JPH09154156A - YC separation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize configuration of a BPF with the similar scale by using the YC separator circuit so as to reduce a capacity of a line memory by a specific sample than that of a conventional device through adaptive configuration thereby reducing the circuit scale. SOLUTION: Each of line memories 10, 11, 14, 15 is a FIFO memory whose delay stage number is, e.g. 910. A composite video signal is sampled by a frequency synchronously with a phase of a color burst and which is a multiple of 910 of a horizontal scanning frequency and given to a BPF 12 and the line memory 10. The BPF 12 is a BPF whose center frequency is a chrominance subcarrier frequency 4.43MHz of the PAL system and extracts a chrominance signal component of a current line. Similarly the composite video signal delayed by 2H at the memories 10, 11 is given to a BPF 13, from which the signal is extracted as a chrominance signal component before 2H. Furthermore, the chrominance signal component is delayed by 2H further in the line memories 14, 15 and the presence of correlation is detected between the current line signal being an output of the line memory 15 and a signal before 4H is detected so as to reduce the memory capacity by the specific sampling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a YC separation circuit used in a television or VTR compatible with the NTSC system and the PAL system.

[0002]

2. Description of the Related Art In recent years, as televisions have become larger and wider in Japan, televisions or V
TRs are being introduced to the market one after another, but most of them are
The mainstream is a digital signal processing technique using a memory represented by a YC separation circuit.

As a circuit configuration, for example, in the NTSC system, it is large in view of easiness of signal processing as described in "Multidimensional signal processing of TV image" (Takahiko Fukibuki, Nikkan Kogyo Shimbun, P85-86). The part selects a frequency that is four times the color subcarrier (about 3.58 MHz) and is synchronized with the phase of the color burst as the sampling frequency. PAL
Also in the system, as disclosed in, for example, Japanese Patent Laid-Open No. 4-170890, a color subcarrier (about 4.43 MH) is used.
A YC separation circuit has been proposed which operates at a sampling frequency which is four times z) and which is synchronized with the phase of the color burst. The purpose of this conventional technique is to perform high-precision YC separation by accurately switching between two-dimensional processing for performing arithmetic operation in the vertical direction of a video signal and three-dimensional processing for performing processing in the time direction. The line memory used in the two-dimensional processing is 2270 with 2 lines according to the above sampling frequency.
A sample volume is required.

A system compatible with both the NTSC system and the PAL system is proposed in Japanese Patent Laid-Open No. 4-188990. In this conventional technique, as shown in FIG. 5, a transfer function of a bandpass filter 56 (hereinafter referred to as BPF) is generated by generating four times the frequency of a color subcarrier in both the NTSC system and the PAL system by a clock generation circuit 50. And the circuit is completely shared, and the memory 53 for delaying the composite signal is also unified with the capacity according to the PAL method with a high sampling frequency, so that the delay according to each method can be obtained. 52 controls the memory 53.

[0005]

In the above prior art,
The sampling frequency is set to four times the frequency of the color subcarrier for all PAL processing. One of the reasons for selecting this frequency is that the BPF for extracting the color signal can be realized with a very simple structure. However, on the other hand, the sampling frequency becomes higher, and the amount of one horizontal synchronizing signal period stored in the memory is 910 of the NTSC system.
Compared to the sample, the PAL method has 1135 samples, which is an increase of about 25%.

Further, in the case of the PAL system, two lines are required in consideration of the phase of the color signal, and a memory for four lines in total is required to perform the adaptive processing. If this case is converted to the NTSC system, it corresponds to a memory amount of about 5 lines. The first of the above-mentioned conventional techniques does not refer to the amount of memory used, and the second case is premised on mounting outside the LSI.

However, line memory is currently LS
Since it is almost always on-chip on I, such a large-capacity memory has a problem that the chip area of the LSI is remarkably increased, resulting in a significant cost increase. The present invention solves the above-mentioned conventional problems.
The sampling frequency of the L method is set to the horizontal scanning frequency of 910.
Double the frequency and synchronize with the phase of the color burst to reduce the memory usage and realize the BPF with a very simple structure. Furthermore, even when shared with the NTSC system, the selection of the delay amount is output to the memory. It is an object of the present invention to provide a YC separation circuit which is switched and does not require memory control.

[0008]

In order to achieve this object, the present invention is a YC separation circuit for separating a PAL system composite signal into a luminance signal and a chrominance signal, and a bandpass for band limiting the composite signal. It has a filter and a memory that delays the composite signal or the output of the bandpass filter for a predetermined period, and the bandpass filter and the memory operate at a frequency 910 times the horizontal scanning frequency and in synchronization with the phase of the color burst. A characteristic YC separation circuit, a YC separation circuit for separating a composite signal of the NTSC system and the PAL system into a luminance signal and a chrominance signal, the transfer function of a bandpass filter for band limiting the composite signal, and the composite signal or The output of the memory that delays the output of the bandpass filter for a predetermined period NTSC or has a configuration that switches between the PAL system, four times the frequency of the color subcarrier in the case of the band-pass filter and memory NTSC system, P
Provided is a YC separation circuit which operates at a frequency 910 times the horizontal scanning frequency in the case of the AL system, both of which are synchronized with the phase of the color burst.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a YC separation circuit for separating a composite signal of the PAL system into a luminance signal and a chrominance signal, and a band pass filter for limiting the band of the composite signal, the composite signal or the band signal. A memory for delaying the output of the pass filter for a predetermined period, and the band pass filter and the memory operate at 910 times the horizontal scanning frequency and at a frequency synchronized with the phase of the color burst. Circuit, or a YC separation circuit for separating a composite signal of the NTSC system and the PAL system into a luminance signal and a chrominance signal, the transfer function of a bandpass filter for band limiting the composite signal, and the composite signal or Memory for delaying the output of the bandpass filter for a predetermined period The output is switched between the NTSC system and the PAL system, and the bandpass filter and the memory are four times the frequency of the color subcarrier in the case of the NTSC system and the horizontal scanning frequency in the case of the PAL system. The YC separation circuit is characterized in that it operates at a frequency of 910 times, both of which are synchronized with the phase of the color burst. Therefore, when the input composite signal is the PAL system, the number of samples in the horizontal direction is At 910 samples, all vertical sampling positions are aligned.

In the PAL system, since the phase of the color signal is inverted every two lines, the color signal is extracted by subtracting the composite signal two lines before, and the color signal band-limited by the BPF is subtracted from the input composite signal. Then, a luminance signal can be obtained. In this case, the capacity of the line memory is 1820 samples. Further, in the case of sharing with the NTSC system, the capacity of the memory for one line is the same, so that when the delay amount is switched, the phase-reversed color signal of each system is obtained only by selecting the output of the memory.

Here, in order to obtain the above-mentioned color signal, BP
Although it is necessary to switch F, in reality, most of the circuits are shared and the frequency characteristics of the NTSC system and the PAL system can be realized, so that the NTSC system and the NTSC system can be used with almost the same circuit configuration without significantly increasing the circuit scale. PAL YC separation can be realized. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram for explaining the first embodiment of the YC separation circuit of the present invention. FIG.
In the above, the line memories 10, 11, 14, and 15 are all FIFO memories having a delay stage number 910. The composite signal sampled at a frequency that is 910 times the horizontal scanning frequency and synchronized with the phase of the color burst is the BPF.
12 and the line memory 10.

The BPF 12 is a PAL color subcarrier 4.
A bandpass filter having a center frequency of 43 MHz extracts the color signal component of the current line (hereinafter, the signal that has passed through the BPF is referred to as a color signal component). In addition, the composite signal delayed by 2H (H: horizontal synchronizing signal period) in the line memories 10 and 11 is input to the BPF 13 and 2
It is similarly extracted as the color signal component before H.

Further, the color signal components extracted by the BPF 13 are further delayed by 2H in the line memories 14 and 15. The arithmetic circuit 16 is a comb-shaped filter for separating color signals, and the presence or absence of correlation between the current line, which is the output of the BPF 12, the line memory 15, and 4H before, based on the color signal 2H before the output of the BPF 13. Is detected and the calculation is performed with the line having a stronger correlation.

Finally, the luminance signal is obtained by subtracting the chrominance signal output from the arithmetic circuit 16 from the 2H delayed composite signal output from the line memory 11 by the subtractor 17. FIG. 2 is a block diagram showing a specific configuration of the BPFs 12 and 13, and the transfer function is H (z) = 27/25.
Represented by ^{6 · (1-z -1)} 2 · (1-z -2) 2, its frequency characteristic is shown in FIG.

As described above, only the filter block 20 represented by the term (1-z ^-2 ), the filter block 21 represented by the term (1-z ^-1 ), and the coefficient circuit 22 are compatible with the PAL system. The BPF can be easily constructed. (Second Embodiment) FIG. 3 is a block diagram for explaining a second embodiment of the YC separation circuit of the present invention.

In FIG. 3, line memories 300 and 30 are provided.
1, 306 and 307 are all FIFs with a delay stage number of 910.
O memory. When the input signal is the NTSC system, the composite signal sampled at a frequency synchronized with the color burst at four times the color subcarrier is NTSCBPF30.
4 (NTSC system BPF, the same applies hereinafter)
Is input to the line memory 300.

The NTSC BPF 304 has a color subcarrier 3.
A band pass filter having a center frequency of 58 MHz, which band-limits the composite signal of the current line. In addition, the composite signal delayed by 1H in the line memory 300 passes through the selector 302 and NTSCBPF3.
The color signal component of 1H before is input to 10 and extracted.

Further, the color signal component extracted by the NTSCBPF 310 is further delayed by 1H in the line memory 306 through the selector 311. The arithmetic circuit 312 is a comb filter that separates the color signals, and the selector 30 uses the color signal component of 1H before which is the output of the selector 311 as a reference.
Whether or not there is a correlation between the current line, which is the output of 5,308, and the color signal component 2H before is detected, and the calculation is performed with the line having a stronger correlation.

Finally, the color signal output from the arithmetic circuit 312 is subtracted from the composite signal delayed by 1H output from the selector 302 by the subtractor 313 to obtain a luminance signal. On the other hand, when the input signal is the PAL system, the composite signal sampled at a frequency 910 times the horizontal scanning frequency and synchronized with the phase of the color burst is P
The ALBPF 303 (in the sense of the BPF for the PAL system, the same applies hereinafter) and the line memory 300 are input.

The PALBPF 303 has a color subcarrier 4.43.
A bandpass filter having a center frequency of MHz extracts the color signal component of the current line. The composite signal delayed by 2H in the line memories 300 and 301 is input to the PALBPF 309 through the selector 302 and similarly extracted as the color signal component 2H before.

Further, the color signal components extracted by the PALBPF 309 pass through the selector 311 and the line memory 3
It is further delayed by 2H at 06 and 307. Arithmetic circuit 312
Is a comb-shaped filter for separating color signals, and the selector 3
Based on the color signal of 2H before that which is the output of 11, the selector 3
The presence / absence of correlation between the current line, which is the output of 05, 308, and 4H before is detected, and calculation is performed with the line with stronger correlation.

Finally, the color signal output from the arithmetic circuit 312 is
Signal delayed by 2H which is the output of selector 302
The luminance signal is subtracted from the output signal by the subtractor 313.
can get. FIG. 4 shows a concrete example of the filter blocks 30 and 31.
It is a block diagram showing various configurations and the transfer function is NTSC method.
In the formula, H_NTSC(Z) = 1/16 · (1-z^-2)^FourTona
In the PAL system, H_PAL(Z) = 27/256
(1-z^-1)^Two・ (1-z^-2) ^TwoBecomes

That is, the transfer function (1-z ^-2 ) ² is H
_NTSC, H _PAL both common BPF40,41 next, the remaining (1-z ^{-1) 2} and (1-z ^{-2) 2} is, BPF42,4
As shown in FIG. 3, the number of unit delay elements z ⁻¹ may be switched between the PAL system and the NTSC system by the selector. Finally, the coefficient circuit 44 multiplies each coefficient to realize two characteristics easily.

Therefore, the filter block 30 of FIG.
The filter block 31 and the filter block 31 do not need to switch independent filters, but can be practically shared. Finally, FIG. 7 shows a characteristic diagram showing the frequency characteristic of the NTSC BPF shown in the present embodiment. In each of the embodiments of the present invention, a two-dimensional Y using line memory is used.
Although the C separation circuit has been described, it goes without saying that the C separation circuit can also be applied to a three-dimensional YC separation circuit using a field or frame memory.

[0026]

When the YC separation circuit of the present invention is used, the capacity of the line memory in the adaptive configuration is reduced by 900 samples compared with the conventional example, so that the circuit scale is reduced by about 3000 gates and the BPF configuration is also improved. Since it is very simple, it can be realized on the same scale as the conventional one. Further, in the sharing with the NTSC system as well, the memory control circuit is not required because the memory selection only needs to switch the output.

On the other hand, in the BPF, the number of circuits is increased because the frequency characteristics are switched. In this case, however, the unit delay element and the subtractor are shared to constitute the circuit, so that the increase in the circuit scale is almost negligible. Is. Further, as a ripple effect, the sampling frequency is about 14.3 MHz in the NTSC system and about 14.2 MHz in the PAL system, which are very close to each other. Therefore, in the television or VTR to which the present invention is applied, the signal after YC separation is performed. When the processing is performed digitally, both types of processing can be performed with almost the same circuit, and the circuit can be shared here as well, which greatly improves the development efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram of a YC separation circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of BPFs 12 and 13 of the YC separation circuit.

FIG. 3 is a block diagram of a YC separation circuit according to a second embodiment of the present invention.

FIG. 4 is a filter block 30, 31 of the same YC separation circuit.
Block diagram showing the configuration of

FIG. 5 is a block diagram of a conventional YC separation circuit.

FIG. 6 is a characteristic diagram showing frequency characteristics of a PAL-type BPF.

FIG. 7 is a characteristic diagram showing frequency characteristics of an NTSC BPF.

[Explanation of symbols]

10, 11, 14, 15, 300, 301, 306, 3
07 line memory 12, 13, 303, 309 PAL bandpass filter 304, 310 NTSC bandpass filter 302, 305, 308, 311 selector 16, 312 arithmetic circuit 17, 313 subtractor

Claims (4)

[Claims] 1. A YC separation circuit for separating a PAL-type composite signal into a luminance signal and a chrominance signal, wherein a bandpass filter for limiting the band of the composite signal and an output of the composite signal or the bandpass filter are predetermined. A memory for delaying for a period, wherein the bandpass filter and the memory have a horizontal scanning frequency of 910.
A YC separation circuit, which operates at a frequency doubled and synchronized with the phase of the color burst. 2. The YC separation circuit according to claim 1, wherein the band-pass filter uses z ⁻¹ as a unit delay element and the transfer function is represented by a combination of a term of 1-z ^{−1 and} a term of 1-z ^−2. . 3. A YC separation circuit for separating an NTSC composite signal and a PAL composite signal into a luminance signal and a chrominance signal, the transfer function of a bandpass filter for band limiting the composite signal, and the composite signal or the band. The output of the memory for delaying the output of the pass filter for a predetermined period is switched between the NTSC system and the PAL system. When the band pass filter and the memory are of the NTSC system, the frequency is four times the frequency of the color subcarrier. , PAL system, the horizontal scanning frequency of 91
A YC separation circuit, which operates at a frequency of 0 times and both of which are synchronized with the phase of the color burst. 4. The band-pass filter uses z ^-1 as a unit delay element, and in the PAL system, the transfer function is 1-z ^-1 and 1
4. The YC separation circuit according to claim 3, which is represented by a combination of a term with −z ^−2, and the transfer function is represented by a term with only 1−z ⁻² in the NTSC system.