JPH0252585A - Digital television set - Google Patents

Abstract

PURPOSE:To improve the contrast of a picture and saturation and to improve the picture quality by adopting the constitution such that an arithmetic means multiplying a prescribed coefficient with a picture still data read from a memory is provided and a loop writing the data into the memory is formed. CONSTITUTION:In the pattern still mode, the arithmetic means 8 multiplies (1+k) with a picture still data Sn-1 read from a field memory 6 to form a data Sn and a control circuit 7a throws a changeover switch circuit 9 to the position of the arithmetic means 8 and the write/readout of buffer memories A4, B5 and the field memory 6 is applied repetitively. When one of the data Sn obtained by the means 8 in the feedback loop reaches a relation of (1+k)Sn<=1, the circuit 9 is opened and the loop is opened. Thus, the still picture data stored in the memory 6 is subject to arithmetic processing automatically till the contrast and color saturation reach the maximum value and the S/N of the picture, that is, the picture quality is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to digital television that uses field memory to obtain still images, and more specifically, to "lowering the contrast and color saturation of the image." This is related to digital television that allows for

[Conventional example] In recent years, digital
Memory was added to televisions, allowing them to be equipped with various functions. One of its functions is a screen freeze function that freezes the image by digitizing the video signal and storing it in the memory. The additional function circuit has a configuration shown in FIG. 3, for example.

In the figure, input television and video signals are processed by a video processing circuit 1 into a luminance (Y) signal and two color difference (R-Y,
B-Y) signal. These Y.

The R-Y and B-Y signals are outputted in a time division manner by the switching circuit 2, for example, a Y signal, a R-Y signal, and a B-Y signal.

The Y signal, . . . are digitized in order by the A/D conversion circuit 3. One scanning line of the Y, RY, BY signal data is stored in the buffer memory (A) 4, and then one scanning line of the fifth order is stored in the buffer memory (B) 5.

At this time, one scanning line stored in the buffer memory (A) 4 is transferred to the field memory 6 and written therein. In this way, the buffer memory (A) 4 and the buffer memory (B) 5 alternately store Y, R-Y for one scanning line.
, B-Y signal data is stored, and this stored 1
Y, RY, B-Y signal data for scanning lines are alternately transferred to the field memory 6 and written therein.

In this way, the field memory 6 stores Y, R-Y,
B-Y signal data (still image data) is stored. The switching control signal of the switching circuit 2, the timing control signal of the A/D conversion circuit, and the address control signals of the buffer memory (A) 4, buffer memory (B) 5, and field memory 6 are generated when the digital television screen is still. It is output from the control circuit 7 when the mode is operated.

Next, in the screen still mode of the digital television, as described above, after the still image data is stored in the field memory 6, the still image data is repeatedly read out. Furthermore, one image of still data is not shown.
The signal is converted into an analog signal by the /A conversion circuit, and mixed by the mixing circuit to form an R/G/B signal. In this way, by repeatedly reading out the same still image data stored in the field memory 6, a still image is displayed on the CRT device of the digital television.

[Problems to be Solved by the Invention] By the way, in the screen still mode of the digital television, the same still image data from the field memory 6 is simply read out repeatedly, and no processing is performed on the data. Therefore, the S/N ratio of the still image on the screen is determined by the data stored in the field memory 6.

That is, depending on the still image data stored in the field memory 6, the contrast and saturation may be poor, and in such a case, there is a problem that the image quality of the still image is degraded.

In particular, due to the visual characteristics of the human eye, the image quality of still images is much more likely to be judged harshly than that of moving images, and such deterioration in image quality is noticeable.

Furthermore, it is thought that in future display devices, for example, non-interlaced scanning devices, EDTVs, and HDTVs (high-definition televisions) will have higher image quality.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a digital television that can increase the contrast and saturation of still images stored in a memory and improve the image quality.

[Means for Solving Problem i] In order to achieve the above object, the present invention digitizes a video signal through digital signal processing to generate a luminance (Y) signal and two color difference signals (R-Y, B-Y). ) signal data,
In a digital television equipped with an additional functional circuit that stores these data in a memory and obtains a still image using the data stored in the memory, a predetermined arithmetic process is performed to multiply the data read from the memory by a predetermined coefficient. and a changeover switch means for feeding back the data obtained by the calculation means to the memory, the calculation means and the changeover switch forming a feedback loop to the memory, When the means obtains data that maximizes the contrast and color saturation of the still image, the loop is turned off.

[Function] With the above configuration, when the screen of the digital television is in the static screen mode, the feedback loop is applied to the memory, and the data read from the memory is subjected to a predetermined value by the calculation means of the feedback loop. Arithmetic processing for multiplying by coefficients is performed. When the contrast and color saturation of the still image reach their maximum values through this calculation process,
The feedback loop is turned off by the changeover switch means, and writing to the memory is no longer performed.

That is, the memory remains stored with data that maximizes the contrast and color saturation of the still image, and the same stored data is repeatedly read out.

In this way, when the screen is set to the above-mentioned static mode.

The still image data stored in memory is automatically changed through arithmetic processing to maximize the contrast and color saturation of the still image, so that the contrast and color saturation of the still image on the screen are automatically adjusted. It can be raised.

[Example] Hereinafter, an example of the present invention will be described based on the drawings. In addition, in the figure, the same parts as in FIG. 3 are given the same reference numerals, and redundant explanation will be omitted.

In FIG. 1, still image data (Y, RY, BY signal data) read from the feed memory 6 is input to the calculation means 8, and processing is performed to change the contrast and color saturation of the image. . The still image data processed by the calculation means 8 is stored in the buffer memory (A) 4 or buffer memory (B) 5 via the changeover switch circuit 9. Note that once the image still data is stored in the field memory 6 in the screen still mode, the changeover switch circuit 9 is activated by the control circuit 7a, and the image still data processed by the calculation means 8 is stored in the buffer memory (A). 4. (B) 5 will be input.

Furthermore, the still image data processed by the control circuit 7a is stored in the buffer memory (A) 4 or the buffer memory (B) 5 for each scanning line, and the stored data is stored in the field memory 6. Ru. That is, the contents of the field memory 6 are rewritten to still image data with the contrast and color saturation of the image changed.

Next, the operation of the digital television equipped with the screen freeze function circuit configured as described above will be explained. It should be noted that a multiplier, for example, is used as the arithmetic means 8, and its coefficient is k(
<1).

First, it is assumed that the digital television is in the screen still mode, predetermined image still data is stored in the field memory 6, and the image still data is repeatedly read out. Here, the changeover switch circuit 9 is switched to the calculation means 8 side by the control circuit 7a, and the buffer memory (
A) 4, buffer memory (B) 5 and field memory 6 are written and read. Then, the still image data (sn
=1) is multiplied to (t+k)Sn-t=sr+, and is transferred to the buffer memory (A
) 4 or buffer memory (B) 5. The stored data is transferred to the field memory 6 and stored therein. In this way, the multiplication process is repeated in the feedback loop formed by the arithmetic means 8 and the changeover switch circuit 9, and the still image data is integrated each time. Data S obtained by the calculation means 8. One of them is (1+k
) When Sn-0≦1, for example, if the data is the maximum value of the dynamic range (luminance, brightness) of the digital television, the feedback loop becomes OFl?
For example, the selector switch circuit 9 is open. Then, the additional function circuit is returned to the normal screen still mode, and only data is read from the field memory 6. That is, the contrast and color saturation of the image on the digital television will be increased to their maximum values, thereby improving the image quality.

Moreover, since the maximum value was set to the maximum dynamic range of the digital television, the S/N of the image
This will increase the ratio.

Further, as the calculation means 8, as shown in FIG.
An adder circuit may also be used.

In the figure, still image data read out from the field memory 6 is temporarily stored in a latch circuit 8a, and
The signal is shifted by α bits and temporarily stored in the shift/latch circuit 8b. In this case, the output data of the shift/latch circuit 8b is -8, -0 (k=1/2) when the input database is 5n-x. These latched data are added by an adder 8c.

As shown in FIG. 1, the data obtained by the adder 8c is sent to the buffer memory (
A) 4 or buffer memory (B) 5.

Buffer memory (A)4. The data stored in the buffer memory (B) 5 is written to the field memory 6. In this way, as in the previous embodiment, the still image data in the field memory 6 is rewritten, and the contrast and color saturation of the screen of the digital television are linearly changed by the data. Then, the data addition process is repeated in a feedback loop by the addition circuit. In that process, data S. When one of them becomes (i+k)Sn-x≦1, the feedback loop is turned off, the additional function circuit is returned to the normal screen still mode, and only data is read from the field memory 6.

Note that the number of bits to be shifted down by the shift/latch circuit 8 is the input data S. It may be changed depending on the value of -1, and for example, when contrast and color saturation are to be performed little by little, it may be increased. Furthermore, in order to provide a circuit that changes the number of bits, it is necessary to provide a determining means, and the determining means determines the number of bits in accordance with the value of the input data 5n-t.

[Effects of the Invention] As explained above, according to the digital television of the present invention, still image data is stored in the memory, and an additional function circuit for obtaining a still image on the screen using this data reads out the data from the memory. A calculation means is provided to multiply the still image data by a predetermined coefficient, and this calculation means forms a loop in which the still image data is written to the memory. Image quality can be improved. Further, according to the present invention, the image still data is processed by the calculation means up to the dynamic range of the digital television, so that the image S/N
ratio can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic partial circuit block diagram of a digital television showing an embodiment of the present invention, FIG. 2 is a schematic partial circuit block diagram of a digital television showing a modified embodiment of the invention, and FIG. The figure is a schematic partial circuit block diagram of a conventional digital television. In the figure, 1 is a video processing circuit, 2 is a switching circuit, 3 is an A/D conversion circuit, 4 is a buffer memory (A), 5 is a buffer memory (B), 6 is a field memory, 7 is a control circuit, and 8 is a Arithmetic means (multiplier/adder), 8a is latch circuit, 8b
8 is a shift/latch circuit, 8C is an adder, and 9 is a changeover switch circuit (changeover switch means).

Claims (3)

[Claims] (1) The video signal is digitized by digital signal processing to generate a luminance (Y) signal and two color difference signals (R-Y, B-Y).
) A digital television equipped with an additional functional circuit that stores these data in a memory and obtains a still image using the data stored in the memory, wherein a predetermined coefficient is applied to the data read out from the memory. a calculation means for performing a predetermined calculation process, and a changeover switch means for returning data obtained by the calculation means to the memory, and a feedback loop to the memory is established by the calculation means and the changeover switch means. 1. A digital television set comprising: a loop that is turned off when the calculation means obtains data that maximizes the contrast and color saturation of the still image. (2) The digital television according to claim 1, wherein the calculation means is a multiplier that multiplies contrast and color saturation data by the predetermined coefficient. (3) The calculation means includes a latch circuit that temporarily stores data read from the memory, a shift/latch circuit that shifts the data by a predetermined bit and temporarily stores the data, and a shift/latch circuit that transfers the data of the latch circuit to the shift/latch circuit. A digital television consisting of an adder that adds the data and an adder.