JPH058631B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is a method for controlling the playback level and recording level of a color signal among color video signals to be recorded or played back to a constant level during recording and playback of a magnetic recording/playback device (VTR). A color signal that has an ACC operation function that controls the color signal input to the frequency converter, which performs frequency conversion of the carrier color signal or low-frequency conversion color signal during recording and playback, to an appropriate level for the circuit. It relates to a processing device.

Conventional configuration and its problems An example of the conventional configuration of a functional color signal processing device for ACC operation will be described with reference to FIG. Figure 1 shows ACC
1 is a block diagram showing the configuration of a conventional color signal processing device having operational functions.

First, during recording, a carrier color signal with a carrier frequency _SC separated from the color video signal is input from the input terminal 1, and after being amplified to an appropriate level by the variable gain amplifier (ACC) 3, one of the frequency converters 4 supplied to the input. A signal generator (OSC1) 5 generates a frequency synchronized in phase with the burst of the carrier color signal.
The frequency and phase are controlled to generate a carrier wave of _SC , and the carrier wave of frequency _SC is supplied to one input of a frequency converter 7, and the signal generator (OSC2) 6 generates a carrier wave of frequency _C (NTSC television signal recording). When 1 horizontal frequency is _H ,
In the VHS system, _C = 40 _H , and the phase is shifted by 90 degrees every horizontal period, and in the β system, _C = (44-1/4).
_H and the phase was reversed every horizontal period. ) Generates a low frequency conversion carrier wave, and during recording, creates a signal with a frequency that is an integral multiple of the horizontal synchronization frequency of the color video signal, and further performs frequency division and phase shift or phase inversion processing for each horizontal period. A low frequency converted carrier wave is created by using the frequency converter 7, and is supplied to the other input of the frequency converter 7. The frequency converter 7 multiplies the supplied carrier wave of the frequency _SC by the low frequency converted carrier wave of the frequency _C , and supplies the result to the bandpass filter (BPF) 8. The frequency of the multiplication result is
The signal of _SC + _C and the frequency become the sum of the signal of _SC - _C , but due to the bandpass filter 8, the frequency _SC + _C
only the signal is extracted and supplied to the other input of the frequency converter 4. Like the frequency converter 7, the frequency converter 4 multiplies the two supplied signals,
A low-pass filter (LPF) 9 extracts only the low-frequency converted color component of the carrier frequency _C from the multiplication result, and a recording low-frequency converted color signal is sent to the output terminal 2 via the output changeover switch 10.

During reproduction, a low frequency conversion color signal of a carrier frequency _C separated from a recorded signal reproduced from a magnetic tape is inputted from an input terminal 1, and is amplified to an appropriate level by a variable gain amplifier 3. The signal generator 5 generates a carrier wave with a reference color subcarrier frequency _SC and supplies it to one input of the frequency converter 7, and the signal generator 6
A low frequency conversion carrier wave of frequency _C synchronized with the burst of the low frequency conversion color signal inputted from the input terminal 1 is generated and supplied to the other input of the frequency converter 7. The frequency converter 7 multiplies the two input signals in the same way as during recording, and the multiplication result passes through a bandpass filter 8 to extract only the signal with the frequency _SC + _C , which is supplied to one input of the frequency converter 4. be done.
The other input of the frequency converter 4 is supplied with the low-pass conversion color signal amplified to an appropriate level by the variable gain amplifier 3, multiplied by the signal of the frequency _SC + _C , and filtered from the multiplication result by a bandpass filter. A carrier color signal having a reference carrier frequency _SC synchronized with the carrier wave generated by the signal generator 5 is extracted by the (BPF) 11, and a reproduced carrier color signal is sent to the output terminal 2 via the output changeover switch 10.

Controls the gain of the variable gain amplifier 3, corrects the level of the color signal input from the input terminal 1, and level fluctuations, and corrects the level of the color signal supplied to the frequency converter 4 and the level of the color signal sent to the output terminal. The ACC operation is used to maintain the color signal level at a predetermined level, and has conventionally been performed in the following manner.

First, the switching circuit 12 takes in the carrier color signal after passing through the variable gain amplifier 3 during recording, and takes in the carrier color signal converted to the carrier frequency _SC after passing through the bandpass filter 11 during playback.
A burst gate (BG) 13 extracts only the burst portion of the captured carrier color signal. The extracted burst is subjected to peak level detection by a detection circuit (ACCDET) 14,
The detection result is passed through a low pass filter (LPF) 15 to suppress sudden fluctuations, and then supplied to the variable gain amplifier 3 as a control signal. variable gain amplifier 3
For example, if the peak value of the carrier color signal that is the source of the control signal is high, the gain is decreased, and if the peak value is low, the gain is increased.
3. A feedback loop formed by the detection circuit 14 and the low-pass filter 15 allows the variable gain amplifier 3, the frequency converter 4, the banner pass filter 11, the switching circuit 12, the burst gate 13, the detection circuit 14, and the low-pass filter 15 to be activated during reproduction. The feedback loop formed by this keeps the burst level of the color signal constant.

In the conventional color signal processing device as described above, the detection circuit 14 detects the carrier frequency _SC during both recording and reproduction.
(NTSC television signal: 3.58 MHz) bursts are detected at peak level, so high speed response is required, resulting in high current consumption.Furthermore, bursts are intermittent waves, so peak hold characteristics However, it also has the disadvantage that it requires characteristics that are the exact opposite of speed, making the circuit complex.
In addition, in recent years, the parts of color signal processing devices that traditionally performed analog processing have been digitized and converted to MOSIC.
There is a trend toward higher performance, lower power consumption, and fewer external components in devices, but this has been difficult to achieve with ACC detection circuits due to the high frequencies they handle. In addition, when the variable gain amplifier 3 and the detection circuit 14 are configured with linear circuits,
There is a drawback that the burst level controlled by the ACC operation drifts and becomes inconsistent, and the detection circuit 14 is configured to rectify the burst and hold its peak value, so the hold characteristic is such that the burst level is small. It is necessary to make the time constant small so as to be able to respond to fluctuations in different directions, which has the disadvantage that ripples of one horizontal period occur in the color signal level.

Purpose of the Invention The purpose of the present invention is to enable burst peak level detection at the color subcarrier frequency _SC , which was a drawback in the conventional example, by detection at a low low-pass conversion frequency _C , and to simplify the conventional killer detection circuit. The objective of the present invention is to provide a color signal processing device that is highly integrated and has low power consumption, is suitable for digital ICs, and is capable of integration and improved performance.

Structure of the Invention The color signal processing device of the present invention records and reproduces a color video signal, and during recording, converts the frequency of a carrier color signal separated from the color video signal into a low frequency converted color signal, and performs frequency conversion on the carrier color signal separated from the color video signal during recording. In some cases, in a recording and reproducing device that frequency-converts a reproduced low-pass converted color signal into a sending color signal and outputs the same, a frequency converter that performs frequency conversion during recording and reproduction, and an input signal of the frequency converter are used. a variable gain amplifier that varies the level of the frequency converter; a switching circuit that selects the output signal of the frequency converter during recording and the input signal of the frequency converter during playback; and a burst of the low frequency converted color signal selected by the switching circuit. a detection circuit that detects the level of the color signal and obtains a gain control signal to be supplied to the variable gain amplifier, detects the burst level of the color signal after passing through the variable gain amplifier, and uses the detection result as a control signal to drive the variable gain amplifier. A feedback loop that controls the color signal during recording and playback to a predetermined level.
It performs ACC operation.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of a color signal processing device in one embodiment of the present invention. In the figure, input terminal 1, output terminal 2, variable gain amplifier 3,
frequency converter 4, signal generator 5, signal generator 6,
The frequency converter 7, bandpass filter 8, lowpass filter 9, output changeover switch 10, and bandpass filter 11 operate in the same manner as in the conventional example during recording and reproduction. The method of controlling the color signal level is
First, the switching circuit 16 captures the recording low-pass converted color signal that has passed through the low-pass filter 9 during recording, and captures the low-frequency converted color signal that has passed through the variable gain amplifier 3 and has not been frequency-converted during playback. A burst gate (BG) 17 extracts only the burst portion of the captured carrier color signal. The extracted burst is subjected to peak level detection by a detection circuit (ACC DET) 18,
After passing the detection result through a low pass filter (LPF) 19, it is supplied to the variable gain amplifier 3 as a control signal.

As described above, according to this embodiment, during recording, the variable gain amplifier 3, the frequency converter 4, the switching circuit 16,
The ACC operation is performed by a feedback loop consisting of the burst gate 17, the detection circuit 18, and the low-pass filter 19. During playback, the variable gain amplifier 3, the switching circuit 16, the burst gate 17, the detection circuit 18,
A feedback loop consisting of a low-pass filter 19
ACC operation is performed.

Next, other embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram of a color signal processing device in another embodiment of the present invention.

The carrier color signal inputted from the input terminal 1 during recording passes through the variable gain amplifier 3, and is converted into a low-frequency converted color signal with carrier frequency _C in the same manner as in the conventional example or the first embodiment of the present invention, and is output. The signal is supplied to terminal 2 as a recording low frequency conversion color signal. However, 20,
22 is the signal generator [OSC1) (OSC2), 21 is 1/4
Frequency divider (1/4), 23 is signal generation circuit (PS/PI)
The signal generator 20 generates a signal with a frequency 4 _SC that is four times the color subcarrier frequency _SC , and the 4 _SC signal is divided by a 1/4 frequency divider 21 to create a color subcarrier with a frequency _SC . However, during recording, the signal generator 20 adjusts the generated signal so that the color subcarrier of frequency _SC created by the 1/4 frequency divider 21 is synchronized with the burst of the carrier color signal after passing through the variable gain amplifier 3. Frequency and phase are controlled. That is, signal generator 20 and 1/4 frequency divider 2
1, the signal generator 5 of the conventional example or the first embodiment of the present invention operates. In addition, the signal generator 22 performs an operation of multiplying the horizontal synchronizing signal of the color video signal to be recorded. For example, when recording a color video signal of the NTSC system in the VHS recording system, the horizontal synchronizing signal has a frequency 160 times higher, that is, low frequency conversion. The color signal _C is multiplied by 4 times and supplied to the signal generation circuit 23 which performs frequency division and phase shift or phase inversion processing every horizontal period, and the signal generation circuit 23 performs the above processing to obtain the frequency _C A low frequency converted carrier wave is created and supplied to the frequency converter 7. That is, the signal generator 22 and the signal generating circuit 23 perform the operation of the signal generator 6 of the conventional example or the first embodiment of the present invention.

Unlike the conventional example or the first embodiment of the present invention, the frequency converters 4, 7 and the bandpass filter 8 are not used during reproduction. First, the reproduced low frequency conversion color signal inputted from the input terminal 1 is amplified to an appropriate level by the variable gain amplifier 3, and then supplied to the A/D converter (A/D) 25 via the switching circuit 24. .
The conversion clock of the A/D converter 25 has a frequency 4 _C that is four times the low frequency conversion color signal _C from the signal generator 22.
signals are used. The frequency of the signal from the signal generator 22 is determined by the frequency of the low frequency converted carrier wave obtained by passing through the signal generation circuit 23 during reproduction and the burst of the reproduced low frequency converted color signal after passing through the variable gain amplifier 3. The phases are controlled to be synchronized, and the A/D converter 25 performs sampling and A/D.
The converted reproduced low frequency converted color signal becomes repeated data of color difference signal components BY, RY, -(B-Y), -(RY). Decoder (DECODE) 26
is to invert the sign of the repeated data and separate the data according to the timing of the low-frequency conversion carrier wave from the signal generation circuit 23 and the timing of the signal from the signal generator 22 that generates a signal with a frequency four times that of the low-frequency conversion carrier wave. The two color difference signal data, B
-Y and RY, and the two color difference signal data are supplied to digital comb filters 27 and 28, respectively, which remove crosstalk components of the reproduced signal and harmonic components due to sampling. Digital comb filter (COMB) 27,
The R-Y and BY data of the color difference signal after passing through 28 are supplied to an encoder (NECODE) 29 as (RY)' and (B-Y)'. The signal generator 21 becomes a fixed oscillator that generates a signal with a frequency of 4 _SC , which is four times the reference color subcarrier frequency _SC , during reproduction.
The encoder 29 inverts the sign of the color difference signal data (R-Y)' and (B-Y)' to create digital data -(R-Y)' and -(B-Y)'. Based on the count information from the frequency generator 21, (RY)',
The data of (B-Y)', -(R-Y)', -(B-Y)' are repeatedly sent out in the order of cycle 1/ _SC and sent to the D/A converter (D/A) as carrier color signal data. Supply to 30. The carrier color signal data is transmitted to the D/A converter 3.
After the signal is converted into an analog signal at 0, harmonics caused by sampling are removed by a band pass filter (BPF) 31, and the signal is sent to the output terminal 2 via the output selector switch 10 as a reproduced carrier color signal. As described above, in the color signal processing device according to the other embodiment of the present invention, as a frequency conversion method during reproduction, the reproduced low-frequency converted color signal after passing through the variable gain amplifier 3 is converted into an A/D converter.
A digital demodulation circuit consisting of a converter 25, a decoder 26, and digital comb filters 27 and 28 digitally demodulates the data into two color difference signal data, and then modulates it at a reference frequency to obtain a predetermined carrier color signal. I have to.

The ACC operation is performed by calculating an amplitude value from the value of the burst portion of the demodulated color difference signal data and feeding back that value.The operation will be explained below.

First, during recording, via the signal switching circuit 24,
The shogi recording low-pass conversion color signal after passing through the low-pass filter 9 is supplied to the A/D converter 25, which is used as part of a digital demodulation circuit for frequency conversion during reproduction. During recording, the signal generator 22 is controlled to generate a signal that is an integral multiple of the horizontal synchronization frequency and four times the low frequency conversion frequency _C , as described above, and furthermore, the recording low frequency conversion color signal is generated by its carrier wave. It is controlled by changing the frequency 4 _SC of the signal generated by the signal generation circuit 20 so that it is synchronized with the low frequency converted carrier wave generated by the signal generation circuit 23. Therefore, the A/D converter 25 and the decoder 26 can demodulate the low frequency converted color signal into two color difference signal data RY and BY. During reproduction, as explained above, the reproduced low frequency converted color signal is demodulated into two color difference signal data RY and BY for frequency conversion. For this reason, the low frequency converted color signal is digitally demodulated into two color difference signal data during both recording and reproduction, and the color difference signal data is used to output the burst amplitude value. Digital comb filter 2 is used as color signal data for calculating the amplitude of the burst.
Color difference signal data (R-Y) after passing through 7 and 28
(B-Y)' is used. This is because the circuit is used both during recording and reproduction, and therefore, the color difference signal data R-Y, B-Y are passed through the comb filter 27,
28, but if the low-frequency conversion color signal does not include a crosstalk component, it is not necessary to pass it through. Color difference signal data (RY)', (B-) after passing through the digital comb filters 27 and 28
Y)' is the burst part (RY)', (B
-Y)' is extracted and supplied to the detection circuit 33.
The detection circuit (ACCDET) 33 can be thought of as a circuit composed of a digital data calculation circuit and a D/A converter. For example, when a carrier color signal of the NTSC system is low-frequency converted, it is shown in the vector diagram of Fig. 4. As shown in FIG. is equivalent to the size of vector B, and as a first method, it is possible to D/A convert the absolute value of the (BY)' data extracted by the burst gate to obtain the peak level detection result. Also, as a second method, the data is supplied to the A/D converter 25 and decoder 26.
_4C clock and the phase of the burst of the low-frequency conversion color signal due to a delay in the response of the frequency/phase control of the signal generators 20 and 22, the burst will change to its original state as shown in Fig. 4B'. In some cases, the magnitude of vector B' cannot be determined due to an angle deviation of Δα with respect to the vector. To prevent this, B'b and B'a in Fig. 4 are set as B'b = |B' Using the fact that |∞Δα B′a=|B′|sinΔα, the color difference signal data of the burst part ((RY)′(B−Y)′, B′=√(′) ² +(′ ) ² =√(′) ² +(′) ² may be digitally calculated and the result obtained may be D/A converted and used as the peak level detection result.Also, as a third method, the circuit of the detection circuit 33 The setting value for controlling the burst level is given above, and for example, if the setting value is BC, when B'≦BC, the digital data is "H", and when B'>BC, the digital data is "L". configuring the detection circuit 33,
By smoothing the signal using a low-pass filter (LDF) 34 and supplying it to the variable gain amplifier 3 as a control signal, it is possible to control the burst level so that its magnitude is close to the BC of the digital data set by the detection circuit 33. be. Also burst level
Various methods can be used to obtain B', such as using the data with the largest value among the data obtained in the burst interval as B', or averaging the data in the burst interval to obtain B' data. be. Here, the detection circuit 18 of the first embodiment is considered to be almost equivalent to the circuit block composed of the A/D converter 25, decoder 26, comb filters 27, 28, and detection circuit 33 in other embodiments of the present invention. The principle of performing ACC operation by feeding back the burst level to the variable gain amplifier 3 via the low-pass filter 34 is as follows.
This is the same as the conventional example and the first embodiment of the present invention.
Figure 5 shows the vector of the low frequency converted color signal when the PAL carrier color signal is low frequency converted.
The R-Y axis is reversed every 1H like a and b, and the burst vector is also different from the vector in the (R-Y)' axis direction of the demodulation axis and (B-
The vector is a one-to-one addition of vectors in one direction with respect to the Y)' axis. However, when the PAL carrier color signal is low-frequency converted, the burst level of the low-frequency converted color signal is also B′=√(′) ² +(′) ² =√(−)′ ² +(−)′ ² It is obtained in the same way as the NTSC method, and the detection circuit 33 is also
This can be realized with the same configuration as the second and third methods in the case of the NTSC system.

Effects of the Invention As is clear from the above description, the present invention records and reproduces a color video signal, and during recording, frequency converts a carrier color signal separated from the color video signal into a low frequency converted color signal. In a recording and reproducing apparatus that converts the frequency of the reproduced low-pass converted color signal into a carrier color signal and outputs the same during reproduction, a frequency converter that performs frequency conversion during recording and reproduction, and a frequency converter that performs frequency conversion during recording and reproduction; a variable gain amplifier that varies the level of the input signal of the device; a switching circuit that selects the output signal of the frequency converter during recording and the input signal of the frequency converter during playback; and a low frequency conversion selected by the switching circuit. Conventionally, the configuration includes a detection circuit that detects the level of the burst portion of the color signal and obtains a gain control signal to be supplied to the variable gain amplifier.
Burst peak level detection, which was previously performed using a high-frequency color subcarrier frequency, can now be performed using a low-frequency, low-pass conversion color signal, and can be achieved with low-speed circuit operation, reducing circuit current consumption. Moreover, it has the advantage of being compatible with digitalization and MOSIC conversion at low speed.

Furthermore, the detection circuit is clocked at four times the frequency of the low frequency conversion color signal synchronized with the low frequency conversion carrier wave.
This configuration includes a decoder that samples and demodulates the two color difference signals in the burst portion of the decoder, and an arithmetic circuit that calculates the level of the burst to be fed back to the variable gain amplifier from the information of the two color difference signals in the burst portion of the decoder. It has become possible to detect various burst levels, which was difficult with conventional analog circuits.
This has the advantage that a detection circuit suitable for the low-frequency conversion color signal to be processed can be provided. In addition, it is possible to set the burst level in the digital data detection circuit that performs ACC operation, so that drift of the burst level due to ring temperature changes will not occur in the digital data part, and ACC operation due to ring temperature changes will not occur. This has the effect of reducing level fluctuations in color signals after the process. Furthermore, when detecting the peak level of a burst using conventional analog processing, it was difficult to increase the time constant during hold because it responded to level fluctuations in the direction of decreasing the burst level. ,
Since the burst level is detected and a signal for controlling the gain of the variable gain amplifier is created based on the result, the response to level fluctuations of the converted color signal is quick.
By holding the digital data in the hold characteristic, the detection result for one horizontal period is maintained as it is, which has the effect of not causing ripples for one horizontal period.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional color signal processing device.
FIG. 2 is a block diagram of a color signal processing device in one embodiment of the invention, FIG. 3 is a block diagram of a color signal processing device in another embodiment of the invention, and FIG. 4 is a block diagram of a color signal processing device in another embodiment of the invention.
FIG. 5 is a vector diagram of a low frequency conversion burst when a carrier color signal of the NTSC system is low frequency converted. FIG. 5 is a vector diagram of a low frequency conversion burst when a carrier color signal of the PAL system is low frequency converted. 1... Input terminal, 2... Output terminal, 3... Variable gain amplifier, 4, 7... Frequency converter, 5, 6... Signal generator, 8... Band pass filter, 9... Low pass filter, 10... Output selector switch, 11 ...Band pass filter, 16...Switching circuit, 17...Burst gate, 18...Detection circuit, 19...Low pass filter, 20, 22...Signal generator, 21...1/4 frequency divider,
23...Signal creation circuit, 24...Switching circuit, 25...
A/D converter, 26...decoder, 27, 28...digital comb filter, 29...encoder, 30
...D/A converter, 31...Band pass filter, 3
2... Burst gate, 33... Detection circuit, 34... Low pass filter.

Claims (1)

[Scope of Claims] 1 Recording and reproducing a color video signal, converting the frequency of a carrier color signal separated from the color video signal into a low frequency converted color signal during recording, and converting the frequency of a carrier color signal separated from the color video signal into a low frequency converted color signal during playback. In a recording and reproducing apparatus that frequency converts a low frequency converted color signal into a carrier color signal and outputs the same, a frequency converter that performs frequency conversion during recording and reproduction;
a variable gain amplifier that varies the level of the input signal of the frequency converter; a switching circuit that selects the output signal of the frequency converter during recording and the input signal of the frequency converter during playback; A color signal processing device comprising a detection circuit that detects the level of a burst portion of a low frequency converted color signal and obtains a gain control signal to be supplied to the variable gain amplifier. 2. The detection circuit includes a decoder that samples and demodulates the low frequency conversion color signal into two color difference signals using a clock with a frequency four times higher than the low frequency conversion carrier wave, and a decoder that samples and demodulates the low frequency conversion color signal into two color difference signals, and a signal that is variable based on the information of the two color difference signals in the burst portion of the decoder. 2. The color signal processing device according to claim 1, further comprising an arithmetic circuit that calculates the level of the burst that is fed back to the gain amplifier. 3. The frequency converter that converts the frequency of the low frequency conversion color signal during reproduction includes a decoder that constitutes a detection circuit,
3. The color signal processing device according to claim 2, further comprising an encoder that performs orthogonal two-phase modulation on the two color difference signals demodulated by the decoder and converts them into a carrier color signal.