JPS63187894A - Color signal processing circuit - Google Patents

Abstract

PURPOSE:To reduce cross color disturbance by providing a demodulation band variable means varying a demodulation band of an I (orange, cyan group) depending on a control signal outputted by a movement detection circuit in a television signal color signal processing circuit demodulating the I and Q axis color using moving adaptive Y/C (luminance signal/chrominance signal) separator circuit. CONSTITUTION:A movement detection circuit 16 detects the moving quantity of a composite video signal and outputs a control signal (k) controlling mixers 8, 11. A chrominance signal Cp obtained from an inter-frame C separator circuit 6 and a chrominance signal Cf obtained from an in-field C separator circuit 7 are given to an input of a mixer 8 respectively. The control signal (k) increases the ratio of addition of the CF when the moving quantity is small and increases the addition ratio of the Cf when the moving quantity is large. A mixer 11 as a demodulation band variable means receives a narrow band chrominance signal obtained from a BPF 9 and a wide band chrominance signal obtained from a delay circuit 10 and is subjected to control so as to increase the addition ratio of the wide band chrominance signal when the moving quantity is small and to increase the narrow band chrominance signal addition ratio when the moving quantity is large depending on the control signal (k) given through a delay circuit 17 and mixes the both.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color signal processing circuit for a television signal that performs I-axis and Q-axis color demodulation using a motion adaptive fail Y/C separation circuit.

[Conventional technology]

In current NTSC receivers, the color signal (hereinafter referred to as C) is frequency-multiplexed with the luminance signal (hereinafter referred to as Y), which causes cross color interference and dot interference, resulting in image quality deterioration. was inviting.

A motion-adaptive Y/C separation circuit is known as a means for eliminating these image quality deterioration factors and achieving high two-dimensional image quality.

This detects the movement of the image, performs Y/C separation by interframe processing using a frame comb filter for still image areas, and uses a line/ High image quality was achieved by performing Y/C separation through in-field processing using a low-pass filter (hereinafter referred to as LPF).
There is.

As a color signal processing circuit using this Aki Y/C separation circuit,
, for example, JP-A-58-129892, JP-A-55
Examples include those described in Japanese Patent No.-125280.

[Problem that the invention seeks to solve]

In the NTSC system, the demodulation axes selected during color demodulation include the (R-y) axis, the (B-Y) axis, the I-axis, and the Q-axis.

The signals corresponding to the (R-y) and (B-y) axes are both 0.
．． The signal corresponding to the I-axis has a band of 5jfHz, whereas the signal corresponding to the I-axis is 'L5MHr:, and the signal corresponding to the Q-axis is 0.5MHZ.
It has a band of z.

In general, the human eye has a visual characteristic of superior color resolution compared to orange/white and cyan (I-axis), and high image quality can be achieved with a motion-adaptive Y/C separation circuit. For television W7 receivers, I-axis and Q-axis demodulation with high color resolution is suitable.

However, in the above-mentioned prior art, no consideration was given to Q-axis demodulation.

In-field Y/C separation in a moving image area according to the prior art described above can in principle perform complete separation, but only reduces kissing, dot interference, and cross-color interference.

For this reason, when I-axis and Q-axis demodulation is applied, crosstalk with the Y signal increases because the I signal has a wide band, and the (R-Y) axis in the video area increases.

With respect to (s-y) axis demodulation, there is a problem in that the image quality is degraded because the deterioration due to cross color interference becomes more severe than the improvement in color resolution.

An object of the present invention is to provide a color signal processing circuit optimal for a motion adaptive Y/C separation circuit that performs I-axis and Q-axis demodulation.

[Means for solving problems]

The above purpose is! This is achieved by providing a demodulation band variable means for varying the demodulation band of the signal by degrees Celsius according to the control signal output from the motion detection circuit.

[Effect]

The motion detection circuit detects motion from the difference in signal level between frames, and outputs a control signal for controlling the mixing ratio of the output of the interframe Y/C separation circuit and the output of the intrafield Y/C separation circuit. do.

The demodulation band variable means varies the demodulation band to a wide band (for example, 0 to 15 MHz) in the still image area and to a narrow band (for example, 0 to (L5Mfz)) in the moving image area based on the control signal.

As a result, it is possible to reduce the amount of cross color with the Y signal in the moving image area, and it is possible to reduce cross color interference.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of a color signal processing circuit according to the present invention, in which 1.18 is an input terminal;
4, 10, 17 are delay circuits, 3 is a subtracter, 5゜14
, 15 is an output terminal, 6 is an inter-frame C separation circuit, 7 is an intra-field C separation circuit, 8.11 is a mixer, 9 is a BPF consisting of an acyclic (hereinafter referred to as FIR) digital filter, and 12 is a BPF consisting of an acyclic (hereinafter referred to as FIR) type digital filter. Multiplexer, 13 is color demodulation circuit, 1
6 is a motion detection circuit.

In the figure, an A/D converted digital composite video signal from an input terminal 1 is passed through a delay circuit 2 to a subtracter 3. Interframe C separation circuit 6. Intra-field C separation circuit 72. and the motion detection circuit 16.

Note that the sampling frequency selected during A/D conversion is generally the color subcarrier frequency fsc (medium 58 MHz).
) 3 times 5fsc (medium 1α74MHz) or 4 times 4fscC 14.3:? M#z). Hereinafter, in the embodiment of the present invention, a case where the sampling frequency is 4 fsc will be described.

The inter-frame C separation circuit 6 is composed of an FIR type digital filter having a tap delay circuit of at least one frame cycle, and performs band limitation on the time-frequency axis to extract color signal components from the composite video signal. It separates and extracts the

The intra-field C separation circuit 7 is composed of an FIR type digital filter having one or both of tap delay circuits in units of 1H (H indicates a horizontal scanning period) or in units of 1 pixel. By performing the above band limitation, color signal components are separated and extracted from the composite video signal.

Color demodulation! In order to obtain color signals with high color resolution, the color signals obtained from the inter-frame C separation circuit 6 and the intra-field C separation circuit 7 must be converted into color subcarriers at least as components on the horizontal frequency axis. Frequency fsc (K55
8nfz) A bandpass characteristic of ±1.5 JfHz or more is required at the center of 'Sc'.

The motion detection circuit 16 is composed of an FIR type digital filter having a tap delay circuit for at least one frame period, detects the amount of motion of the composite video signal, and detects the amount of motion of the composite video signal.
It outputs a control signal k for controlling 11.

The color signal CF obtained from the inter-frame C separation circuit 6 and the color signal C7 obtained from the intra-field C separation circuit 7 are respectively applied to the input of a mixer 80.

The mixer 8 adds C and C7 at an addition ratio determined by the control signal k. This control signal has a value in the range of 0≦≦1 so that when the amount of motion is small, the addition ratio of C is increased, and when the amount of movement is large, the addition ratio of C1 is increased.

The color signal obtained from the output of this mixer 8 is sent to a subtracter 5. B
PF9. The signal is applied to the delay circuit 10.

A luminance signal is obtained from the output of the subtracter 3 by removing the color signal component in the composite video signal, and the extracted luminance signal is outputted from the output terminal 5 via the delay circuit 4.

The EPF 9 limits the band of the input color signal to a narrow band, and has a band-pass characteristic of approximately ±0.5 MHz around fsc, for example.

The delay circuit 10 corrects the delay time difference between the narrowband chrominance signal obtained from the BPF 9 and the wideband chrominance signal that is its input, and can actually be replaced with the tap delay circuit of the BPF 9. There is no need to provide a separate delay circuit 10.

A mixer 11 serving as a demodulation band variable means inputs the narrowband chrominance signal obtained from the BPF 9 and the wideband chrominance signal obtained from the delay circuit 10. When the amount of motion is small, the addition ratio of the wideband color signal is increased, and when the amount of motion is large, the addition ratio of the narrowband color signal is controlled to be increased, thereby mixing the two.

Here, when the sampling frequency during A/D conversion is 4 fsc, four sampling points are obtained in the color subcarrier period. At this time, if the sampling clock is phase-locked to the I and Q axes, these four sampling points will be I.

Q, -1, -Q! Sample points for only the component and sample points for only the Q component are obtained in a time-division multiplexed manner.

Therefore, the output of the BPF 9 is introduced into one input of the multiplexer 12, and the output of the mixer 11 is introduced into the other input, and these are controlled by a timing signal supplied from the input terminal 18.
The sample value of the Q component is obtained from the output of F9, and the sample value of the Q component is obtained from the output of mixer 11! Sample values of the components are alternately selected pixel by pixel and output to the color demodulation circuit 13.

The color demodulation circuit 13 detects a sample point whose sign is reversed (-bar Q
) is inverted or thinned out, and the baseband I and Q signals are obtained by separating the I-component sample value sequence and the q-component sample value sequence.

The timing signal can be easily derived from a clock regeneration circuit that regenerates the clock.

According to this example! Regarding the signal sample values, the demodulation band of the I signal can be made variable by changing the bandpass characteristics according to the movement.

As a side note, since the high-frequency components of the I signal can be sufficiently attenuated in the moving image area, cross-color interference can be reduced without sacrificing the advantages of I-axis and Q-axis demodulation in the still image area.

FIG. 2 is a block diagram showing a second embodiment of the present invention, in which 19 is an inter-frame Y/C separation circuit, 20 is an intra-field Y/C separation circuit, 21 and 22 are mixers, and others. The symbols correspond to the same parts as in FIG.

In the figure, the digital composite video signal from the input terminal 1 is transmitted to the interframe Y/C separation circuit 19. In the field Y/
C separation circuit 20. The signal is applied to the motion detection circuit 16.

The inter-frame Y/C separation circuit 19 is an FIR type digital filter having a tap delay circuit of at least one frame cycle, and separates and extracts the luminance signal and color signal by applying band limitation on the time-frequency axis. It is something.

The intra-field Y/C separation circuit 20 is an FI having one or both of tap delay circuits of 11 units or 1 stroke unit.
This is an R-type digital filter that separates and extracts a luminance signal and a chrominance signal by band limiting on the horizontal frequency axis and the vertical frequency axis.

Note that also in this embodiment, the interframe Y/C separation circuit 1
The color signals obtained from the Y/C separation circuit 9 and the intra-field Y/C separation circuit 20 must have the same band as in the first embodiment.

This inter-frame Y/C separation circuit 19 and intra-field Y
A luminance signal Y obtained from each of the /C separation circuits 20.

Y is applied to the input of the mixer 21, and the color signals C,,C.

is applied to the input of mixer 22.

The mixers 21 and 22 perform addition at an addition ratio determined by the control signal k output from the motion detection circuit 16, as in the first embodiment. can get.

The color signal obtained from this mixer 22 is given as a narrowband color signal and a wideband color signal to two inputs of the mixer 11 via a BPF 9 and a delay circuit 10 as in the first embodiment.
The addition ratio is controlled by the control signal k obtained via the delay circuit 17.

The multiplexer 12 and the color demodulation circuit 16, which receive the color signal obtained from the mixer 11 and the color signal obtained from the EPF 9, operate in the same manner as in the first embodiment, and demodulate the I signal and Q signal. Output.

Therefore, this embodiment is also similar to the first embodiment! The demodulation band of the signal can be varied, and cross-color interference in the moving image area can be reduced without impairing the advantages of I-axis and Q-axis demodulation in the still image area.

FIG. 3 is a block diagram showing the sixth embodiment of the present invention, in which 23, 27 and 29 are delay circuits, 24, 25 and 26 are LPFs consisting of FIR type digital filters, and 28 is a mixer. , and other symbols are the same as in the previous embodiment.

In the same figure, Y/C separation is performed by delay circuits 2 and 2, similarly to the first embodiment shown in FIG. Interframe C separation circuit 6. In-field C separation circuit7. Mixer 8° motion detection circuit 16
．． The subtracter 3 outputs the luminance signal and the mixer 8 outputs the chrominance signal.

The color signal obtained from mixer 8 is applied to the input of color demodulation circuit 13. The q signal obtained from the color demodulation circuit 13 is passed through an LPF 24 with a passband of approximately O-0.5 MHz in order to remove crosstalk with the high frequency components (0.5 to i, 5 JfHz) of the I signal. is applied to the output terminal 14, band-limited, and output to the output terminal 14.

Further, the I signal obtained from the color demodulation circuit 13 is passed through the LPF.
25 and 26, respectively. LPF 25
This is to limit the band of the I signal to a narrow band, and this can be done by setting the passband to about 0 to 0.5 MHz, for example.

The LPF 26 limits the I signal to a wide band, and the passband is set to approximately O=t5MHz.

The output of the LPF 26 is connected to the LPF by a delay circuit 27.
The delay time difference with the output of F 25 is corrected, and the mixer 28
is given to one input of Further, the output of the LPF 25 is applied to the other input of the mixer 28, and the addition ratio is controlled by the control signal k obtained via the delay circuit 23.

This operates to increase the addition ratio of the broadband I signal when the amount of motion is small, and to increase the addition ratio of the narrowband I signal when the amount of motion is large.

Therefore, this example is similar to the previous example! The demodulation band of the signal can be varied according to the amount of motion, and in the moving image region, the high frequency components of the I signal can be attenuated, so cross-color interference can be reduced.

In this embodiment, the sampling frequency is set to 4fsc, for example.
If the harmonics generated due to demodulation are to be treated in the same way as the harmonics generated due to sampling, it is necessary to limit the band on the horizontal frequency axis of the color signal in the previous Y/C separation process. , the LPF 26 can be made unnecessary by performing this in accordance with the demodulation band of the I signal determined by the LPF 26.

Furthermore, when the LPF 26 is removed, a tap delay circuit constituting the LPF 25 can be substituted for the delay circuit 27.

In addition, as mentioned earlier, when the sampling frequency is 4fSC, the I component sample value and the Q component sample value are obtained in a time-division multiplexed form, so the LPF
25 and 26 can be shared, and the circuit scale can also be reduced.

Furthermore, by connecting the output of the mixer 22 shown in FIG. 2 to the input of the color demodulation circuit 1SO shown in FIG.
It is clear that it can be applied to the embodiment of the C isolation circuit.

FIG. 4 is a block diagram showing a fourth embodiment of the present invention, in which 30, 31, 32, and 34 are delay circuits, and 33 is an FIR
The other symbols are the same as those in the previous embodiment.

In the figure, an inter-frame Y/C separation circuit 19 and an intra-field Y/C separation circuit 20 each have the configuration described in the previous embodiment, and convert the digital composite video signal input from the input terminal 1 into a luminance signal. and color signals.

The luminance signal Y, output from the inter-frame y7c separation circuit 19, is applied to one input of the mixer 21 via the delay circuit 50, and the color signal C, is applied to the mixer 21 via the delay circuit 31.
is applied to one input of 2.

The luminance signal Y7 output from the intra-field Y/C separation circuit 20 passes through the delay circuit 62 and becomes the other input of the mixer 21, and the color signal C1 passes through the BPF 55 and becomes the other input of the mixer 22. It becomes input.

The BPF 33 narrows the broadband color signal extracted from the intra-field Y/C separation circuit 20, for example, f
The passband is approximately ±0.5 MHz centered on SC.

The mixers 21 and 22 are connected from the motion detection circuit 16 to the delay circuit 34.
Similarly to the previous embodiment, the addition ratio is controlled by the control signal k applied through the mixer 21, and the output of the mixer 21 provides the luminance signal, and the output of the mixer 22 provides the chrominance signal. The color signal obtained from the mixer 22 is demodulated and separated into baseband I and q signals by a color demodulation circuit 15.

According to this embodiment, the path for providing the color signal from the intra-field Y/C separation circuit 20 to the mixer 22 has a narrow band or PF.
By providing 33, it is possible to narrow the band of the I signal in the moving image area, and it is also possible to share the mixer for varying the demodulation band of the I signal.

Furthermore, in the first embodiment shown in FIG.
In the path connecting the separation circuit 7 and the mixer 8.

By providing the narrowband EPF 55 as in this embodiment, the temperature difference in the embodiment shown in FIG. It is obvious that the variable means of this embodiment can be applied in place of the signal demodulation band variable means.

FIG. 5 is a block diagram showing a fifth embodiment of the present invention, in which 55 and 56 are E
PF, 57, 42, 46, 50, 51.52 are delay circuits, 38 is a multiplexer, 69 is a color demodulation circuit, 40 is an inter-frame C separation circuit, and 41 is an intra-field C separation circuit.

43 is an LPF consisting of an FIR type digital filter, 4
4.

53 is a mixer, 45 is a demultiplexer, 48 is an interframe Y separation circuit, 49 is an intrafield Y separation circuit, and the other symbols are the same as in the previous embodiment.

In the same figure, the degree Celsius, frame difference amount Y separation circuit 48, and interframe C separation circuit 40 are composed of FIR type digital filters having a tag delay circuit of at least one frame period, and the brightness is It separates and extracts signals and color signals.

The intra-field Y separation circuit 49 and the intra-field C separation circuit 41 are composed of FIR type digital filters having one or both of tap delay circuits in units of 1H or in units of pixels. The luminance signal and color signal are separated and extracted by band limiting.

The digital composite video signal input from input terminal 1 is B
PF 55 and the motion detection circuit 16 via the delay circuit 46. Interframe Y separation circuit 48. It is applied to each input of the intra-field Y separation circuit 49.

The outputs Yy and Yl of the inter-frame Y separation circuit 48 and the intra-field Y separation circuit 49 are each outputted by a delay circuit 51.5.
2 to the input of the °C mixer 53, and the luminance signals added and adaptively separated according to the addition ratio determined by the control signal k given from the motion detection circuit 16 via the delay circuit 50 are obtained at the output terminal 5. nru.

The EPF 55 passes the color signals that are multiplexed by 9 degrees in the input composite video signal, and each output is provided to the input of the multiplexer 38 via the EPF 56 and the delay circuit 37.

This BPF 35 determines the demodulation band of the I signal, and has a pass band of about 15 MHz centered around fsc, for example.

Further, the EPF 36 determines the demodulation band of the q signal, and has a pass band of approximately ±0.5 MHz centered on fsc, for example.

As explained earlier, when the sampling frequency is 4f sc,! Sample values of the component and the Q component are obtained in a time-division multiplexed manner.

Therefore, the multiplexer 38 outputs the sample value of the Q component from the output of the BPF 36 and the sample value of the Q component from the output of the delay circuit 37 according to the timing signal supplied from the input terminal 1! Sample values of the components are alternately selected pixel by pixel and output to the color demodulation circuit 39.

As a result, the I component in the color signal supplied to the color demodulation circuit 39 can be restricted to a wide band, and the Q component can be restricted to a narrow band, respectively.

In the color demodulation circuit 39, the input color signal is demodulated by the means described above, and the inter-frame c+separation circuit 40 and the intra-field C
It is applied to each input of the separation circuit 41.

The output CF of the inter-frame C separation circuit 40 is sent to one input of the mixer 44 via the delay circuit 42, and the output C7 of the intra-field C separation circuit 41 is sent to the mixer 44 via the LPF 45.
The mixer 44 adds the c, , c, according to the addition ratio determined by the control signal k.

The output of mixer 44 is given to demultiplexer 45,
By said timing signal! It is divided into a signal sample value sequence and a Q signal sample value sequence and output.

The LPF 43 narrows the band of sampled values of the I component, and provides a band of about 0 to 0.5 MHz, for example.

Therefore, in this embodiment, it is possible to narrow the I signal O demodulation band in the video domain, and also in the still picture domain. Cross color can be reduced without sacrificing the advantages of axial and Q@ demodulation.

FIG. 6 is a block diagram showing a sixth embodiment of the present invention, in which 54 is a color demodulation circuit, and other symbols are the same as those in the fifth embodiment of FIG.

In the figure, the brightness signal obtained at the output terminal 5 is obtained by the same operation as in the fifth embodiment explained in FIG.

The color demodulation circuit 39 includes an EPF 55, a delay circuit 37,
The BPF 56 and the multiplexer demodulate the color signal in which the sample values of the I signal band-limited to a wide band and the sample values of the Q signal band-limited to a narrow band are time-division multiplexed, and output to the next interframe C separation circuit 40. give.

The color demodulation circuit 54 inputs the output of the BPF 56, and! Both the color signal and the Q signal are demodulated into narrow band chrominance signals, and outputted to the next intra-field C separation circuit 41.

The outputs of the inter-frame C separation circuit and the intra-field C separation circuit 41 are input to a mixer 44, added by an addition ratio determined by the control signal k output from the motion detection circuit 16, and then sent to a demultiplexer 45. , I
It is separated into a signal sample value sequence and a Q signal sample value sequence and output.

According to this embodiment, the inter-frame C separation circuit 40 demodulates in a wide band! Since the Q signal demodulated into a narrow band can be supplied in advance to the intra-field C separation circuit 41, crosstalk colors in the moving image area can be reduced.

〔Effect of the invention〕

As explained above, according to the present invention, the I-axis.

When performing Q-axis demodulation, cross-color interference in the video area can be reduced, and color resolution can be improved in the still image area.
By maximizing the advantages of axial and Q-axis demodulation, the image quality of television receivers is improved, solving the problems of the conventional technology described above, and providing a color signal processing circuit with new and superior functionality. can do.

[Brief explanation of the drawing]

FIGS. 1, 2, 3, 4, 5, and 6 are block diagrams showing each embodiment of the color signal processing circuit according to the present invention. 5・・・・・・・・・・・・・・・・・・・・・・・・
・・・Subtractor 6.40・・・・・・・・・・・・・・・
...Inter-frame CG separation circuit 7.41...
......In-field C separation circuit 8.11
, 21, 22, 28, 44.55... mixer 13, 3
9.54・・・・・・Shirofumaro circuit 16・・・・・・
・・・・・・・・・・・・・・・・・・Motion detection circuit 19・・・・・・・・・・・・・・・・・・・・・
・Inter-frame Y/C separation circuit 20...
・・・・・・・・・・・・・・・In-field Y/C separation circuit

Claims (1)

[Claims] 1. An interframe color signal separation circuit consisting of an FIR type digital filter having a tap delay circuit of at least one frame period, and an FIR type digital filter having one or both of a tap delay circuit of one horizontal scanning period or one pixel. an intra-field color signal separation circuit, a mixer for mixing the outputs of the inter-frame color signal separation circuit and the intra-field color signal separation circuit, a motion detection circuit for controlling the mixer, and an I-axis and a Q-axis. A color signal processing circuit comprising a color demodulation circuit that performs demodulation includes a demodulation band variable means that is controlled by the motion detection circuit to vary the demodulation band of the I signal, and eliminates crosstalk between the Y signal in the moving image area and the still image area. A color signal processing circuit characterized in that it is configured to reduce.