JPH0896304A - Secam system color signal processor - Google Patents

Abstract

PURPOSE: To simplify the recording and reproducing processing system for a SECAM modulated color signal and also to stabilize color picture quality. CONSTITUTION: An SECAM video signal is separated into a luminance signal and the modulated color signal by a luminance signal and color signal separating circuit 15, and the modulated color signal is inputted to a multiplier 191 and a demodulation circuit 17. A voltage control oscillation circuit 18 is set for its oscillation center frequency to 3/4 or 5/4 of a carrier frequency of the modulated color signal, oscillating with a frequency corresponding to a voltage of a demodulated output signal inputted from a demodulation circuit 17 and supplying an oscillation output to the multiplier 191. Consequently, the modulated color signal equivalent to 1/4-stepdown demultiplied one is outputted from an LPF 192. This signal is added to an FM luminance signal outputted from a luminance signal processing circuit 16 by an adder 20, becoming the recording SECAM video signal. Consequently, the circuit structural scale is reduced when compared with a conventional one, while circuits to exert an adverse effect upon the color picture quality are eliminated, thus obtaining the stable color picture quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus capable of recording / reproducing in a SECAM system, and more particularly to a recording / reproducing color signal processing apparatus for recording / reproducing a SECAM-modulated color signal.

[0002]

2. Description of the Related Art The recording method of SECAM-modulated color signals in the current VHS method is that the color signals are divided by 1/4 (divided by 4).
The method of recording after conversion to the low frequency range is adopted. FIG. 7 is a diagram for explaining the above-mentioned conventional method. First, the SECAM-modulated chrominance signal 100 having the bell characteristic of the center frequency F0 as shown in FIG. 8A is input to the bell filter 1 of the center frequency F0 having the characteristic opposite to the input signal bell characteristic. This SECAM-modulated color signal 100 has a center frequency F
0 (= about 4.3 MHz), the frequency transition ΔD (= about 0.3.
85 MHz) and bell characteristics (carrier suppression). The SECAM-modulated color signal 100 has its energy flattened by the bell filter 1 and has a signal 1 as shown in FIG.
After becoming 01, it is input to the limiter 2 and becomes a square wave 102 suitable for frequency division as shown in FIG.
Entered in. The square wave 102 is divided into four by the frequency divider 4 to be converted into a low frequency range, and becomes a signal 103 as shown in FIG. 8D, which is further input to the recording equalizer 4. The recording equalizer 4 has an equalizer characteristic of a center frequency F / 4, and the signal passing through this equalizer 4 is an input SECAM-modulated color signal 1 as shown in FIG.
00 becomes a recording low-range SECAM modulation signal 104 having a frequency 1/4 and a frequency transition 1/4, which is input to the adder 6 via the cleaning gate 5. In the recording low-range SECAM modulation signal 104, the noise of the no-signal portion in the horizontal retrace line and the synchronizing signal section is amplified and appears by the limiter 2, the recording equalizer 4, etc., and therefore, the FM modulation luminance signal 200 and the adder 6 are used as they are. However, since a problem occurs when the data is added to and recorded on the tape, the noise is erased or compressed by the cleaning gate circuit 5 by the timing signal 106 as shown in FIG. Adding with the luminance signal 200,
A SECAM video signal 300 for recording is obtained.

FIG. 9 shows a low-frequency SECAM reproduced from a tape.
It is a conventional example showing a reproduction system of a modulation signal. Center frequency F
A reproduction low-range SECAM-modulated color signal 107 as shown in FIG. 10A reproduced from the tape is input to the reproduction equalizer 7 having 0/4. The reproduced low-range SECAM-modulated color signal 107 is flattened by the reproduction equalizer 7 and then input to the quadrupler 9 through the limiter 8. The quadrupler 9 multiplies the input signal by 4 and then outputs it to the bell filter 10 having the center frequency F0. The bell filter 10 reproduces an input signal having a bell characteristic of a center frequency F0 and has a reproduction high frequency band SEC.
After forming the AM-modulated color signal 108, this is output to the adder 12 via the cleaning gate 11. The cleaning gate 11 removes noise by gating an input signal with a timing signal 109 as shown in FIG. 10 (B) generated from a synchronization signal, and a reproduced SECAM-modulated color signal 108 as shown in FIG. 10 (C). Is output to the adder 12. The adder 12 adds the reproduction luminance signal 250 to the reproduction SECAM-modulated color signal to obtain the reproduction SECAM video signal 400, and outputs this to the next stage.

Unlike the PAL signal frequency conversion method, the conventional technique described with reference to FIGS.
It has a unique structure for AM processing. Therefore, SECA
If the above-mentioned conventional technique is used as it is for a PAL / SECAM compatible VTR which is becoming mainstream from the M single-function VTR (video tape recorder), there is a drawback that the circuit scale becomes large and the cost of the apparatus increases. Further, the F0 shift due to noise generation by the limiters 2 and 8 or the environmental change of the characteristics of the bell filter 10 or the F0 adjustment shift in the manufacturing process, and further, the gate pulse timing signals 106 and 109.
Is not always the same as the non-signal timing of the original signal,
There are many factors that adversely affect the SECAM-modulated color signal, and such a conventional technique has a drawback that the color image quality is not stable.

[0005]

The conventional SECAM system recording / reproducing color signal processing device has a unique configuration for SECAM processing, unlike the PAL signal frequency conversion system. Therefore, the PAL / SECAM type VTR, which is becoming the mainstream, needs a circuit for processing the PAL type color signal and the SECAM type color signal independently. Then, there is a drawback that the circuit scale becomes large and the cost of the apparatus becomes high. or,
In the conventional SECAM-type color signal processing device, the deviation of the center frequency F0 of the bell filter due to the occurrence of noise by the limiter or the change of the characteristic environment of the bell filter and the gate pulse timing signal for noise removal are not always the non-signal timing of the original signal. There are many factors that adversely affect the color signal of the SECAM system to be processed, such as inconsistency, and there is a drawback that the color image quality is not stable.

Therefore, the present invention eliminates the above-mentioned drawbacks and provides SE
The CAM system color signal recording / reproducing processing system can be shared with the PAL system color signal processing system, and the SECAM system color signal to be processed has a configuration unique to the SECAM system such as a cleaning gate and a limiter. It is an object of the present invention to provide a SECAM type recording / reproducing color signal processing device capable of obtaining stable color image quality by removing an adverse effect element.

[0007]

According to a first aspect of the present invention, there is provided a demodulation circuit for demodulating a SECAM type modulated color signal, and a voltage control for controlling an oscillation frequency corresponding to an output signal voltage of the demodulation circuit. An oscillation circuit and a frequency conversion circuit for multiplying the output of the voltage control oscillation circuit and the modulated color signal and deriving a signal of a predetermined frequency band of the output, the frequency of the voltage control oscillation circuit and the frequency shift The width is such that the output of the frequency conversion circuit is 1 /
The frequency spectrum is set to have a frequency spectrum equivalent to that of the frequency spectrum divided by n.

The present invention according to claim 2 has a carrier frequency of 1
/ N demodulation circuit for demodulating the SECAM-mode modulated color signal, a voltage control oscillation circuit whose oscillation frequency is controlled according to the output signal voltage of this demodulation circuit, and the output of this voltage control oscillation circuit And a frequency conversion circuit that multiplies the modulated color signal and derives a signal in a predetermined frequency band from the output, the frequency and the frequency shift width of the voltage controlled oscillation circuit, and the output of the frequency conversion circuit is the It has a configuration in which it is set so as to have a frequency spectrum equivalent to that obtained by multiplying the modulated color signal by n times.

[0009]

In the color signal processing apparatus of the SECAM system according to the first aspect of the present invention, the demodulation circuit demodulates the modulated color signal. The voltage controlled oscillator circuit oscillates at a frequency corresponding to the output voltage of the demodulation circuit. The frequency conversion circuit multiplies the signal output from the voltage controlled oscillation circuit by the modulated color signal,
A signal in a predetermined frequency band is output from the multiplication output. At this time, the frequency of the voltage controlled oscillator circuit and the width of frequency shift are such that the output of the frequency converter circuit is 1 /
The frequency spectrum is set to have the same frequency spectrum as that of the frequency spectrum down to n. As a result, components can be made common to the PAL system color signal processing system, the circuit scale can be reduced, and elements such as limiters, bell filters, and cleaning gates that adversely affect color image quality can be omitted, so that stable color can be obtained. Image quality can be obtained.

According to the second aspect of the present invention, the demodulation circuit demodulates a SECAM type modulated color signal whose carrier frequency is reduced to 1 / n. The voltage controlled oscillator circuit oscillates at a frequency corresponding to the output signal voltage of this demodulator circuit. The frequency conversion circuit multiplies the signal output from the voltage controlled oscillation circuit by the modulated color signal, and outputs a signal in a predetermined frequency band from the multiplication output. At this time, the frequency and the frequency shift width of the voltage controlled oscillation circuit are set so that the output of the frequency conversion circuit has a frequency spectrum equivalent to that obtained by multiplying the modulated color signal by n times. This allows PA
It is possible to use the same components as the L system color signal processing system to reduce the circuit scale, and to obtain stable color image quality because elements that adversely affect color image quality such as limiters, bell filters, and cleaning gates can be omitted. be able to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a SECAM type recording color signal processing apparatus of the present invention. 15 is S
From the ECAM video signal 400 to the FM modulated luminance signal and SE
A luminance signal color signal separation circuit for separating a CAM modulation color signal,
Reference numeral 16 is a luminance signal processing circuit for performing various processes on the FM modulated luminance signal, 17 is a demodulation circuit for converting the SECAM modulated color signal into a voltage (color information signal voltage) corresponding to the frequency, 18
Is a voltage-controlled oscillation circuit whose oscillation frequency is controlled by the input color information signal voltage, and 19 is a frequency conversion circuit for converting the frequency of the SECAM-modulated color signal into a low frequency band, which includes a multiplier 191 and a low-pass filter (LPF) 192. Made of. 20 is an FM modulated luminance signal and low frequency conversion SECAM
It is an adder that adds the modulated color signal.

Next, the operation of this embodiment will be described. The luminance signal color signal separation circuit 15 separates the luminance signal and the modulation color signal (SECAM color difference signal) from the input SECAM video signal 400, the luminance signal is FM-modulated by the luminance signal processing circuit 16, and the modulation color signal is frequency converted. It is supplied to the multiplier 191 of the device 19 and the demodulation circuit 17. The demodulation circuit 17 generates a color information signal voltage corresponding to the frequency of the input SECAM-modulated color signal, and outputs this to the voltage controlled oscillator circuit 18. Here, the oscillation frequency of the voltage controlled oscillator circuit 18 is adjusted to be 3/4 or 5/4 of the frequency of the SECAM-modulated color signal.

Therefore, the SEC input to the demodulation circuit 17
When the frequency characteristic of the AM-modulated chrominance signal is as shown in FIG. 2 (A) and the signal B of the frequency F0 as shown in FIG. Outputs a signal B having a frequency of 3F0 / 4 as shown in FIG. 2B, which is input to the multiplier 191 of the frequency conversion circuit 19. At this time, if the LPF 192 removes the high frequency component from the output component of the multiplier 191,
A recording low-range SECAM-modulated color signal C having a frequency of F0 / 4 as shown in (B) is obtained, and this is input to the adder 20. Similarly, when a signal D having a frequency Fmax as shown in FIG. 2C is input to the demodulation circuit 17, the voltage controlled oscillator circuit 18 outputs 3Fmax / 4 as shown in FIG. 2C.
The signal e having the frequency of is output and is input to the multiplier 191 of the frequency conversion circuit 19. At this time, when the high frequency component is removed from the output component of the multiplier 191 by the LPF 192, a recorded low frequency SECAM modulated color signal having a frequency of Fmax / 4 as shown in FIG. 2C is obtained, and this is added. Input to the container 20. Similarly, in the demodulation circuit 17, as shown in FIG.
When a signal of frequency Fmin as shown in (D) is input, the voltage controlled oscillator circuit 18 outputs a signal H having a frequency of 3Fmin / 4 as shown in FIG. 2 (D). It is input to the multiplier 191 of the conversion circuit 19.
At this time, the high-frequency component from the output component of the multiplier 191 is converted to LPF.
When removed at 192, Fmin / as shown in FIG.
A recording low-range SECAM-modulated color signal with a frequency of 4 is obtained, and this is input to the adder 20. After all, from the frequency conversion circuit 19, the band shown in FIG.
Recording low-frequency SE with SECAM-modulated color signal downgraded to 1/4
A CAM-modulated color signal is obtained, which is added to the FM-modulated luminance signal by the adder 20 to form a recorded SECAM video signal.

FIG. 3 is a block diagram in which the color signal processing system shown in FIG. 1 is rewritten based on the color information signal voltage (SECAM color difference signal in FIG. 3). Where the color subcarrier is f
_OR and f _OB, and conversion carriers are f _CR and f _CB .

FIG. 4 is a diagram in which a general modulation wave is applied to the circuit of FIG. 3, and in this case, one carrier is A _S · sin.
{Ω _S (t + t _s )}, the other carrier is A _C · sin
If {ω _C (t + t _C )}, the following relationship holds.

E _S = A _S · sin {ω _S (t + t _s ) +
Δω _S · sin (ω _P · t)} where Δω _S = maximum displacement angle E _C = A _C · sin {ω _C (t + t _C ) + Δω _C · si
n (ω _P · t)} where Δω _C = maximum displacement angle Therefore, E _S × E _C = 1/2 · A _S · A _C [cos {(ω
_S −ω _C ) t + ω _S ts _s −ω _C t _C + (Δω _S −Δ
ω _C ) sin ω _P t} -cos {(ω _S + ω _C ) t + ω
_{S t s + ω C t C} + (Δω S + Δω C) sinω
_P t}] In the subsequent LPF, the angular frequency (ω _S + ω _C ) component is removed, and the amplitude term and the constant term are put together: LPF output signal = B · cos {(ω _S + ω _C ) t + ( Δω _S −Δω _C ) sin ω _P t + Δθ} (1) If ω _C = 3ω _S / 4 and Δω _C = 3Δω _S / 4, then the LPF output signal = Bcos (ω _S / 4 · t + Δ
ω _S / 4 · sin ω _P t + Δθ) (2) and E _S
Angular frequency 1/4, maximum displacement angle or deviation 1 /
4 conversions are possible. Next, in the above, the modulated wave is SE
When represented by a CAM color difference signal (D ^* : color difference signal subjected to emphasis),

[0017]

[Equation 1]

[0018]

[Equation 2]

[0019]

[Equation 3]

Now, a color signal processing system at the time of reproduction for processing the SECAM video signal obtained by reproducing the SECAM video signal recorded on the tape by the head through the above processing will be described with reference to FIG. The color signal processing system at the time of reproduction has almost the same configuration as the color signal processing system at the time of recording shown in FIG. The difference is that the reproduction SECAM video signal is input to the luminance signal color signal separation circuit 15, and the oscillation frequency of the voltage controlled oscillator 18 is the reproduction low frequency band S.
The only difference is that the ECAM-modulated color signal is determined to be multiplied by 4. The rest of the configuration is the same as that of the recording system of FIG. 1. By performing the same operation, the reproduction SEC from the adder 20 is performed.
An AM video signal can be obtained. That is, the center oscillation frequency of the voltage controlled oscillator is set to 3 times or 5 times the carrier frequency of the regular modulated color signal.

According to this embodiment, the SECA shown in FIG.
Voltage control oscillator 1 used for M type color signal processing device
As is well known, the frequency converter 8 and the frequency converter 19 are also present in the PAL system color signal processing system, so that they can be shared with the PAL system color signal processing system, and the cleaning gate, limiter, bell filter, etc. , Conventional SE
Since the constitution peculiar to the CAM is unnecessary, the circuit scale of the device can be reduced accordingly. Especially PAL / SEC
The above effect becomes significant in the AM compatible VTR. Also, S
Since the ECAM-modulated color signal is converted into the low frequency band only by the frequency conversion by the frequency converter 19, there is no adverse effect such as the noise generation due to the limiter which has been conventionally present, the error of the gate cleaning timing, the environment resistance characteristic of the bell filter characteristic, etc.
More faithful down-gradation (or multiplication) with respect to the original signal can be achieved, and stable color image quality can be obtained.

[0022]

As described above, according to the SECAM type recording / reproducing color signal processing apparatus of the present invention as set forth in claims 1 and 2, the SECAM type color signal recording / reproducing processing system is a P-system.
By making it possible to share with the AL system color signal processing system, and by removing the elements such as cleaning gates and limiters that are unique to the SECAM system and have an adverse effect on the SECAM system color signal to be processed, stable operation is achieved. It is possible to obtain excellent color image quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a SECAM recording color signal processing apparatus of the present invention.

FIG. 2 is a diagram for explaining the frequency conversion operation of FIG.

3 is a block diagram in which the color signal processing system shown in FIG. 1 is rewritten based on a color information signal voltage.

FIG. 4 is a block diagram when a general modulated wave is applied to the circuit of FIG.

FIG. 5 is a diagram showing bell characteristics.

FIG. 6 is a diagram showing an example of a color signal processing system during reproduction according to the present invention.

FIG. 7 is a block diagram showing a conventional SECAM recording color signal processing system.

FIG. 8 is a waveform diagram illustrating the operation of FIG.

FIG. 9 is a block diagram showing a conventional SECAM system reproduction color signal processing system.

10 is a waveform chart illustrating the operation of FIG.

[Explanation of symbols]

15 ... Luminance signal color signal separation circuit 16 Luminance signal processing circuit 17 ... Demodulation circuit 18 ... Voltage control oscillation circuit 19 ... Frequency conversion circuit 20 ... Adder 191 ... Multiplier 192 ... LPF

Claims (2)

[Claims] 1. A demodulation circuit for demodulating a SECAM-type modulated color signal, a voltage control oscillation circuit whose oscillation frequency is controlled according to an output signal voltage of the demodulation circuit, an output of the voltage control oscillation circuit, and And a frequency conversion circuit for deriving a signal of a predetermined frequency band from the output of the modulated color signal, wherein the frequency and frequency shift width of the voltage controlled oscillation circuit are the output of the frequency conversion circuit and the modulated color signal. SECAM is characterized in that it is set so as to have a frequency spectrum equivalent to that of a signal that is divided into 1 / n.
System color signal processor. 2. An SEC in which the carrier frequency is stepped down to 1 / n.
A demodulation circuit for demodulating an AM modulated color signal, a voltage controlled oscillator circuit whose oscillation frequency is controlled according to the output signal voltage of the demodulated circuit, an output of the voltage controlled oscillator circuit and the modulated color signal A frequency conversion circuit that multiplies and derives a signal in a predetermined frequency band from the output, the frequency and the frequency shift width of the voltage controlled oscillation circuit are such that the output of the frequency conversion circuit multiplies the modulated color signal by n times. A SECAM type color signal processing device, characterized in that it is set so as to have a frequency spectrum equivalent to that obtained by multiplication.