JP2608905B2 - Television signal processing circuit - Google Patents

Description

The present invention relates to a television signal processing circuit.
The present invention relates to a signal processing circuit having a delay circuit such as a field memory or a frame memory having a delay time equal to or longer than a vertical scanning cycle of a television signal.

[Conventional technology]

Taking the NTSC system as an example of a composite color television signal, a color subcarrier is modulated with a chrominance signal to transmit a chrominance signal, and multiplexed in a 2.1 to 4.2 MHz portion in a 4.2 MHz video signal band. ing. At this time, the color subcarrier fsc and the horizontal scanning frequency fh are Have a relationship. Also, the horizontal scanning frequency fh and the vertical scanning frequency fv are Have a relationship. Therefore, the phase of the color subcarrier is 1
The phases are opposite between signals separated by a frame period. By utilizing this property, for a still image, it is possible to separate a luminance signal by a sum between frames and a color signal by a difference. As a result, it is possible to almost completely remove cross component components such as cross color and dot interference, thereby achieving high image quality.

However, when such inter-frame processing is performed on a moving image, image quality is degraded, such as a double image, a loss of the effect of removing cross component components, and dot interference.

On the other hand, the motion of the image is detected from the difference between the signals separated by one frame period. If the motion of the image is large, an adaptive process such as separating the luminance signal and the chrominance signal by performing intra-field processing on the assumption that the image is a moving image can be considered.

On the other hand, there is a technique in which interlaced scanning performed by the NTSC system is interpolated into scanning lines on the receiver side, converted into scanning signals, and displayed. Using field memory, 1
If an interpolated scanning line signal is created using the scanning line signal before the field, and converted to sequential scanning and displayed, line flicker occurring at the edge of the horizontal line can be removed. However, this inter-field interpolation has a great effect on a still image, but has a great effect on a moving image, such as a comb-like double image.

In the example disclosed in Japanese Patent Application Laid-Open No. 59-40772, the motion of an image is detected based on the difference signal between one frame, inter-field interpolation is performed if the motion of the image is small, and transmission is performed if the motion of the image is large. Motion adaptive processing such as creating an interpolated scanning line signal using the scanning line signal in the field thus performed.

FIG. 2 is a block diagram showing an example of a television signal processing circuit in which the above-described conventional YC separation circuit and scanning line interpolation circuit are connected in cascade. In FIG. 2, 1 is an input terminal, 2 is an analog / digital conversion circuit (hereinafter referred to as ADC) for converting a composite color television signal of an analog signal input from the input terminal 1 into a digital signal, and 3 is A
A frame memory that delays the signal from DC2 by one frame period, 4 is a line comb filter circuit that separates a luminance signal and a chrominance signal (hereinafter, referred to as YC separation) in a field from the signal from ADC2, and 5 is a frame memory. 3, a frame comb filter circuit for inputting an input signal and an output signal of 3 and performing YC separation between frames; 6, a detection circuit for inputting an input signal and an output signal of the frame memory 3 to detect a motion of an image; A first method of mixing the output signal of the line comb filter circuit 4 and the output signal of the frame comb filter circuit 5
The output signal of the motion detection circuit 6 is provided as a control signal for the mixing ratio. 8 is a line memory that delays the output signal of the first mixing circuit 7 by 1H (1H is one horizontal scanning cycle), 9 is an addition circuit that inputs and adds the input signal and the output signal of the line memory 8, and 10 is an addition circuit. 9 output signals
A coefficient circuit for multiplying by 1/2, 11 a first field memory for delaying the output signal of the first mixing circuit 7 by one field period,
12 is an output signal of the coefficient circuit 10 and the first field memory 11
And a second mixing circuit that mixes the output signal of the motion detection circuit 6 with the output signal of the motion detection circuit 6 as a control signal. Reference numeral 13 denotes a double speed changing circuit for receiving the output signal of the first mixing circuit 7 and the output signal of the second mixing circuit 12 and converting the input signal into a progressively scanned television signal. Reference numeral 14 denotes an output terminal.

The frame comb filter circuit 5 performs YC separation for a still image using the correlation between signals separated by one frame period. As described above, the luminance signal is calculated by the sum between frames, and the color signal is calculated by the difference. Can be separated. The line comb filter circuit 4 is a circuit for obtaining a YC separation signal for a moving image, and performs YC separation based on the correlation between lines in the same field. The mixing ratio of the first mixing circuit 7 is controlled by the motion signal of the image detected by the motion detection circuit 6. When the motion is small, the signal from the frame comb filter circuit 5 is mainly selected and output, and when the motion is large, the signal from the line comb filter 4 is mainly selected and output.

Next, scanning line interpolation will be described. In the interlaced scanning performed by the NTSC system, a signal one field before scans a position where an interpolation scanning line in a certain field is to be created. Therefore, in the case of a still image, a scanning line signal one field before can be used as an interpolation scanning line as it is. As described above, since the interpolation between the fields for the moving image causes deterioration rather than the above, in this example, the interpolated scanning line signal for the moving image is obtained by averaging two consecutive lines in the same field. The mixing ratio of the second mixing circuit 12 is controlled by the output signal of the motion detection circuit 6. When the movement is small, the signal from the first field memory 11 is mainly selected and output, and when the movement is large, the signal from the coefficient circuit 10 is mainly selected and output.

The double-speed conversion circuit 13 inputs the output signal of the first mixing circuit 7 as a current scanning line signal and the output signal of the second mixing circuit 12 as an interpolation scanning line signal. The current scanning line / interpolated scanning line is alternately switched for each scanning line, and sequentially output as a scanning line signal.

[Problems to be solved by the invention]

FIG. 3 shows the above signal processing in which the horizontal axis is the time axis and the vertical direction of the screen is the vertical axis, and the scanning signal is represented by a circle. In FIG. 3A, S (n) represented by ◎ in the (M) field is a signal input to the ADC2.

In the case of a still image, YC separation is performed by the operation of S (n) and S (n-525), and the current scanning line signal is obtained. The interpolated scanning line signal is obtained by delaying this by one field period, and is calculated by calculating S (n-263) and S (n-788). Therefore, the center of gravity of the image in the time direction is (M−
1) It is between the field and the (M-2) th field.

On the other hand, in the case of a moving image, YC separation is S (n) and S (n-1).
The interpolation scanning line signal is calculated by averaging the signal obtained by delaying the interpolation scanning line signal by 1H. Since all the operations are performed in the same field, the center of gravity of the image in the time direction is in the (M) th field.

In the above conventional example, no consideration is given to the point that the center of gravity in the time direction differs between the still image signal and the moving image signal. Therefore, in the case of an image that moves or stops, the center of gravity of the still image signal and the center of the moving image signal are separated by 1.5 fields on the time axis, which may seem to be an unnatural movement.
On the other hand, in an example disclosed in Japanese Patent Application Laid-Open No. Sho 62-281579, a signal delayed by one frame by a frame memory is input to a moving image processing circuit to eliminate a center of gravity shift.

Considering the application of this method to the present circuit, since the center tap of the delay circuit is used as an input signal for moving image processing, it becomes necessary to add one field memory for scanning line interpolation to obtain the center tap. Would.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a motion-adaptive television signal processing circuit at which image motion does not become unnatural at a low cost without adding a new large circuit. .

[Means for solving the problem]

The above object is to provide a signal input to either the intra-field YC separation circuit for moving images or the intra-field scanning line interpolation circuit for moving images as a signal delayed by a frame memory or a field memory, and a moving image signal and a still image This is achieved by canceling the center-of-gravity shift on the time axis with the signal by the center-of-gravity shifts generated in the opposite directions of the YC separation process and the scanning line interpolation process.

[Action]

In either the YC separation circuit or the scanning line interpolation circuit, a signal delayed by a frame memory or a field memory is used as an input signal of an in-field processing circuit for generating a moving image signal. This allows
The difference between the center of gravity of the moving image signal on the time axis generated in the opposite direction in each of the YC separation process and the scanning line interpolation process and the center of gravity of the still image signal is eliminated or reduced. Therefore,
Even if the switching circuit operates between the still image mode and the moving image mode depending on the magnitude of the motion of the image, the motion of the image does not become unnatural.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. In FIG. 1, 1 is an input terminal, 2 is an ADC that converts a composite color television signal of an analog signal input from the input terminal 1 into a digital signal, 3 is a frame memory that delays a signal from the ADC 2 by one frame period, Reference numeral 4 denotes a line comb filter circuit for performing YC separation in a field with respect to a signal from the frame memory 3. Reference numeral 5 denotes a frame comb filter circuit for inputting an input signal and an output signal of the frame memory 3 and performing YC separation between frames. And 6, a motion detection circuit for inputting the input signal and the output signal of the frame memory 3 to detect the motion of the image, and 7 mixing the output signal of the line comb filter circuit 4 and the output signal of the frame comb filter circuit 5. The output signal of the operation detection circuit 6 is provided as a control signal for the mixing ratio. 8 is a line memory that delays the output signal of the first mixing circuit 7 by 1H, 9 is an addition circuit that inputs and adds the input signal and the output signal of the line memory 8, and 10 is a half of the output signal of the addition circuit 9. A coefficient circuit 11 for multiplying the output signal of the first mixing circuit 7 by one field period;
Is a second mixing circuit that mixes the output signal of the first field memory 11 with the output signal of the first field memory 11, and the output signal of the motion detection circuit 6 is provided as a control signal. Reference numeral 13 denotes a double-speed conversion circuit which receives an output signal of the first mixing circuit 7 and an output signal of the second mixing circuit 12 and converts the input signal into a progressively scanned television signal. Reference numeral 14 denotes an output terminal.

First, the operation in the case where there is no or little image motion, the detection result of the motion detection circuit becomes motion 0, and the circuit enters the still image mode will be described. The first mixing circuit 7 selects and outputs an output signal of the frame-comb filter circuit 5 as a YC separation signal for a still image. The output signal of the first field memory 11 is selected and output as a still image interpolation scanning line signal of the second mixing circuit 12. The double-speed conversion circuit 13 inputs the output signal of the first mixing circuit as a current scanning line signal and the output signal of the second mixing circuit as an interpolation scanning line signal, and after time-compressing, outputs the current scanning line for each scanning line. By switching and outputting / interpolated scanning lines, the signals are converted into progressive scanning signals. This time axis compression can be easily realized, for example, by using a line memory and setting the frequency of the read clock to twice the frequency of the write clock.

Therefore, the current scanning line signal is calculated from the signals of the (M) th field and the (M-2) th field in FIG. 4 (a). Since the interpolation scanning line signal is obtained by delaying this by one field period, it is calculated from the signals of the (M-1) th field and the (M-3) th field. As described above, the center of gravity of the image in the still image mode in the time direction is located between the (M-1) th field and the (M-2) th field as shown in FIG. .

Next, in the moving image mode, the first mixing circuit 7 selects and outputs the output signal of the line comb filter circuit as the YC separated signal for the moving image. The second mixing circuit 12 selects and outputs the output signal of the coefficient circuit 10 as a moving image interpolation scanning line signal. The double speed conversion circuit 13 outputs the output signal of the first mixing circuit 7 and the second mixing circuit 12 in the same manner as in the still image mode.
, And is converted into a sequential scanning signal and output.

Since the input of the line comb filter circuit 4 is the output signal of the frame memory 3, the center of gravity of the image in the moving image mode in the time direction is in the (M-2) th field in FIG. 4 (b).

As described above, in the present embodiment, the difference on the time axis between the still image signal and the moving image signal is suppressed to 0.5 field. Therefore, even when the image moves or stops, it is possible to prevent the movement from looking unnatural. Further, the output signal of the frame memory 3 to be processed as a moving image signal has a relationship between the input signal from the ADC 2 and the even fields or the odd fields, and processes the scanning line at the same position as the input signal. Even when the input signal has jitter, it is possible to reduce the influence of the jitter.

In the above description, the output of the first mixing circuit 7 is neither a luminance signal nor a chrominance signal, but it goes without saying that the present invention can be applied to both the luminance signal and the chrominance signal.

FIG. 5 shows another embodiment according to the present invention. In FIG. 5, reference numeral 15 denotes a selection circuit, and the other components are the same as those in FIG. Fifth
In the embodiment shown in the figure, a selection circuit 15 is provided in front of the line comb filter circuit 4 for creating a moving image signal, and a signal delayed by the frame memory 3 and a signal not delayed are switched.

According to the configuration of the present embodiment, the image at a certain moment can be kept being held by stopping the updating of the frame memory 3, and the input signal during that time is transmitted to the selection circuit 15 by the AD circuit.
Display can be continued by tilting to C2 side. Further, since the input signal from the ADC 2 and the output signal of the frame memory 3 are signals for scanning the same position, there is no unnatural feeling when switching.

In the above-described embodiment, the output signal of the frame memory is selected as the reference signal of the moving image signal, but the present invention is not limited to this. The output signal of the field memory may be selected. FIG. 6 is a block diagram of another embodiment according to the present invention. In FIG. 6, reference numerals 16 and 17 denote second and third field memories, respectively, and the others are the same as those in the embodiment of FIG.

In this embodiment, the frame memory is composed of two field memories 16 and 17 which are cascaded. The line comb filter circuit 4 receives the output signal of the second field memory 16 and obtains a moving image YC separation signal. The other operations are the same as those of the embodiment shown in FIG.

In the present embodiment, the position of the center of gravity of the image on the
Shown in the figure. As in the previous embodiment, the position of the center of gravity in the still image mode is located between the (M-1) th field and the (M-2) th field. On the other hand, the position of the center of gravity in the moving image mode is in the (M-1) th field.

As described above, in the present embodiment, the difference on the time axis between the still image signal and the moving image signal is suppressed to 0.5 field.
In addition, the still image signal and the moving image signal also have the same vertical center of gravity. Therefore, even when the image moves or stops, it is possible to prevent the movement from looking unnatural. In addition, since the signal serving as the reference for the moving image signal is used as the output signal of the second field memory 16, the time difference between the image and the sound can be reduced.

In the above description, similar processing is performed on the separated luminance signal and color signal, but the present invention is not limited to this. Compared with the luminance signal, the color signal is less likely to cause a decrease in vertical resolution and line flicker, so the color signal may be interpolated only within the field.
For example, in the configuration in FIG. 6, the interpolation of the color signal may be fixed to the average interpolation within the field.

FIG. 8 shows the position of the center of gravity of the luminance signal and the color signal in this case. In the still image mode, the center of gravity of the luminance signal is located between the (M-1) th and (M-2) th fields, and the center of gravity of the chrominance signal is in the (M-1) th field. On the other hand, in the moving image mode, both the center of gravity of the luminance signal and the center of the
1) In the field.

Therefore, according to the above configuration, it is possible to reduce the displacement of the center of gravity between the still image signal and the still image signal for both the luminance signal and the chrominance signal, and to eliminate the need for a field memory for scanning line interpolation of the chrominance signal. Can be smaller.

FIG. 9 shows another embodiment according to the present invention. In this embodiment, since the YC separation is the same as the conventional example,
The description of the operation is omitted. After the output signal of the first mixing circuit 7 is delayed by one field period by the first field memory 11, the line memory 8, the adding circuit 9 and the coefficient circuit 10
The average between the lines is obtained, and this is used as a moving image interpolation scanning line signal. The output signal of the first mixing circuit 7 is used as a still image interpolation scanning line signal.
The 10 output signals are switched in the second mixing circuit 12 according to the magnitude of the motion of the image to obtain an interpolation scanning line signal. The double speed conversion circuit 13 inputs the output signal of the first field memory 11 as a current scanning line signal and the output signal of the second mixing circuit 12 as an interpolation scanning line signal, and converts them into signals for sequential scanning.

In this embodiment, the position of the center of gravity of the image on the time axis is the sixth position.
FIG. 7 shows the same as the embodiment of the figure. As described above, in the present embodiment, the difference between the center of gravity position on the time axis of the still image signal and the moving image signal is suppressed to 0.5 field. Therefore, even when the image moves or stops, it is possible to prevent the movement from looking unnatural.

FIG. 10 shows another embodiment according to the present invention. In FIG. 10, reference numeral 18 denotes a fourth field memory, and the others are the same as those in FIG. In this embodiment, a fourth field memory 18 is provided between the first mixing circuit 7 and the first field memory 11. Other operations are the same as those of the above-described embodiment, and the description of the operations will be omitted.

FIG. 11 shows the relationship between the position of the center of gravity of the image on the time axis according to the present embodiment. In the present embodiment, the difference in the position of the center of gravity on the time axis between the still image signal and the moving image signal can be suppressed to 0.5 field, and it is possible to prevent the motion of the moving or stopped image from appearing unnatural. it can. Further, the output signal of the first field memory 11, which is processed as a moving image signal, has a relationship between the input signal from the ADC 2 and the even fields or the odd fields, and processes the scanning line at the same position as the input signal. Therefore, even if the input signal has jitter, the influence of the jitter can be reduced.

In the above-described embodiments, the intra-field interpolation for a moving image has been described as performing the average interpolation of the upper and lower two lines using a line memory, but the present invention is not limited to this. For example, double-write interpolation may be used in which a scan line signal immediately above the scan line position to be interpolated is repeated. At this time, although the smoothness of the image is slightly lost, the line memory, the addition circuit and the coefficient circuit are not required, and the circuit scale can be reduced.

As described above, the displacement of the center of gravity of the image on the time axis, which has conventionally occurred in the YC separating circuit and the scanning line interpolating circuit, is reduced by combining the two circuits. By obtaining the moving image signal from the output of (1), the total gravity shift can be reduced to less than one field, and the unnatural motion due to the gravity shift can be eliminated.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the shift of the center of gravity position on the time axis of the still image signal and the moving image signal of the motion adaptive television signal processing circuit can be reduced, and the moving or stopped image becomes unnatural. It can be prevented from being seen.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional example, FIGS. 3 and 4 are views showing the position of the center of gravity of an image in the time direction, and FIGS. FIG. 7 is a block diagram of another embodiment of the present invention, FIGS. 7 and 8 are diagrams showing the position of the center of gravity of the image in the time direction, FIGS. 9 and 10 are block diagrams of another embodiment of the present invention, FIG. 11 is a diagram showing the position of the center of gravity of the image in the time direction. 2 ... ADC, 3 ... Frame memory, 4 ... Line comb filter circuit, 5 ... Frame comb filter circuit,
6: a motion detection circuit, 7, 12, a mixing circuit, 8: a line memory, 11, 16, 17, 18, a field memory, 13 a double speed conversion circuit, and a 15 selection circuit.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeru Hirahata 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Home Appliances Research Laboratory, Hitachi, Ltd. (72) Inventor Akihide Okuda 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside Hitachi, Ltd., Home Appliances Research Laboratory (72) Tadashi Kasezawa, 1 Baba Zujo, Nagaokakyo-shi, Kyoto, Japan Inside Electronic Products Development Laboratory, Mitsubishi Electric Corporation (72) Noriyuki Yamaguchi, 1 Baba Zhou, Nagaokakyo-shi, Kyoto, Japan Mitsubishi Electric Corporation Electronic Product Development Laboratory (72) Inventor Yao Politics Nagaokakyo City, Kyoto Prefecture Baba Zusho 1 Mitsubishi Electric Corporation Electronic Product Development Laboratory (56) References JP-A-62-135094 (JP, A) JP-A-59-40772 (JP, A)

Claims (7)

(57) [Claims] A first delay circuit for receiving a television signal and delaying the inputted television signal by a period substantially twice as long as a vertical scanning period of the television signal; an input signal and an output signal of the first delay circuit; And a first intra-field processing circuit for processing the television signal delayed by the first delay circuit in the same field of the signal, and an inter-frame processing circuit for generating both inter-frame processing signals using the same. A motion detection circuit that detects the motion of an image included in the input television signal; and an output signal of the inter-frame processing circuit and a signal of the first intra-field processing circuit depending on the magnitude of the motion of the image detected by the motion detection circuit. A first switching circuit for switching the output signal, a second delay circuit for substantially delaying the output signal of the first switching circuit in a vertical scanning cycle, and an output signal of the first switching circuit in the same field. A second switching circuit for switching between the output signal of the second delay circuit and the output signal of the second intra-field processing circuit according to the magnitude of the motion of the image detected by the motion detection circuit. A television signal processing circuit, comprising: a circuit; and combining means for combining an output signal of the first switching circuit and an output signal of the second switching circuit. 2. A switch circuit for selecting and outputting one of an input television signal and a television signal delayed by a first delay circuit, wherein the first intra-field processing circuit comprises: 2. The television signal processing circuit according to claim 1, wherein the processing circuit processes a television signal selected by a switch circuit in the same field in place of the television signal delayed by the delay circuit. 3. The first delay circuit comprises two vertical scanning period delay circuits connected in series, and the first intra-field processing circuit comprises one vertical scanning period delay circuit of the first delay circuit. 2. The television signal processing circuit according to claim 1, wherein the processing circuit processes a television signal delayed by one vertical scanning period in the same field. 4. A first delay circuit for receiving a television signal, delaying the inputted television signal by a period substantially twice as long as the vertical scanning period, an input signal and an output signal of the first delay circuit. , An inter-frame processing circuit for generating both inter-frame processing signals, a first intra-field processing circuit for processing an input television signal in the same field of the signal, and an input television signal And an output signal of the inter-frame processing circuit and an output signal of the first intra-field processing circuit depending on the magnitude of the motion of the image detected by the motion detection circuit. A first switching circuit, a third delay circuit for delaying the output signal of the first switching circuit by substantially vertical scanning of the television signal, and a substantially vertical scanning period of the output signal of the third switching circuit. A second delay circuit for extending the output signal of the second delay circuit, a second intra-field processing circuit for processing the output signal of the second delay circuit in the same field, and a third delay circuit based on the magnitude of the motion of the image detected by the motion detection circuit. The output signal of the circuit and the second
A second switching circuit for switching between the output signal of the intra-field processing circuit and a synthesizing means for synthesizing the output signal of the second delay circuit and the output signal of the second switching circuit. John signal processing circuit. 5. A first delay circuit for receiving a television signal, delaying the inputted television signal by a period substantially equal to an integral multiple of the vertical scanning period, and an input signal and an output signal of the first delay circuit. And a first intra-field processing circuit for processing the television signal delayed by the first delay circuit in the same field of the signal, and an inter-frame processing circuit for generating both inter-frame processing signals using the same. A motion detection circuit that detects the motion of an image included in the input television signal; and an output signal of the inter-frame processing circuit and a signal of the first intra-field processing circuit depending on the magnitude of the motion of the image detected by the motion detection circuit. A first switching circuit for switching an output signal, a second delay circuit for substantially delaying an output signal of the first switching circuit in a vertical scanning cycle, and a method for controlling the magnitude of the motion of the image detected by the motion detecting circuit. The output signal of the first switching circuit Ri and second
A second switching circuit for switching between the output signal of the delay circuit of
A television signal processing circuit, comprising: synthesizing means for synthesizing an output signal of the first switching circuit and an output signal of the second switching circuit. 6. A switch circuit for selecting and outputting one of an input television signal and a television signal delayed by a first delay circuit, wherein the first intra-field processing circuit comprises: 6. The television signal processing circuit according to claim 5, wherein the processing circuit processes the television signal selected by the switch circuit in the same field in place of the television signal delayed by the delay circuit. 7. A second intra-field processing circuit for processing an output signal of the first switching circuit in the same field is arranged between the first switching circuit and the second switching circuit. The television signal processing circuit according to claim 5.