JP2562696B2 - Television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a television receiver having a still image reproducing function.

(B) Conventional technology Conventionally, from a composite television signal to a luminance signal (Y signal)
As a method for separating the color signal (C signal), there is a method using a motion adaptive YC separation circuit.

FIG. 4 is a block diagram showing the configuration of a conventional motion adaptive YC separation circuit disclosed in Japanese Patent Laid-Open No. 61-123295.
In the figure, the composite video signal is converted into an 8-bit digital signal by an A / D converter (1). This digital signal is delayed by 1H (H is a horizontal synchronizing signal period) in the line memory (2) and further delayed by 524H in the frame memory (3). The input / output signal of the line memory (2) is given to the subtractor (4), and the output signal of the line memory (2) is subtracted from the input signal of the line memory (2). The luminance signal component of the output of the subtracter (4) is canceled by the line correlation of the composite video signal. However, since the high frequency component of the luminance signal in the vertical direction of the screen remains, it is removed by the horizontal band pass filter (5). The output of the horizontal bandpass filter (5) is given to the mixing circuit (9) as the first color signal MC. Also, A / D converter (1)
Output signal and the first color signal MC are given to the subtractor (6), and the first color signal M is subtracted from the output signal of the A / D converter 1. As a result, the color signal components are canceled from the composite video signal which is the output signal of the A / D converter (1), and the first luminance signal MY is obtained. This first luminance signal MY is given to the mixing circuit (9).

On the other hand, the output signal of the A / D converter (1) and the output signal of the frame memory (3) are given to the subtractor (7), and the output signal of the A / D converter (1) is used to output the frame memory (3). The output signal of is subtracted. The output signal of the frame memory (3) is a signal delayed by exactly one frame period compared to the composite video signal output from the A / D converter (1), so the A / D conversion is performed by the frame correlation. The luminance signal component is canceled from the output signal of the device (1) to obtain the second color signal SC. This second color signal SC is given to the mixing circuit (9). Further, the output signal of the A / D converter (1) and the second color signal SC are given to the subtractor (8), and the A / D converter (1)
The second color signal SC is subtracted from the output signal of. As a result, the color signal components are canceled from the composite video signal output from the A / D converter (1), and the second luminance signal SY is obtained.
This second luminance signal SY is given to the mixing circuit (9).

Further, the output signal of the A / D converter (1) and the output signal of the frame memory (3) are given to the motion detection circuit (10). This motion detection circuit (10) subtracts a difference signal between frames in the composite video signal, and based on the difference signal,
It is detected whether the image formed by the current composite video signal is a moving image or a still image. The detection output of the motion detection circuit (10) is given to the mixing circuit (9). When the detection output of the motion detection circuit (10) indicates a moving image, the mixing circuit (9) selects the first luminance signal MY and the first color signal MC separated by using the line correlation. Luminance signal Y
And output as a color signal C. On the other hand, when the detection output of the motion detection circuit (10) shows a still image, the mixing circuit (9) outputs the second luminance signal SY and the second color signal S separated by utilizing the frame correlation. It is selected and output as a luminance signal Y and a color signal C.

The motion detection circuit (10) is configured to output a detection signal whose level changes in an analog manner according to the degree of movement of the image, and the mixing circuit (9) outputs a detection signal at a ratio according to the level of the detection output. The first luminance signal MY and the second luminance signal SY are mixed, and the first color signal MC and the second luminance signal SY are mixed at the ratio.
May be configured to mix the color signals SC of.

According to the motion adaptive YC separation circuit described above, it is possible to separate the luminance signal and the chrominance signal from each other with high quality without mixing and remaining.

By the way, in the case of performing still image reproduction in a television receiver having the above-described motion adaptive YC separation circuit, conventionally, a still image reproduction process is performed using a dedicated frame memory. That is, a frame memory is provided separately from the frame memory provided in the motion adaptive YC separation circuit to perform still image reproduction processing. However, since this frame memory is very expensive, there is a problem in that using a dedicated frame memory is disadvantageous in terms of price.

(C) Problems to be Solved by the Invention The present invention has been made in view of the above points and obtains an inexpensive still image reproducing circuit by using the frame memory of the motion adaptive YC separation circuit for still image reproduction. The purpose is to

(D) Means for Solving the Problems The present invention utilizes an input means to which a composite video signal is input, and at least one line delay means to which the composite video signal is input from the input means, to utilize line correlation. A first luminance signal and a first chrominance signal to obtain a first luminance signal and a first chrominance signal, and a composite video signal input from the input means, and at least one frame delay means. A second YC separation circuit that obtains a two-color signal is provided with a motion detection circuit that detects the motion of the image, and the output of this motion detection circuit causes the first and second
In a television receiver including a mixing circuit that controls a mixing ratio of a luminance signal and a mixing ratio of the first and second color signals, a control signal generating circuit that generates a control signal in response to a still image reproduction command, Controlled by this control signal, a cyclic path for circulating the composite video signal output from the frame delay means is formed, and the first YC separation circuit and the second YC separation circuit are connected.
Provided with the switch circuit formed in the previous stage of the YC separation circuit,
During still image playback, based on the output extracted from the patrol route
This is a television receiver characterized by performing YC separation.

(Operation) Operation The present invention operates so as to perform YC separation based on the output extracted from the patrol path during still image reproduction.

(F) Embodiment First, an embodiment of the present invention will be described with reference to FIG. In the figure, the embodiment shown in FIG. 1 has the same configuration as the conventional motion adaptive YC separation circuit shown in FIG. 4 except for the following points, and the same reference numerals are given to corresponding parts. , The description is omitted. In the embodiment shown in FIG. 1, a switch circuit (11), a control signal generating circuit (12), and a chroma inverter circuit (13) are provided in order to give the motion adaptive YC separation circuit a still image reproducing function. And have been added. The switch circuit (11) selects either the output signal of the A / D converter (1) or the output signal of the frame memory (3) and outputs it to the line memory (2). The control signal generation circuit (12) generates a control signal in response to a still image reproduction command from a still image reproduction switch (not shown) manually operated by the user, for example. This control signal is given to the switch circuit (11), the mixing circuit (9) and the chroma inverter circuit (13). The switch circuit (11) is switch-controlled in response to this control signal.
The mixing circuit (9) is configured to select and output the first luminance signal MY and the first color signal MC in response to the control signal. The chroma inverter circuit (13) is activated by the control signal, and inverts the polarity of the color signal for each frame (525H) in order to maintain the sequence of the color subcarrier for every two frames during still image reproduction.

 Next, the operation of the embodiment shown in FIG. 1 will be described.

First, during normal reproduction, the control signal from the control signal generation circuit (12) is at the "L" level, so the switch circuit (11) is A /
The output signal of the D converter (1) is switched to the position where it is selected. Therefore, the motion adaptive YC separation circuit operates similarly to the conventional circuit shown in FIG. At this time, the Chromibater circuit (13) is disabled and does not operate. That is, the chromaver circuit (13) outputs the color signal C given from the mixing circuit (9) as it is.

Next, when the still image reproducing switch (not shown) is pressed, the control signal from the control signal generating circuit (12) becomes "H" level. Therefore, the switch circuit (11) is switched to the position for selecting the output signal of the frame memory 3. As a result, a cycle of one frame (525H) is formed by the switch circuit (11), the line memory (2) and the frame memory (3).

Therefore, the first and second supplied to the mixing circuit (9)
The luminance signals MY, SY and the first and second color signals MC, SC of are
It becomes a cyclic signal of a frame, that is, a still image signal. Here, since the two signals input to the subtractor (7) are the same, the phases of the color signals are also in phase, and the frame correlation is used to three-dimensionally separate the luminance signal and the color signal. It is not possible. Therefore, when reproducing a still image, it is necessary to two-dimensionally separate the luminance signal and the chrominance signal using only the line correlation in the field. Therefore, in the present embodiment, when the control signal from the control signal generation circuit (12) becomes the "H" level, the mixing circuit (9) is forced to output 2 regardless of the detection output of the motion detection circuit (10). Only the first luminance signal MY and the first color signal MC obtained by the dimension processing are selected and output.

Further, the color signal selected by the mixing circuit (9) cannot maintain the phase sequence for every two frames as it is, but the chroma inverter circuit (13) is activated by the control signal of "H" level. The chroma inverter circuit (13) inverts the phase of the color signal for each frame. Therefore, the sequence of every two frames of the color signal is maintained and a continuous color subcarrier is obtained.

In addition, the control signal "L" from the control signal generation circuit (12)
The timing of switching between the level and the “H” level is selected so as to coincide with the vertical blanking period. Therefore, the timing of switching of the switch circuit (11), that is, the timing of the discontinuity of the phase of the color sub-carrier coincides with the timing of phase inversion by the chroma inverter circuit (13), and complete continuity of the color signal is achieved. Is maintained.

Further, in the above-described embodiment, the cyclic route of one frame (525H) is formed at the time of reproducing the still image.
If the number is increased to form a cyclic route of 2 frames (1050H), the luminance signal and the color signal will be 3 when reproducing a still image.
It becomes possible to separate dimensionally. In this case, cross-color and dot interference are likely to occur in the two-dimensional separation, but since such a problem does not occur, a still image with higher image quality can be obtained. Further, in this case, since the sequence of the color subcarriers having the two-frame period is always maintained, the chromaver circuit (13) is not necessary. Hereinafter, an embodiment will be described in which still image reproduction is obtained by a composite video signal obtained from a cyclic path of two frames.

In the embodiment shown in FIG. 2, a frame memory (14) is added between the frame memory (3) and the switch circuit (11). This frame memory (14) receives 1 input signal
It is configured to delay the frame period (525H). The other structure is the same as that of the embodiment shown in FIG. 1, and the corresponding parts are designated by the same reference numerals. According to the embodiment shown in FIG. 2, a two-frame cyclic path is formed by the switch circuit (11), the line memory (2), the frame memory (3) and the frame memory (14) at the time of reproducing a still image. Therefore, the two mixed video signals input to the subtractor (7) at the time of still image reproduction are shifted by one frame period from each other, and as a result, the color signals can be separated by the frame correlation. Similarly, the subtractor (8) can also separate the luminance signal. As described above, in the embodiment of FIG. 2, when the still image is reproduced, the luminance signal and the chrominance signal are two-dimensionally separated by using the line correlation, and the luminance signal and the chrominance signal are three-dimensionally separated by using the frame correlation. It is also possible to separate the signal and the color signal. Therefore, the mixing circuit (9) is controlled by the detection output from the motion detection circuit (10) even during still image reproduction. That is, the mixing circuit (9) selects the first luminance signal MY and the first chrominance signal MC when there is a motion between the composite video signals of the two frames that circulate on the cyclic path during still image reproduction. When there is no movement between the composite video signals, the second luminance signal SY and the second color signal SC are selected and output. Therefore, in the embodiment of FIG.
The control signal from the control signal generation circuit (12) is not input to the mixing circuit (9).

Next, another embodiment in which a two-frame cyclic route is formed during still image reproduction will be described with reference to FIG. In the embodiment of FIG. 3, the output signal of the switch circuit (11) is stored in the frame memory (15) for one frame period (525
H) After being delayed, it is delayed by 1H in the line memory (16),
Furthermore, it is delayed by 524H in the frame memory (17). The output signal of the frame memory (17) is input to the switch circuit (11) together with the output signal of the A / D converter (1). The subtractor (4) separates the color signals according to the input / output signals of the line memory (16). The subtractor (6) separates the luminance signal by subtracting the output signal of the horizontal bandpass filter (5) from the output signal of the frame memory (15). The output signal of the switch circuit (11), the output signal of the frame memory (15) and the output signal of the frame memory (17) are respectively coefficient multipliers (18), (19) and (2
Given to 0). The coefficient multipliers (18) and (20) multiply the input signal by -1/4, and the coefficient multiplier (19) multiplies the input signal by 1/2. These coefficient multipliers (18),
The output signals of (19) and (20) are given to the adder (21) and added. Here, the frame memory (15), the line memory (16), the frame memory (17), the coefficient multipliers (18) to (20), and the adder (21) constitute a three-dimensional comb filter. The three-dimensional comb filter separates the second color signal SC. The subtractor (8) outputs the second signal from the output signal of the frame memory (15).
The second luminance signal SY is obtained by subtracting the color signal SC of. Other configurations are similar to those of the embodiment shown in FIG. In the embodiment shown in FIG. 3, the switch circuit (11), the frame memory (15), the line memory (16) and the frame memory (17) are used to reproduce the still image.
A patrol path of frames is formed. Then, at the time of still image reproduction, the luminance signal and the color signal are two-dimensionally separated and three-dimensionally separated by the composite video signal obtained from this cyclic path. Therefore, in the embodiment of FIG. 3 as well, as in the embodiment of FIG. 2, the mixing circuit (9) is controlled by the detection signal from the motion detection circuit (10) during reproduction of the still image, and the first luminance The signal MY, the first color signal MC, the second luminance signal SY, and the second color signal SC are selected and output.

According to the embodiment shown in FIG. 2 or FIG. 3, as described above, the frame correlation is used in 3
Since the luminance signal and the color signal can be separated dimensionally, a high-quality still image without cross color or dot interference can be obtained. Further, the chroma inverter circuit 13 used in the embodiment of FIG. 1 is also unnecessary.

(G) Effect of the Invention As described above, according to the present invention, since the frame memory of the motion adaptive YC separation circuit is also used as the still image reproduction circuit, a high quality still image reproduction image can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram of a YC separation circuit according to an embodiment of the present invention, FIGS. 2 and 3 are block diagrams showing other embodiments, and FIG. 4 is a block diagram of a conventional YC separation circuit. is there. (1) …… A / D converter, (2) …… Line memory,
(3) (14) …… Frame memory, (4) (6) (7)
(8) ... Subtractor, (9) ... Mixing circuit, (10) ... Motion detection circuit, (11) ... Switch circuit, (12) ... Control signal generating circuit, (13) ... Chroma inverter circuit.

Continuation of the front page (56) Reference JP 62-295593 (JP, A) JP 61-123295 (JP, A) JP 57-25782 (JP, A)

Claims (5)

(57) [Claims] 1. A first luminance signal and a first luminance signal using line correlation having an input unit to which a composite video signal is input and at least one line delay unit to which the composite video signal from the input unit is input. 1st YC to get color signal
A separation circuit, a second YC separation circuit to which the composite video signal from the input means is input, and which has at least one frame delay means to obtain a second luminance signal and a second color signal by utilizing frame correlation; A television provided with a motion detection circuit for detecting a motion, and a mixing circuit in which an output of the motion detection circuit controls a mixing ratio of the first and second luminance signals and a mixing ratio of the first and second color signals. In the John receiver, a control signal generation circuit that generates a control signal according to a still image reproduction command, and a cyclic path that is controlled by this control signal and that circulates the composite video signal output from the frame delay means, The first YC separation circuit and the second YC
By providing a switch circuit formed in the previous stage of the separation circuit, when reproducing a still image, YC is based on the output extracted from the patrol path.
A television receiver characterized by separation. 2. The television receiver according to claim 1, wherein during reproduction of a still image, the mixing circuit is controlled by the control signal and selects and outputs only the first luminance signal and the first color signal. 3. A television receiver according to claim 1, further comprising a chroma inverter circuit which is controlled by the control signal and reproduces a color signal output from the mixing circuit for each frame when reproducing a still image. 4. The television receiver according to claim 3, wherein the switching of the switch circuit and the inversion of the chroma inverter circuit are performed within a vertical blanking period. 5. The television receiver according to claim 1, wherein a plurality of the frame delay means are provided and the cyclic route has a cycle of two frames or more.