure, the same components as those in the conventional example are designated by the same reference numerals, and the description thereof is omitted.
[0017]
The operation of the color signal processing apparatus configured as described above will be described with reference to FIGS. 1, 2, and 3 with a focus on differences from the conventional example. FIG. 2 is a schematic diagram for explaining the operation of the color signal processing apparatus according to the first embodiment of the present invention, and FIG. 3 is a block diagram showing a detailed configuration of the color signal processing apparatus 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 into baseband color difference signals Pr and Pb by a color signal demodulation circuit 2, passes through a low-pass filter 3, and is averaged by circuits 51 and 52. The color signal recording processing circuit 16 and the color signal modulation circuit 18 are supplied. The above operation is the same as that of the conventional example, and Pr and Pb are multiplexed on the time axis in the supplied color signal. 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. The burst gate pulse shown in FIG. 2B is the same as that generated by the burst gate pulse generation circuit 104 in the conventional example, and is a pulse having a substantially normal burst width or a slightly narrower width (hereinafter referred to as this pulse). Abbreviated as BGP1). The timing pulse shown in FIG. 2C is active (high in the figure) in the first half and the second half of the burst (hereinafter, the pulse that becomes active in the first half is BGP2, and the pulse that becomes active in the second half is BGP3. Abbreviated). The averaging circuit 51 performs a process of averaging the color difference signals Pr and Pb multiplexed on the time axis during the period in which BGP1 is active. The averaging circuit 52 similarly averages the components of the color difference signals Pr and Pb during the period in which BGP2 and BGP3 are active. Therefore, when BGP1, BGP2, and BGP3 change from high to low, averaged data of Pr and Pb in each burst gate period is obtained. The averaged data of Pr and Pb in a period in which BGP1 is active is denoted as Mpr1 and Mpb1, respectively, and the averaged data is expressed as Φ1 = (Mpr1, Mpb1) as a pair. Similarly, if the averaged data in the period in which BGP2 and BGP3 are active is also expressed as Φ2 = (Mpr2, Mpb2) and Φ3 = (Mpr3, Mpb3), respectively, the outputs of the averaging circuits 51 and 52 are shown in FIG. (E) is expressed (actually, the average value Mpr of Pr and the average value Mpb of Pb in a period in which BGP is active are multiplexed on the time axis and transmitted alternately). The multiplexer 6 further multiplexes the output of the averaging circuit 51 (FIG. 2D) and the output of the averaging circuit 52 (FIG. 2E) by further switching in time. For example, by using the pulse of BGP1 (FIG. 2B), the multiplexer 6 performs switching so that the output of the averaging circuit 51 is selectively output when BGP1 is Low and the output of the averaging circuit 52 is selectively output when BGP1 is High. And its output is as shown in FIG. The angle detection circuit 7 converts the averaged data of Pr and Pb multiplexed in this way into a phase angle signal. Specifically, the phase θ1 when BGP1 is active is θ1 = Atan (Mpr1 / Mpb1), the phase θ2 when BGP2 is active is θ2 = Atan (Mpr2 / Mpb2), and the phase θ3 when BGP3 is active , A converted output is obtained as θ3 = Atan (Mpr3 / Mpb3), and is output as shown in FIG. As shown in FIG. 3, the register 8 includes four registers (register A, register B, register C, and register D). FIG. 3 is a block diagram showing the detailed configuration around the register 8. In FIG. 3, the same components as those in FIG. The registers A to D store (latch) respective input signals at the timings T1, T2, T3, and T4 shown in FIG. 2 (h), so that the registers A, B, and C have θ1, θ2, θ3, respectively. And the output of the switching circuit 11 one line before is stored in the register D. The comparison circuit 9 compares the values of θ1, θ2, and θ3, and based on the results, the control circuit 10 controls the switching circuit 11 and the color signal recording processing circuit 16 as follows. First, when the difference between θ2 and θ3 is equal to or 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 is switched so that one of the following (1) to (3) is selectively output. (1) Output θ3. (2) The output result (register D output) of the switching circuit 11 one line before is output (that is, the same output as one line before is held). (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. Therefore, the carrier color signal is output to the monitor. 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 is in reverse phase, if (3) is output, the phase error is disturbed and does not make sense. This is one of the options for preventing the phase error from being disturbed even in the case of a signal to which a split burst is added such that the first half is a normal phase and the second half is an opposite phase. Which of the above (1) to (3) is selected and output may be uniquely determined, but may be switched according to the use condition or the like under the control of a microcomputer or the like. As described above, the control circuit 10 controls the switching circuit 11 based on the comparison result of θ1 to θ3 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 controls the color signal recording processing circuit 16 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 greater than a predetermined value, it is determined that the signal has a split burst added, and therefore processing for deteriorating the recording color signal may be performed for that line, or It is determined whether or not a line to which a split burst is added appears in a cycle as shown in FIG. 5A or 5B, and when it is determined that a color stripe type copy guard signal is added, a recording operation is performed. Control may be performed so as to prohibit it.
[0018]
As described above, according to the present embodiment, the color stripe type copy guard signal is surely sensitive in the recording system to prevent copy, and the monitor output is normal without being affected by the copy guard signal. Can be displayed.
[0019]
In the above description, the angle detection circuit 7 detects the burst phase during the period when the burst gate pulse is active, and the subtractor 12 subtracts the reference burst phase value to determine the phase error. The angle detection circuit 7 may output a result obtained by subtracting the reference burst phase value in advance and omit the subtractor 12.
[0020]
Further, in the above description, the method of obtaining the burst phase using both information of the color difference signals Pr and Pb has been described. However, this is a simple method of obtaining the phase error using only one of Pr and Pb. Also good.
[0021]
【The invention's effect】
As described above, the present invention reliably responds to the color stripe type copy guard signal in the recording system and prevents copy, and the monitor output can be normally displayed without being affected by the copy guard signal. Excellent effect is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a color signal processing apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram for explaining the operation of the color signal processing apparatus according to Embodiment 1 of the present invention. 4 is a block diagram showing a detailed configuration of the color signal processing apparatus according to the first embodiment of the present invention. FIG. 4 is a schematic diagram of a pseudo guard pulse type copy guard signal. FIG. 5 is a schematic diagram of a color stripe type copy guard signal. FIG. 6 is a block diagram showing the configuration of a conventional color signal processing apparatus. FIG. 7 is a schematic diagram for explaining the operation of the conventional color signal processing apparatus.
DESCRIPTION OF SYMBOLS 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 Subtractor 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

Claims (3)

A color demodulation circuit that demodulates the carrier color signal into a color difference signal Pr and a color difference signal Pb, a low-pass filter that limits the band of the output of the color demodulation circuit, and a first active that is active during a general burst period of the output of the low-pass filter A burst gate pulse generating circuit that generates 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; An averaging circuit that averages the Pr component and the Pb component of the output of the low-pass filter for each period of the first burst gate pulse, the second burst gate pulse, and the third burst gate pulse, and the averaging circuit Output Pr component and Pb component values are converted into phase angle values of the Pr and Pb components. A difference between 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 is less than or equal to a predetermined value. Performs a burst lock operation according to the first phase angle detected during the first burst gate pulse period, otherwise the burst lock operation is stopped, the second phase angle, or the third phase angle A color signal processing apparatus which performs a burst lock operation according to a phase angle. The averaging circuit includes a first averaging circuit that performs averaging of the first burst gate pulse period, and averaging of the second burst gate pulse period and averaging of the third burst gate pulse period. 2. The color signal processing apparatus according to claim 1, further comprising a second averaging circuit that performs multiplexing and processing in the axial direction. 2. The phase angle of each burst signal is detected by one angle processing detection circuit by multiplexing the color difference signals averaged in each of three kinds of burst gate pulse periods in the time axis direction. The color signal processing apparatus described.

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