KR101525202B1 - Frequency Transform Block Coding Method and Apparatus and Image Encoding/Decoding Method and Apparatus Using Same - Google Patents

Abstract

An embodiment of the present invention relates to a frequency conversion block coding method and apparatus using a frequency mask table and a method and apparatus for image coding / decoding using the same.
According to an embodiment of the present invention, a frequency conversion block is masked using a frequency mask table to generate a masked frequency conversion block, information on a masked frequency conversion block and information on a frequency mask table used for masking are decoded, Extracts information on the frequency mask table, extracts a masked quantized frequency coefficient sequence recorded in the bitstream, and quantizes the position of the masked quantized frequency coefficient sequence not recorded in the bitstream using information on the extracted frequency mask table A frequency transform block coding method and apparatus using a frequency mask table for generating a quantized frequency coefficient sequence by setting all frequency coefficients to 0 and generating and decoding a quantized frequency transform block by inversely scanning the generated quantized frequency coefficient sequence, Use It provides a video encoding / decoding method and apparatus.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency transform block coding method and apparatus using a frequency mask table and an image encoding /

An embodiment of the present invention relates to a frequency conversion block coding method and apparatus using a frequency mask table and a method and apparatus for image coding / decoding using the same. More particularly, in coding and decoding a frequency transform block of a residual signal, a frequency transform block is improved by using a frequency mask table including non-coding information according to the position of a frequency coefficient of a residual block And a method and apparatus for encoding / decoding an image using the same.

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 was called H.264 / AVC (Advanced Video Coding) and jointly announced as MPEG-4 Part 10 AVC and ITU-T Recommendation H.264.

In H.264 / AVC (hereinafter abbreviated as 'H.264') standard, an intra / inter prediction process is performed on a macro block unit having various types of sub-blocks to generate a residual signal, The encoding unit performs frequency conversion, quantization, entropy encoding, and the like on the frequency conversion unit of the unit.

In recent years, video compression technology has been developed to meet the demand for ultra-high resolution images, and MPEG and VCEG international standards organizations are jointly developing the HEVC video encoding standard under the name of JCT. It has been experimentally proven that, in addition to the 4x4 and 8x8 frequency units used in conventional image compression techniques, a large frequency conversion unit such as 16x16 is very useful for improving image compression efficiency. However, there is a problem in that it is difficult to design an efficient encoding of frequency coefficients according to the characteristics of an image, and to design and implement such an encoding device by scanning and encoding the entire 16x16 in a conventional manner at a time.

In order to solve such a problem, an embodiment of the present invention compresses a frequency transform block by reflecting a characteristic of an image using a frequency mask table including non-coding information according to a position of a frequency coefficient of a residual block, The main purpose is to improve efficiency and facilitate implementation.

According to an embodiment of the present invention, there is provided a method of decoding a quantized frequency coefficient sequence included in a bitstream into a size of a conversion unit, the method comprising the steps of: Extracting the location information from the bitstream; Generating a transform block having a magnitude of the transform unit by deriving coefficients of a position preceding the non-zero last coefficient in the scan order from the bit stream, based on the extracted position information; And de-quantizing and inverse transforming the generated transform block.

The step of generating the transform block sets a coefficient of a position after the last non-zero coefficient in the scan order to zero.

The generating of the transform block may include extracting, from the bitstream, a value indicating whether a coefficient of a position preceding the non-zero last coefficient in the scan order is 0; If the extracted value is a first value, deriving a coefficient of the position from the bitstream; And setting a coefficient of the corresponding position to 0 if the extracted value is a second value.

On the other hand, the value indicating whether the position information and each coefficient are 0 may be a value encoded by an arithmetic coding method.

The conversion unit has a block size of 2 ⁿ * 2 ⁿ (n is a natural number within a certain range), and may include a block size larger than 8 * 8, and n may be a value within a range of 2 to 5 inclusive.

The position information and a value indicating whether each coefficient is 0 may be defined as a frequency mask table and included in the bitstream.

According to another embodiment of the present invention, there is provided an apparatus for decoding a quantized frequency coefficient sequence included in a bitstream into a size of a conversion unit, the apparatus comprising: position information indicating a position of a last non- Extracts the position information from the bitstream, and derives coefficients at positions preceding the non-zero last coefficient in the scan order from the bitstream based on the extracted position information, A decoding unit for generating a decoding signal; A dequantizer for dequantizing the generated transform block; And an inverse transformer for inversely transforming the inversely quantized transform block.

The decoding unit sets a coefficient of a position after the last non-zero coefficient in the scan order to zero.

Wherein the decoding unit extracts, from the bitstream, a value indicating whether a coefficient at a position preceding the non-zero last coefficient in the scan order is 0, and if the extracted value is a first value, And if the extracted value is the second value, the coefficient of the corresponding position may be set to zero.

On the other hand, the value indicating whether the position information and each coefficient are 0 may be a value encoded by an arithmetic coding method.

The conversion unit has a block size of 2 ⁿ * 2 ⁿ (n is a natural number within a certain range), and may include a block size larger than 8 * 8, and n may be a value within a range of 2 to 5 inclusive.

The position information and a value indicating whether each coefficient is 0 may be defined as a frequency mask table and included in the bitstream.

As described above, according to the embodiment of the present invention, the frequency conversion block is encoded by reflecting the characteristics of the image using the frequency mask table including the non-coding information according to the position of the frequency coefficient of the residual block, There is an effect of improving the efficiency.

1 is a block diagram schematically illustrating an image encoding apparatus according to an embodiment of the present invention.
2 is a diagram illustrating a frequency transform block coding apparatus 200 according to an embodiment of the present invention.
3 is a diagram showing an example of a frequency mask table for an 8x8 frequency conversion block.
4A is a diagram illustrating a quantized residual frequency transform block in a frequency transform unit of 8x8 size, FIG. 4B is a diagram illustrating a quantized residual transform block in FIG. 4A by masking the quantized frequency transform block of FIG. Fig.
5 is a flowchart illustrating a method of encoding a slice by generating a frequency mask table according to an embodiment of the present invention.
FIG. 6A illustrates a zigzag scan of the coefficients of the frequency mask table of FIG. 3, and FIG. 6B illustrates a frequency mask coefficient sequence after scanning.
Fig. 7 is a diagram showing an example of coding the frequency mask coefficient of Fig. 6. Fig.
FIG. 8 is a block diagram of a video decoding apparatus according to an embodiment of the present invention. Referring to FIG.
FIG. 9 is a block diagram schematically illustrating the configuration of a frequency coefficient thermal decoding apparatus 900 according to an embodiment of the present invention.
10 is a diagram illustrating a flow chart for decoding a slice according to a frequency mask table.
11 is a diagram illustrating a frequency transform block encoding apparatus 1100 according to another embodiment of the present invention.

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 even though 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 constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

The Video Encoding Apparatus and the Video Decoding Apparatus to be described below may be implemented as a personal computer (PC), a notebook computer, a personal digital assistant (PDA), a portable multimedia player (PMP) A portable terminal, a portable multimedia player, a PlayStation Portable (PSP), a wireless communication terminal, a smart phone, a TV, a server terminal such as an application server and a service server, A communication device such as a communication modem for performing communication with various devices or wired or wireless communication networks, a memory for storing various programs and data for inter or intra prediction for encoding or decoding an image, coding or decoding for image, And a microprocessor for controlling It can mean a variety of devices.

In addition, the image encoded by the video encoding apparatus can be transmitted in real time or in non-real time through a wired or wireless communication network such as the Internet, a local area wireless communication network, a wireless LAN network, a WiBro network, a mobile communication network, A serial bus, and the like, and can be decoded and reconstructed into an image and reproduced by an image decoding apparatus.

The moving picture may be generally composed of a series of pictures, and each picture may be divided into a predetermined area such as a frame or a block. When an image area is divided into blocks, the divided blocks can be classified into an intra block and an inter block according to a coding method. The intra-block refers to a block that is coded using Intra Prediction Coding (P-Coding) scheme. The intra-prediction coding is performed by using the pixels of previously decoded and decoded blocks in the current picture, A prediction block is generated by predicting the pixels of the block and a difference value between the pixel of the current block and the pixel of the current block is encoded. Inter-block refers to a block that is coded using Inter Prediction Coding. Inter-prediction coding refers to one or more past pictures or a future picture to generate a prediction block by predicting a current block in the current picture, And the difference value is encoded. Here, a frame to be referred to in encoding or decoding a current picture is referred to as a reference frame.

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

An image encoding apparatus 100 according to an exemplary embodiment of the present invention includes an intra prediction unit 110, an inter prediction unit 120, a subtraction unit 130, a transform and quantization unit 140, An encoding unit 150, an inverse quantization and inverse transform unit 160, an adding unit 170, and a frame memory 180. [

In the present invention, a macroblock is of an M × N type, M and N have a size of 2 ⁿ , and M and N may be the same or different. have. Therefore, it may be the same as or larger than the macroblock of H.264.

The intra prediction unit 110 generates a prediction block using adjacent pixels to predict a current macroblock. That is, the intra-prediction unit 110 generates a prediction block according to the mode of the intra-prediction unit 110 using the neighboring pixels of the current macroblock, which have already undergone the encoding process and are reconstructed.

The inter-prediction unit 120 generates a prediction block using another frame to predict the current macroblock. That is, the inter-prediction unit 120 generates a motion vector by performing motion estimation according to the mode of the inter-prediction unit 120 in a previous frame that has already undergone the encoding process and generates a prediction block in a motion compensation process using a motion vector do.

The subtraction unit 130 subtracts the prediction block from the current block to generate a residual block. That is, the subtraction unit 130 subtracts the pixel value of the current block from the pixel value of the intra prediction unit 110 or the prediction block generated by the inter prediction unit 120 to generate a residual block.

The transform and quantization unit 140 transforms the residual blocks generated by the subtraction unit 130 into frequency coefficients and quantizes them. That is, the transforming and quantizing unit 140 generates a residual block having a frequency coefficient as a residual coefficient of the residual block generated by the subtracting unit 130, and quantizes a residual block of the generated frequency coefficient. A technique for transforming an image signal in a spatial domain into a frequency domain such as Hadamard Transform and a Discrete Cosine Transform Based Integer Transform is used. In the quantization scheme, a dead zone uniform boundary Various quantization techniques such as a DZUTQ (Dead Zone Uniform Threshold Quantization) (DZUTQ) or a Quantization Weighted Matrix can be used.

The encoding unit 150 can generate encoded data by encoding the quantized residual block transformed and quantized by the transforming and quantizing unit 140. [ 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).

At this time, unlike H.264, in the present invention, in coding residual blocks of quantized frequency coefficients, a frequency mask table including 'non-coding' information according to the position of a frequency coefficient of a residual block is used, Is scanned and encoded. The related contents will be described in detail with reference to FIG. 2 in the following process.

The inverse quantization and inverse transform unit 160 performs inverse quantization and inverse transform of the transformed and quantized residual block by the transform and quantization unit 140 to reconstruct the residual block. The inverse quantization and inverse transform can be performed by reversing the conversion process and the quantization process performed by the transform and quantization unit 140. That is, the inverse quantization and inverse transform unit 160 transforms and quantizes the transformed and quantized data using information about the transform and quantization generated from the transform and quantization unit 140 (for example, information on the transform and the quantization type) 140 inversely quantizing and inverse-transforming the inverse quantization and inverse quantization.

The adder 170 adds the residual block generated by the inverse quantization and inverse transform unit 160 to the prediction block generated by the intra prediction unit 110 or the inter prediction unit 120 to generate a reconstructed block.

The frame memory 180 stores the reconstructed block in the adder 170 and is used as a reference block to generate a predictive block when intra or inter prediction is performed.

2 is a block diagram of a frequency transform block coding apparatus 200 according to an embodiment of the present invention. Referring to FIG. 1, the coding unit 150 includes a frequency transform block coding apparatus 200 according to an embodiment of the present invention. . ≪ / RTI >

The frequency conversion block coding apparatus 200 may be a motion compensation apparatus existing as an independent hardware or software module.

The frequency transform block coding apparatus 200 includes a frequency mask unit 210, a frequency scan unit 220, a mask block coding unit 230, and a table information coding unit 240.

The frequency mask unit 210 generates a masked frequency transform block by masking the quantized frequency transform block using the frequency mask table.

The frequency scan unit 220 scans the masked frequency conversion block to generate a masked frequency coefficient sequence.

The mask block coding unit 230 codes the masked frequency coefficient sequence.

The table information encoding unit 240 encodes information on the frequency mask table used to mask the quantized frequency conversion block.

3 is a diagram showing an example of a frequency mask table for an 8x8 frequency conversion block.

The frequency mask table as shown in FIG. 3 may be defined for all frequency translation blocks of size NxM (where N may be equal to or different from M). The values in the frequency mask table indicate information indicating whether the corresponding frequency coefficient is encoded or not in the bit stream generated by encoding at the corresponding frequency coefficient position of the frequency conversion block. The frequency conversion block proceeds from the lower left to the lower right of the block to the high frequency coefficient from the low frequency coefficient (the frequency mask table also goes from the lower left to the lower right and goes from the low frequency coefficient to the high frequency coefficient). In the case of the portion corresponding to '1' in the frequency mask table of FIG. 3, the frequency coefficient at the corresponding position of the frequency transform block is entropy-encoded and output to the bit stream. In the case of the portion corresponding to '0' Is not entropy-encoded and the frequency coefficient is set to '0'.

4A is a diagram illustrating a quantized residual frequency transform block in a frequency transform unit of 8x8 size, FIG. 4B is a diagram illustrating a quantized residual frequency transform block in FIG. 4A by masking the quantized frequency transform block of FIG. Fig. Conventionally, the residual frequency transform block of FIG. 4A constructs a frequency coefficient sequence composed of 64 quantized frequency coefficients by a scanning method such as zigzag scanning and encodes all of them.

When the frequency mask unit 210 masks the quantized residual frequency transform block of FIG. 4A using the frequency mask table of FIG. 3 as an embodiment of the present invention, Only the six frequency positions represented by '1' are scanned, and the mask block coding unit 230 encodes the coefficient sequence scanned only at six frequency positions, thereby improving the compression efficiency. Therefore, if the quantized frequency transform block of FIG. 4A is masked with the frequency mask table of FIG. 3, the result shown in FIG. 4B can be obtained.

The mask block coding unit 230 may use an entropy coding technique as a coding technique similar to the coding unit 150 in coding the masked frequency coefficient sequence, .

On the other hand, the frequency mask unit 210 compares rate-distortion among a plurality of frequency mask tables for any one of a block, a macro block, a picture, and a slice including at least one frequency conversion unit, The frequency mask table can be used to generate masked frequency translation blocks.

In addition, the frequency mask unit 210 may be configured such that, when there are a plurality of frequency conversion units constituting one image unit among a block, a macro block, a picture, and a slice including at least one frequency conversion unit, The frequency transform block having the lowest coding cost can be used to compare the rate-distortion and generate the masked frequency transform block.

The frequency scan unit 220 may generate masked frequency transform blocks using the same frequency mask table for each slice or picture.

The table information encoding unit 240 can scan and code the frequency mask table.

The table information encoding unit 240 may encode the frequency mask table into a bit stream by sending one common frequency conversion unit for each frequency conversion unit instead of sending one for each frequency conversion unit in order to improve compression efficiency.

In one embodiment, the table information encoding unit 240 includes one frequency mask table in the header information of the slice so that not only the image encoding apparatus but also all the frequency conversion blocks in one slice are masked by the image decoding apparatus, You can use tables.

In another embodiment, the table information encoding unit 240 includes one frequency mask table in the header information of the picture, so that not only the image encoding apparatus but also all the frequency conversion blocks of one slice are masked by the image decoding apparatus, You can use tables.

In another embodiment, the table information encoding unit 240 includes a plurality of frequency mask tables and their identification information (e.g., indexes) in the slice header, and stores the frequency information of each block including each macroblock or a plurality of frequency conversion units The index of the mask table can be encoded and output to the bit stream.

In another embodiment, the table information encoding unit 240 includes a plurality of frequency mask tables and indexes in the picture header, and indexes corresponding frequency mask tables for each block including each macroblock or a plurality of frequency conversion units And output it to the bit stream.

In another embodiment, the table information encoding unit 240 includes a plurality of frequency mask tables and indexes in a sequence header, and stores indexes of corresponding frequency mask tables for each block including each macro block or a plurality of frequency conversion units And output it to the bit stream.

In this embodiment, the frequency mask unit 210 may include an image encoding unit (picture, slice, and the like) that share a frequency mask table (may be generated from a set of various preset frequency mask tables) to generate a frequency mask table to be used for masking. The table information encoding unit 240 can select the best frequency mask table in terms of RD (Bit-Rate Distortion) by using various frequency mask tables for the macro block, the frequency conversion unit set) A single frequency mask table is encoded and output to a bit stream, thereby improving the compression ratio.

11 is a diagram illustrating a frequency transform block encoding apparatus 1100 according to another embodiment of the present invention.

The frequency transform block coding apparatus 1100 includes a frequency mask unit 1110, a frequency scan unit 1120, a mask block coding unit 1130, and a table information encoding unit 1140.

11, the processing sequence of the frequency scan unit 1120 and the frequency mask unit 1110 in the frequency conversion block coding apparatus 1100 is the same as that of the frequency scan unit 220 and the frequency mask unit 210 It may be the reverse of the order.

The frequency scan unit 1120 scans the quantized frequency conversion block to generate a frequency coefficient sequence. The frequency scan unit 1120 scans the quantized frequency transform block as shown in FIG. 4A to generate a frequency coefficient sequence.

The frequency mask unit 1110 scans the frequency mask table and generates a masked frequency coefficient sequence by masking the frequency coefficient sequence by the scanned frequency mask sequence. The frequency mask unit 1110 scans the frequency mask table shown in FIG. 3 and generates a masked frequency coefficient sequence by masking only the frequency coefficient column at a position corresponding to '1' in the scanned frequency mask row.

The mask block coding unit 1130 entropy-codes the generated masked frequency coefficient sequence. Mask block encoding unit 230 of the mask block encoding unit 1130, detailed description thereof will be omitted.

The table information encoding unit 1140 can encode information on the used frequency mask table and encode the scanned frequency mask table. Other operations of the table information encoding unit 1140 are similar to those of the table information encoding unit 240, and thus detailed description thereof will be omitted.

5 is a flowchart illustrating a method of encoding a slice by generating a frequency mask table according to an embodiment of the present invention. 5 shows a case where the size of the frequency conversion block of the slice is constant.

According to the embodiment of the present invention, if the size of the frequency transform block constituting the slice is larger than one, the frequency mask unit 210 performs an optimal frequency mask having a minimum coding cost in terms of rate- And generates a masked frequency transform block using the optimal frequency mask table. The frequency scan unit 220 scans the masked frequency transform block to generate a masked frequency coefficient sequence, 230 encodes the masked frequency coefficient sequence generated in the frequency scan unit 220 and the table information encoding unit 240 encodes information about the frequency mask table used for masking the quantized frequency transform block Which may be frequency mask table identification information). In this embodiment, the frequency mask table can be set for frequency conversion blocks (4x4, 4x8, 8x4, 8x8, 8x16, 16x8, 16x16, 16x32, 32x16, 32x32, 64x32, 32x64, 64x64) of various sizes. In addition, various types of frequency mask tables may be set for the frequency conversion blocks of the respective sizes, and the frequency mask unit 210 may use one of the frequency mask tables.

The table encoding unit 240 may encode a frequency mask coefficient string by scanning the frequency mask table to entropy-encode the frequency mask coefficient string.

FIG. 6A illustrates a zigzag scan of the coefficients of the frequency mask table of FIG. 3, and FIG. 6B illustrates a frequency mask coefficient sequence after scanning.

In the present embodiment, the coefficient scanning of the frequency mask table may employ zigzag scanning, horizontal scanning, vertical scanning, or the like, which is the same or similar to the method used for coding the frequency coefficient block in the previous image coding.

The method of entropy encoding the frequency mask coefficient sequence according to the embodiment of the present invention may be performed using a variable length coding method, an arithmetic coding method, or the like, but the present invention is not limited thereto.

In the present embodiment, as a method of entropy encoding the frequency mask coefficient sequence, '0' can be encoded as a bit value 0 and '1' as a bit value 1.

As a method for entropy-encoding a frequency mask coefficient string in the present embodiment, a method similar to 4x4 Context Adaptive Variable Length Coding (MPEG-4) is used. When a frequency mask coefficient sequence starts at a high frequency and ends at a low frequency, Attention is focused on the fact that 0 is concentrated in the second half of the frequency mask coefficient string as the characteristic, so that the position information in which the frequency mask coefficient '1' firstly starts is encoded starting from the beginning and the frequency mask coefficients '0' and '1' Can be encoded.

Fig. 7 is a diagram showing an example of coding the frequency mask coefficient of Fig. 6. Fig.

The frequency mask coefficient column of FIG. 6 can be recorded as shown in FIG. In FIG. 7, 5 ('000101': 6 bits are used to record 64 coefficient positions), which is the position information of the frequency mask coefficient '1' for the first time starting from the beginning, Record the factor '11111'. Accordingly, '00010111111' is recorded in the bit stream, so that the frequency mask table can be efficiently encoded.

Here, the position information in which the frequency mask coefficient '1' appears for the first time starting from the beginning can be encoded by a variable length coding, an arithmetic coding method or the like based on the probability.

According to the quantization method according to the embodiment of the present invention, in the quantization step, only a frequency coefficient position having a value of '1' is quantized and scanned using a frequency mask table to generate a frequency mask coefficient column, thereby reducing the complexity of calculation . That is, the frequency mask unit 210 transmits information on a frequency mask table to be used to the transform and quantization unit 140, and the transform and quantization unit 140 uses a frequency mask table when quantizing the frequency transform block Only a frequency coefficient position whose value is '1' can be quantized.

FIG. 8 is a block diagram of a video decoding apparatus according to an embodiment of the present invention. Referring to FIG.

An image decoding apparatus 800 according to an embodiment of the present invention includes a decoding unit 810, an inverse quantization and inverse transform unit 820, an intra prediction unit 830, an inter prediction unit 840, an adder 850, And a frame memory 860, as shown in FIG.

The decoding unit 810 can extract the information necessary for block decoding by decoding the encoded data. That is, the decoding unit 810 decodes the encoded data, extracts the frequency mask table information, extracts the quantized frequency coefficient sequence using the extracted frequency mask table information, and inversely scans the quantized frequency coefficient sequence to obtain a quantized frequency coefficient A residual block can be generated. At this time, the decoding unit 810 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, The information required for prediction may be transmitted to the intra prediction unit 830 or the inter prediction unit 840 so that the prediction unit predicts the current block in the same manner as the corresponding prediction unit of the image coding apparatus 100. [

The inverse quantization and inverse transform unit 820 generates inverse quantized residual blocks by inverse-quantizing the residual blocks, and generates the residual blocks by inverse transforming the generated quantized blocks.

The intra prediction unit 830 generates a prediction block for the current block using information required for intraprediction transmitted from the decoding unit 810. [

The inter-prediction unit 830 generates a prediction block for the current block using the information required for inter-prediction transmitted from the decoding unit 810. [

The adder 850 adds the inverse transform residual block and the prediction block to reconstruct the current block. The current block restored by the adder 850 is transferred to the frame memory 860, and can be utilized for predicting another block in the predictor.

The frame memory 860 stores reconstructed images to enable intra and inter prediction block generation.

Meanwhile, the decoding unit 810 can decode or extract not only the transformed and quantized residual blocks but also the information necessary for decoding by decoding the encoded data. For example, information on a block type, information on an intra-prediction mode when the prediction mode is an intra-prediction mode, information on an intra-prediction mode, information on a block type, In the case of the prediction mode, information on the motion vector, information on the transform and the quantization type, and the like may be used.

FIG. 9 is a block diagram schematically illustrating the configuration of a frequency coefficient thermal decoding apparatus 900 according to an embodiment of the present invention. The decoding unit 810 of FIG. 8 may include a frequency coefficient thermal decoding apparatus 900 according to an embodiment of the present invention.

The frequency coefficient thermal decoding apparatus 900 according to an embodiment of the present invention includes a frequency coefficient column extractor 910, a table information extractor 920, and a quantization coefficient column generator 930.

The table information extracting unit 920 extracts information on the frequency mask table from the bit stream. Here, the information on the frequency mask table may be a frequency mask table or frequency mask table identification information, and the frequency mask table may be the same for each slice or picture, and the frequency mask table may be different for each block including one or more frequency conversion units . Here, the information on the frequency mask table may be identification information for the corresponding frequency mask table for each block including the macroblock or one or more frequency conversion units.

The frequency coefficient column extractor 910 extracts the masked quantization frequency coefficient row recorded in the bitstream using the frequency mask table. The frequency coefficient column extractor 910 uses the frequency mask table to set the quantized frequency coefficients of positions not recorded in the bit stream from the masked quantized frequency coefficient columns to 0 to generate a quantized frequency coefficient row. Here, the frequency mask table used by the frequency coefficient column extractor 910 may be the same for each slice or picture, and the frequency mask table may be different for each block including at least one frequency conversion unit.

The quantization coefficient column generation unit 930 generates a quantized frequency conversion block by inversely scanning the quantization frequency coefficient column generated by the frequency coefficient column extraction unit 910. [

The operation of the frequency coefficient column extracting unit 910 and the quantization coefficient column generating unit 930 may be slightly different in the frequency coefficient thermal decoding apparatus 900 according to another embodiment of the present invention.

That is, after extracting information on the frequency mask table from the bitstream, the frequency-coefficient-stream extracting unit 910 of the frequency-coefficient-stream extracting unit 910 according to another embodiment of the present invention extracts frequency- The masked quantized frequency coefficient sequence recorded in the bitstream is extracted using the mask table, and then the masked quantized frequency coefficient sequence is inversely scanned to generate the masked frequency transform block.

The quantization coefficient column generating unit 930 fills the low frequency region of the block having the size of the frequency conversion unit with the coefficient of the masked frequency conversion block generated by the frequency coefficient column extracting unit 910, And sets the frequency coefficients of the remaining regions to 0 to generate a quantized frequency conversion block.

10 is a diagram illustrating a flow chart for decoding a slice according to a frequency mask table.

As shown in FIG. 10, the decoding of a slice includes receiving a frequency mask table FMi in a slice header from a bitstream (S1010), restoring a quantized frequency coefficient sequence from a bitstream using the received frequency mask table The quantized frequency conversion block is generated by backscanning and decoded (S1020).

The image encoding / decoding apparatus according to an exemplary embodiment of the present invention includes an encoder (data bitstream) output unit of the image encoding apparatus 100 shown in FIG. 1 as encoded data (bitstream) of the image decoding apparatus 800 shown in FIG. To the input terminal.

The image encoding / decoding apparatus according to an embodiment of the present invention generates a residual block by generating a predicted block by predicting a current block, subtracting the predicted block from the current block, transforming and quantizing the residual block, Generating a masked frequency transform block by masking the frequency transform block using a frequency mask table, encoding the masked frequency transform block and information on a frequency mask table used for masking; And extracting information on the frequency mask table from the bit stream, extracting the masked quantization frequency coefficient sequence recorded in the bitstream, and writing the bitstream from the masked quantization frequency coefficient sequence using information on the extracted frequency mask table And generates a quantized frequency coefficient sequence by setting all the quantized frequency coefficients at positions where the quantized frequency coefficients are not zero, and generates an quantized frequency transform block by inverse scanning the generated quantized frequency coefficient sequence to decode the generated frequency transform block.

Here, the image encoder can be implemented by the image encoding apparatus 100 according to an embodiment of the present invention, and the image decoder can be implemented with the image decoding apparatus 800 according to an embodiment of the present invention.

Meanwhile, a method of encoding an image according to an embodiment of the present invention includes a prediction step (S1110) of generating a prediction block by predicting a current block, a subtraction step (S1120) of subtracting a prediction block from a current block to generate a residual block, Transforming and quantizing the residual block to generate a frequency transform block, and quantizing the frequency transform block (S1130) and masking the frequency transform block using the frequency mask table to generate a masked frequency transform block, And encoding the information on the frequency mask table used in step S1140.

Here, the prediction step S1110 corresponds to the operation of the predictor 110 or 120, the subtraction step S1120 corresponds to the operation of the subtraction unit 130, and the transformation and quantization step S1130 corresponds to the operation of the transform and quantization unit 140, and the encoding step S1140 corresponds to the operation of the encoding unit 150, and a detailed description thereof will be omitted.

Meanwhile, the image decoding method according to an embodiment of the present invention extracts information about a frequency mask table from a bitstream, extracts a masked quantized frequency coefficient sequence recorded in the bitstream, and uses the extracted frequency mask table Generating a quantized frequency coefficient sequence by setting all quantization frequency coefficients at positions not recorded in the bitstream from the masked quantization frequency coefficient sequence to 0 and generating the quantized frequency transform block by inverse scanning the generated quantized frequency coefficient sequence A decoding step (S1210), an inverse quantization and inverse transform step (S1220) of restoring a residual block by inversely quantizing and inversely transforming the frequency transform block, a prediction step (S1230) of generating a prediction block by predicting a current block, (S1240) for adding the prediction block to the current block and restoring the current block The.

The decoding step S1210 corresponds to the operation of the decoding unit 810 and the dequantization and inverse transformation step S1220 corresponds to the operations of the inverse quantization and inverse transformation unit 820. In the prediction step S1230, (830 or 840), and the adding step (S1240) corresponds to the operation of the adding unit 850, and thus a detailed description thereof will be omitted.

The frequency conversion block coding method according to an embodiment of the present invention includes a frequency mask step (S1310) of generating a masked frequency conversion block by masking a frequency conversion block using a frequency mask table (S1310), scanning the masked frequency conversion block A frequency mask scan step S1320 of generating a masked frequency coefficient sequence, a mask block encoding step S1330 of encoding the masked frequency coefficient sequence, and a table information encoding information on a frequency mask table used for masking the frequency transform block And encoding step S1340.

Here, the frequency mask step S1310 corresponds to the operation of the frequency mask unit 210, the frequency scan step S1320 corresponds to the operation of the frequency scan unit 220, The table information encoding step S1340 corresponds to the operation of the table information encoding unit 240, and thus the detailed description thereof will be omitted.

The frequency conversion block coding method according to another embodiment of the present invention includes a frequency scanning step (S1410) of generating a frequency coefficient string by scanning a frequency conversion block, scanning the frequency mask table, A frequency mask step (S1420) for generating a masked frequency coefficient sequence by masking the coefficient sequence, a mask block coding step (S1430) for coding the masked frequency coefficient sequence, and a frequency mask table used for masking the frequency transform block And a table information encoding step (S1440) for encoding the information on the information.

Here, the frequency mask step S1420 corresponds to the operation of the frequency mask unit 1110, the frequency scan step S1410 corresponds to the operation of the frequency scan unit 1120, and the mask block encoding step S1430 includes the mask block And corresponds to the operation of the encoding unit 1130. The table information encoding step S1440 corresponds to the operation of the table information encoding unit 1140, and a detailed description thereof will be omitted.

An image encoding / decoding method according to an embodiment of the present invention can be realized by combining an image encoding method according to an embodiment of the present invention and an image decoding method according to an embodiment of the present invention.

The image encoding / decoding method according to an embodiment of the present invention includes generating a prediction block by predicting a current block, generating a residual block by subtracting the prediction block from the current block, transforming and quantizing the residual block, Generating a masked frequency transform block by masking the frequency transform block using a frequency mask table, encoding the masked frequency transform block and information on a frequency mask table used for masking, Extracts information on the frequency mask table from the stream, extracts the masked quantized frequency coefficient sequence recorded in the bitstream, and extracts information on the frequency band from the masked quantized frequency coefficient sequence Quantum of position Setting to zero both the frequency coefficients and a picture decoding step of decoding the quantized frequency coefficients to generate heat and to scan the generated inverse quantized frequency coefficient sequence to generate the quantized frequency transform block.

Here, the image encoding step may be implemented as an image encoding step according to an embodiment of the present invention, and the image decoding step may be implemented as an image decoding step according to an embodiment of the present invention.

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, according to the embodiment of the present invention, the frequency conversion block is divided into the frequency domain by encoding the frequency domain encoded information by applying the technique to a technique for encoding and decoding an image, Is a very useful invention which can efficiently increase the coding efficiency in consideration of the characteristics of a general image.

Claims (7)

An apparatus for decoding a quantized frequency coefficient sequence included in a bitstream into a size of a conversion unit,
Extracting the position information from the bitstream including positional information indicating a position of a last non-zero coefficient in the conversion unit, and based on the extracted positional information, Generating a transform block having a size of the transform unit by deriving coefficients of a position to be transformed from the bit stream;
A dequantizer for dequantizing the generated transform block; And
And an inverse transformer for inversely transforming the inversely quantized transform block,
Wherein the decoding unit sets a coefficient of a position that is later than the non-zero last coefficient in the scan order to zero. delete The method according to claim 1,
Wherein the decoding unit comprises:
Extracting, from the bitstream, a value indicating whether a coefficient at a position preceding the non-zero last coefficient in the scan order is 0,
If the extracted value is a first value, deriving a coefficient of the position from the bitstream,
And sets the coefficient of the corresponding position to 0 if the extracted value is a second value. The method of claim 3,
Wherein the position information and a value indicating whether each coefficient is 0 are values coded by an arithmetic coding method. The method according to claim 1,
Wherein the conversion unit has a block size of 2 ⁿ * 2 ⁿ (n is a natural number within a certain range), and includes a block size larger than 8 * 8. 6. The method of claim 5,
And n is a value within a range of 2 or more and 5 or less. The method of claim 3,
Wherein the position information and the value indicating whether each coefficient is 0 are defined as a frequency mask table and included in the bitstream.

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