WO2019059736A1 - Image encoding device, image decoding device, image encoding method, and image decoding method - Google Patents

Abstract

An image encoding device according to an embodiment comprises: a slice partitioner for partitioning an input image into multiple slices; a sub-slice partitioner for partitioning each of the multiple slices into multiple sub-slices; and an encoding module for determining a predicted value for data of the input image by processing the data of the input image in units of the slices, generating symbols by using the predicted value, and outputting a bitstream for the input image by performing entropy encoding of the symbols in units of the sub-slices.

Description

Video encoding device, video decoding device, video encoding method and video decoding method

An image encoding apparatus and an image encoding method for encoding image data, an image decoding apparatus and an image decoding method for decoding encoded data.

As the image compression technology develops, it becomes possible to view large-capacity high-definition images on various devices. The image data may be encoded according to a predetermined data compression standard, and the encoded image data may be transmitted in the form of a bit stream.

In the case of transmitting video data wirelessly, an error may occur in data transmission depending on the transmission environment. If an error occurs in the data transmission, a request for retransmission of the image data to the transmitting end may cause a time delay. In order to prevent such a time delay, errors can be restored at the receiving end, and there is a difference in the image quality of the image output to the display device according to the restoring method.

Therefore, it is necessary to study a method for effectively recovering an error in transmitted image data.

The entropy encoding is performed in units of sub slices, and the rest of the processing is performed in units of slices, thereby improving the average image quality of the image. When an error occurs, data is initialized and restored in units of sub slices, An image decoding apparatus, an image encoding method, and an image decoding method, which can be performed by the image decoding apparatus.

According to an embodiment of the present invention, a video encoding apparatus includes: a slice distributor for dividing an input image into a plurality of slices; A sub slice divider dividing the plurality of slices into a plurality of sub slices; And processing the data of the input image by the slice unit to determine a predicted value for the data of the input image, generating a symbol using the predicted value, and performing entropy encoding on the symbol for the sub- And an encoding module for outputting a bit stream for the input image.

The image encoding apparatus includes a marker generator for generating a division marker for identifying the plurality of sub slices and inserting the division marker for each position where data for the plurality of sub slices starts in the output bit stream .

The encoding module may determine the predicted value of the current block by referring to information of at least one neighboring block included in the same slice as the current block to be predicted.

Wherein the encoding module generates a transform coefficient by performing frequency conversion on the residual data generated by subtracting the data of the current block from the determined predicted value and quantizes the transform coefficient to generate the quantized coefficient type symbol can do.

The encoding module may perform inverse quantization and dequantization on the symbol to recover residual data, and generate restored data using the residual data and the predicted value.

And a memory for storing the restored data, wherein when the predicted value of the data of the current block is determined, restoration data of the neighboring block among the restored data stored in the memory can be referred to.

The encoding module may refer to information of at least one neighboring block included in the same sub-slice as the current block when entropy encoding is performed on the current block.

The sub slice distributor may divide the plurality of slices based on a parameter relating to the number of the plurality of sub slices.

An apparatus for decoding an image according to an exemplary embodiment includes a slice separator for detecting a slice start code in an input bitstream to separate a plurality of slices; A sub slice separator for separating a plurality of sub slices by detecting a division marker in the input bit stream; An error detector for checking an error for the input bit stream and for initializing data of the sub slice in which the error is detected; A decoding module for decoding a bitstream in which the error is not detected to generate a reconstructed image; And an image restorer for recovering data of the sub slice in which the error is detected to generate a restored image.

The plurality of slices may each include a plurality of sub-slices.

The image restorer can recover data of a block located at a boundary between the sub slice in which the error is detected and a sub slice in which the error is detected among a plurality of blocks included in a neighboring slice adjacent thereto.

The decoding module may perform entropy decoding on the bit stream in which the error is not detected for each sub-slice to generate a quantized coefficient type symbol.

The decoding module may perform inverse quantization and inverse transform on the symbol to recover the residual signal, and may generate a restored block by summing the residual value and the predicted value determined by the prediction performed on a slice-by-slice basis.

According to an embodiment, an image encoding method includes: dividing an input image into a plurality of slices; Dividing the plurality of slices into a plurality of sub slices; Processing the data of the input image by the slice unit to determine a predicted value for the data of the input image; Generate a symbol using the predicted value; And performing entropy encoding on the sub-slice basis for the symbol to output a bit stream for the input image.

Wherein the image encoding method comprises: generating a division marker for identifying the plurality of sub slices; And inserting the segmentation marker at a position where data for the plurality of sub slices is started in the bit stream for the input image.

The determination of the predicted value may refer to information of at least one neighboring block included in the same slice as the current block when determining a predicted value for data of the current block.

Generating the symbol comprises generating residual data by subtracting the data of the current block from the determined predicted value; Performing frequency conversion on the residual data to generate a transform coefficient; And performing quantization on the transform coefficients to generate the symbols of the form of quantized coefficients.

The image encoding method may include performing inverse quantization and inverse quantization on the symbols to recover residual data; And generating reconstruction data using the reconstructed residual data and the predicted values.

The image encoding method according to claim 1, further comprising storing the restored data, wherein the step of determining the predicted value comprises: when determining a predicted value for data of a current block, Or < / RTI >

Performing the entropy encoding may include referring to information of at least one neighboring block included in the same sub-slice as the current block when entropy encoding is performed on the current block.

According to an embodiment of the present invention, there is provided an image decoding method comprising: detecting a slice start code in an input bitstream to divide a plurality of slices; Detecting a division marker in the input bit stream to separate a plurality of sub slices; Checking an error for the input bitstream; Initializing data of the sub slice in which the error is detected; Generating a reconstructed image by decoding a bitstream in which the error is not detected; And recovering the data of the sub slice in which the error is detected to generate a restored image.

And restoring data of a block located at a boundary between the sub-slice in which the error is detected and the sub-slice in which the error is detected, among a plurality of blocks included in the neighboring slice adjacent to the sub-slice.

The generation of the reconstructed image may include entropy decoding on the sub-slice basis for a bit stream in which the error is not detected to generate a quantized coefficient type symbol.

Generating the reconstructed image comprises performing inverse quantization and inverse transform on the symbol to reconstruct the residual signal; And generating a reconstruction block by summing the predicted value determined by the prediction performed in the slice unit and the residual signal.

According to the video encoding apparatus, the video decoding apparatus, the video encoding method, and the video decoding method according to the above-described embodiments, the entropy encoding is performed in units of sub slices and the remaining processing is performed in units of slices, , And when an error occurs, initialization and restoration of data in units of sub slices can minimize the deterioration of image quality due to an error occurrence.

1 is a diagram illustrating an example in which a transmitting apparatus and a receiving apparatus exchange image data.

FIG. 2 is a diagram showing a unit that is independently processed at the time of encoding or decoding an image.

3 is a diagram showing a range of an influence of an error when an error occurs in a specific slice.

4 is a control block diagram of a video encoding apparatus according to an embodiment.

5 and 6 are views showing examples of slices that are divided by the image encoding apparatus according to an embodiment.

FIG. 7 is a control block diagram illustrating a configuration of an encoding module in a video encoding apparatus according to an exemplary embodiment.

8 is a diagram illustrating an example of an operation in which the video encoding apparatus according to the embodiment performs encoding on a block basis.

9 is a diagram illustrating an example of bitstream data generated by a video encoding apparatus according to an exemplary embodiment.

10 is a control block diagram of an image decoding apparatus according to an embodiment.

FIG. 11 is a control block diagram illustrating a decoding module of an image decoding apparatus according to a single-shot type.

12 and 13 are views illustrating an example of a method of decoding an error by an image decoding apparatus according to an embodiment.

FIG. 14 is a diagram showing an error influence range when error is recovered on a slice-by-slice basis.

15 is a flowchart of a video encoding method according to an embodiment.

16 is a flowchart of an image decoding method according to an embodiment.

Like reference numerals refer to like elements throughout the specification. The present specification does not describe all elements of the embodiments, and redundant description between general contents or embodiments in the technical field of the present invention will be omitted. As used herein, the term " module, module " may be embodied in software or hardware, and may be embodied as a single component or as a plurality of subsystems, modules, It is also possible for 'part, module, member' to include a plurality of components.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only the case directly connected but also the case where the connection is indirectly connected, and the indirect connection includes connection through the wireless communication network do.

Also, when an element is referred to as " comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

The singular forms " a " include plural referents unless the context clearly dictates otherwise.

In each step, the identification code is used to identify each step and does not describe the order of the steps, and each step may be performed differently from the order specified unless the context clearly states a particular order.

Hereinafter, embodiments of an image encoding apparatus, an image decoding apparatus, an image encoding method, and an image decoding method according to one aspect will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram illustrating an example of transmitting and receiving image data between a transmitting apparatus and a receiving apparatus, FIG. 2 is a diagram illustrating a unit that is independently processed at the time of encoding or decoding an image, and FIG. Fig. 9 is a diagram showing the range of the influence of errors in the case of Fig.

Referring to FIG. 1, the transmitting apparatus 10 compresses image data according to a certain compression standard for transmitting image data in a wireless transmission environment, and transmits the compressed image data to the receiving apparatus 20 in the form of a bit stream. The receiving apparatus 20 decodes the received image data and outputs the image to the display apparatus 30.

In such a wireless transmission environment, a packet loss (packet loss), packet deformation (packet corruption), or the like occurs due to various variables such as an obstacle existing between the transmission apparatus 10 and the reception apparatus 20, An error may occur in data transmission.

It is possible to detect an error in the receiving apparatus 20 and recover the data in which the error is detected. However, the area where the data is recovered from the output image is lower in image quality than the area where no error occurs.

In image compression technology, images can be hierarchically defined and processed independently according to defined hierarchy. In the embodiments described below, the video may include both moving images and still images, and the moving image and the still image may be frames.

Referring to FIG. 2, one frame may be divided into smaller units defined by slices. That is, one frame may be composed of a plurality of slices. A plurality of slices constituting one frame may be divided in various ways according to an image compression standard.

Each slice can be processed independently. Here, being independent may mean not referring to information included in another slice in encoding and decoding for a single slice. Therefore, the slice # 1, the slice # 2, the slice # 4, ..., and the slice #N are independently processed, and the information contained in the other slice can not be used during encoding and decoding.

The minimum processing unit of an image in which encoding and decoding are performed may be referred to as a block. A single slice may include at least one block. For example, the block may be a Coding Tree Unit, a Prediction Unit, or a Transform Unit.

For example, a block may be defined by a plurality of pixel sets, such as 8x8 pixels, 16x16 pixels, etc., but this corresponds to an example, and in the embodiment of the video encoding apparatus 100, no.

Image compression is to reduce the amount of data to transmit the image. For this purpose, surrounding block information can be used in encoding and decoding the image in units of blocks. Therefore, the surrounding block must be decoded to enable encoding or decoding of the current block to be processed. As described above, since each slice is processed independently, only information of neighboring blocks in the same slice can be used. Therefore, the smaller the number of slices constituting one frame, the wider the range of the peripheral blocks to be used, and the higher the average image quality is.

As shown in the example of FIG. 3, when an error occurs in the slice # 2, the receiving apparatus 20 can detect the generated error and discard or initialize the data of the slice # 2.

Since each slice is processed independently, the remaining slices except the slice # 2 are decoded normally, and the slice # 2 in which an error occurs can be restored by using the neighboring slice information or the neighboring frame information.

Even if an error occurs only in some blocks in a single slice, since the processing is performed on a slice-by-slice basis, the entire data of the slice is discarded. Therefore, the larger the number of slices constituting one frame, the smaller the size of the single slice, and the degradation in image quality due to the occurrence of errors can be seen in a narrow region.

The image encoding apparatus and the image decoding apparatus according to an embodiment divide a single slice into sub-slices of a smaller unit and apply different steps of processing in units of slices and steps of processing in units of sub slices, And degradation of image quality in the event of an error can be minimized.

FIG. 4 is a control block diagram of a video encoding apparatus according to an embodiment, and FIGS. 5 and 6 are views illustrating an example of a slice divided by a video encoding apparatus according to an exemplary embodiment.

4, an apparatus 100 for encoding an image according to an exemplary embodiment of the present invention includes an encoding module 110 for encoding an input image, a slice distributor 120 for dividing an input image into a plurality of slices, And a marker generator 140 for inserting a division marker for separating a sub-slice into a bit stream output from the encoding module 110 and a sub-slice distributor 130 for distributing to a slice.

The slice distributor 120, the sub-slice distributor 130 and the marker generator 140. However, when the components are physically divided into physical components such as physical It is not necessarily separated. The encoding module 110, the slice distributor 120, the sub-slice distributor 130, and the marker generator 140 may be implemented by a single processor and a single memory, and may be implemented as a single chip As shown in FIG. In the latter case, each component can share memory with the processor.

The slice distributor 120 may divide the input image into a plurality of slices according to the slice setting parameters. The slice configuration parameter may include information such as the number or shape of slices. The slice setting parameter may be set by a designer or a user, may be set by information input from the outside, or may be set by the video encoding apparatus 100.

Similarly, the sub slice distributor 130 may divide the input image into a plurality of sub slices based on the sub slice setting parameters, and the sub slice setting parameters may include information such as the number or shape of the sub slices. The sub-slice is a unit smaller than the slice. For example, the size of a single slice may be an integer multiple of the size of a single sub-slice. That is, the sub slice distributor 130 may divide each slice into sub slice units.

The encoding module 110 may perform entropy encoding to convert the image data into a bit stream format. The encoding module 110 performs entropy encoding on a sub slice basis, and a process for generating symbols such as prediction, conversion, and quantization before entropy encoding can be performed on a slice basis. Hereinafter, the operation of the encoding module 110 in units of sub slice units / slices will be described in detail.

5, the slice distributor 120 divides one frame into N slices (where N is an integer of 1 or more), and the sub slice distributor 130 divides each of the slices into n (n is 1 Slices of sub-slices). The slice distributor 120 and the sub-slice distributor 130 may perform slice division and sub-slice division on a plurality of frames constituting an input image.

As described above, the encoding module 110 can perform operations other than entropy encoding in slice units. Therefore, the N slices can be independently processed, and the blocks included in the same slice can be referred to each other.

The sub slice is not necessarily divided into one dimension along the longitudinal direction of the frame, but it may be divided two-dimensionally as in the example of Fig. The sub-slice division method is determined by the sub-slice setting parameters. In the embodiment of the video encoding apparatus 100, the arrangement and the number shape are not limited.

FIG. 7 is a control block diagram illustrating a configuration of an encoding module in an image encoding apparatus according to an exemplary embodiment. FIG. 8 is a diagram illustrating an example of an operation in which an image encoding apparatus according to an embodiment performs encoding on a block basis And FIG. 9 is a diagram illustrating an example of bitstream data generated by a video encoding apparatus according to an exemplary embodiment.

The encoding module 110 processes the data of the input image in units of slice to determine a predicted value for the data of the input image, generates a symbol using the predicted value, and performs entropy encoding on the symbol in units of the sub-slice And outputs a bitstream of the input image.

Referring to FIG. 7, the encoding module 110 includes a predictor 111, a subtractor 112, a transformer 113, a quantizer 114, an entropy encoder 115, an inverse quantizer 116, an inverse transformer 117 ), An adder 118, a filter 119, and a memory 119a.

The predictor 111 performs prediction on the input image based on the slice unit divided by the slice distributor 120. [ That is, prediction can be performed independently for each slice.

The video encoding apparatus 100 according to an exemplary embodiment may encode an image using an Intraframe method or an Interframe method. In the intra frame method, compression is performed frame by frame, and in the interframe method, compression is performed using information of the previous frame.

Therefore, when the intra frame method is applied, the predictor 111 performs intra frame prediction. When the interframe method is applied, the predictor 111 performs interframe prediction. That is, the current frame is predicted from neighboring temporally adjacent frames such as a previous frame or a subsequent frame. In the following embodiments, the case of applying the intra frame method is referred to as an intra mode, and the case of applying the interframe method is referred to as an inter mode.

In the intra mode, the predictor 111 can generate a prediction block by referring to information of neighboring blocks spatially adjacent to the current block to be processed. The reference block may be referred to as a reference block.

Specifically, the predictor 111 may determine a predicted value for the samples of the current block by referring to the pixel values of the restored block around the current block. The prediction block means a block composed of prediction values. Therefore, generating a prediction block may mean that a prediction value for the block is determined.

In this embodiment, a sample means data to be processed as data assigned to a sampling position of an image. For example, in an image in a spatial domain, pixel values and transform coefficients on a transform domain may correspond to samples.

The case where the slice distributor 120 divides a frame as in the example of FIG. 5 described above will be described as an example. Referring to FIG. 8, the sub slices # 1 (SS ₁₁ ) and # 2 (SS ₁₂ ) included in the same slice S ₁ may be composed of a plurality of blocks. For example, if the current block is B _43, the neighboring blocks _{(B 32, B 33, B} 34, B 42, B 44, B 52, B 53, B 54) already using the pixel value of the restored block of the The predicted value can be determined. Here, the available neighboring blocks may vary depending on the image compression method or order, and Fig. 8 is merely an example.

In the surrounding block of B _32, B _33, B ₃₄ is the current block B ₄₃ and the other sub-slices, but the predicted value determining step in the sub-slices are the determination of the predicted value for the current block B ₄₃ because it can cross-reference is not treated as independent The information of the blocks included in the sub slice # 1 can also be referred to. Therefore, the average image quality of the image can be improved as compared with the case of processing in units of sub slices.

In the inter mode, the predictor 111 can predict a motion by searching a region (reference block) having the best match with the current block in the previous frame that has already undergone the encoding process and obtaining a motion vector. Here, the motion vector may be a two-dimensional vector and may represent an offset between the current block and the reference block. The predictor 111 can determine a predicted value and generate a predicted block by performing motion compensation using a motion vector.

The subtracter 112 may generate a residual block by subtracting the current block from the prediction block. That is, the residual data can be generated by differentiating the data of the current block and the data of the prediction block.

The converter 113 converts the generated residual block or residual data from the spatial domain to the frequency domain. The converter 113 may use a technique of converting a video signal in a spatial domain into a frequency domain such as Discrete Sine Transform, Discrete Cosine Transform, Hadamard Transform, and the like.

The converter 113 may perform the above-described frequency conversion to output the conversion coefficient.

The quantizer 114 quantizes the transform coefficient output from the transformer 113 according to a quantization parameter to output a symbol of a quantized coefficient type.

The symbols output from the quantizer 114 may be input to the dequantizer 116 as well as to the entropy encoder 115. [

The inverse quantizer 116 may inverse quantize the quantized coefficients to recover the frequency coefficients. At this time, inverse quantization can be performed based on the quantization parameters used by the quantizer 114.

The inverse transformer 117 may inversely transform the recovered frequency coefficient from the frequency domain into the spatial domain to recover the residual block. The inverse transformer 117 may perform an inverse transform on the frequency transform technique performed by the transformer 113. [

The adder 118 may generate a reconstruction block for the input image by adding the prediction block generated by the predictor 111 to the reconstructed residual block. The generated restoration block may be stored in the memory 119a and used as a reference block of the predictor 111. [

The generated restoration block may be stored in the memory 119a after being filtered by the filter 119. [ The filter 119 includes a deblocking filter for eliminating block distortion at the boundary between blocks, a sample adaptive offset filter for adding a proper offset value to a pixel value to compensate for coding error, And an adaptive loop filter that performs filtering based on a value obtained by comparing an original image with an original image.

The entropy encoder 115 may perform entropy encoding on the quantized coefficients output from the quantizer 114 to output a bitstream.

Entropy encoding is a technique for receiving symbols having various values and expressing them as a decodable bit stream while eliminating statistical redundancy.

The symbol means a syntax element to be encoded / decoded, a coding parameter, a value of a residual signal, and the like.

The encoding parameter is a parameter necessary for encoding and decoding, and may include information that can be inferred in an encoding or decoding process as well as information encoded in the encoding device and transmitted to the decoding device, such as a syntax element, It means the information that is needed when doing.

The encoding parameters include values or statistics such as, for example, intra / inter modes, motion vectors, reference picture indexes, coding block patterns, residual signal presence, transform coefficients, quantized transform coefficients, quantization parameters, block sizes, can do.

The entropy encoder 115 may perform entropy encoding by applying a technique such as Context-Adaptive Variable Length Coding (CAVLC), Context-Adaptive Binary Arithmetic Coding (CABAC), or Exponential Golomb to the quantized coefficients. It is also possible to entropy encode quantized coefficients as well as additional information necessary for decoding the image.

For example, a table for performing entropy encoding such as a variable length coding / code (VLC) table may be stored in the entropy encoder 115. The entropy encoder 115 may perform entropy encoding using a stored variable length coding (VLC) table.

The entropy encoder 115 derives a binarization method of the object symbol and a probability model of a target symbol or bin and then performs entropy encoding using the derived binarization method or probability model You may.

According to the entropy encoding, a small number of bits may be allocated to a symbol having a high probability of occurrence, and a symbol may be represented by allocating a large number of bits to a symbol having a low probability of occurrence. As a result, the size of the bit stream for the symbols to be encoded can be reduced and the compression performance of the image encoding can be enhanced.

For example, when the entropy encoder 115 applies the CABAC scheme, the non-binarized symbol is binarized and converted into a bin, and encoding information of a neighboring block and a current block or information of a symbol or bin encoded in a previous step is used To determine the context model. The entropy encoder 115 may generate a bitstream by performing arithmetic encoding of the bin by predicting the probability of occurrence of the bean according to the determined context model. At this time, after the context model is determined, the context model can be updated using the information of the encoded symbol / bean for the context model of the next symbol or bean.

The entropy encoder 115 may perform entropy encoding on the basis of the sub-slice unit divided by the sub-slice distributor 130. Thus, a sub-slice may be referred to as an entropy slice.

The entropy encoder 115 can perform entropy encoding by independently processing each sub slice without referring to information of other sub slices. Therefore, when performing the entropy encoding, only the information of the neighboring blocks included in the same sub-slice can be referred to, and even if they belong to the same slice, the blocks included in different sub-slices can be independently processed without referring to each other.

The marker generator 140 may generate and insert a division marker for identifying a sub slice in the bit stream generated by the entropy encoder 115. [ Specifically, the marker generator 140 may insert a division marker for each position where data for a plurality of sub slices is started in the bitstream. As an example, the division markers may include a column of feature binary numbers.

9, the bit stream generated by the video encoding apparatus 100 includes information on each of the slices S ₁ , S ₂ , S, and S _N , and the bit stream for a single slice includes information on a slice start code Slice header information, a division marker for dividing a sub-slice, and data for blocks constituting a sub-slice.

For example, a bitstream (BS ₇ ) for slice # 7 includes a slice start code (BSC ₇ ), slice header information (BSH ₇ ), a division marker 1 (BSM ₇₁ ) of sub slice # 1, Slice # 2, and encoding data for the blocks constituting the encoding data (BSS ₇₁ ), the division marker 2 of the sub slice # 2, and the sub-slice # 2 for the constituent blocks, and the division markers n (BSM _7n ), and encoding data for the blocks constituting the sub-slice #n.

The encoding module 110 may include a memory for storing a program for performing the above-mentioned operations, and a processor for executing the stored program. Each of the components included in the encoding module 110 need not be physically separated or separated, but they can share the processor with the memory. For example, a program for performing the operations of the encoding module 110 described above may be stored in a single memory, and a single processor may execute the stored program to perform the operations of the encoding module 110 described above.

The video encoding apparatus 100 may be included in the transmission apparatus 10. [ The bit stream of the input image generated by the video encoding apparatus 100 is transmitted from the transmission apparatus 10 to the reception apparatus 20. [ The receiving apparatus 20 may include an image decoding apparatus for decoding the transmitted bit stream.

FIG. 10 is a control block diagram of an image decoding apparatus according to an embodiment, and FIG. 11 is a control block diagram in which a decoding module of an image decoding apparatus according to a single thread type is embodied.

10, the image decoding apparatus 200 includes a slice separator 210, a sub-slice separator 220, an error detector 250, a decoding module 230, and an image restorer 240 ).

The respective components included in the video decoding apparatus 200 need not be physically separated or separated, but they can share the processor with the memory. For example, a program for performing an operation described later may be stored in a single memory, and a single processor may execute a stored program to perform an operation of each of the video decoding apparatuses 200. [

The slice separator 210 separates a plurality of slices constituting a frame by detecting a slice start code from the input bit stream, and the sub slice separator 220 detects a division marker from a bit stream for a single slice A plurality of sub slices constituting a single slice can be distinguished from each other.

The error detector 250 checks the error of the input bitstream. As described above, an error may occur in the process of transmitting the bitstream from the video encoding apparatus 100 to the video decoding apparatus 200 according to the transmission environment. The types of errors that occur are a single-bit error in which only one bit of data is changed, and a burst error in which two or more consecutive bits are changed.

The error detector 250 includes a parity check for adding a redundant bit called a parity bit to a data unit, a parity check for collecting even parities of all the bytes, Error checking can be performed by applying a method such as checking, cyclic redundancy check using binary division (CRC), check sum used in upper layer protocol, and the like. However, the above-described methods are merely examples, and the embodiment of the image decoding apparatus 200 is not limited thereto. Therefore, it goes without saying that an error can be detected by applying a method other than the above-mentioned examples.

The error detector 250 may check the error for each sub-slice. The error detector 250 may discard or initialize the bitstream data for the sub-slice in which the error was detected. The data for the sub-slice in which an error is detected can be recovered in the image restorer 240. That is, the image restorer 240 can generate a restoration image for the sub-slice in which an error is detected.

Since the error detector 250 inspects errors in units of sub-slices and initializes the data, it is possible to reduce image quality deterioration that occurs when an error occurs, as compared with a case where errors are detected in units of slices and data is initialized. The related operation will be described later.

The decoding module 230 may decode the input bit stream to restore the image. Hereinafter, this will be described in detail with reference to FIG.

11, the decoding module 230 includes an entropy decoder 231, an inverse quantizer 232, an inverse transformer 233, an adder 234, a filter 235, a memory 236 and a predictor 37, . ≪ / RTI >

The entropy decoder 231 may entropy-decode the input bitstream according to a probability distribution to generate symbols including symbols of a quantized coefficient type. Entropy decoding is a method of generating each symbol by receiving a binary sequence.

For example, when Variable Length Coding (VLC) such as CAVLC is used to perform entropy encoding in the video encoding apparatus 100, the entropy decoder 231 is also used in the video encoding apparatus 100 The same VLC as the VLC table can be stored and the entropy decoding can be performed using the VLC.

In addition, when CABAC is used to perform entropy encoding in the video encoding apparatus 100, the entropy decoder 231 may also perform entropy decoding using CABAC in correspondence thereto.

Specifically, when entropy decoding is performed using the CABAC, the entropy decoder 231 receives the bean corresponding to each syntax element in the bitstream, and decodes the decoding target syntax element information, the decoding information of the neighboring block and the decoding target block In the previous step, the context model can be determined using the information of the decoded symbol or bin. The arithmetic decoding of the bean can be performed by predicting the occurrence probability of the bean according to the determined context model, and a symbol corresponding to the value of each syntax element can be generated. In addition, after the context model determination, the context model can be updated using the information of the decoded symbol or bean for the context model of the next symbol or bean.

The operation of processing the quantized coefficients output from the entropy decoder 231 is similar to the operation in which the encoding module 110 performs dequantization, inverse transform, addition, and the like on the quantized coefficients again to generate a reconstruction block.

The quantized coefficients output from the entropy decoder 231 are input to the inverse quantizer 232 and are inverse-quantized. The inverse-quantized frequency coefficients are input to the inverse transformer 233 and can be inversely transformed from the frequency domain to the spatial domain. In this way, the inverse transformer 233 can generate the reconstructed residual block or reconstructed residual data.

The inverse quantizer 232 may perform inverse quantization based on the quantization parameter provided by the image encoding apparatus 100 and the inverse transformer 233 may perform inverse quantization using the inverse quantization performed by the inverse quantizer 232, Can be performed.

Meanwhile, the entropy decoder 231 may transmit information for generating a prediction block among the decoded information to the predictor 237. The predictor 237 can generate a prediction block based on the information related to the prediction block generation provided from the entropy decoder 231 and the already reconstructed block or frame information provided from the memory 236. [

When the prediction mode for the current block is the intra mode, the predictor 237 can generate the prediction block by referring to the pixel information of the neighboring block in the current frame.

If the prediction mode for the current block is the inter mode, the predictor 237 can generate the prediction block by referring to the pixel information included in the neighboring frame (the previous frame or a subsequent frame) of the current frame. At this time, the predictor 237 can perform inter-frame prediction using motion information (e.g., motion vector, reference frame index, etc.) necessary for inter-frame prediction of the current block provided in the video encoding apparatus 100. [

When the predictor 237 refers to the surrounding information for generating the prediction block, the slice unit may be used as a reference. The blocks included in the same slice can be cross-referenced when generating a prediction block for each block. Therefore, even when blocks belonging to different sub slices belong to the same slice, they can be cross-referenced.

The adder 234 may add the residual block output from the inverse transformer 233 and the predictive block output from the predictor 237 to generate a reconstructed block.

The filter 235 may apply deblocking filtering, adaptive offset filtering, or adaptive loop filtering to filter the restored blocks, and the filtered restored blocks may be stored in the memory 236 and used to generate the predicted blocks.

FIGS. 12 and 13 are views showing an example of a method of decoding an error by an image decoding apparatus according to an embodiment, and FIG. 14 is a diagram showing an error influence range when an error is recovered in slice units.

12, when an error is detected in the data of the sub-slice # 1 (SS ₁₁ ) in the image received in the bit stream form, the data of the sub-slice # 1 (SS ₁₁ ) is initialized.

The image restorer 240 can recover the image of the sub-slice # 1 (SS ₁₁ ) using the neighboring frame information, the neighboring sub-slice information, and the like. The image restorer 240 can recover the image of the sub slice by applying at least one of various techniques for recovering errors generated in the compressed image data.

Restoration of the image or image restoration performed by the image restorer 240 may mean restoring the initialized data due to an error using other information or supplementing data affected by the error using other information have.

The bit stream for the remaining sub-slices in which no error is detected may be decoded by the decoding module 230 and output as a reconstructed image.

On the other hand, since no error is detected in the sub slice # 1 (SS ₁₁ ) and the adjacent sub slice # 2 (SS ₁₂ ) in which an error is detected, the bit stream for the sub slice # 2 (SS ₁₂ ) Lt; / RTI >

However, at the time of decoding the bit stream for the sub slice # 2 (SS ₁₂ ), it may happen that the reference block is insufficient due to the data initialization of the sub slice # 1 (SS ₁₁ ). Therefore, according to another example of the video decoding apparatus 200, as shown in FIG. 14, when the image restorer 240 decodes decoded data for the sub-slice # 2 (SS ₁₂ ), surrounding sub-slice information, It is also possible to recover the image of the sub slice # 2 (SS ₁₂ ). At this time, the data to be restored may be the data of the block located at the boundary with the sub slice # 1 (SS ₁₁ ) among the blocks included in the sub slice # 2 (SS ₁₂ ).

An error is detected the sub-slices 1 # (SS ₁₁₎ and the remaining sub-slices that are not adjacent are decoded normally and restored as sub-slice image, a video, a recovered sub-slice of the recovered sub-slice _{# 1 (SS 11) # 2} ( SS ₁₂ ) and the remaining sub-slices may constitute an output image.

(S ₁₁ ), even if an error occurs only in the data of the sub-slice # 1 (SS ₁₁ ) as shown in FIG. 14, initialization of the data and need to recover the image of the entire slice # 1 (S _11). Therefore, there is a large area where image quality degradation due to an error occurs.

On the other hand, according to the image decoding apparatus 200 according to the embodiment, only a partial region of the sub slice # 1 (SS ₁₁ ) in which an error is detected and the adjacent sub slice # 2 (SS ₁₂ ) Since the remaining sub-slices are independently processed and are not affected by errors, degradation in image quality due to errors can be minimized.

An error occurrence environment and a high extrusion rate transmission environment are respectively generated. In each case, a bitstream of an image is transmitted from the image encoding apparatus 100 to the image decoding apparatus 200, When capturing, we can confirm that the size of the blocking artifacts of the two captured images are different.

According to the video encoding apparatus 100 and the video decoding apparatus 200 according to the above-described embodiments, the compression efficiency of an image can be increased. Accordingly, when the image decoding apparatus 200 decodes the bit stream encoded by the image encoding apparatus 100 using an image of a specific pattern having a high entropy coding efficiency as an input image and outputs the decoded image to the display apparatus 30, Can be confirmed.

Hereinafter, an image encoding method and an image decoding method according to an embodiment will be described. The image encoding apparatus 100 according to the above-described embodiment may be applied to the image encoding method according to an embodiment, and the image decoding apparatus 200 according to the above-described embodiment may be applied to the image decoding method. Therefore, the contents of FIGS. 1 to 14 described above can also be applied to the image encoding method and the image decoding method according to the embodiment.

15 is a flowchart of a video encoding method according to an embodiment.

When an image is input to the video encoding apparatus 100, the input image is divided into a plurality of slices as shown in FIG. 15 (310). The input image may be a moving image or a still image. In either case, the input image may be composed of frames. The slice distributor 120 may divide the input image into slice units according to the slice setting parameters. The slice configuration parameter may include information such as the number or shape of slices. The slice setting parameter may be set by a designer or a user, may be set by information input from the outside, or may be set by the video encoding apparatus 100.

The sub-slice distributor 30 may divide the input image into a plurality of sub-slices (311). The sub slice distributor 130 may divide the input image into sub slice units based on the sub slice setting parameters, and the sub slice setting parameters may include information such as the number or shape of the sub slices. The sub-slice is a unit smaller than the slice. For example, the size of a single slice may be an integer multiple of the size of a single sub-slice.

For example, the slice distributor 120 divides one frame into N (N is an integer of 1 or more) slices, and the sub slice distributor 130 divides each slice into n (n is an integer of 1 or more) It can be divided into slices (see Fig. 5).

The predictor 111 performs prediction on the input image to generate a predicted block (312). The predictor 111 can generate a prediction block by referring to the information of neighboring blocks spatially adjacent to the current processing target block. The predictor 111 performs prediction independently for each slice. Therefore, the information of the blocks belonging to the slice other than the current block can not be referred to, but the information of the blocks belonging to the same slice can be referred to even if they belong to different sub slices.

The subtracter 112 generates a residual block by subtracting the current block from the prediction block (313).

The transformer 113 performs a frequency transform to transform the residual block from the spatial domain to the frequency domain (314). The converter 113 may perform frequency conversion and output a transform coefficient.

The quantizer 315 quantizes the output transform coefficient according to the quantization parameter and outputs the quantized coefficient (315).

The quantized coefficients output from the quantizer 315 are input to the entropy encoder 115 and the inverse quantizer 318a.

The dequantizer 116 may dequantize the quantized coefficients (319a) and recover the frequency coefficients. At this time, inverse quantization can be performed based on the quantization parameters used by the quantizer 114.

The inverse transformer 117 may invert the reconstructed frequency coefficient from the frequency domain to the spatial domain (319b) to recover the residual block. The inverse transformer 117 may perform an inverse transform on the frequency transform technique performed by the transformer 113. [

The adder 118 adds the prediction block generated by the predictor 111 to the reconstructed residual block to generate a reconstruction block for the input image (319c). The generated restoration block may be stored in the memory 119a and used as a reference block of the predictor 111. [

It may also be stored in the memory 119a after being filtered by the filter 119. [ The filter 119 may apply deblocking filtering, sample adaptive offset filtering, or adaptive loop filtering to filter the restoration block.

The entropy encoder 115 performs entropy encoding on the quantized coefficients output from the quantizer 114 (316). The entropy encoder 115 may perform entropy encoding on the basis of a sub-slice unit. Therefore, the entropy encoder 115 can perform entropy encoding by independently processing each sub-slice without referring to information of other sub-slices.

The marker generator 140 generates and inserts a division marker for identifying a sub slice in the bit stream generated by the entropy encoder 115 (317). As an example, the division markers may include a column of feature binary numbers.

The video encoding apparatus 100 outputs a bitstream in which a division marker is inserted for each sub slice (318). For example, the output bitstream may have a structure as shown in FIG. The output bit stream may be transmitted to the receiving apparatus 20 via the transmitting apparatus 10. [

According to the embodiment of FIG. 15, in the process excluding entropy encoding, independent processing is performed in units of slices, not in units of sub slices, so that peripheral information that can be referred to increases, and thus the average image quality of the image can be improved.

16 is a flowchart of an image decoding method according to an embodiment.

When the bit stream transmitted from the transmitting apparatus 10 is input to the video decoding apparatus 200, as shown in FIG. 16, the slice separator 210 detects a slice start code from the inputted bit stream and forms a frame A plurality of slices are divided (330), and a sub-slice separator 220 detects a division marker from a bit stream of a single slice to separate a plurality of sub-slices constituting a single slice (331).

The error detector 250 detects an error in the input bitstream (332). The error detector 250 can detect an error for each sub-slice. The error detector 250 may discard or initialize the bitstream data for the sub-slice in which the error was detected. The image restorer 240 may recover the sub-slice image in which the error is detected (338).

The bit stream for the sub-slice in which no error is detected is input to the entropy decoder 231. [

The entropy decoder 231 can entropy-decode the input bitstream according to the probability distribution (333). The entropy decoder 231 may perform entropy decoding to generate symbols including symbols of a quantized coefficient type.

The inverse quantizer 232 performs inverse quantization on the quantized coefficients based on the quantization parameters provided in the video encoding apparatus 100 (334). The frequency coefficients can be output through inverse quantization.

The inverse transformer 233 performs an inverse transform on the frequency transform performed by the transformer 113 of the image encoding apparatus 100 with respect to the frequency coefficient (335). A residual block may be generated through an inverse transform (336).

The adder 234 generates a reconstruction block using the residual block and the prediction block output from the predictor 237 (337). Here, the predictor 237 may generate a prediction block based on the information related to the prediction block generation provided from the entropy decoder 231 and the already reconstructed block or frame information provided from the memory 236.

It is also possible to perform deblocking filtering, adaptive offset filtering, or adaptive loop filtering on the generated restoration block, and then store the restored block in the memory 236 for use in generation of a predicted block.

The image decoding apparatus 200 outputs reconstructed images including reconstructed blocks for the sub-slices in which no error is detected and reconstructed sub-slice images (339).

On the other hand, at the time of decoding the bit stream for the sub slice in which the error is detected and the adjacent sub slice, it may happen that the reference block is insufficient due to the data initialization of the sub slice in which the error is detected. Accordingly, in the image decoding method according to an embodiment, a sub-slice in which an error is detected using the decoded data of a sub-slice in which an error is detected, neighboring sub-slice information, or neighboring frame information, It is also possible to further include restoring.

According to the embodiment of FIG. 16, only a sub-slice in which an error is detected and a partial area of a sub-slice adjacent thereto are influenced by errors, and the remaining sub-slices are independently processed and are not affected by errors.

The foregoing description is merely illustrative of the technical idea of the present invention, and various modifications, alterations, and permutations thereof may be made without departing from the essential characteristics of the present invention.

Therefore, the embodiments and the accompanying drawings described above are intended to illustrate and not limit the technical idea, and the scope of the technical idea is not limited by these embodiments and the accompanying drawings. The scope of which is to be construed in accordance with the following claims, and all technical ideas which are within the scope of the same shall be construed as being included in the scope of the right.

According to the video encoding apparatus, the video decoding apparatus, the video encoding method, and the video decoding method according to the above-described embodiments, only the entropy encoding is performed in units of sub slices and the remaining processing is performed in units of slices, , And when an error occurs, initialization and restoration of data in units of sub slices can minimize the deterioration of image quality due to an error occurrence.

Claims (15)

1. A slice distributor for dividing the input image into a plurality of slices;

   A sub slice divider dividing the plurality of slices into a plurality of sub slices; And

   Processing the data of the input image by the slice unit to determine a predicted value for the data of the input image, generating a symbol using the predicted value, performing entropy encoding on the symbol for each sub-slice, And an encoding module for outputting a bit stream for the image.
2. The method according to claim 1,

   And a marker generator for generating a division marker for identifying the plurality of sub slices and inserting the division marker for each position where data for the plurality of sub slices starts in the output bit stream, .
3. The method according to claim 1,

   Wherein the encoding module comprises:

   Wherein the predicted value of the current block is determined with reference to information of at least one neighboring block included in the same slice as the current block to be predicted.
4. The method of claim 3,

   Wherein the encoding module comprises:

   Generating residual data by performing a difference operation on the data of the current block and the determined predictive value, performing frequency conversion on the residual data to generate a transform coefficient, and performing quantization on the transform coefficient to generate the symbol of the quantized coefficient type / RTI >
5. 5. The method of claim 4,

   Wherein the encoding module comprises:

   And performing inverse quantization and inverse quantization on the symbols to reconstruct residual data and generate reconstructed data using the residual data and the predicted values.
6. 6. The method of claim 5,

   And a memory for storing the restored data,

   Wherein the encoding module comprises:

   Wherein the restored data for the neighboring block among the restored data stored in the memory is referenced when the predicted value for the data of the current block is determined.
7. The method according to claim 1,

   Wherein the encoding module comprises:

   Wherein information on at least one neighboring block included in the same sub-slice as the current block is referred to when entropy encoding is performed on the current block.
8. The method according to claim 1,

   Wherein the sub-

   And divides the plurality of slices based on parameters relating to the number of the plurality of sub slices.
9. Dividing the input image into a plurality of slices;

   Dividing the plurality of slices into a plurality of sub slices;

   Processing the data of the input image by the slice unit to determine a predicted value for the data of the input image;

   Generate a symbol using the predicted value;

   And outputting a bitstream for the input image by performing entropy encoding on the sub-slice basis for the symbol.
10. 10. The method of claim 9,

    Generating a division marker for identifying the plurality of sub slices;

    And inserting the segmentation marker at a position where data for the plurality of sub slices is started in the bitstream for the input image.
11. 10. The method of claim 9,

    Determining the predicted value may comprise:

    Wherein information on at least one neighboring block included in the same slice as the current block is referred to when determining a predicted value for data of the current block.
12. 12. The method of claim 11,

    The generating of the symbol comprises:

    Generating residual data by difference between the data of the current block and the determined predicted value;

    Performing frequency conversion on the residual data to generate a transform coefficient;

    And performing quantization on the transform coefficients to generate the symbol of a quantized coefficient type.
13. 13. The method of claim 12,

    Performing inverse quantization and inverse quantization on the symbols to recover residual data;

    And generating reconstruction data using the reconstructed residual data and the predicted value.
14. 14. The method of claim 13,

    Further comprising storing the restoration data,

    Determining the predicted value may comprise:

    And determining reconstruction data for a neighboring block among the stored reconstruction data when determining a predicted value for data of the current block.
15. Detecting a slice start code in an input bit stream to divide a plurality of slices;

    Detecting a division marker in the input bit stream to separate a plurality of sub slices;

    Checking an error for the input bitstream;

    Initializing data of the sub slice in which the error is detected;

    Generating a reconstructed image by decoding a bitstream in which the error is not detected;

    And recovering the data of the sub slice in which the error is detected to generate a restored image.

Images