KR101307406B1 - Encoding/decoding apparatus with reference frame compression - Google Patents

Abstract

In an encoding / decoding technique of an image, an image encoding / decoding apparatus capable of adaptively compressing a reference frame and storing the same in a memory is disclosed. In an image encoding / decoding apparatus, a memory compression unit for storing a reference frame is designated, and an original pixel value is assigned to an original bit unit (B) for the first pixel in the memory compression unit, and the remaining pixels except for the first pixel. For example, the memory compression unit compresses a reference frame by sequentially allocating a difference value, which is a difference value between a reconstructed pixel value of a pixel located immediately before the pixel and the pixel value, in compression bit units (N), which is a predetermined number of bits. In the memory and memory compression unit that stores the reference frame compressed by the memory compression unit, the first pixel is assigned the original pixel value as it is, and the remaining pixel value is the reconstructed pixel value of the pixel immediately preceding the pixel. Restores the compressed reference frame by sequentially allocating the sum of the difference values allocated in compression bit units (N) An image encoding / decoding apparatus for compressing and storing a reference frame including a portion is provided.

Description

Image encoding / decoding device for compressing and storing reference frames {ENCODING / DECODING APPARATUS WITH REFERENCE FRAME COMPRESSION}

The present invention relates to a technique for encoding and decoding an image, and more particularly, to an image encoding and decoding apparatus for adaptively compressing a reference frame and storing it in a memory.

Starting from the phone and facsimile, the information media dealt with in recent DMB, mobile phone, and internet communication network is gradually becoming larger capacity. Accordingly, interest and demands for high-speed multimedia data communication are increasing, and as the transmission speed of transmitting and receiving data is dramatically improved, even video data having a large data size can be transmitted / received in real time via a wired / wireless communication network It was possible.

In recent years, the use of video data through wired / wireless communication networks has exploded due to the appearance of smart phones and smart TVs.

An apparatus for encoding / decoding an image requires a frame memory for storing an image reconstructed from a predicted image. Typical portable video devices consume a lot of power when using external frame memory. In addition, the spread of portable video devices such as digital camcorders, mobile phones, smart phones, and PMPs has recently been expanded, and research on low power and low complexity video codecs that can operate in these devices is required. Since portable imaging devices operate in a limited environment, memory usage and power usage are important considerations.

Among the international standards organizations, the MPEG standard has three types of prediction: intra coded frame (I frame), predictive coded frame (P frame), and bi-directionally-predicitve coded frame (B frame). A coding scheme is used, and P frames and B frames achieve high compression efficiency by using motion estimation and compensation techniques.

In addition, H.264 / AVC, which is currently commercially available, supports multiple reference frames and various macroblock modes to improve image compression performance, and uses a deblocking filter to improve image quality. These methods not only increase the complexity of encoding but also increase the bandwidth of the memory. Therefore, it is necessary to perform compression before storing the reference frame and to decode the image before referring to the reference frame. Therefore, the technique of adaptively compressing and storing the reference frame may be utilized not only in H.264 / AVC but also in the next generation codec (HEVC).

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide an image encoding apparatus capable of adaptively compressing and storing a reference frame in a memory in an image encoding technique.

Another object of the present invention for solving the above problems is to provide an image decoding apparatus capable of adaptively compressing a reference frame and storing it in a memory in an image decoding technique.

According to the present invention for achieving the above object, in the image encoding apparatus, a memory compression unit for storing a reference frame is designated, and the original pixel value is assigned to the first pixel in the memory compression unit in the original bit unit (B), The remaining pixels except for the first pixel are sequentially referred to as the compression bit unit (N), which is a predetermined number of bits, which is a difference between the reconstructed pixel value of the pixel immediately preceding the pixel and the pixel value. In the memory compression unit for compressing a frame and the memory and memory compression unit for storing the reference frame compressed by the memory compressor, the first pixel is assigned the original pixel value, and the remaining pixel value is the value of the pixel. Compressed reference by sequentially assigning the reconstructed pixel value of the immediately preceding pixel plus the difference allocated in compression bit unit (N) Provided is an image encoding apparatus for compressing and storing a reference frame including a memory reconstruction unit for reconstructing a frame.

Here, the reconstructed pixel value is a pixel located immediately before the corresponding pixel, wherein the value is reconstructed from the previous pixel.

Here, the difference value in the memory compression unit is allocated to the value closest to the quantization table corresponding to the compression bit unit (N).

Here, the memory compression unit sequentially calculates and adds an error corresponding to a difference between the value of the pixel and the value of the pixel located immediately before the pixel, plus a difference value allocated in compression bit units (N). If the value is larger than the set value, the number of bits in the compression bit unit N is increased to allocate a difference value, and the information value b for the compression bit unit N is stored together.

Here, the memory compression unit may compress the reference frame in the horizontal direction or the vertical direction, respectively, and determine a direction in which the value obtained by adding the error generated in the process of allocating the difference value in the compression bit unit (N) is small as the memory compression direction. have.

Here, when the difference value is greater than the preset value, the memory compression unit may determine that the image boundary is between the pixel and the pixel located immediately before the pixel.

According to another aspect of the present invention for achieving the above object, in the image decoding apparatus, the memory compression unit for storing the reference frame is specified and the original pixel value in the first pixel in the memory compression unit is assigned in the original bit unit (B) The remaining pixels except for the first pixel are sequentially assigned a difference value, which is a difference between the reconstructed pixel value of the pixel immediately preceding the pixel and the pixel value, in a compression bit unit (N), which is a predetermined number of bits. In the memory compression unit compressing the reference frame and the memory and memory compression unit storing the reference frame compressed by the memory compression unit, the original pixel value is assigned to the first pixel as it is, and the value of the corresponding pixel in the remaining pixels is The reconstructed pixel value of the pixel located immediately before the pixel is sequentially added with the difference value allocated in compression bit unit (N). Compressing a reference frame including a memory recovery to restore a tarred reference frame and provides the image decoding apparatus to store.

When using the image encoding / decoding apparatus for compressing and storing the reference frame according to the present invention as described above, the amount of memory for storing the reference frame can be reduced, and the bandwidth of the memory can be reduced.

In addition, when using an image encoding / decoding apparatus for compressing and storing a reference frame according to the present invention, there is an advantage in that the compression method of a memory can be adaptively selected according to the characteristics of the reference frame.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

1 is a block diagram of a video encoding apparatus according to an embodiment of the present invention.
2 is a block diagram of an image decoding apparatus according to an embodiment of the present invention.
3 is a conceptual diagram illustrating a method of compressing and storing a reference frame according to an embodiment of the present invention.
4 is a quantization table used to compress and store a reference frame according to an embodiment of the present invention.
5 is a conceptual view illustrating a method of compressing and storing a reference frame according to another embodiment of the present invention.
6 is a conceptual view illustrating a method of compressing and storing a reference frame according to another embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

A video encoding apparatus (Video Encoding Apparatus), a video decoding apparatus (Video Decoding Apparatus) to be described below is a personal computer (PC), notebook computer, personal digital assistant (PDA), portable multimedia player (PMP) It may be a user terminal such as a portable multimedia player (PSP), a PlayStation Portable (PSP), a wireless communication terminal, a smart phone, a TV, or a server terminal such as an application server or a service server. Communication device, such as a communication modem for communicating with various devices or a wired / wireless communication network, memory for storing various programs and data for inter- or intra-prediction for encoding or decoding an image, or for encoding or decoding an image, and executing a program Microprocessor for operation and control 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. In the case where 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 in-picture block refers to a block that is coded using an Intra Prediction Coding scheme. The intra-picture prediction coding refers to a method of coding a block of pixels of previously decoded and decoded blocks in a current picture, A prediction block is generated by predicting the pixels of the current block and a difference value between 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. It is also to be understood that the term "picture" described below may be used in place of other terms having equivalent meanings such as image, frame, etc., If you are a child, you can understand.

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

1 is a block diagram of a video encoding apparatus according to an embodiment of the present invention. Referring to FIG. 1, the encoding apparatus 100 according to the present invention includes a subtractor 110, a transform unit 120, a quantization unit 130, an entropy coder 140, an inverse transform unit 121, and an inverse quantizer ( 131, an adder 150, a memory compressor 160, a memory 161, a memory reconstructor 162, and a predictor 170.

The subtractor 110 generates a residual image between the current image and the predicted image by subtracting the predicted image generated by the predictor 170 from the target image to be encoded (the current image) which is the provided input image.

The converter 120 converts the residual image generated by the subtractor 110 from the spatial domain to the frequency domain. Here, the transform unit 120 may convert the residual image into the frequency domain by using a technique of transforming an image signal of a spatial axis into a frequency axis, such as a Hadamard transform, a discrete cosine transform, or the like.

The quantization unit 130 quantizes the transformed data (frequency coefficients) supplied from the transform unit 120. [ That is, the quantization unit 130 calculates a quantization result value by approximating the frequency coefficients, which are data converted by the transform unit 120, by dividing the frequency coefficients by a quantization step size.

The entropy coder 140 generates a bitstream by entropy encoding a quantization result value calculated by the quantizer 130. In addition, the entropy coder 140 may entropy-encode the quantization result calculated by the quantization unit 130 using a context-adaptive variable length coding (CAVLC) or context-adaptive binary arithmetic coding (CABAC) technique. In addition to the quantization result, entropy encoding may be performed on index information of a reference frame, information on a motion vector, and the like, which are information necessary for decoding an image.

The inverse quantization unit 131 dequantizes the quantization result value calculated by the quantization unit 130. [ That is, the inverse quantization unit 131 restores the value (frequency coefficient) of the frequency domain from the quantization result value.

The inverse transformer 121 restores the residual image by converting a value (frequency coefficient) of the frequency domain provided from the inverse quantizer 131 from the frequency domain to the spatial domain, and the adder 150 is predicted by the predictor 170. The reconstructed image of the input image is generated by adding the residual image reconstructed by the inverse change unit 121 to the generated prediction image, and provides the reconstructed image to the memory compressor 160.

The memory compressor 160 compresses the reconstructed image of the current image and stores it in the memory 161. In particular, the memory compression unit 160 according to the present invention designates a memory compression unit for storing a reference frame, and assigns an original pixel value to an original bit unit (B) to the first pixel in the memory compression unit. The reference frame is compressed by sequentially assigning a difference value, which is a difference value between the reconstructed pixel value of the pixel immediately preceding the pixel and the corresponding pixel value in the remaining pixels except the pixel, in compression bit units (N). However, when the pixel located immediately before the pixel is the first pixel, a difference value from the original pixel value of the first pixel is used as a difference value. That is, the memory compressor 160 stores the reference frame compressed in the memory compression unit in the memory 161.

In addition, the memory restoring unit 162 that receives the compressed reference frame from the memory 161 allocates the original pixel value to the first pixel in the memory compression unit as it is, and the value of the pixel in the remaining pixels is immediately determined by the pixel. The compressed reference frame is reconstructed by sequentially assigning the reconstructed pixel value of the preceding pixel to the difference value allocated in compression bit units (N).

The reference frame reconstructed by the memory reconstructor 162 is provided to the predictor 170 and used to generate a predicted image.

That is, the memory compressor 160 compresses the current image and stores the current image in the memory 161, thereby reducing the memory bandwidth. In addition, by reducing the memory bandwidth it is possible to improve the performance of the image encoding apparatus and at the same time reduce the power consumption.

The prediction unit 170 may be configured to include an intra prediction unit that performs intra prediction and an inter prediction unit that performs inter prediction. The intra prediction unit generates a prediction block using pixels of blocks previously encoded, decoded, and reconstructed in the current image, and the inter prediction unit generates a prediction block in the current image by referring to one or more past or future images. That is, the prediction unit 170 performs a function of generating a prediction image by performing intra prediction or inter prediction.

Accordingly, in the image encoding apparatus, the present invention designates a memory compression unit for storing a reference frame, assigns an original pixel value to an original bit unit (B) to the first pixel in the memory compression unit, and assigns the first pixel. A memory compressor 160 for compressing a reference frame by sequentially assigning a difference value, which is a difference between a reconstructed pixel value of the pixel immediately preceding the pixel and the pixel value, in compression bit units (N) from the remaining pixels; In the memory 161 and the memory compression unit storing the reference frame compressed by the memory compression unit 160, the original pixel value is assigned to the first pixel as it is, and the value of the pixel in the remaining pixels is immediately before the pixel. Memory that restores the compressed reference frame by sequentially assigning the reconstructed pixel value of the located pixel plus the difference value allocated in compression bit unit (N). Compressing a reference frame comprising a moped 162 provides an image encoding apparatus for storing.

In addition, the present invention is characterized in that the original bit unit (B) is larger than the compressed bit unit (C). That is, the compression efficiency can be obtained by storing the difference value by making the original bit unit B larger than the compressed bit unit C.

In addition, the present invention provides an image encoding apparatus for compressing and storing a reference frame, characterized in that the difference value is allocated in the quantization table corresponding to the compression bit unit (N) in the memory compression unit 160.

In particular, the memory compression unit 160 provided in the present invention corresponds to a difference between a value of a corresponding pixel and a value obtained by adding a difference value allocated in compression bit units (N) to a reconstructed pixel value of a pixel located immediately before the corresponding pixel. When the result of calculating and summing the errors sequentially is larger than the preset value, the bit number of the compression bit unit (N) is increased to allocate a difference value, and the information value (b) of the compression bit unit (N) is stored together. Characterized in that.

A method of compressing and storing a reference frame according to the present invention Example  #One

3 is a conceptual diagram illustrating a method of compressing and storing a reference frame according to an embodiment of the present invention. Referring to FIG. 3, the memory compressor 160 compresses a reference frame obtained by adding a predicted image generated by the predictor 170 and a reconstructed residual image provided from the inverse transform unit 121 to the memory 161. Save it. The memory compressor 160 may designate a compression unit to compress the memory. Referring to the conceptual diagram illustrated in FIG. 3, the memory compression unit is designated as 1 × 8, but is not limited thereto. Here, B represents the original bit unit, N represents the compressed bit unit, and b represents the information value for the compressed bit unit (N). In addition, the arrow indicates a difference direction that is a direction for calculating a difference value between the pixel value located immediately before the pixel value and the pixel value. In the memory compression unit, the first pixel is assigned the original pixel value in the original bit unit (B), and the reconstructed pixel value of the pixel immediately preceding the pixel and the value of the pixel in the remaining pixels except the first pixel. The difference value, which is a difference between and is sequentially allocated in compression bit unit (N). That is, if the pixel is the second pixel, the difference value, which is the difference between the first pixel value and the second pixel value, is assigned to the second pixel. Similarly, if the pixel is the third pixel, the difference value, which is the difference between the reconstructed pixel value of the pixel and the third pixel value by adding the difference value allocated to the second pixel to the first pixel value, is assigned to the third pixel. At this time, the first pixel value is allocated in the original bit unit (B), and the difference value is sequentially assigned in the compressed bit unit (N).

For example, if the original bit unit B is 8 bits, the compressed bit unit N can be designated as 1 to 7 bits smaller than 8 bits. Here, it is assumed that the compression bit unit N is designated by four bits of 3, 4, 5, and 6 bits. The first pixel is assigned the original pixel value in 8 bits, which is the original bit unit (B). For the remaining pixels except the first pixel, the difference between the reconstructed pixel value of the pixel immediately preceding the pixel and the value of the pixel. The difference is sequentially assigned to 3 bits, which is the smallest number of bits in the compression bit unit (N).

4 is a quantization table used to compress and store a reference frame according to an embodiment of the present invention. Referring to FIG. 4, when the compression bit unit N is 3, 4, 5, or 6, an example of each quantization value from the left is shown. If the compression bit unit N is 3 bits, eight quantization values may be allocated. If the compression bit unit N is three bits, eight quantization values may be allocated. That is, since 2 ^N quantization values may be allocated according to the compression bit unit (N), increasing the compression bit unit (N) may reduce an error occurring in the quantization process, while reducing the compression efficiency. . If the compression bit unit (N) is 3 bits, the quantization value by the quantization table is {-3, -2, -1, 0, 1,2, 3, 4}, and when the difference value -4 occurs, the quantization value is -3. By assigning to the difference value, an error of 1 is generated. Therefore, an error corresponding to the difference between the pixel value and the reconstructed pixel value of the pixel immediately before the pixel, plus the difference value allocated in the compression bit unit (N) (the reconstructed pixel value of the pixel of the pixel). When the result of calculating and adding sequentially is larger than a predetermined value, compression is performed by increasing the number of bits in the compression bit unit (N). That is, when the compression bit unit (N) is 3 bits and the sum of the errors generated during the compression process is larger than the preset value, the compression is increased while sequentially increasing the compression bit unit (N) to 4, 5, and 6, respectively. To perform. In addition, the memory compressor 160 may store the information value b for the compressed bit unit N together. For example, the information value (b) for the compression bit unit (N) is a value displayed for the designated compression bit unit (N), and if the compression bit unit (N) is specified in 3, 4, 5, 6, , 2 for 00, 4 for 01, 5 for 10, 6 for 11, and so on.

For example, the memory compression unit is specified as 1 × 8, the original bit unit (B) is 8 bits, the compression bit unit (N) is 3 bits, and the information value (b) for the compression bit unit (N) is 2 If specified as bits, 8+ (3 × 7) + 2 = 31 bits of memory are required, so that 4 bytes of memory can be allocated. Alternatively, the memory compression unit is specified as 1x8, the original bit unit (B) is 8 bits, the compression bit unit (N) is 4 bits, and the information value (b) for the compression bit unit (N) is 2 bits. In this case, since 8 + (4 x 7) + 2 = 38 bits of memory are required, 5 bytes of memory can be allocated.

A method of compressing and storing a reference frame according to the present invention Example  #2

5 is a conceptual view illustrating a method of compressing and storing a reference frame according to another embodiment of the present invention. Referring to FIG. 5, the memory compression unit 160 provided by the present invention may designate a horizontal direction or a vertical direction in the memory compression direction. That is, according to the present invention, a direction in which a value obtained by summing errors generated in the process of compressing a reference frame in a horizontal direction or a vertical direction and assigning a difference value in compression bit units (N) is determined as a memory compression direction. Provided is an image encoding apparatus for compressing and storing a reference frame.

In addition, the memory compression unit 160 further stores the information value (d) for the memory compression direction, and the memory reconstruction unit 162 stores the information value (b) for the compression bit unit (N) and the memory compression direction. And reconstructing the reference frame corresponding to the information value d.

FIG. 5A is a conceptual diagram of a method of compressing a reference frame in a vertical direction, and FIG. 5B is a conceptual diagram of a method of compressing a reference frame in a horizontal direction. Referring to FIG. 5, the reference frame may be compressed in the vertical direction or the horizontal direction in the fixed compression bit unit N as in the first embodiment. That is, if the compression bit unit (N) is fixed to 5, 5 bits are allocated to the difference value between the reconstructed pixel value of the pixel immediately preceding the pixel and the pixel value, respectively, in the vertical direction or the horizontal direction, respectively. Compression can be performed. Therefore, the compression may be performed by determining a direction in which the value obtained by adding the errors generated in the compression in the vertical direction or the horizontal direction is small as the memory compression direction.

In addition, although FIG. 5 shows that 8 × 8 may be used as a reference in determining the memory compression direction, a unit for determining the memory compression direction may be adaptively selected.

In addition, the information value d for the determined memory compression direction may be represented by 1 bit, such as 0 or 1. FIG.

In addition, the present invention can adaptively determine the compression bit unit (N) and the memory compression direction according to the first and second embodiments described above, and preferably determine the compression bit unit (N) after determining the memory compression direction. Decide

A method of compressing and storing a reference frame according to the present invention Example  # 3

6 is a conceptual view illustrating a method of compressing and storing a reference frame according to another embodiment of the present invention. Referring to FIG. 6, when the difference value is greater than a preset value, the memory compression unit 160 provided by the present invention may determine that an image boundary is between the pixel and the pixel immediately before the pixel. . In addition, the memory compression unit 160 included in the image encoding apparatus for compressing and storing the reference frame according to the present invention allocates the original pixel value in the original bit unit (B) from the value of the corresponding pixel located next to the image boundary, An information value C for the number of pixels to which the difference value is allocated may be further allocated in the compression bit unit N located in front of the boundary. Here, the method of assigning the difference value can be performed as in the first embodiment. In addition, the memory reconstructor 162 may assign an original pixel value to a pixel value located next to an image boundary corresponding to the information value C of the number of pixels.

For example, if the memory compression unit is set to 1 × 8, the original bit unit (B) is set to 8 bits, and the compression bit unit (N) is set to 5 bits, the original pixel value is assigned to the first pixel with 8 bits. . For the remaining pixels except for the first pixel, the difference value is represented by 5 bits, which is a compression bit unit (N), as in the first embodiment. When the difference value is larger than a preset value, it is determined that an image boundary exists between the pixel and the pixel located immediately before the pixel. Referring to FIG. 6, an image boundary exists between the fifth pixel and the sixth pixel. That is, the difference between the fifth pixel value and the sixth pixel value is large. Therefore, from the sixth pixel value located next to the image boundary, the original pixel value is represented by 8 bits, which is the original bit unit (B). In addition, the number of pixels for which the difference value is allocated in the compression bit unit N is four, and may be represented as an information value C for the number of pixels. Through this, the compression rate can be somewhat reduced. However, the boundary part, which is a large error occurring in the process of allocating the difference value in the compression bit unit (N), is determined and the original pixel value is allocated after the boundary. To reduce errors.

2 is a block diagram of an image decoding apparatus according to an embodiment of the present invention. 2, the decoding apparatus 200 according to the present invention includes an entropy decoder 210, an inverse quantizer 220, an inverse change unit 230, an adder 240, a memory compressor 250, and a memory. 251 and a prediction unit 260.

The image restoration process of the image decoding apparatus 200 shown in FIG. 2 may be performed in the same manner as the image restoration process of the image encoding apparatus 100 shown in FIG. 1, which will be described briefly.

The entropy decoder 210 entropy decodes the bitstream generated from the image encoding apparatus 100 shown in FIG. 1, and the inverse quantizer 220 dequantizes the data transmitted from the entropy decoder 210 to decode the frequency. Restore the value (frequency coefficient) of the domain. In addition, the inverse transformer 230 inversely converts a value (frequency coefficient) in the frequency domain from the frequency domain to the spatial domain. The adder 240 generates a reconstructed image of the current image by adding the residual image reconstructed by the inverse transform unit 230 to the predicted image generated by the predictor 260.

In particular, in an image decoding apparatus, a memory compression unit for storing a reference frame is designated, and an original pixel value is assigned to an original bit unit (B) for the first pixel in the memory compression unit, and the remaining pixels except for the first pixel. The memory compression unit 250 and the memory compression unit compressing a reference frame by sequentially assigning a difference value, which is a difference value between the reconstructed pixel value of the pixel immediately preceding the pixel and the pixel value, in compression bit units (N). In the memory and the memory compression unit storing the reference frame compressed by, the original pixel value is assigned to the first pixel as it is, and the value of the pixel in the remaining pixels is compressed in the reconstructed pixel value of the pixel immediately preceding the pixel. And a memory restoring unit 252 for restoring a compressed reference frame by sequentially assigning a sum of the difference values allocated in units N. Compressing a reference frame and provides the image decoding apparatus to store.

In addition, the memory compression unit 250 included in the image decoding apparatus 200 that compresses and stores the reference frame according to the present invention may compress the bit unit N to the value of the pixel and the reconstructed pixel value of the pixel immediately before the pixel. If the difference corresponding to the difference between the difference value and the sum value is sequentially calculated, and the sum result is larger than the preset value, the difference value is allocated by increasing the number of bits in the compression bit unit (N) and assigning the difference value. Information (b) for (N) may be stored together.

In addition, the memory compressor 250 compresses a reference frame in a horizontal direction or a vertical direction, respectively, and compresses a direction in which a value obtained by adding the error generated in the process of allocating a difference value in compression bit units (N) is small. If the difference is greater than the preset value, the pixel is determined to be the image boundary between the pixel and the pixel immediately before the pixel. From the pixel value next to the image boundary, the original pixel value is the original bit unit. (B).

In addition, even if omitted below, the contents of the embodiment and the like with respect to the image encoding apparatus 100 shown in FIG. 1 may be applied to the image decoding apparatus 200 according to the present invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

100: video encoding apparatus 200: video decoding apparatus
110: subtractor 120: change unit
121, 230: inverse transform unit 130: quantization unit
131 and 220: inverse quantization unit 140: entropy coding unit
150, 240: adder 160, 250: memory compression unit
161 and 251: memory 162 and 252: memory restoring unit
170, 260: prediction unit

Claims (14)

A video encoding apparatus comprising:
Designates a memory compression unit for storing a reference frame, and assigns the original pixel value to the first pixel in the first pixel in the memory compression unit, and the remaining pixels except for the first pixel are immediately related to the pixel. A memory compression unit configured to compress the reference frame by sequentially assigning a difference value, which is a difference between a reconstructed pixel value of a preceding pixel and the corresponding pixel value, in compression bit units (N), which is a predetermined number of bits;
A memory for storing the reference frame compressed by the memory compression unit; And
In the memory compression unit, the original pixel value is allocated to the first pixel as it is, and the value of the corresponding pixel in the remaining pixels is equal to the compression bit unit (N) to the reconstructed pixel value of the pixel immediately preceding the corresponding pixel. And a memory reconstructing unit which sequentially reconstructs the compressed reference frame by sequentially allocating the sums of the difference values allocated to. The method of claim 1,
And the reconstructed pixel value is a value obtained by reconstructing and storing a reference frame, wherein a pixel located immediately before the corresponding pixel is a value reconstructed from a previous pixel. The method of claim 1,
And the difference value is allocated by the memory compression unit in a quantization table corresponding to the compression bit unit (N). The method of claim 1,
The memory compressor sequentially calculates an error corresponding to a difference between the value of the corresponding pixel and a value obtained by adding the difference value allocated in the compression bit unit N to the reconstructed pixel value of the pixel immediately before the corresponding pixel. When the sum result is larger than a preset value, the bit number of the compressed bit unit N is increased to allocate the difference value, and the information value b for the compressed bit unit N is stored together. An image encoding device for compressing and storing a reference frame. The method of claim 1,
And the memory compression unit compresses and stores the reference frame, wherein the reference frame can be designated as a horizontal direction or a vertical direction in the memory compression direction. The method of claim 5,
The memory compression unit compresses the reference frame in the horizontal direction or the vertical direction, respectively, and the direction in which a value obtained by adding up an error generated in the process of allocating the difference value to the compression bit unit N is small. And a reference frame compressed and stored in the compression direction. The method according to claim 6,
The memory compression unit further stores the information value (d) for the memory compression direction,
The memory restoring unit compresses and stores the reference frame according to the information value (b) of the compression bit unit (N) and the information value (d) of the memory compression direction. Video encoding device. The method of claim 1,
And when the difference is greater than a predetermined value, the memory compression unit compresses and stores a reference frame, wherein the reference frame is determined to be an image boundary between the pixel and the pixel located immediately before the pixel. 9. The method of claim 8,
The memory compression unit allocates an original pixel value in original bit units (B) from the value of the corresponding pixel next to the image boundary, and allocates the difference value in the compression bit unit (N) located in front of the image boundary. Allocate an information value C for the number of pixels,
And the memory reconstructing unit compresses and stores the reference frame as it is, and assigns an original pixel value to a pixel value located next to the image boundary corresponding to the information value (C) of the number of pixels. In the image decoding apparatus,
Designates a memory compression unit for storing a reference frame, and assigns the original pixel value to the first pixel in the first pixel in the memory compression unit, and the remaining pixels except for the first pixel are immediately related to the pixel. A memory compression unit configured to compress the reference frame by sequentially assigning a difference value, which is a difference between a reconstructed pixel value of a preceding pixel and the corresponding pixel value, in compression bit units (N), which is a predetermined number of bits;
A memory for storing the reference frame compressed by the memory compression unit; And
In the memory compression unit, the original pixel value is allocated to the first pixel as it is, and the value of the corresponding pixel in the remaining pixels is equal to the compression bit unit (N) to the reconstructed pixel value of the pixel immediately preceding the corresponding pixel. And a memory reconstructing unit which sequentially reconstructs the compressed reference frame by sequentially assigning the sum of the difference values allocated to the subframes. The method of claim 10,
And the original bit unit (B) is larger than the compressed bit unit (N). The method of claim 10,
The memory compressor sequentially calculates an error corresponding to a difference between the value of the corresponding pixel and a value obtained by adding the difference value allocated in the compression bit unit N to the reconstructed pixel value of the pixel immediately before the corresponding pixel. When the sum result is larger than a preset value, the number of bits in the compression bit unit N is increased to allocate the difference value, and the information b for the compression bit unit N is stored together. An image decoding apparatus for compressing and storing a reference frame. The method of claim 10,
The memory compression unit compresses the reference frame in a horizontal direction or a vertical direction, respectively, and selects a direction in which a value obtained by adding an error generated in the process of assigning the difference value to the compression bit unit N is smaller than the memory compression direction. And a reference frame is compressed and stored. The method of claim 10,
If the difference is greater than a preset value, the memory compression unit determines that the pixel is an image boundary between the pixel and the pixel located immediately before the pixel, and the original pixel value starts from the value of the pixel located next to the image boundary. And compresses and stores a reference frame, wherein the reference frame is allocated in the original bit unit (B).

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