KR100209879B1 - Apparatus for emphasizing image quality partially using variable quantization - Google Patents

Abstract

The present invention relates to a partial image quality enhancing apparatus using variable quantization.

The apparatus of the present invention selects a variable amount of quantization numbers, key input unit for selecting a desired window box on the monitor, a system controller for controlling and controlling all operations of each configuration according to the key input, and a preset screen On the monitor, variable quantization means for quantizing image data in a window box by adding a variable quantization number to the entire quantization number, and quantizing the data through the whole screen quantization number, and quantized data through the variable quantization means. And a frame memory for storing the data restored for display, and a memory controller for controlling the frame memory.

Thus, the present invention provides the effect of improving the partial image quality for the image displayed on the monitor.

Description

Partial Image Quality Enhancement Device Using Variable Quantization

1 is a block diagram showing a video signal processing system in a general digital VCR.

2 is a block diagram showing a partial image quality enhancing apparatus using variable quantization according to the present invention.

3 shows a monitor having a window formed by the FIG. 2 device.

* Explanation of symbols for main parts of the drawings

21: key input 22: system control

23: window box setting section 24: quantization number table

25: delay 26: adder

27: memory controller 28: frame memory

29: D / A converter SW: switch

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for recording and reproducing digital video signals, and more particularly, to a partial image quality enhancing apparatus using variable quantization that enables partial image quality enhancement using variable quantization.

Currently, video signal recording and reproducing apparatus is undergoing a process of transition from analog equipment to digital equipment. The reason for developing the digital video signal recording and reproducing apparatus as described above is that it has the advantage of obtaining high quality image quality and no deterioration of image quality even after repeating dubbing several times. This digital video signal recording and reproducing apparatus is shown in FIG.

1 is a block diagram showing a video signal processing system in a general digital VCR. As shown in the drawing, the digital VCR system performs an A / D converter 11 for converting a video signal applied through an input stage into digital data, and performs a DCT conversion on the block data, and then quantizes the conversion coefficient. And a code block (A) comprising means (12, 13) for making the data and means (14) for compressing the data by encoding the quantized data by Huffman code. The digital VCR system further includes means for decompressing the data encoded by the Huffman code to extend the data, means for dequantizing and inversely converting the decoded data (16, 17), and converting the inversely converted data into an analog signal. The decoding block B which consists of a D / A converter 18 for this purpose is provided. The transmission path 19 is configured to be connected between the code block A and the decoding block B.

The operation of the general digital VCR system configured as described above will be briefly described.

First, the code block A converts an input video signal into digital data in the A / D converter 11. The digitally converted video signal is input to the DCT unit 12. The DCT unit 12 converts the input image data into data in the frequency domain, and the energy of the converted conversion coefficient is mainly collected toward the low frequency side. The quantization unit 13 converts the transform coefficients into representative values of a predetermined level through a predetermined quantization process. That is, in the quantization unit 13, the DCT unit 12 quantizes the output data by a predetermined quantization weighting matrix. In this case, the quantization weighting matrix has a larger quantization step size in the high frequency region than in the low frequency region. This means that the visual effect of the error between the quantization coefficients is less sensitive in the high frequency region than in the low frequency region when quantizing the image data. In the high frequency region, the amount of quantized data is reduced by the large quantization step size. For the quantized quantization coefficients, the Huffman coding unit 14 compresses the data transmitted through the transmission path 19 by taking advantage of the statistical characteristics of the representative values.

The decoding block B decodes and transmits the encoded data transmitted by the Huffman decoding unit 15. The decoded data is inversely quantized by the inverse quantization unit 16 and the inverse DCT unit 17 and then inversely transformed into image data of the spatial domain. The image data output from the inverse DCT unit 17 is converted into an analog signal by the D / A converter 18 and input to the display unit (not shown).

In this case, quantization generally compresses transmission data amount by obtaining a quantization matrix and quantizing DCT transformed coefficients before Huffman coding using the quantization matrix. The quantization matrix is obtained through experimentation, and the quantization step of quantizing the DCT coefficients must be appropriately determined to obtain good quality without loss in coding. For example, the determination of quantization step in Standard Digital (SD) -VCR is performed by class number, area number, and quantization number, as negotiated by the specification of international standard. QNO). That is, a class is assigned to each DCT block, and each block divides AC coefficients excluding DC into four areas according to the importance of the coefficients. In the quantization process for the AC coefficients of the DCT block, the quantization process proceeds with a quantization step size based on a combination of a given quantization number, four class information, and four regions. For this quantization process, each block is classified into classes of 0, 1, 2, and 3 according to the characteristics of the DCT coefficients. Here, the classification of the class reflects the activity of the input DCT block. In the case of class 0, the quantization error may be noticeable because it is composed of plain information. The quantization error is relatively less noticeable. Therefore, when the class information of each block is used in the quantization process, a more efficient quantization process can be achieved. In the DCT block, the area of AC coefficients except DC component is divided into four stages from important information to less important information. The code length generated by the quantization number (QNO) is determined for each macroblock consisting of four luminance component (Y) blocks and two chrominance component (Cr, Cb) blocks, so that the quantization number closest to a given target code length is determined. Choose. Usually, the area information of each block is fixed, and the quantization step size according to the class information is also fixed. Therefore, the values to be substantially divided into DCT coefficients, that is, the quantization step size, are determined for each area of the block by the selected quantization number. The DCT coefficients have a value other than ≤ 0 ≤ for the low frequency, and the coefficients corresponding to the high frequency have a high probability of ≤ 0 ≤. In order to increase the coding efficiency, the quantization number QNO is selected as one step of making the value? In SD-VCR, a quantization number (QNO) is formed in a table in advance. As described above, in the SD-VCR, quantization is performed by using a quantization number (QNO). The quantization number QNO is determined in units of macro blocks (MBs) and depends on the complexity of the image.

However, since encoding is performed in units of one segment consisting of 5 MB, there is a limit in improving the quantization number (QNO) in consideration of the image quality of the entire screen.

Accordingly, an object of the present invention is to solve the above-mentioned problem and to quantize a quantization number (QNO) that is different from normal recording or reproduction when the user wants to emphasize or edit a part of the screen, thereby processing the entire quantization number (QNO). It is to provide a partial image quality enhancement device using variable quantization that can further improve the () limit and improve the image quality.

Partial image quality enhancing apparatus using the variable quantization of the present invention for achieving the above object, in the image data recording and reproducing apparatus which is compressed through the quantization and encoding process, and restored through the decoding and dequantization process, A key input unit for selecting a variable and selecting a desired window box on the monitor, a system controller for controlling all operations of each component in accordance with a key input of the key input unit, and a window box under control of the system controller A window box setting unit for setting and a variable amount inputted through the system control unit are added to a preset whole screen quantization number, and the image data in the window box set by the window box setting unit is quantized with a variable quantization number. Otherwise, the variable quantization number and the preset number are quantized to a preset quantization number. A quantization number selection means for selectively switching and outputting a quantization number, a frame memory for recording and reading reconstruction data for quantized data according to the quantization number selected by the quantization number selection means, and data read out from the frame memory. Includes a monitor for presentation.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing a partial image quality enhancing apparatus using variable quantization according to the present invention. As shown, the apparatus of the present invention selects the amount of change in the quantization number (QNO), and sets the key input section 21 and key input section 21 for setting a specific area (hereinafter referred to as a window box) on the monitor. A system controller 22 is provided for controlling various operations of each component in response to a key input. One side output terminal of the system control unit 22 is connected to the window box setting unit 23 for setting the window box. The other side output terminal of the system controller 22 is connected to an adder 26 that adds a change amount α selected by the user to the quantization number QNO of the entire screen. The adder 26 is connected to a quantization number table 24 which comprises a quantization number QNO as a table. The quantization number table 24 is connected in parallel with the adder 26, a delayer 25 for delaying the entire screen quantization number QNO by the time required for the addition process in the adder 26, and the adder 26. Contacts are connected to the two output terminals of the < RTI ID = 0.0 > and < / RTI >

The memory controller 27 is connected to the other output terminal of the system controller 22. The frame memory 28 is connected between the memory controller 27 and the means not shown to record and read image data under the control of the memory controller 27. An output terminal of the frame memory 28 is configured to connect a D / A converter 29 for converting image data into an analog signal so as to be displayed on a monitor.

The operation of the partial image quality enhancing apparatus using the variable quantization according to the present invention configured as described above will be described in more detail.

First, the user inputs the change amount α for the quantization number QNO by using a remote controller or a function key of the key input unit 21. The user also enters the size and position of the window box to highlight on the screen. The system controller 22 supplies the size and position of the input window box to the window box setting unit 23. The window box setting unit 23 controls the switch SW so that the quantization number applied to the video signal part existing in the window box corresponding to the size and position of the input window box and the video signal part existing in the remaining parts are different. do. The system controller 22 supplies the change amount α with respect to the input quantization number QNO to the adder 26 and adds it to the entire screen quantization number QNO. Here, the picture full quantization number (QNO) is one of the parameters for determining the picture quality of the whole screen in the normal recording and playback operations, and is set in advance in a table as shown in Table 1 below.

Here, the quantization number QNO exists from 0 to 15 and is represented by 4 bits. The quantization number obtained by adding the change amount α to the entire quantization number also exists between 0 and 15 (0 ≦ dQNO + α ≦ d15), and the change amount α also exists between 0 and 15 (0 ≦ dα ≦ d15). ). The quantization number QNO is used to quantize the transform coefficients. Techniques for selecting and outputting one of a plurality of quantization numbers stored in the quantization number table 24 are well known and thus not described. In general, however, quantization numbers are selected in consideration of image characteristics. The whole picture quantization number QNO read out from the quantization number table 24 is delayed for a time required for the addition process in the adder 26 through the delay unit 25. The entire screen quantization number QNO output from the delay unit 25 is input to the first contact point A1 and the variable quantization number QNO + α output from the adder 26 is input to the second contact point A2. The contact A3 of the receiving switch SW is switched to the second contact A2 so that the picture quality can be further emphasized in the window box on the screen selected by the user, and is otherwise switched to the first contact A1. The quantization number switched from the switch SW is used to quantize the image data supplied to the quantization unit. The quantized data is compressed through encoding and then recorded on a predetermined recording medium or reproduced through an opposite process of recording. The reproduced video data is recorded or read out in the frame memory 28 under the control of the memory controller 27. The data read out from the frame memory 28 is converted into an analog signal through the D / A converter 29 and displayed on the monitor as shown in FIG.

3 shows a monitor having a window formed by the FIG. 2 device. In FIG. 3, 'X' refers to the entire screen on the monitor, and the shaded area 'Y' in the center is about 'M' in the horizontal direction and 'N' in the vertical direction by the control signal CTL. Represents a window. The video signal displayed inside the window 'Y' and outside the window is quantized by different quantization number values so that the picture quality can be changed between the inside and the outside of the window, thereby partially emphasizing the picture quality.

As described above, the partial image quality enhancing apparatus using the variable quantization according to the present invention can improve the image quality in the partial screen used in normal editing or performing the PIP function by varying the quantization number which is an important parameter for determining the overall screen quality. Has the effect.

Claims (3)

An image data recording and reproducing apparatus for compressing through quantization and encoding, and reconstructing through decoding and inverse quantization, the apparatus comprising: a key input unit for selecting a quantization number variable and selecting a desired window box on a monitor; A system controller for controlling various operations of each component according to key input of the key input unit; A window box setting unit for setting a window box according to the control of the system controller; The variable amount inputted through the system control unit is added to a preset whole screen quantization number, and the image data in the window box set by the window box setting unit is quantized by a variable quantization number and otherwise quantized by a preset quantization number. Quantization number selection means for selectively switching the mask quantization number and the predetermined quantization number and outputting them; A frame memory for recording and reading reconstruction data for quantized data according to the quantization number selected by the quantization number selection means; And a monitor for presenting the data read out from the frame memory. 2. The apparatus of claim 1, wherein the quantization number selecting means comprises: an adder for adding a variable amount input through the system control unit and a preset quantization number; A delayer for delaying a predetermined quantization number by the time required for addition processing in the adder; And a first contact for receiving a variable quantization number obtained by the adder and a second contact for receiving a quantization number delayed by the delayer, and selectively switching one of the two contacts under the control of the window box setting unit. Partial image quality enhancement device using a variable quantization, characterized in that consisting of a switch for. 3. The apparatus of claim 2, wherein a quantization number table comprising a plurality of quantization numbers as a table is connected to a front end of the adder and the delayer.