KR101539045B1 - Quantization Parameter Determination Method and Apparatus and Video Encoding/Decoding Method and Apparatus - Google Patents

Abstract

The present invention relates to a quantization coefficient determination method and apparatus, and a method and apparatus for image coding / decoding using the same.

An apparatus for determining quantization coefficients, the apparatus comprising: a complexity calculator for calculating a complexity of a neighboring block; A threshold value setting unit for setting a threshold value for determining the degree of complexity; And determines a predetermined basic quantization coefficient as a quantization coefficient of the current block if the complexity is less than or equal to a threshold value and determines a quantization coefficient smaller than the basic quantization coefficient as a quantization coefficient of the current block if the complexity exceeds the threshold value And a quantization coefficient determination unit.

According to the present invention, a quantization coefficient can be adaptively determined according to characteristics of an image, and quantization can be performed using different quantization coefficients for each block, and coding considering characteristics of an image can be performed through the quantization coefficient. Even if a block having a complex characteristic and a block having a plain characteristic are mixed in the picture of FIG. 5A, the coding can be efficiently performed, and the compression performance can be improved.

Image, coding, decoding, quantization, coefficient, block, complexity, adaptive

Description

[0001] The present invention relates to a quantization coefficient determination method and apparatus, and a video encoding / decoding method and apparatus using the same.

The present invention relates to a quantization coefficient determination method and apparatus, and a method and apparatus for image coding / decoding using the same. More particularly, the present invention relates to a method and an apparatus for improving compression efficiency by encoding quantized coefficients by adaptively determining quantization coefficients on a block-by-block basis in consideration of characteristics of blocks to be encoded, .

The Moving Picture Experts Group (MPEG) and the Video Coding Experts Group (VCEG) have developed superior video compression techniques that are superior to the existing MPEG-4 Part 2 and H.263 standards. This new standard is called H.264 / AVC (Advanced Video Coding) and is jointly announced as MPEG-4 Part 10 AVC and ITU-T Recommendation H.264.

In H.264 / AVC (hereinafter, abbreviated as H.264), orthogonally transformed components can be represented by a smaller integer value, and compression is performed by applying a quantization process for encoding with a smaller number of bits. The conventional quantization coding is performed on the encoder side to predict pixel information of a current block to be coded and to perform a DCT (Discrete Cosine Transform) operation on difference information between pixel information of an actual block to be coded, ), Generates a frequency coefficient, and quantizes the frequency coefficient according to a given quantization parameter (QP) to generate a quantization frequency coefficient. The quantization frequency coefficients are encoded and transmitted to the decoder in the form of a bitstream.

In this case, in H.264, only a fixed quantization coefficient is used when quantizing the blocks. When quantization is performed using only a fixed quantization coefficient, a block having a complex image characteristic and a block having a normal image characteristic are mixed in one picture of the image , It is difficult to efficiently quantize the characteristics of different images for each block, thereby reducing the coding efficiency or the compression efficiency.

According to an aspect of the present invention, there is provided a method of encoding an image, comprising the steps of: determining a quantization coefficient for each block in consideration of characteristics of a block to be encoded and encoding the quantization coefficient using the determined quantization frequency coefficient; The main purpose is to improve compression efficiency.

According to an aspect of the present invention, there is provided an apparatus for determining a quantization coefficient, the apparatus including: a complexity calculator for calculating a complexity of a neighboring block; A threshold value setting unit for setting a threshold value for determining the degree of complexity; And determines a predetermined basic quantization coefficient as a quantization coefficient of the current block if the complexity is less than or equal to a threshold value and determines a quantization coefficient smaller than the basic quantization coefficient as a quantization coefficient of the current block if the complexity exceeds the threshold value And a quantization coefficient determination unit.

According to another aspect of the present invention, there is provided a method of determining a quantization coefficient, the method comprising: calculating a complexity of a neighboring block; A comparison step of comparing the complexity with a predetermined threshold value; A quantization coefficient holding step of determining a predetermined basic quantization coefficient as a quantization coefficient of the current block if the complexity is equal to or less than a preset threshold value; And a quantization coefficient determination step of determining a value smaller than a predetermined basic quantization coefficient as a quantization coefficient of the current block when the complexity exceeds a preset threshold value.

According to another aspect of the present invention, there is provided an apparatus for encoding an image, the apparatus comprising: a prediction unit for predicting a current block to generate a prediction block; A subtractor for subtracting the current block from the predicted block to generate a residual block; A transform unit for transforming the residual block into a frequency domain; A quantization unit for determining a quantization coefficient of a current block according to a complexity of a neighboring block and quantizing the transformed residual block; And an encoding unit encoding the quantized residual block to generate encoded data.

According to another aspect of the present invention, there is provided a method of encoding an image, the method comprising: a prediction step of generating a prediction block by predicting a current block; A subtraction step of subtracting a current block from a prediction block to generate a residual block; A transforming step of transforming the residual block into a frequency domain; A quantization step of quantizing the transformed residual block by determining a quantization coefficient of a current block according to a complexity of a neighboring block; And a coding step of coding the quantized residual block to generate coded data.

According to still another aspect of the present invention, there is provided an apparatus for decoding an image, comprising: a decoding unit decoding a coded data to extract a residual block; A dequantizer for determining a quantization coefficient of a current block according to a complexity of a neighboring block and dequantizing the residual block using the determined quantization frequency coefficient of the current block; An inverse transform unit for inversely transforming the dequantized residual block; A prediction unit for generating a prediction block by predicting a current block; And an adder for adding the inverse transformed residual block and the predicted block to reconstruct the current block.

According to still another aspect of the present invention, there is provided a method of decoding an image, the decoding method comprising: a decoding step of decoding encoded data and extracting a residual block; A dequantization step of determining a quantization coefficient of a current block according to a complexity of a neighboring block and dequantizing the residual block; An inverse transform step of inversely transforming the dequantized residual block; A prediction step of generating a prediction block by predicting a current block; And an addition step of adding the inversely transformed residual block and the prediction block to reconstruct the current block.

As described above, according to the present invention, quantization coefficients can be adaptively determined according to characteristics of an image, and quantization can be performed using different quantization coefficients on a block-by-block basis. have. Therefore, even when a block having a complex characteristic and a block having a plain characteristic are mixed in one picture of an image, efficient coding can be performed, and compression performance can be improved.

According to the present invention, even when quantization is performed using different quantization coefficients on a block-by-block basis, it is unnecessary to further include bits for identifying quantized coefficients changed in the encoded data, thereby improving compression performance.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals whenever possible, even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the components from other components, and the term does not limit the nature, order or order of the components. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected or connected to the other component, Quot; may be "connected," "coupled," or "connected. &Quot;

1 is a block diagram schematically illustrating a configuration of an image encoding apparatus according to an embodiment of the present invention.

The image encoding apparatus 100 according to an embodiment of the present invention encodes an image and includes a prediction unit 110, a subtractor 120, a transform unit 130, a quantization unit 140, an encoding unit 150 ), An inverse quantization unit 160, an inverse transform unit 170, and an adder 180. The image encoding apparatus 100 may be a personal computer (PC), a notebook computer, a personal digital assistant (PDA), a portable multimedia player (PMP), a PlayStation Portable ), A mobile communication terminal, and the like, and may be a communication device such as a communication modem for performing communication with various devices or wired / wireless communication networks, a memory for storing various programs for encoding an image and data, a program And a microprocessor for calculating and controlling the microprocessor.

The prediction unit 110 generates a prediction block by predicting a current block of an image. That is, the predicting unit 110 predicts a current block to be encoded in an image using Intra Prediction or Inter Prediction, thereby calculating a predicted pixel value (Predicted Pixel Value) And generates a predicted block having pixel values of the pixels.

Subtraction unit 120 subtracts the prediction block from the current block to generate a residual block. That is, the subtraction unit 120 calculates a difference value between the original pixel value of each pixel of the current block and the predicted pixel value of each pixel of the prediction block, and generates a residual block having a residual signal do.

The transforming unit 130 transforms the residual block into the frequency domain. That is, the transform unit 130 transforms the residual signal of the residual block generated by the subtraction unit 120 into a frequency domain, and generates a residual block having a frequency coefficient. Here, the transform unit 130 transforms the residual signal using a variety of transform techniques for transforming a spatial domain image signal, such as Hadamard Transform, Discrete Cosine Transform Based Transform, Frequency domain, and the residual signal transformed into the frequency domain becomes the frequency coefficient.

The quantization unit 140 quantizes a residual block having a frequency coefficient converted into a frequency domain by the transform unit 130. [ The quantization unit 140 quantizes the transformed residual block using various quantization techniques such as dead zone uniformity threshold quantization (DZUTQ) or a quantization weighted matrix It can be quantized.

In quantization of the residual block, the quantization unit 140 determines a quantization parameter (QP) of the current block according to the complexity of the neighboring block around the current block and quantizes the quantization coefficient. That is, the quantization unit 140 does not quantize each block of the image using the same quantization coefficient, but quantizes the quantization coefficient adaptively for each block of the image and quantizes the quantized coefficient. In this case, the criterion for determining the quantization coefficient for each block is the characteristic of the image, more specifically, the complexity of the block. For this purpose, the quantization unit 140 calculates the complexity of the neighboring blocks around the current block, compares the complexity of the calculated neighboring blocks with a preset threshold value, and determines the complexity of the calculated neighboring blocks to a predetermined threshold value The quantization coefficient of the current block can be changed to a value smaller than a predetermined basic quantization coefficient. The quantization unit 140 calculates the complexity of the neighboring blocks and determines the quantization coefficients of the current block using the calculated complexity will be described in detail with reference to FIG. 2 in the following description.

The encoding unit 150 encodes the quantization frequency coefficients of the residual block quantized by the quantization unit 140 to generate encoded data. As such an encoding technique, entropy encoding technology may be used, but various other encoding techniques may be used without being limited thereto.

In addition, the encoding unit 150 may include not only the bit stream obtained by encoding the quantized frequency coefficients, but also various information necessary for decoding the encoded bit stream in the encoded data. That is, the coded data includes a first field including a coded block pattern (CBP), a delta quantization parameter, and a quantized frequency coefficient coded bit stream and information necessary for prediction (for example, A motion vector in the case of intra prediction, or a motion vector in the case of inter prediction).

The delta quantization coefficient included in the encoded data is a bit representing information on the difference between the quantization coefficient of the current block and the quantization coefficient of the previous block. In the conventional quantization such as H.264, when the quantization coefficient of the block is changed, the encoder includes the delta quantization coefficient representing the difference between the values of the two quantization coefficients as bits in the encoded data, and in the decoder, And extracts the coefficients and dequantizes them with a quantization coefficient equal to the quantization coefficient used in the encoder.

However, in the present invention, when the quantization coefficient is changed by the quantization unit 140, the encoding unit 150 may encode the quantization frequency coefficient, and then re-change the quantization coefficient of the changed current block to a predetermined basic quantization coefficient . In this way, the encoding unit 150 can prevent the additional bit from being allocated for information on the difference between the values of the quantization coefficients by re-changing the quantization coefficients of the changed current block to predetermined basic quantization coefficients, Performance can be increased. In this case, when the image data is inversely quantized by the image decoding apparatus, the quantization coefficient of the current block is determined in the same manner as the method of determining the quantization coefficient of the current block in the quantization unit 140 so that the inverse quantization can be performed using the same quantization coefficient have.

The inverse quantization unit 160 inverse quantizes the quantized residual block by the quantization unit 140 to generate a dequantized residual block. That is, the dequantizer 160 dequantizes the quantized frequency coefficients of the quantized residual block to generate a residual block having the dequantized frequency coefficients. At this time, the de-quantization unit 160 may dequantize the quantized residual block according to the quantization coefficient of the current block transmitted from the quantization unit 140. [ That is, when the quantization unit 140 quantizes using the basic quantization coefficient, the inverse quantization unit 160 also performs inverse quantization using the basic quantization coefficient, and the quantization unit 140 quantizes the quantization coefficient having a value smaller than the basic quantization coefficient The inverse quantization unit 160 also performs inverse quantization using the same quantization coefficient as the quantization coefficient used in the quantization unit 140. For example,

The inverse transform unit 170 inverse transforms the inversely quantized residual block to generate an inverse transformed residual block. That is, the inverse transform unit 170 inversely transforms the dequantized frequency coefficients of the dequantized residual block into a spatial domain, and generates an inverse transformed residual block having a pixel value.

The adder 180 restores the current block by adding the predicted block predicted by the predictor 110 and the inverse transformed residual block by the inverse transform unit 170 and outputs the restored current block to the predictor 110 Output.

Although not shown in FIG. 1, a deblocking filter unit (not shown) may be additionally connected between the predictor 110 and the adder 180. The deblocking filter unit deblocking filters the current block restored by the adder 180. Here, deblocking filtering refers to a task of reducing block distortion caused by coding an image block by block. The deblocking filter may be applied to a block boundary or a macro block boundary, a deblocking filter may be applied to a macro block boundary, Can be selectively used.

1, the quantization unit 140 may include a quantization coefficient determination unit for determining a quantization coefficient of a current block and a quantization processing unit for quantizing the quantization coefficient using the determined quantization coefficient. In a conventional quantization, the quantization processing unit quantizes using a fixed quantization coefficient, as described later. For example, when the residual signal of the residual block is quantized by performing the DCT transform, the basic quantization operation can be expressed by Equation (1).

In Equation (1), Y _ij represents the elements expressed by a matrix after DCT transforming and scaling each residual signal of the residual block, and Q _step represents the size of the quantization step.

According to the H.264 standard, the value of the quantization coefficient is proportional to the value of the quantization step. If the quantization coefficient increases by 6, the size of the quantization step increases by two. As a result, even if the quantization coefficient changes in proportion to the signal-to-noise ratio (SNR), the variation of the signal-to-noise ratio can be kept constant without fluctuating significantly.

Equation (2) and Equation (3) can be expressed by expressing a basic quantization operation performed as Equation (1) to be applied to an actual quantization process.

In Equation (2), W _ij denotes elements represented by a matrix after DCT transforming each residual signal of the residual block, MF denotes a multiplication factor determined according to a quantization coefficient, f denotes a quantization coefficient It is an element that determines the error caused by the round and the size of the dead zone. It is 2 ^qbits / 3 when the current block is predicted by intra prediction, and 2 ^qbits / 6 when predicted by inter prediction. do. Here, qbits represents 15 + floor (QP / 6), and floor represents a round down operation.

In H.264, since the value of the quantization coefficient is defined to have a value from 0 to 51, the maximum value of the quantization step size is 256 times the minimum value. H.264 with a large difference between the minimum value and the maximum value of the quantization step size can correspond to a bit rate lower to a higher bit rate than that of MPEG-2. The introduction of the concept that the size of the quantization step is doubled every time the quantization coefficient is increased by 6 facilitates the processing of the inverse quantization.

Because H.264 uses quantization, compression efficiency can be improved when compared with other methods that do not use quantization. However, since the conventional quantization such as H.264 uses only the fixed quantization coefficient, it is difficult to quantize the block according to the characteristics of the image, so that it can not be efficiently compressed. For example, if the change in the value of each pixel in the block is larger than a certain size, it can be determined that the complexity of the block is large. If the change in the value of each pixel in the block is smaller than a certain size, the complexity of the block is small It can be judged. When the complexity of blocks constituting an image is small, quantization using a fixed quantization coefficient does not greatly affect the performance of compression. However, when the complexity of blocks constituting an image is large, quantization is performed using a fixed quantization coefficient The compression performance may be greatly affected.

In the present invention, unlike the existing quantization method of quantizing using only a fixed quantization coefficient, such as H.264, each block constituting one picture of an image is quantized using a variable quantization coefficient according to the characteristic, Quantization is performed by reflecting the characteristics of the image. In this case, the characteristic of the image may be the complexity of the image. The complexity may be calculated for each block, and the quantization coefficient may be determined according to the calculated complexity.

The quantization coefficient determination unit included in the quantization unit 140 may be a quantization coefficient determination apparatus that exists as an independent hardware or software module, and may be configured as shown in FIG.

FIG. 2 is a block diagram showing a configuration of a quantization coefficient determination apparatus according to an embodiment of the present invention. Referring to FIG.

The apparatus 200 for determining a quantization coefficient according to an embodiment of the present invention may include a complexity calculation unit 210, a threshold value setting unit 220, and a quantization coefficient determination unit 230.

The complexity calculation unit 210 calculates the complexity of neighboring blocks around the current block. Here, the neighboring block may be one or more blocks around the current block. In particular, the neighboring block may be a block that has been already encoded or encoded before decoding the current block, and decoded and reconstructed. The neighboring blocks may be neighboring blocks that are adjacent to the current block among the reconstructed blocks that have been already encoded or encoded before encoding the current block, and one or more of the adjacent blocks may be selectively used . That is, as shown in FIG. 3, the neighboring block may be a left block adjacent to the current block, an upper left block, an upper block, an upper right block, and the like, but the present invention is not limited thereto. Or may be some or all of the blocks adjacent to the current block and may be some or all of the blocks that are not adjacent to the current block.

The complexity calculator 210 may calculate a complexity of a neighboring block by using a coefficient bitrate of one or more neighboring blocks in calculating a complexity of a neighboring block. The complexity of the neighboring blocks can be an indicator of how complex the neighboring blocks are with the image characteristics, which can be calculated as the average of the coefficient bit rates of neighboring blocks. In this case, if neighboring blocks are as shown in FIG. 3, the complexity ( adj _coeffff ) of the neighboring blocks can be calculated using Equation (4).

In Equation (4), a _coeff represents the coefficient bit rate of the left block located on the left side of the current block, b _coeff represents the coefficient bit rate of the upper block located at the upper end of the current block, c _coeff represents the coefficient bit rate of the upper D _coeff represents the coefficient bit rate of the upper left block located at the upper left of the current block.

Here, the coefficient bit rate of the block refers to the number of bits of the bit stream generated by encoding the quantization frequency coefficient per block. For example, assuming that the bit stream generated by coding the quantization frequency coefficient in the left block a _coeff of the current block is "00110011101100", the coefficient bit rate of the left block a _coeff is 14. Therefore, for example, if a _coeff is 10, b _coeff is 20, c _coeff is 30, and d _coeff is 40, the complexity ( adj _coeffff ) of the neighboring blocks of the current block = (10 + 20 + 30 + 40) / 4 = 25.

The threshold value setting unit 220 sets a threshold value for determining the degree of complexity of a neighboring block. It is difficult to evaluate the degree of complexity with the complexity of the neighboring blocks calculated by the complexity calculation unit 210. [ Therefore, in order to evaluate the complexity of a neighboring block, a threshold value serving as a criterion for evaluation should be appropriately set.

The threshold value for determining the degree of complexity of the neighboring blocks may be calculated in advance and input to the threshold value setting unit 220. The threshold value setting unit 220 may be configured to adapt The threshold value can be determined. When the threshold value setting unit 220 adaptively determines the threshold value, the threshold value may be determined using the coefficient bit rate of the block that has already been coded before coding the current block. It may be all blocks or some blocks in the current picture. The threshold value is calculated using the coefficient bit rate of the already coded block.

In Equation (5), n represents the number of the current block, MBcoeff represents the coefficient bit rate of the block, and i represents the number of the block already coded.

The quantization coefficient determination unit 230 determines the quantization coefficient of the current block according to the complexity of the neighboring block calculated by the complexity calculation unit 210. [ That is, when the complexity of the neighboring block is small, the quantization coefficient determiner 230 determines the quantization coefficient of the current block as a quantization coefficient set as a basis, and when the complexity of the neighboring block is large, Is determined as a quantization coefficient smaller than the coefficient. In this case, a predetermined criterion is required to determine whether the complexity of the neighboring block is large or small.

To this end, the quantization coefficient determination unit 230 compares the complexity of the neighboring block calculated by the complexity calculation unit 210 with a preset threshold value by the threshold value setting unit 220, And determines a predetermined basic quantization coefficient as a quantization coefficient of the current block. If the complexity of a neighboring block exceeds a predetermined threshold value, a quantization coefficient smaller than a predetermined basic quantization coefficient is quantized Can be determined as a coefficient.

That is, when the complexity of the neighboring block is less than or equal to a predetermined threshold value, it is determined that the complexity of the neighboring block is not large and the basic quantization coefficient is determined as the quantization coefficient of the current block. If the complexity of the neighboring block exceeds a predetermined threshold It is determined that the complexity of the neighboring block is large and the quantization coefficient of the current block is determined as the quantization coefficient of the value smaller than the basic quantization coefficient for efficient quantization so that it can be quantized to a small quantization step, So that the quantization can be properly performed. Here, the basic quantization coefficient refers to a quantization coefficient promised to be basically used in advance by the image encoding apparatus 100 and a video decoding apparatus to be described later, and is a fixed value such as a quantization coefficient used in a quantization process according to H.264 And

Here, the quantization coefficient having a value smaller than the predetermined basic quantization coefficient may have any value if it is smaller than the value of the basic quantization coefficient. For example, if the basic quantization coefficient is 50, a quantization coefficient having a value of 1 to 49 smaller than 50 can be determined as a quantization coefficient of the current block, and if the basic quantization coefficient is 10, 1 to 9 The quantization coefficient having a certain value can be determined as the quantization coefficient of the current block.

As described above, the quantization coefficient having a value smaller than the predetermined basic quantization coefficient may have a value specified using the complexity of the neighboring block among the values smaller than the value of the basic quantization coefficient. For example, when the complexity of a neighboring block exceeds a predetermined threshold value, a ratio of a value smaller than the basic quantization coefficient can be determined according to the exceeding ratio. The quantization coefficient having a value obtained by subtracting 1 from the value of the basic quantization coefficient may be determined as the quantization coefficient of the current block every time the complexity of the neighboring block exceeds a predetermined threshold by 10.

4 is a flowchart illustrating a method of determining a quantization coefficient according to an embodiment of the present invention.

In order to determine the quantization coefficient of the current block, the quantization coefficient determination apparatus 200 calculates a complexity of a neighboring block around the current block (S410). At this time, the quantization coefficient determination apparatus 200 may select one or more blocks previously coded before coding the current block or one of the blocks adjacent to the current block as neighboring blocks, The complexity of the neighboring blocks can be calculated by averaging the coefficient bit rates.

When the complexity of the neighboring block is calculated, the quantization-coefficient determination apparatus 200 compares the complexity of the calculated neighboring block with a preset threshold value to determine whether the complexity of the neighboring block exceeds a predetermined threshold value (S420) If the complexity of the neighboring block is less than or equal to the predetermined threshold value, it is determined that the degree of complexity of the neighboring block is not large, and the predetermined basic quantization coefficient is determined as the quantization coefficient of the current block (S430) If it is determined that the complexity of the neighboring block is large, the quantization coefficient having a value smaller than the basic quantization coefficient is determined as the quantization coefficient of the current block (S440).

2 to 4, the quantization coefficient determining unit 200 can adaptively determine a quantization coefficient suitable for an image characteristic of a block for each block of an image, and the quantization unit 140 quantizes the block It is possible to quantize efficiently using the quantization coefficients determined adaptively.

Hereinafter, a process of encoding an image by quantizing using the quantization coefficient determined by the quantization coefficient determination apparatus 200 will be described with reference to FIG.

5 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.

1, an image encoding apparatus 100 according to an embodiment of the present invention divides an image into blocks, such as a macro block or a sub-block, Technique to generate a prediction block by predicting the current block of the image, and subtracting the current block from the prediction block to generate a residual block (S510). When the residual block is generated, the image encoding apparatus 100 converts the residual block into the frequency domain to generate a residual block having a frequency coefficient (S520).

In order to quantize the residual block having a frequency coefficient, the image coding apparatus 100 determines a quantization coefficient of the current block according to the complexity of a neighboring block of the current block (S530) The transformed residual block is quantized using the quantization coefficient (S540). When the quantization coefficient is determined in step S530, the image encoding apparatus 100 calculates the complexity of the neighboring block and compares the complexity of the neighboring block with a preset threshold value. If the complexity of the neighboring block is equal to or less than a preset threshold value, Block is determined as the quantization coefficient of the block, and when the complexity exceeds the preset threshold value, a value smaller than the predetermined basic quantization coefficient can be determined as the quantization coefficient of the current block.

The image encoding apparatus 100 encodes the quantized frequency coefficients of the quantized residual block to generate encoded data (S550). The image encoding apparatus 100 that has generated the encoded data generates various types of information so that the image decoding apparatus can decode the encoded data, and includes the generated information in the encoded data. Therefore, the finally generated encoded data includes a first field including a bit string generated by coding an encoded block type (CBP), a delta quantization coefficient, and a quantization frequency coefficient, and a second field including a bit for information required for prediction Field. In this case, when the complexity of the neighboring block exceeds a preset threshold value and a value smaller than the basic quantization coefficient is determined as the quantization coefficient of the current block, the quantization coefficient is changed so that the delta quantization coefficient included in the first field is '0' And in this case, additional bits must be allocated for the delta quantization coefficients, thereby reducing the compression efficiency.

To this end, when the complexity of the neighboring block exceeds a preset threshold value and the quantization coefficient having a value smaller than the basic quantization coefficient is the quantization coefficient of the current block, the image encoding apparatus 100 changes the value of the current block The quantization coefficient can be changed back to the basic quantization coefficient. For example, when the basic quantization coefficient is '30' and the quantization coefficient of the current block is determined to be '10', when the residual block is quantized in step S450, the quantization coefficient is quantized with a quantization coefficient having a value of '10' Thereafter, the quantization coefficient of the current block is changed back to the basic quantization coefficient '30' so that the delta quantization coefficient becomes '0'.

As described above, by using the image encoding apparatus 100 and the image encoding method using the image encoding apparatus 100 according to an embodiment of the present invention, the quantization coefficient can be adaptively determined for each block in consideration of the image characteristics of the block, Quantization can be performed with a quantization coefficient suited to the characteristics of an image, and the compression efficiency can be improved accordingly. As described above, the image encoded with the encoded data by the image encoding apparatus 100 can be transmitted through a wired / wireless communication network such as the Internet, a local area wireless communication network, a wireless LAN network, a WiBro network, a mobile communication network, (USB: Universal Serial Bus) or the like, and can be decoded and reconstructed into an image and reproduced by an image decoding apparatus.

FIG. 6 is a block diagram of a video decoding apparatus according to an embodiment of the present invention. Referring to FIG.

The image decoding apparatus 600 according to an embodiment of the present invention may be implemented as a personal computer (PC), a notebook computer, a personal digital assistant (PDA), a personal computer Digital assistant, a portable multimedia player (PMP), a PlayStation Portable (PSP), a mobile communication terminal, or the like, and may be a communication modem for performing communication with various devices or wired / wireless communication networks A memory for storing various programs for decrypting images and data, and a microprocessor for executing and controlling programs and the like.

An image decoding apparatus 600 according to an embodiment of the present invention includes a decoding unit 610, an inverse quantization unit 610, an inverse transformation unit 630, a prediction unit 640, and an adder 650, .

The decoding unit 610 decodes the encoded data to extract residual blocks. That is, the decoding unit 610 decodes the encoded data to extract the quantized frequency coefficient sequence, and inversely scans the quantized frequency coefficient sequence using various inverse scanning methods such as inverse zigzag scanning to generate residual blocks having quantized frequency coefficients. At this time, the decoding unit 610 can extract and decode the residual block encoded in the first field included in the encoded data, extract information necessary for prediction in the second field included in the encoded data, Information necessary for prediction to the prediction unit 640 so that the prediction unit 640 predicts the current block in the same manner as the prediction unit 110 of the image encoding apparatus 100. [ If the delta quantization coefficient is included in the first field, the decoding unit 610 can extract the delta quantization coefficient.

The inverse quantization unit 620 dequantizes the residual block to generate a dequantized residual block. At this time, the dequantizer 620 dequantizes the residual block, determines the quantization coefficient of the current block according to the complexity of the neighboring block, and dequantizes the residual block using the determined quantization frequency coefficient of the current block. The inverse quantization unit 620 may include the quantization coefficient determination apparatus 200 described above with reference to FIG. 2 like the quantization unit 140 described above with reference to FIG. ) Can determine the quantization coefficient of the current block in the same manner as the manner in which the quantization coefficient of the current block is determined. If it is determined that the complexity of the neighboring block is less than a predetermined threshold value and is quantized using the basic quantization coefficient, the inverse quantization unit 620 identifies the quantized value by using the delta quantization coefficient extracted from the encoded data by the decoding unit 610 Can be determined as the quantization coefficient of the current block.

The inverse transform unit 630 inversely transforms the inverse quantized residual block by the inverse quantization unit 620. The prediction unit 640 predicts the current block to generate a prediction block. The prediction unit 640 can predict a current block using information required for prediction transmitted from the decoding unit 620. [ The adder 650 adds the inverse transformed residual block and the predicted block to reconstruct the current block. The current block reconstructed by the adder 650 is transferred to the predictor 640 and can be used to predict other blocks in the predictor 640. [ Although not shown in FIG. 6, a deblocking filter unit (not shown) may be additionally connected between the predicting unit 640 and the adding unit 650. Since the deblocking filter unit is as described above with reference to FIG. 1, a detailed description thereof will be omitted.

7 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

The video decoding apparatus 600 receives encoded video data through a wired / wireless communication network or a cable, and stores the decoded video data. The video decoding apparatus 600 decodes and decodes the video in order to reproduce the video according to a user's selection or an algorithm of another program being executed.

To this end, the image decoding apparatus 600 decodes the encoded data to extract residual blocks (S710). At this time, the image decoding apparatus 600 can extract and decode the residual block encoded in the first field included in the encoded data, extract information necessary for prediction in the second field included in the encoded data, An intra prediction mode for intra prediction or a motion vector for inter prediction can be identified using information necessary for prediction. Also, the image decoding apparatus 600 can extract the delta quantization coefficient when the delta quantization coefficient is included in the first field. When the image is quantized with the basic quantization coefficient in the image encoding apparatus 100, the delta quantization coefficient may be included in the first field. If the quantization coefficient is smaller than the basic quantization coefficient, the delta quantization coefficient is added to the first field May not be included.

The image decoding apparatus 600 that has extracted the residual block determines a quantization coefficient to dequantize the residual block, and determines a quantization coefficient according to the complexity of the neighboring block (S720). That is, the image decoding apparatus 600 calculates the complexity of a neighboring block, compares the complexity of the neighboring block with a preset threshold value, and determines whether the complexity of the neighboring block exceeds a preset threshold value. By thus determining whether the residual block is quantized using the basic quantization coefficient Or quantized using a quantization coefficient having a value smaller than the basic quantization coefficient. If it is determined that the complexity of the neighboring block is less than a preset threshold and is quantized using the basic quantization coefficient, the quantization coefficient identified by the delta quantization coefficient extracted from the encoded data is determined as the quantization coefficient of the current block in step S710, If it is determined that the complexity of the neighboring block exceeds a preset threshold and is quantized using a quantization coefficient having a value smaller than the basic quantization coefficient, a quantization coefficient having a value smaller than the basic quantization coefficient is determined as a quantization coefficient of the current block .

At this time, the image decoding apparatus 600 calculates a quantization coefficient having a value smaller than the basic quantization coefficient according to a scheme predetermined by the image encoding apparatus 100. [ The predetermined method is to select a quantization coefficient equal to the quantization coefficient selected by the image coding apparatus 100 among the values smaller than the value of the basic quantization coefficient or to use the complexity of the neighboring block among the values smaller than the value of the basic quantization coefficient Quot; is selected. Since this has been described above with reference to FIG. 2, detailed description is omitted.

If the quantization coefficient is determined in step S720, the image decoding apparatus 600 dequantizes the residual block extracted in step S710 using the determined quantization coefficient (S730), and inversely transforms the dequantized residual block into a spatial domain S740). Also, the image decoding apparatus 600 generates a prediction block by predicting the current block (S750), and restores the current block by adding the predicted prediction block and the inverse transformed residual block in step S740 (S760).

The reconstructed current block may be accumulated as a reconstructed picture on a picture-by-picture basis, and may be stored as a reference picture for predicting a next block.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them. In addition, although all of the components may be implemented as one independent hardware, some or all of the components may be selectively combined to perform a part or all of the functions in one or a plurality of hardware. As shown in FIG. The codes and code segments constituting the computer program may be easily deduced by those skilled in the art. Such a computer program can be stored in a computer-readable storage medium, readable and executed by a computer, thereby realizing an embodiment of the present invention. As the storage medium of the computer program, a magnetic recording medium, an optical recording medium, a carrier wave medium, or the like may be included.

Furthermore, the terms "comprises", "comprising", or "having" described above mean that a component can be implanted unless otherwise specifically stated, But should be construed as including other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

As described above, the present invention can be applied to a technique for encoding and decoding an image, so that a quantization coefficient can be adaptively determined according to characteristics of an image, and quantization can be performed using different quantization coefficients for each block. Encoding can be performed in consideration of the characteristics of an image so that even when a block having a complex characteristic and a block having a complex characteristic are mixed in one picture of an image, efficient coding can be performed, Which is a very useful invention.

1 is a block diagram schematically illustrating a configuration of a video encoding apparatus according to an embodiment of the present invention;

FIG. 2 is a block diagram schematically illustrating a configuration of a quantization coefficient determination apparatus according to an embodiment of the present invention. FIG.

3 is a diagram illustrating a current block and neighboring blocks according to an exemplary embodiment of the present invention.

4 is a flowchart illustrating a method of determining a quantization coefficient according to an embodiment of the present invention.

5 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.

6 is a block diagram schematically showing a configuration of an image decoding apparatus according to an embodiment of the present invention;

7 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

Claims (22)

delete delete delete delete delete delete delete An apparatus for encoding an image, the apparatus comprising: A prediction unit for generating a prediction block by predicting a current block; A subtracting unit for subtracting the current block from the prediction block to generate a residual block; A transform unit for transforming the residual block into a frequency domain; A quantizer for determining a quantization coefficient of the current block according to a complexity of a neighboring block and quantizing the transformed residual block; And And an encoding unit for encoding the quantized residual block to generate encoded data, Wherein the quantization unit comprises: And changes the quantization coefficient of the current block to a value smaller than a predetermined basic quantization coefficient if the complexity of the neighboring block exceeds a preset threshold value. 9. The apparatus of claim 8, And after the quantized residual block is encoded, re-modifies the quantized coefficient of the changed current block to a basic quantized coefficient. An apparatus for encoding an image, the apparatus comprising: A prediction unit for generating a prediction block by predicting a current block; A subtracting unit for subtracting the current block from the prediction block to generate a residual block; A transform unit for transforming the residual block into a frequency domain; A quantizer for determining a quantization coefficient of the current block according to a complexity of a neighboring block and quantizing the transformed residual block; And And an encoding unit for encoding the quantized residual block to generate encoded data, Wherein the quantization unit comprises: And determines the quantization coefficient of the current block as a preset basic quantization coefficient if the complexity of the neighboring block is less than or equal to a preset threshold value. delete A method of encoding an image, A prediction step of generating a prediction block by predicting a current block; A subtraction step of subtracting the current block from the prediction block to generate a residual block; A transforming step of transforming the residual block into a frequency domain; A quantization step of quantizing the transformed residual block by determining a quantization coefficient of the current block according to a complexity of a neighboring block; And And a coding step of coding the quantized residual block to generate encoded data, Wherein the quantization step comprises: A complexity calculation step of calculating a complexity of the neighboring block; A comparison step of comparing the complexity with a predetermined threshold value; A quantization coefficient holding step of determining a predetermined basic quantization coefficient as a quantization coefficient of the current block if the complexity is equal to or less than the preset threshold value; A quantization coefficient changing step of, when the complexity exceeds the predetermined threshold value, determining a value smaller than the predetermined basic quantization coefficient as a quantization coefficient of the current block; And Quantizing the transformed residual block using the determined quantization coefficient of the current block Wherein the image encoding method comprises: 13. The image encoding method of claim 12, And changing a quantization coefficient of the current block to a basic quantization coefficient if the quantization coefficient of the current block is changed to a value smaller than a predetermined basic quantization coefficient. Encoding method. delete An apparatus for decoding an image, the apparatus comprising: A decoding unit decoding the encoded data to extract a residual block; A dequantizer for determining a quantization coefficient of a current block according to a complexity of a neighboring block and dequantizing the residual block using the determined quantization coefficient of the current block; An inverse transform unit for inversely transforming the dequantized residual block; A prediction unit for generating a prediction block by predicting the current block; And And an adder for adding the inversely transformed residual block and the prediction block to reconstruct the current block, Wherein the inverse- And changes the quantization coefficient of the current block to a value smaller than a preset basic quantization coefficient if the complexity of the neighboring block exceeds a preset threshold value. An apparatus for decoding an image, the apparatus comprising: A decoding unit decoding the encoded data to extract a residual block; A dequantizer for determining a quantization coefficient of a current block according to a complexity of a neighboring block and dequantizing the residual block using the determined quantization coefficient of the current block; An inverse transform unit for inversely transforming the dequantized residual block; A prediction unit for generating a prediction block by predicting the current block; And And an adder for adding the inversely transformed residual block and the prediction block to reconstruct the current block, Wherein the inverse- And determines a quantization coefficient of the current block as a preset basic quantization coefficient if the complexity of the neighboring block is less than or equal to a preset threshold value. delete delete delete delete delete delete

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