WO2019131400A1

WO2019131400A1 - Image filter device, image decoding device, and image encoding device

Info

Publication number: WO2019131400A1
Application number: PCT/JP2018/046859
Authority: WO
Inventors: 知宏猪飼; 天洋周
Original assignee: シャープ株式会社
Priority date: 2017-12-26
Filing date: 2018-12-19
Publication date: 2019-07-04

Abstract

A filter corresponding to image characteristics is applied to input image data. A loop filter (305) which generates an output image by acting on an input image configured from multiple basic unit regions, is provided with: a de-blocking filter (305_1) which acts on block boundaries including the boundaries of basic unit regions; and an adaptive filter (305_2). A boundary filter of slice boundaries or tile boundaries can be turned on and off in the de-blocking filter (305_1). The adaptive filter (305_2) sets a virtual boundary in different positions depending on whether filter processing by the de-blocking filter (305_1) is on or is off in the slice boundaries or the tile boundaries, and performs filter processing referring to the pixel values located within said virtual boundary.

Description

Image filter device, image decoding device, and image encoding device

Embodiments of the present invention relate to an image filter device, an image decoding device, and an image coding device.

A moving picture coding apparatus that generates coded data by coding a moving picture to efficiently transmit or record a moving picture, and a moving picture that generates a decoded picture by decoding the coded data. An image decoding device is used.

As a specific moving picture coding method, for example, a method proposed in H.264 / AVC or High-Efficiency Video Coding (HEVC) may be mentioned.

In such a moving picture coding method, an image (picture) constituting a moving picture is a slice obtained by dividing the image, a coding unit obtained by dividing the slice (coding unit (coding unit (Coding Unit)). (Also referred to as CU) and a hierarchical structure including a prediction unit (PU) which is a block obtained by dividing a coding unit and a transform unit (TU), and coding / It is decoded.

Also, in such a moving picture coding method, a predicted picture is usually generated based on a locally decoded picture obtained by coding / decoding an input picture, and the predicted picture is generated from the input picture (original picture). The prediction residual obtained by subtraction (sometimes referred to as "difference image" or "residual image") is encoded. As a method of generating a prediction image, inter-screen prediction (inter prediction) and intra-screen prediction (intra prediction) can be mentioned.

In addition, Non-Patent Document 1 can be cited as a technology for moving picture encoding and decoding in recent years.

The present invention has been made in view of the above problems, and an object thereof is to realize application of a filter according to an image characteristic to input image data as compared with a conventional configuration.

In order to solve the above problems, an image filter device according to the present invention is an image filter device that generates an output image by acting on an input image composed of a plurality of basic unit regions, and the basic unit region And an adaptive filter unit, wherein the boundary filter unit is capable of turning on and off the boundary filter of the slice boundary or the tile boundary, and the adaptive filter unit includes the boundary filter unit. Different virtual boundaries are set depending on whether the filtering process by the boundary filter unit is on or off at slice boundaries or tile boundaries, and filtering is performed with reference to pixel values located within the virtual boundaries. I do.

In order to solve the above-mentioned subject, the image filter device concerning the present invention is provided with the filter part which generates an output picture by acting on an input image, and the object pixel in the above-mentioned input picture is processed by the filter processing by the above-mentioned filter part. And a process of multiplying each of the pixels around the target pixel and the activity calculated by referring to at least a part of the surrounding pixels by a weighting factor.

Compared to the conventional configuration, a filter according to image characteristics can be applied to input image data.

It is a figure which shows the hierarchical structure of the data of the encoding stream which concerns on 1st Embodiment. It is a figure which shows the pattern of PU split mode. (A) to (h) show the partition shapes when the PU division mode is 2Nx2N, 2NxN, 2NxnU, 2NxnD, Nx2N, nLx2N, nRx2N, and NxN, respectively. It is a conceptual diagram which shows an example of a reference picture and a reference picture list. It is a block diagram which shows the structure of the image coding apparatus which concerns on 1st Embodiment. It is the schematic which shows the structure of the image decoding apparatus which concerns on 1st Embodiment. It is the schematic which shows the structure of the inter estimated image generation part of the image coding apparatus concerning 1st Embodiment. It is a block diagram which shows the structure of the loop filter with which the moving image decoding apparatus which concerns on 1st Embodiment is provided. It is a flowchart which shows the process by the reference area setting part of the loop filter which concerns on 1st Embodiment, and a filter process part. . It is a figure for demonstrating the reference restriction line in 1st Embodiment. It is a flowchart which shows the detailed process which the reference area setting part of the loop filter which concerns on 1st Embodiment performs. It is a flowchart which shows the detail of the process which the reference area setting part of the loop filter which concerns on 1st Embodiment performs when the filter processing by a deblocking filter is OFF. It is a figure for demonstrating the detail of the reference area in 1st Embodiment, (a) shows a reference area in case an object pixel is located in top part, (b) is an object pixel located in bottom part Indicates the reference area of the case. It is a flowchart which shows the detail of the process which the filter process part of the loop filter which concerns on 1st Embodiment performs. It is an example of the table which the filter process part of the loop filter which concerns on 1st Embodiment refers. It is a figure which shows the other example of the reference restriction line which the reference area setting part of the loop filter which concerns on 1st Embodiment sets. It is a figure which shows the example of the process of the reference pixel position setting by the filter process part of the loop filter which concerns on 1st Embodiment. It is a figure which shows the reference area | region in a comparative example. It is a figure which shows the reference area according to on / off of the deblocking filter in a comparative example, (a) shows the reference area when the deblocking filter is on, (b) shows the case where the deblocking filter is off Indicates a reference area. It is a block diagram which shows the structure of the loop filter with which the moving image decoding apparatus which concerns on 8th Embodiment is provided. It is a figure which shows an example of the reference pixel in 9th Embodiment. It is a figure which shows the other example of the reference pixel in 10th Embodiment. It is a figure which shows the other example of the reference pixel in 11th Embodiment. It is a figure which shows the other example of the reference pixel in 12th Embodiment. It is a figure which shows the other example of the reference pixel in 13th Embodiment. The filter coefficients derived by the adaptive filter 305_2 are visualized in class units. (A) is a figure which showed the residual reduction amount gain which is the difference of the quantity of the remainder before and behind applying the filter factor derived | led-out by adaptive filter 305_2 in a class unit, (b) is adaptive filter 305_2 Indicates the frequency of appearance of classified classes. It is the figure shown about the composition of the transmitting device carrying the picture coding device concerning this embodiment, and the receiving device carrying a picture decoding device. (A) shows a transmitting apparatus equipped with an image coding apparatus, and (b) shows a receiving apparatus equipped with an image decoding apparatus. It is the figure shown about the recording device carrying the picture coding device concerning this embodiment, and the composition of the reproduction device carrying a picture decoding device. (A) shows a recording apparatus equipped with an image coding apparatus, and (b) shows a reproduction apparatus equipped with an image decoding apparatus. It is a schematic diagram showing composition of an image transmission system concerning this embodiment.

First Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 29 is a schematic view showing the configuration of the image transmission system 1 according to the present embodiment.

The image transmission system 1 is a system that transmits a code obtained by coding an image to be coded, decodes the transmitted code, and displays the image. The image transmission system 1 is configured to include an image encoding device (moving image encoding device) 11, a network 21, an image decoding device (moving image decoding device) 31, and an image display device 41.

An image T representing an image of a single layer or a plurality of layers is input to the image coding device 11. A layer is a concept used to distinguish a plurality of pictures when there is one or more pictures that constitute a certain time. For example, if the same picture is encoded by a plurality of layers having different image quality and resolution, it becomes scalable coding, and if a picture of different viewpoints is encoded by a plurality of layers, it becomes view scalable coding. When prediction (inter-layer prediction, inter-view prediction) is performed between pictures of a plurality of layers, coding efficiency is greatly improved. Also, even in the case where prediction is not performed (simulcast), encoded data can be summarized.

The network 21 transmits the encoded stream Te generated by the image encoding device 11 to the image decoding device 31. The network 21 is the Internet, a wide area network (WAN), a small area network (LAN), or a combination of these. The network 21 is not necessarily limited to a two-way communication network, and may be a one-way communication network for transmitting broadcast waves such as terrestrial digital broadcasting and satellite broadcasting. In addition, the network 21 may be replaced by a storage medium recording a coded stream Te such as a DVD (Digital Versatile Disc) or a BD (Blue-ray Disc).

The image decoding apparatus 31 decodes each of the encoded streams Te transmitted by the network 21 and generates one or more decoded images Td which are respectively decoded.

The image display device 41 displays all or a part of one or more decoded images Td generated by the image decoding device 31. The image display device 41 includes, for example, a display device such as a liquid crystal display or an organic EL (Electro-luminescence) display. In spatial scalable coding and SNR scalable coding, when the image decoding device 31 and the image display device 41 have high processing capabilities, they display enhancement layer images with high image quality and have only lower processing capabilities. , The base layer image which does not require the processing capability and the display capability as high as the enhancement layer.

<Operator>
The operators used herein are described below.

>> is a right bit shift, << is a left bit shift, & is a bitwise AND, | is a bitwise OR, and | = is a sum operation (OR) with another condition.

X? Y: z is a ternary operator that takes y if x is true (other than 0) and z if x is false (0).

Clip3 (a, b, c) is a function that clips c to a value between a and b, and returns a if c <a, b if c> b, otherwise Is a function that returns c (where a <= b).

<Structure of Coded Stream Te>
Prior to detailed description of the image encoding device 11 and the image decoding device 31 according to the present embodiment, the data structure of the encoded stream Te generated by the image encoding device 11 and decoded by the image decoding device 31 will be described. .

FIG. 1 is a diagram showing a hierarchical structure of data in a coded stream Te. The coded stream Te illustratively includes a sequence and a plurality of pictures forming the sequence. (A) to (f) in FIG. 1 respectively represent a coded video sequence defining the sequence SEQ, a coded picture defining the picture PICT, a coding slice defining the slice S, and a coding slice defining slice data. It is a figure which shows a coding tree unit contained in data, coding slice data, and a coding unit (Coding Unit; CU) contained in a coding tree unit.

(Encoded video sequence)
In the encoded video sequence, a set of data to which the image decoding device 31 refers in order to decode the sequence SEQ to be processed is defined. As shown in FIG. 1A, the sequence SEQ includes a video parameter set (Video Parameter Set), a sequence parameter set SPS (Sequence Parameter Set), a picture parameter set PPS (Picture Parameter Set), a picture PICT, and an addition. It includes supplemental information SEI (Supplemental Enhancement Information). Here, the value shown after # indicates a layer ID. Although FIG. 1 shows an example in which coded data of # 0 and # 1, that is, layer 0 and layer 1 exist, the type of layer and the number of layers do not depend on this.

A video parameter set VPS is a set of coding parameters common to a plurality of moving pictures and a set of coding parameters related to the plurality of layers included in the moving picture and each layer in a moving picture composed of a plurality of layers. A set is defined.

In the sequence parameter set SPS, a set of coding parameters to be referred to by the image decoding device 31 for decoding the target sequence is defined. For example, the width and height of the picture are defined. In addition, multiple SPS may exist. In that case, one of a plurality of SPSs is selected from PPS.

In the picture parameter set PPS, a set of coding parameters to which the image decoding device 31 refers to to decode each picture in the target sequence is defined. For example, a reference value of quantization width (pic_init_qp_minus 26) used for decoding a picture and a flag (weighted_pred_flag) indicating application of weighted prediction are included. In addition, multiple PPS may exist. In that case, one of a plurality of PPSs is selected from each picture in the target sequence.

(Coded picture)
In the coded picture, a set of data to which the image decoding device 31 refers in order to decode the picture PICT to be processed is defined. The picture PICT includes slices S0 to _SNS-1 (NS is the total number of slices included in the picture PICT), as shown in (b) of FIG.

In the following, when there is no need to distinguish between slices S0 to _SNS-1 , suffixes of reference numerals may be omitted and described. Further, the same is true for other data that is included in the encoded stream Te described below and that is suffixed.

(Coding slice)
In the coding slice, a set of data to which the image decoding device 31 refers in order to decode the slice S to be processed is defined. The slice S includes a slice header SH and slice data SDATA as shown in (c) of FIG.

The slice header SH includes a coding parameter group to which the image decoding device 31 refers in order to determine the decoding method of the target slice. The slice type specification information (slice_type) for specifying a slice type is an example of a coding parameter included in the slice header SH.

As slice types that can be designated by slice type designation information, (1) I slice using only intra prediction at the time of encoding, (2) P slice using unidirectional prediction at the time of encoding or intra prediction, (3) B-slice using uni-directional prediction, bi-directional prediction, or intra prediction at the time of encoding.

Note that the slice header SH may include a reference (pic_parameter_set_id) to the picture parameter set PPS included in the encoded video sequence.

(Encoding slice data)
In the encoded slice data, a set of data to which the image decoding device 31 refers in order to decode the slice data SDATA to be processed is defined. The slice data SDATA includes a coding tree unit (CTU: Coding Tree Unit, basic unit area) as shown in (d) of FIG. The CTU is a block of a fixed size (for example, 32x32, 64x64, 128x128) that configures a slice, and may also be referred to as a largest coding unit (LCU: Largest Coding Unit).

(Encoding tree unit)
As shown in (e) of FIG. 1, a set of data to which the image decoding device 31 refers in order to decode a coding tree unit to be processed is defined. The coding tree unit is divided by recursive quadtree division. A tree-structured node obtained by recursive quadtree division is called a coding node (CN). The intermediate nodes of the quadtree are coding nodes, and the coding tree unit itself is also defined as the top coding node. The CTU includes a split flag (cu_split_flag), and when cu_split_flag is 1, the CTU is split into four coding nodes CN. When cu_split_flag is 0, the coding node CN is not split, and has one coding unit (CU: Coding Unit) as a node. The coding unit CU is an end node of the coding node and is not further divided. The coding unit CU is a basic unit of coding processing.

When the size of the coding tree unit CTU is 64x64 pixels, the size of the coding unit can be 64x64 pixels, 32x32 pixels, 16x16 pixels, or 8x8 pixels.

(Coding unit)
As shown in (f) of FIG. 1, a set of data to which the image decoding device 31 refers in order to decode a coding unit to be processed is defined. Specifically, the coding unit is composed of a prediction tree, a transformation tree, and a CU header CUH. In the CU header, a prediction mode, a division method (PU division mode), and the like are defined.

In the prediction tree, prediction information (reference picture index, motion vector, etc.) of each prediction unit (PU) obtained by dividing the coding unit into one or more is defined. Stated differently, a prediction unit is one or more non-overlapping regions that make up a coding unit. Also, the prediction tree includes one or more prediction units obtained by the above-mentioned division. In addition, below, the prediction unit which divided | segmented the prediction unit further is called a "subblock." The sub block is composed of a plurality of pixels. If the size of the prediction unit and the subblock is equal, there is one subblock in the prediction unit. If the prediction unit is larger than the size of the subblock, the prediction unit is divided into subblocks. For example, when the prediction unit is 8x8 and the subblock is 4x4, the prediction unit is divided into four subblocks, which are horizontally divided into two and vertically divided into two.

The prediction process may be performed for each prediction unit (sub block).

Broadly speaking, there are two types of division in the prediction tree: intra prediction and inter prediction. Intra prediction is prediction in the same picture, and inter prediction refers to prediction processing performed between mutually different pictures (for example, between display times, between layer images).

In the case of intra prediction, there are 2Nx2N (the same size as the coding unit) and NxN as a division method.

Also, in the case of inter prediction, the division method is encoded according to PU division mode (part_mode) of encoded data, 2Nx2N (the same size as the encoding unit), 2NxN, 2NxnU, 2NxnD, Nx2N, nLx2N, nRx2N, and There are NxN etc. Note that 2NxN and Nx2N indicate 1: 1 symmetric division, and 2NxnU, 2NxnD and nLx2N and nRx2N indicate 1: 3 and 3: 1 asymmetric division. The PUs included in the CU are expressed as PU0, PU1, PU2, PU3 in order.

(A) to (h) of FIG. 2 specifically illustrate the shapes of partitions (positions of boundaries of PU division) in respective PU division modes. (A) of FIG. 2 shows a 2Nx2N partition, and (b), (c) and (d) show 2NxN, 2NxnU, and 2NxnD partitions (horizontally long partitions), respectively. (E), (f) and (g) show partitions (vertical partitions) in the case of Nx2N, nLx2N and nRx2N, respectively, and (h) shows a partition of NxN. Note that the horizontally long partition and the vertically long partition are collectively referred to as a rectangular partition, and 2Nx2N and NxN are collectively referred to as a square partition.

Also, in the transform tree, the coding unit is divided into one or more transform units, and the position and size of each transform unit are defined. In other words, a transform unit is one or more non-overlapping regions that make up a coding unit. Also, the transformation tree includes one or more transformation units obtained by the above-mentioned division.

Partitions in the transform tree may be allocated as a transform unit a region of the same size as the encoding unit, or may be based on recursive quadtree partitioning as in the case of CU partitioning described above.

A conversion process is performed for each conversion unit.

(Prediction parameter)
The prediction image of a prediction unit (PU: Prediction Unit) is derived by prediction parameters associated with PU. The prediction parameters include intra prediction prediction parameters or inter prediction prediction parameters. Hereinafter, prediction parameters for inter prediction (inter prediction parameters) will be described. The inter prediction parameter includes prediction list use flags predFlagL0 and predFlagL1, reference picture indexes refIdxL0 and refIdxL1, and motion vectors mvL0 and mvL1. The prediction list use flags predFlagL0 and predFlagL1 are flags indicating whether a reference picture list called an L0 list or an L1 list is used, respectively, and a reference picture list corresponding to a value of 1 is used. In the present specification, when "a flag indicating whether or not it is XX", if the flag is other than 0 (for example, 1) is XX, it is assumed that 0 is not XX; Treat 1 as true, 0 as false, and so on. However, in an actual apparatus or method, other values may be used as true values or false values.

Syntax elements for deriving inter prediction parameters included in encoded data include, for example, PU split mode part_mode, merge flag merge_flag, merge index merge_idx, inter prediction identifier inter_pred_idc, reference picture index refIdxLX, predicted vector index mvp_LX_idx, There is a difference vector mvdLX.

(Reference picture list)
The reference picture list is a list of reference pictures stored in the reference picture memory 306. FIG. 3 is a conceptual diagram showing an example of a reference picture and a reference picture list. In FIG. 3A, the rectangle is a picture, the arrow is a reference of the picture, the horizontal axis is time, and I, P and B in the rectangle are intra pictures, uni-predicted pictures, bi-predicted pictures, and numbers in the rectangle are decoded. Show the order. As shown in the figure, the decoding order of pictures is I0, P1, B2, B3, B4, and the display order is I0, B3, B2, B4, B1, P1. FIG. 3B shows an example of the reference picture list. The reference picture list is a list representing reference picture candidates, and one picture (slice) may have one or more reference picture lists. In the example of the figure, the target picture B3 has two reference picture lists, an L0 list RefPicList0 and an L1 list RefPicList1. Reference pictures when the target picture is B3 are I0, P1, and B2, and the reference pictures have these pictures as elements. In each prediction unit, which picture in the reference picture list RefPicListX is actually referred to is designated by the reference picture index refIdxLX. The figure shows an example in which reference pictures P1 and B2 are referenced by refIdxL0 and refIdxL1.

(Merge forecast and AMVP forecast)
The prediction parameter decoding (encoding) method includes a merge prediction (merge) mode and an AMVP (Adaptive Motion Vector Prediction) mode. The merge flag merge_flag is a flag for identifying these. The merge prediction mode is a mode used to be derived from the prediction parameter of the already processed neighboring PU without including the prediction list use flag predFlagLX (or inter prediction identifier inter_pred_idc), the reference picture index refIdxLX, and the motion vector mvLX in the encoded data. The AMVP mode is a mode in which the inter prediction identifier inter_pred_idc, the reference picture index refIdxLX, and the motion vector mvLX are included in the encoded data. The motion vector mvLX is encoded as a prediction vector index mvp_LX_idx that identifies the prediction vector mvpLX and a difference vector mvdLX.

The inter prediction identifier inter_pred_idc is a value indicating the type and the number of reference pictures, and takes any one of PRED_L0, PRED_L1, and PRED_BI. PRED_L0 and PRED_L1 indicate that reference pictures managed by reference pictures in the L0 list and the L1 list are used, respectively, and indicate that one reference picture is used (uniprediction). PRED_BI indicates using two reference pictures (bi-prediction BiPred), and uses reference pictures managed by the L0 list and the L1 list. The predicted vector index mvp_LX_idx is an index indicating a predicted vector, and the reference picture index refIdxLX is an index indicating a reference picture managed in the reference picture list. LX is a description method used when L0 prediction and L1 prediction are not distinguished, and parameters for L0 list and parameters for L1 list are distinguished by replacing LX with L0 and L1.

Merge index merge_idx is an index which shows whether any prediction parameter is used as a prediction parameter of decoding object PU among the prediction parameter candidates (merge candidate) derived | led-out from PU which processing completed.

(Motion vector)
The motion vector mvLX indicates the amount of deviation between blocks on two different pictures. The prediction vector and the difference vector relating to the motion vector mvLX are referred to as a prediction vector mvpLX and a difference vector mvdLX, respectively.

(Inter prediction identifier inter_pred_idc and prediction list usage flag predFlagLX)
The relationship between the inter prediction identifier inter_pred_idc, and the prediction list use flag predFlagL0, predFlagL1 is as follows, and can be mutually converted.

inter_pred_idc = (predFlagL1 << 1) + predFlagL0
predFlagL0 = inter_pred_idc & 1
predFlagL1 = inter_pred_idc >> 1
The inter prediction parameter may use a prediction list use flag or may use an inter prediction identifier. Further, the determination using the prediction list use flag may be replaced with the determination using the inter prediction identifier. Conversely, the determination using the inter prediction identifier may be replaced with the determination using the prediction list utilization flag.

(Determination of bi-prediction biPred)
The flag biPred of bi-prediction BiPred can be derived depending on whether both of the two prediction list use flags are 1. For example, it can be derived by the following equation.

biPred = (predFlagL0 == 1 && predFlagL1 == 1)
The flag biPred can also be derived based on whether or not the inter prediction identifier is a value indicating that two prediction lists (reference pictures) are used. For example, it can be derived by the following equation.

biPred = (inter_pred_idc == PRED_BI)? 1: 0
The above equation can also be expressed by the following equation.

biPred = (inter_pred_idc == PRED_BI)
For example, a value of 3 can be used as PRED_BI.

(Configuration of image decoding apparatus)
Next, the configuration of the image decoding apparatus 31 according to the present embodiment will be described. FIG. 5 is a schematic view showing the configuration of the image decoding device 31 according to the present embodiment. The image decoding device 31 includes an entropy decoding unit 301, a prediction parameter decoding unit (prediction image decoding device) 302, a loop filter 305, a reference picture memory 306, a prediction parameter memory 307, a prediction image generation unit (prediction image generation device) 308, and an inverse A quantization / inverse DCT unit 311 and an addition unit 312 are included.

Further, the prediction parameter decoding unit 302 is configured to include an inter prediction parameter decoding unit 303 and an intra prediction parameter decoding unit 304. The predicted image generation unit 308 includes an inter predicted image generation unit 309 and an intra predicted image generation unit 310.

The entropy decoding unit 301 performs entropy decoding on the encoded stream Te input from the outside to separate and decode individual codes (syntax elements). The separated codes include prediction information for generating a prediction image and residual information for generating a difference image.

The entropy decoding unit 301 outputs a part of the separated code to the prediction parameter decoding unit 302. The part of the separated code is, for example, prediction mode predMode, PU division mode part_mode, merge flag merge_flag, merge index merge_idx, inter prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, difference vector mvdLX. Control of which code to decode is performed based on an instruction of the prediction parameter decoding unit 302. The entropy decoding unit 301 outputs the quantization coefficient to the inverse quantization / inverse DCT unit 311. The quantization coefficient is a coefficient obtained by performing DCT (Discrete Cosine Transform, discrete cosine transformation) on the residual signal in the encoding process and quantizing the coefficient.

The inter prediction parameter decoding unit 303 decodes the inter prediction parameter with reference to the prediction parameter stored in the prediction parameter memory 307 based on the code input from the entropy decoding unit 301.

The inter prediction parameter decoding unit 303 outputs the decoded inter prediction parameter to the prediction image generation unit 308, and stores the inter prediction parameter in the prediction parameter memory 307. Details of the inter prediction parameter decoding unit 303 will be described later.

The intra prediction parameter decoding unit 304 decodes the intra prediction parameter with reference to the prediction parameter stored in the prediction parameter memory 307 based on the code input from the entropy decoding unit 301. The intra prediction parameter is a parameter used in a process of predicting a CU in one picture, for example, an intra prediction mode IntraPredMode. The intra prediction parameter decoding unit 304 outputs the decoded intra prediction parameter to the prediction image generation unit 308, and stores it in the prediction parameter memory 307.

The intra prediction parameter decoding unit 304 may derive different intra prediction modes for luminance and chrominance. In this case, the intra prediction parameter decoding unit 304 decodes a luminance prediction mode IntraPredModeY as a luminance prediction parameter and a chrominance prediction mode IntraPredModeC as a chrominance prediction parameter. The luminance prediction mode IntraPredModeY is a 35 mode, which corresponds to planar prediction (0), DC prediction (1), and directional prediction (2 to 34). The color difference prediction mode IntraPredModeC uses one of planar prediction (0), DC prediction (1), direction prediction (2 to 34), and LM mode (35). The intra prediction parameter decoding unit 304 decodes a flag indicating whether IntraPredModeC is the same mode as the luminance mode, and if it indicates that the flag is the same mode as the luminance mode, IntraPredModeY is assigned to IntraPredModeC, and the flag indicates the luminance If intra mode is different from the mode, planar prediction (0), DC prediction (1), direction prediction (2 to 34), or LM mode (35) may be decoded as IntraPredModeC.

The loop filter 305 applies a filter such as a deblocking filter, a sample adaptive offset (SAO), or an adaptive filter (ALF) to the decoded image of the CU generated by the adding unit 312. The details of the loop filter 305 will be described later, changing the reference drawings.

The reference picture memory 306 stores the decoded image of the CU generated by the adding unit 312 in a predetermined position for each picture and CU to be decoded.

The prediction parameter memory 307 stores prediction parameters in a predetermined position for each picture to be decoded and each prediction unit (or sub block, fixed size block, pixel). Specifically, the prediction parameter memory 307 stores the inter prediction parameter decoded by the inter prediction parameter decoding unit 303, the intra prediction parameter decoded by the intra prediction parameter decoding unit 304, and the prediction mode predMode separated by the entropy decoding unit 301. . The inter prediction parameters to be stored include, for example, a prediction list use flag predFlagLX (inter prediction identifier inter_pred_idc), a reference picture index refIdxLX, and a motion vector mvLX.

The prediction image generation unit 308 receives the prediction mode predMode input from the entropy decoding unit 301, and also receives a prediction parameter from the prediction parameter decoding unit 302. Further, the predicted image generation unit 308 reads the reference picture from the reference picture memory 306. The prediction image generation unit 308 generates a PU prediction image using the input prediction parameters and the read reference picture in the prediction mode indicated by the prediction mode predMode.

Here, when the prediction mode predMode indicates the inter prediction mode, the inter prediction image generation unit 309 uses the inter prediction parameter input from the inter prediction parameter decoding unit 303 and the read reference picture to interpolate the predicted image of the PU by inter prediction. Generate

The inter-predicted image generation unit 309 uses the reference picture index refIdxLX for the reference picture list (L0 list or L1 list) in which the prediction list use flag predFlagLX is 1, and the motion vector based on the PU to be decoded The reference picture block at the position indicated by mvLX is read out from the reference picture memory 306. The inter-prediction image generation unit 309 performs prediction based on the read reference picture block to generate a PU prediction image. The inter prediction image generation unit 309 outputs the generated prediction image of PU to the addition unit 312.

When the prediction mode predMode indicates the intra prediction mode, the intra prediction image generation unit 310 performs intra prediction using the intra prediction parameter input from the intra prediction parameter decoding unit 304 and the read reference picture. Specifically, the intra predicted image generation unit 310 reads, from the reference picture memory 306, neighboring PUs which are pictures to be decoded and which are in a predetermined range from the PU to be decoded among PUs already decoded. The predetermined range is, for example, one of the left, upper left, upper, and upper right adjacent PUs when the decoding target PU sequentially moves in the so-called raster scan order, and varies depending on the intra prediction mode. The order of raster scan is an order of sequentially moving from the left end to the right end for each row from the top to the bottom in each picture.

The intra predicted image generation unit 310 performs prediction on the read adjacent PU in the prediction mode indicated by the intra prediction mode IntraPredMode to generate a predicted image of PU. The intra predicted image generation unit 310 outputs the generated predicted image of PU to the addition unit 312.

When the intra prediction parameter decoding unit 304 derives an intra prediction mode different in luminance and color difference, the intra prediction image generation unit 310 determines planar prediction (0), DC prediction (1), direction according to the luminance prediction mode IntraPredMode Y. A prediction image of PU of luminance is generated by any of prediction (2 to 34), and planar prediction (0), DC prediction (1), direction prediction (2 to 34), LM mode according to color difference prediction mode IntraPredModeC. The prediction image of color difference PU is generated by any of (35).

The inverse quantization / inverse DCT unit 311 inversely quantizes the quantization coefficient input from the entropy decoding unit 301 to obtain a DCT coefficient. The inverse quantization / inverse DCT unit 311 performs inverse DCT (Inverse Discrete Cosine Transform) on the obtained DCT coefficient to calculate a residual signal. The inverse quantization / inverse DCT unit 311 outputs the calculated residual signal to the addition unit 312.

The addition unit 312 adds, for each pixel, the predicted image of the PU input from the inter predicted image generation unit 309 or the intra predicted image generation unit 310 and the residual signal input from the inverse quantization / inverse DCT unit 311, Generate a PU decoded image. The addition unit 312 stores the generated PU decoded image in the reference picture memory 306, and externally outputs a decoded image Td in which the generated PU decoded image is integrated for each picture.

(Details of loop filter 305)
(Loop filter 305)
The loop filter 305 is an image filter device, and generates an output image by acting on an input image composed of a plurality of encoding tree units CTU (basic unit area which is a processing unit of a filter).

The loop filter 305 has (1) a function as a deblocking filter (DF: Deblocking Filter) that performs smoothing (deblocking processing) of an image around a block boundary in the input image P, and (2) a deblocking filter acts It has a function as an adaptive filter (ALF: Adaptive Loop Filter) that performs adaptive filter processing using the filter parameter FP on the captured image.

FIG. 7 is a block diagram showing the configuration of the loop filter 305. As shown in FIG. As shown in FIG. 7, the loop filter 305 includes a deblocking filter 305_1 operating as a boundary filter unit, an adaptive filter 305_2 operating as an adaptive filter unit, and an internal memory 305_3.

(Deblocking filter 305_1)
The deblocking filter 305_1 operates on the boundaries of blocks (coding tree unit CTU, coding unit CU, or partition). The deblocking filter 305_1 generates the deblocked decoded image P_DB by performing smoothing of the image in the area around the block boundary in the input image P. The loop filter 305 may perform filtering by the deblocking filter 305_1 (if it is on) or not (if it is off).

In addition, the deblocking filter 305_1 switches on and off according to a flag in the encoded data. The flag to switch on / off is a flag (deblocking_filter_disabled_flag) for turning on / off the entire deblocking filter, and at least a flag (loop_filter_across_tiles_enabled_flag) indicating whether to apply a deblocking filter to tile boundaries or a deblocking filter to slice boundaries It has a flag (loop_filter_across_slices_enabled_flag) indicating whether or not it is. The deblocking filter 305_1 derives a flag filterLeftCbEdgeFlag indicating whether or not to apply filtering to the left side of the block boundary. filterLeftCbEdgeFlag is 0 when any of the following conditions are satisfied, and 1 otherwise.
-The left boundary of the target block (target CTU) is the left boundary of the picture.
-The left boundary of the target block (target CTU) is the left boundary of the tile, and loop_filter_across_tiles_enabled_flag is 0.
-The left boundary of the target block (target CTU) is the left boundary of the slice, and loop_filter_across_slices_enabled_flag is 0.

The deblocking filter 305_1 performs filtering on the block left boundary in the vertical direction (the boundary divided by a line along the vertical direction, the boundary divided into left and right blocks) with reference to the flag filterLeftCbEdgeFlag. Specifically, the flag filterLeftCbEdgeFlag, the in-CTU coordinates of the target block, and the division flag are referred to, and a flag edgeFlags indicating whether to filter the boundary pixel is derived. If edgeFlags is 1, apply filtering to the block left boundary. For example, filter processing is performed using the following equation.

p2 '= Clip 3 (p2-2 * tc, p2 + 2 * tc, (2 * p3 + 3 * p2 + p1 + p0 + q0 + 4) >> 3)
p1 '= Clip 3 (p1-2 * tc, p1 + 2 * tc, (p2 + p1 + p0 + q0 + 2) >> 2)
p0 '= Clip 3 (p0-2 * tc, p0 + 2 * tc, (p2 + 2 * p1 + 2 * p0 + 2 * q0 + q1 + 4) >> 3)
q0 '= Clip 3 (q0-2 * tc, q0 + 2 * tc, (p1 + 2 * p0 + 2 * q0 + 2 * q1 + q2 + 4) >> 3)
q1 '= Clip 3 (q1-2 * tc, q1 + 2 * tc, (p0 + q0 + q1 + q2 + 2) >> 2)
q2 '= Clip3 (q2-2 * tc, q2 + 2 * tc, (p0 + q0 + q1 + 3 * q2 + 2 * q3 + 4) >> 3)
Here, p 2, p 1, p 0, q 0, q 1, q 2 are columns of pixels of

distances

2, 1, 0, 0, 1, 2 from the boundary, respectively. p2, p1 and p0 are pixels included in the block P of the block P and the block Q bordering the boundary, and q0, q1 and q2 are pixels included in the block Q. tc is a variable for suppressing filter processing.

On the other hand, when the edgeFlags is 0, no filtering process is applied to the left boundary of the block. If the x coordinate of the in-CTU coordinate is 0, that is, if the target block left boundary is the left boundary of the CTU, set filterLeftCbEdgeFlag in edgeFlags. Accordingly, when the filterLeftCbEdgeFlag is 0, the deblocking filter 305_1 does not apply the filtering process to the left boundary of the CTU.

The deblocking filter 305_1 derives a flag filterTopCbEdgeFlag indicating whether or not the filtering process is performed above the block boundary of the target block. filterTopCbEdgeFlag is 0 when any of the following conditions are satisfied, and 1 otherwise.
-The upper boundary of the target block (target CTU) is the upper boundary of the picture.
-The upper boundary of the target block (target CTU) is the upper boundary of the tile, and loop_filter_across_tiles_enabled_flag is 0.
-The upper boundary of the target block (target CTU) is the upper boundary of the slice, and loop_filter_across_slices_enabled_flag is 0.

The deblocking filter 305_1 performs filtering on the block upper boundary in the horizontal direction (the boundary divided by a line along the horizontal direction, the boundary divided into upper and lower blocks) with reference to the flag filterTopCbEdgeFlag. Specifically, the flag filterLeftCbEdgeFlag, the in-CTU coordinates of the target block, and the division flag are referred to, and a flag edgeFlags indicating whether to filter the boundary pixel is derived. When edgeFlags is 1, filter processing is applied to the block upper boundary. The application method is the same as the above block left boundary in the vertical direction. When edgeFlags is 0, no filtering is applied to the block upper boundary. If the Y coordinate of the in-CTU coordinates is 0, that is, if the target block upper boundary is the upper boundary of the CTU, set filterTopCbEdgeFlag in edgeFlags. As a result, when the filterTopCbEdgeFlag is 0, the deblocking filter 305_1 does not apply the filtering process to the upper boundary of the CTU. According to the above, the deblocking filter 305 _ 1 can turn on / off the boundary filter of slice boundaries or tile boundaries.

(Adaptive filter 305_2)
The adaptive filter 305_2 acts on the deblocked decoded image P_DB after the filtering by the deblocking filter 305_1 when the filtering by the deblocking filter 305_1 is on. On the other hand, the adaptive filter 305_2 acts on the input image P when the filtering process by the deblocking filter 305_1 is off. Also, the adaptive filter 305_2 may operate on filtered decoded images other than the deblocking filter 305_1. For example, it may operate on the adaptive sample offset filter P_SAO.

The adaptive filter 305_2 includes a target pixel setting unit 305_2a, a reference area setting unit 305_2b, and a filter processing unit 305_2c.

(Target pixel setting unit 305_2a)
The target pixel setting unit 305_2a sets each pixel included in the coding tree unit CTU as a target pixel for adaptive filter processing in raster scan order. The target pixel position information indicating the position of the target pixel set by the target pixel setting unit 305_2a is supplied to the reference area setting unit 305_2b. The reference area setting unit 305_2b sets the reference area of the target pixel, and the filter processing unit 305_2c calculates the pixel value of the target pixel.

(Reference area setting unit 305_2b)
The reference area setting unit 305_2b sets a reference area around the target pixel based on the position of the target pixel in the coding tree unit CTU. The reference area is defined by virtually set reference restriction lines (virtual boundaries). That is, "outside reference area" indicates the outside of the target pixel beyond the reference restriction line, and "in reference area" indicates the inside of the reference restriction line from the target pixel. The reference area setting unit 305_2b sets reference restriction lines with different positions depending on whether the filtering process by the deblocking filter 305_1 is on or off. Details of the process performed by the reference area setting unit 350_2b will be described later, with reference to the drawings being referred to.

(Filter processing unit 305_2c)
The filter processing unit 305 _ 2 c is a pixel of (1) a deblocked decoded image (also referred to as “pre-filter image”) of the pixel value of the adaptive-filtered decoded image P_ALF (also referred to as “filtered image”) of the target pixel. The value or (2) the pixel value of the input image P, which is calculated by reference to the pixel value of the pixel included in the reference region set for the target pixel by the reference region setting unit 305_2b. The process of determining the pixel to be referred to by the filter processing unit 305_2c will be described later, with reference to the drawings being referred to. The generated adaptive filtered decoded image P_ALF is temporarily stored in the internal memory 305_3, and then transferred to the reference picture memory 306.

(Processing of adaptive filter)
FIG. 8 is a flowchart showing processing by the reference region setting unit 305_2b and the filter processing unit 305_2c of the loop filter 305 according to the present embodiment. The details of each process will be described later, with reference to the drawings.

(Step S10)
The reference area setting unit 305_2b sets a reference restriction boundary variable which is a variable for setting a reference restriction line. The reference restriction boundary variable will be described with reference to FIG. FIG. 9 is a diagram for describing a reference restriction line in the present embodiment.

In the present embodiment, the reference area setting unit 305_2b sets a reference restriction line extending in the horizontal direction. Specifically, the reference area setting unit 305_2b is a reference restriction boundary variable indicating how many lines the reference restriction line is to be set from the upper side (hereinafter also referred to as "upper CTU boundary") of the encoding tree unit CTU. K1 and a reference restriction boundary variable K2 indicating how many reference restriction lines are to be set on the upper and lower sides of the lines from the lower side of the coding tree unit CTU (hereinafter also referred to as "lower CTU boundary").

Then, the reference area setting unit 305_2b sets the reference restriction line according to the position of the target pixel set by the target pixel setting unit 305_2a.

First, the reference area setting unit 305_2b sets the reference restriction line vbLine2 from the lower side of the encoding tree unit CTU to the upper side of the reference restriction boundary variable K2 with reference to the set reference restriction boundary variable K2. Then, when the position of the target pixel set in the coding tree unit CTU is above the reference restriction line vbLine2, the reference area setting unit 305_2b refers to the reference restriction boundary variable K1 and sets the encoding tree unit CTU. The reference restriction line vbLine1 is set from the upper side to the reference restriction boundary variable K1 line upper side.

On the other hand, when the position of the target pixel set in the coding tree unit CTU is below the reference restriction line vbLine2, the reference region setting unit 305_2b refers to the reference restriction boundary variable K2 and the coding tree unit CTU. A reference restriction line vbLine3 may be set from the lower side to the lower side of the reference restriction boundary variable K2 line.

As shown in FIG. 9, the area of the coding tree unit CTU between the upper CTU boundary and the reference restriction line vbLine2 is top part, and the coding tree between the reference restriction line vbLine2 and the lower CTU boundary The area of the unit CTU is called bottom part. When the target pixel is included in the top part, an area between the reference restriction line vbLine1 and the reference restriction line vbLine2 is a reference area. When the target pixel is included in the bottom part, the area between the reference restriction line vbLine2 and the reference restriction line vbLine3 is a reference area.

The reference area setting unit 305_2b performs the filtering process with reference to the pixel values located in the virtual boundary.

(Step S20)
The reference area setting unit 305_2b sets the position of a reference pixel which is a pixel to be referred to in order to calculate the pixel value of the target pixel. The area where the reference pixel is located is called a "filter reference area". The filter reference area is an area different from the reference area. The processing of the reference area setting unit 305_2b differs depending on whether the pixel in the filter reference area is within the reference area or outside the reference area. When the position of the reference pixel is outside the reference region set in step S10, the reference region setting unit 305_2b does not refer to a pixel outside the reference region, and sets another pixel as the reference pixel. Detailed processing of the reference area setting unit 305_2b in the case where the position of the reference pixel is outside the reference area will be described later, with reference to the drawings being referred to.

(Step 30)
The filter processing unit 305_2c refers to the position of the reference pixel set in step S20, and calculates the pixel value of the target pixel.

(Details of the process executed by the reference area setting unit 305_2b)
FIG. 10 is a flowchart showing an outline of processing performed by the reference area setting unit 305_2b of the loop filter 305 according to the present embodiment.

(Step S12)
The reference area setting unit 305_2b sets different virtual boundaries depending on whether filtering by the deblocking filter 305_1 operating as a boundary filter unit is on or off at slice boundaries or tile boundaries. The reference area setting unit 305_2b determines whether the filtering process by the deblocking filter 305_1 is off. When the filtering process by the deblocking filter 305_1 is off, the process proceeds to step S14. On the other hand, when the filtering process by the deblocking filter 305_1 is on, the process proceeds to step S16.

(Step S14)
The reference area setting unit 305_2b is “K1” when the reference restriction line on the upper side of the reference restriction boundary variable K (the encoding tree unit CTU is set, “K1”, and the reference restriction line on the lower side of the encoding tree unit CTU Is set “0” to “K2”.

(Step S16)
The reference area setting unit 305_2b sets “NDF” to the reference restriction boundary variable K. The NDF is, for example, four.

(When the filtering process by the deblocking filter 305_1 is off)
FIG. 11 is a flowchart showing details of processing executed by the reference region setting unit 305_2b of the loop filter 305 according to the present embodiment. A specific example of the determination as to whether or not the filtering process by the deblocking filter 305_1 is off will be described with reference to FIG. A case will be described with reference to FIG. 11 in which reference restriction boundary variables on the upper side of the encoding tree unit CTU and reference restriction boundary variables on the lower side of the encoding tree unit CTU are individually set.

(Step S12a)
The reference area setting unit 305_2b
(1) When the upper CTU boundary is at the boundary of a picture, or
(2) When filtering by the deblocking filter for tile boundaries is off (loop_filter_across_tiles_enabled_flag == 0) and the upper CTU boundary is at tile boundaries, or
(3) When the filtering process by the deblocking filter for the slice boundary is off ((slice_loop_filter_across_slices_enabled_flag == 0) and the upper CTU boundary is at the slice boundary, it is determined that the filtering process by the deblocking filter 305_1 is off. If the reference area setting unit 305_2b determines that the filtering process by the deblocking filter 305_1 is off, the process proceeds to step S14a, while the reference area setting unit 305_2b determines that the filtering process by the deblocking filter 305_1 is off. If not, the process proceeds to step S16a.

(Step S14a)
The reference area setting unit 305_2b sets “0” to the reference restriction boundary variable K1.

(Step S16a)
The reference area setting unit 305_2b sets “NDB” to the reference restriction boundary variable K1. NDB is four, for example.

(Step S12b)
The reference area setting unit 305_2b
(1) When the lower CTU boundary is at a picture boundary, or
(2) When filtering by the deblocking filter for tile boundaries is off (loop_filter_across_tiles_enabled_flag == 0) and the lower CTU boundary is at tile boundaries, or
(3) It is determined that the filtering by the deblocking filter 305_1 is off when the filtering by the deblocking filter for the slice boundary is off ((slice_loop_filter_across_slices_enabled_flag == 0) and the lower CTU boundary is at the boundary of the slice. If the reference area setting unit 305_2b determines that the filtering process by the deblocking filter 305_1 is off, the process proceeds to step S14b, while the reference area setting unit 305_2b determines that the filtering process by the deblocking filter 305_1 is off. If not determined, the process proceeds to step S16b.

(Step S14b)
The reference area setting unit 305_2b sets “0” to the reference restriction boundary variable K2.

(Step S16b)
The reference area setting unit 305_2b sets “NDB” to the reference restriction boundary variable K2. NDB is four, for example.

(Detail of reference area)
FIG. 12 is a diagram for describing the details of the reference area in the present embodiment. The reference area setting unit 305_2b derives the reference area according to the position of the target pixel and the reference restriction line.

FIG. 12A shows a reference area when the target pixel is located at the top part. When the target pixel tp is in the top part, the reference area setting unit 305_2b sets the area between the first reference restriction line vbLine1 and the second reference restriction line vbLine2 as a reference area. The reference area setting unit 305_2b sets the pixel position yMin at the lower limit in the vertical direction in the reference area to a position separated from the upper CTU boundary by the reference restriction boundary variable K1 pixel. In addition, the reference area setting unit 305_2b sets the pixel position yMax at the upper limit in the vertical direction in the reference area to a position away from the lower CTU boundary by (reference restriction boundary variable K2-1) pixels.

(B) of FIG. 12 shows a reference area when the target pixel is located in the bottom part. When the target pixel bp is in the bottom part, the reference area setting unit 305_2b sets the area between the second reference restriction line vbLine2 and the third reference restriction line vbLine3 as a reference area. The reference area setting unit 305_2b sets the pixel position yMin at the lower limit in the vertical direction in the reference area to a position away from the lower CTU boundary by the reference restriction boundary variable K2 pixels. In addition, the reference area setting unit 305_2b sets the pixel position yMax at the upper limit in the vertical direction in the reference area to a position away from the lower CTU boundary by (reference restriction boundary variable K2-1) pixels.

FIG. 13 is a flowchart showing details of processing executed by the reference region setting unit 305_2b of the loop filter 305 according to the present embodiment.

(Step S22)
The reference area setting unit 305_2b determines whether the target pixel is positioned at the top part or the bottom part. If it is determined that the target pixel is located at the top part, the process proceeds to step S24. On the other hand, if it is determined that the target pixel is located at the bottom part, the process proceeds to step S26.

(Step S24)
The reference area setting unit 305_2b sets the pixel position yMin at the lower limit in the vertical direction in the reference area to the first reference restriction line vbLine1 and sets the pixel position yMax at the upper limit in the vertical direction in the reference area to the second reference restriction line vbLine2. Set to the value obtained by subtracting 1 from.

(Step S26)
The reference area setting unit 305_2b sets the pixel position yMin at the lower limit in the vertical direction in the reference area to the second reference restriction line vbLine2, and the pixel position yMax at the upper limit in the vertical direction in the reference area to the third reference restriction line vbLine3. Set to the value obtained by subtracting 1 from.

(Step S28)
The reference area setting unit 305_2b corrects the position of the reference pixel when the position of the reference pixel is out of the reference area.

FIG. 16 is a diagram showing an example of reference pixel position setting processing by the reference region setting unit 305_2b of the loop filter 305 according to the present embodiment.

In the CTU shown in FIG. 16, the target pixel tp is located at the top part. Also, in the CTU shown in FIG. 16, the filter reference area is a diamond. Since the target pixel tp is located at top part, the upper limit in the vertical direction in the reference area is set to yMax.

(A) of FIG. 16 shows the case where the pixel on the second reference restriction line vbLine2 is used. As illustrated in (a) of FIG. 16, the reference area setting unit 305_2b replaces the pixel value of the reference pixel outside the reference area with the pixel value of the reference pixel on yMax at the same horizontal position.

(B) of FIG. 16 shows the case where the central pixel of the reference pixel group is used. As illustrated in (b) of FIG. 16, the reference area setting unit 305_2b replaces the pixel value of the reference pixel outside the reference area with the pixel value of the central pixel of the reference pixel group. In the case shown in (b) of FIG. 16, the central pixel of the reference pixel group is a target pixel. In the case shown in (b) of FIG. 16, the reference area setting unit 305_2b adds the value of the weighting factor of the reference pixel outside the reference area to the weighting factor of the central pixel within the filter reference area. The weighting factor of the reference pixel is set to 0. More specifically, when the weighting coefficients of reference pixels outside the reference region in the filter reference region are expressed as WA and WB, and the weighting coefficient of the central pixel is expressed as WC, the reference region setting unit 305_2b is After setting the weight coefficient of the central pixel to WC + WA + WB, the weight coefficients WA and WB are set to 0.

FIG. 16C shows the case where a pixel group (also referred to as “center line pixel”) having the same position in the vertical direction as the central pixel of the reference pixel group is used. As shown in (c) of FIG. 16, the reference area setting unit 305_2b replaces the pixel values of the reference pixels outside the reference area with the pixel values of the center line pixels at the same horizontal position.

(D) of FIG. 16 shows the case where the pixel of the position which becomes line symmetry (mirror symmetry) is made centering on the 2nd reference restriction line vbLine2. As shown in (d) of FIG. 16, the reference area setting unit 305_2b sets the pixel values of the reference pixels outside the reference area to the pixel values of the pixels at positions that are line symmetrical with respect to the second reference limit line vbLine2. replace.

(Details of correction of reference pixel position)
The specific flow of correction of the position of the reference pixel by the adaptive filter 305a_2 will be described below. Steps S1-1 to S1-7 are executed for each filter coefficient (i = 0..NALF_FLT_TAP-1) with respect to the coordinates (x, y) of the target pixel, and the position of the reference pixel (xPos [i] , YPos [i]). Step S1-8 is executed using the derived position (xPos [i], yPos [i]) (i = 0. NALF_FLT_TAP-1) of the reference pixel, and the filtering process is performed. Hereinafter, the upper left of the picture is not limited to the picture but may be the upper left of the slice or the upper left of the tile. Here, NALF_FLT_TAP is a parameter indicating the number of taps of the adaptive filter ALF, in other words, the number of pixels on one side of the filter reference area to which the adaptive filter ALF refers.
(Step S1-1) The target pixel setting unit 305_2a calculates the x coordinate xx based on the upper left of the picture by adding x to the x coordinate xCB on the upper left of the CU. Further, y is added to the y coordinate yCB at the upper left of CU to calculate the y coordinate yy based on the upper left of the picture.
(Step S1-2) Subsequently, the target pixel setting unit 305_2a derives coordinates (xInCTU, yInCTU) based on the CTU upper left as coordinates (xx, yy) based on the upper left of the picture. Specifically, the remainder obtained by dividing xx by the CTU size at step S1-1 is substituted into a variable xInCTU, and the remainder calculated by dividing y calculated at step S1-1 by the CTU size is substituted into a variable yInCTU.
(Step S1-3) Subsequently, the reference area setting unit 305_2b sets the horizontal and vertical positions horPos [i] and verPos [i] from the target pixel corresponding to the index i of the filter coefficient as reference pixels. Are substituted as the X coordinate xPos [i] of Y and the Y coordinate yPos [i] of the reference pixel.
(Step S1-4) Subsequently, the reference area setting unit 305_2b substitutes 0 for the reference restriction boundary variable K1 when the process of the deblock filter is off with respect to the upper CTU boundary for the CTU to which the target pixel belongs. When the process is on, NDF is substituted for the reference restriction boundary variable K1. Further, for the CTU to which the target pixel belongs, when the deblock filter processing is off with respect to the lower CTU boundary, 0 is substituted into the reference limit boundary variable K2, and when the processing is on, the reference limit boundary variable K2 is Substitute NDF.
(Step S1-5) Subsequently, the reference area setting unit 305_2b substitutes a value obtained by adding a minus sign to the reference restriction boundary variable K1 to the reference restriction line vbLine1. The reference area setting unit 305_2b substitutes a value obtained by subtracting the reference restriction boundary variable K2 from the CTU size into the reference restriction line vbLine2. The reference area setting unit 305_2b substitutes a value obtained by adding the reference restriction boundary variable K2 to the CTU size, to the reference restriction line vbLine3.
(Step S1-6) Subsequently, when the Y coordinate yInCTU of the target pixel is less than the reference restriction line vbLine2, the reference area setting unit 305_2b substitutes the reference restriction line vbLine1 for the lower limit yMin of the reference area, and the upper limit of the reference area. Substitute the value obtained by subtracting 1 from the reference restriction line vbLine2 into yMax. On the other hand, when the Y coordinate yInCTU of the target pixel is equal to or more than the reference restriction line vbLine2, the reference area setting unit 305_2b substitutes the reference restriction line vbLine2 for the lower limit yMin of the reference area and starts the reference restriction line vbLine3 for the upper limit yMax of the reference area. Substitute 1 minus the value.
(Step S1-7) Subsequently, the reference area setting unit 305_2b corrects the reference position by any of the following methods.
(A) The reference area setting unit 305_2b uses a value obtained by clipping the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel between the lower limit yMin of the reference area and the upper limit yMax of the reference area. The value obtained by subtracting the Y coordinate yInCTU of the target pixel is substituted into the Y coordinate yPos [i] of the reference pixel (see (a) in FIG. 16).
(B) If the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference region, the reference region setting unit 305_2b, or the Y coordinate yInCTU of the target pixel and the reference pixel If the sum with the Y coordinate yPos [i] exceeds the upper limit yMax of the reference area, 0 is substituted for the X coordinate xPos [i] and the Y coordinate yPos [i] of the reference pixel (see (b) in FIG. 16).
(C) If the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference region, the reference region setting unit 305_2b, or the Y coordinate yInCTU of the target pixel and the reference pixel If the sum with the Y coordinate yPos [i] exceeds the upper limit yMax of the reference area, 0 is substituted for the Y coordinate yPos [i] of the reference pixel (see (c) in FIG. 16).
(D) If the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference region, the reference region setting unit 305_2b calculates the target pixel from twice the lower limit yMin of the reference region. The value obtained by subtracting twice the Y coordinate yInCTU of and the Y coordinate yPos [i] of the reference pixel is substituted for the Y coordinate yPos [i] of the reference pixel. In addition, when the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel exceeds the upper limit yMax of the reference region, the reference region setting unit 305_2b calculates twice the upper limit yMax of the reference region to the target pixel A value obtained by subtracting twice the Y coordinate yInCTU and the Y coordinate yPos [i] of the reference pixel is substituted for the Y coordinate yPos [i] of the reference pixel (see (d) in FIG. 16).
(Step S1-8) Subsequently, the filter processing unit 305_2c calculates the reference pixel refSamples [xPos [i]] [yPos [i]] of the derived reference pixel position xPos [i], yPos [i] and the filter coefficient flt. Filter based on [i]. Specifically, for each i (i = 0 .. NALF_FLT_TAP-1), the sum of products of reference pixels and filter coefficients is derived, and the derived product sum is shifted to derive the filter value pixel value. The offset coefficient may be added before shifting.

The above process flow is as follows, using pseudo code as an example.
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCb, yCb) of the CU
xx = xCb + x, yy = yCb + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = xx + horPos [i]
yPos [i] = yy + verPos [i]
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = -K1
vbLine2 = CtuSize-K2
vbLine3 = CtuSize + K2
// Set reference range according to target pixel position
// If the target pixel is in the top part, the restriction between the reference restriction line vbLine1 and the reference restriction line vbLine2
// Otherwise (if the target pixel is in the bottom part), limit between the reference limit line vbLine2 and the next second reference limit line vbLine3
if (yInCTU <vbLine2) {yMin = vbLine1, yMax = vbLine2-1}
if (yInCTU> = vbLine2) {yMin = vbLine2, yMax = vbLine3-1}
// Reference position correction (any one of (a), (b), (c) and (d) below can be used)
yPos [i] = Clip3 (yMin, yMax, yInCTU + yPos [i])-yInCTU // (a) In the case of boundary pixel use
if (yPos [i] <yMin | | yPos [i]> yMax) {xPos [i] = xInCTU, yPos [i] = yInCTU} // (b) When using center pixel
if (yPos [i] <yMin | | yPos [i]> yMax) {yPos [i] = yInCTU} // (c) When using center line
if (yPos [i] <yMin) {yPos [i] = 2 * yMin-yPos [i]} // (d) In the case of using mirror pixels
if (yPos [i]> yMax) {yPos [i] = 2 * yMax-yPos [i]} // (d) In the case of using mirror pixels
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [xPos [i]] [yPos [i]] * fltCoeff [i]
The following pseudo code is also equivalent to the above.
// For each i = 0..NALF_FLT_TAP-1, derive the position xPos [i], yPos [i] of the reference pixel
// CTU position calculation
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCB, yCB) of CU
xx = xCB + x, yy = yCB + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = horPos [i]
yPos [i] = verPos [i]
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = -K1
vbLine2 = CtuSize-K2
vbLine3 = CtuSize + K2
// Set reference range according to target pixel position
// If the target pixel is in the top part, the restriction between the reference restriction line vbLine1 and the reference restriction line vbLine2
// Otherwise (if the target pixel is in the bottom part), limit between the reference limit line vbLine2 and the next second reference limit line vbLine3
if (yInCTU <vbLine2) {yMin = vbLine1, yMax = vbLine2-1}
if (yInCTU> = vbLine2) {yMin = vbLine2, yMax = vbLine3-1}
// Reference position correction (any one of (a), (b), (c) and (d) below can be used)
yPos [i] = Clip3 (yMin, yMax, yInCTU + yPos [i])-yInCTU
// (a) In the case of boundary pixel use
if (yInCTU + yPos [i] <yMin || yInCTU + yPos [i]> yMax) {xPos [i] = 0, yPos [i] = 0} // (b) In the case of central pixel use
if (yInCTU + yPos [i] <yMin || yInCTU + yPos [i]> yMax) {yPos [i] = 0}
// (c) When using center line
if (yInCTU + yPos [i] <yMin) {yPos [i] = 2 * (yMin-yInCTU)-yPos [i]}
if (yInCTU + yPos [i]> yMax) {yPos [i] = 2 * (yMax-yInCTU)-yPos [i]}
// (d) In the case of using mirror pixel
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [xx + xPos [i]] [yy + yPos [i]] * fltCoeff [i]
Here, refSamples [xPos] [yPos] is a reference pixel of coordinates (xPos, yPos) based on the pixel to be filtered (xx, yy). The reference pixel uses the input pixel of the adaptive filter.

According to the present embodiment, the adaptive filter 305 _ 2 sets reference restriction lines at different positions depending on whether the filtering process by the deblocking filter 305 _ 1 is on or off, and the pixel values located in the reference area Can be filtered efficiently.

Second Embodiment
A specific flow of correction of the position of the reference pixel by the adaptive filter 305_2 of the loop filter 305 according to the second embodiment will be described.

The second embodiment differs from the first embodiment in that the same reference restriction boundary variable is set in the upper CTU boundary and the lower CTU boundary.
(Step S2-1) A process similar to the above (step S1-1) is performed.
(Step S2-2) The same processing as the above (Step S1-2) is performed.
(Step S2-3) The same processing as the above (Step S1-3) is performed.
(Step S2-4) Subsequently, the reference area setting unit 305_2b substitutes 0 for the reference restriction boundary variable K when the process of the deblocking filter is off, and the reference restriction boundary variable K when the process is on. Substitute NDF into
(Step S2-5) Subsequently, the reference area setting unit 305_2b substitutes a value obtained by adding a minus sign to the reference restriction boundary variable K to the reference restriction line vbLine1. In addition, the reference area setting unit 305_2b substitutes a value obtained by subtracting the reference restriction boundary variable K from the CTU size into the reference restriction line vbLine2. The reference area setting unit 305_2b substitutes a value obtained by adding the reference restriction boundary variable K to the CTU size for the reference restriction line vbLine3.
(Step S2-6) Subsequently, when the Y coordinate yInCTU of the target pixel is less than the reference restriction line vbLine2, the reference area setting unit 305_2b substitutes the reference restriction line vbLine1 for the lower limit yMin of the reference area, and the upper limit of the reference area. Substitute the value obtained by subtracting 1 from the reference restriction line vbLine2 into yMax. On the other hand, when the Y coordinate yInCTU of the target pixel is equal to or more than the reference restriction line vbLine2, the reference area setting unit 305_2b substitutes the reference restriction line vbLine2 for the lower limit yMin of the reference area and starts the reference restriction line vbLine3 for the upper limit yMax of the reference area. Substitute 1 minus the value.
(Step S2-7) The same processing as the above (step S1-7) is performed.
(Step S2-8) The same processing as the above (step S1-8) is performed.

The above process flow is as follows, using pseudo code as an example.
// For each i = 0..NALF_FLT_TAP-1, derive the position xPos [i], yPos [i] of the reference pixel
// CTU position calculation
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCB, yCB) of CU
xx = xCB + x, yy = yCB + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = horPos [i]
yPos [i] = verPos [i]
// Reference restriction line setting
K = deblocking filter off? 0: NDF
vbLine1 = -K
vbLine2 = CtuSize-K
vbLine3 = CtuSize + K
// Set reference range according to target pixel position
yMin = vbLine1, yMax = vbLine3-1
if (yInCTU <vbLine2) {yMax = vbLine2-1}
if (yInCTU> = vbLine2) {yMin = vbLine2}
// Reference position correction (any one of (a), (b), (c) and (d) of step S1-7 can be used, only (a) is displayed here)
yPos [i] = Clip3 (yMin, yMax, yInCTU + yPos [i])-yInCTU
// (a) In the case of boundary pixel use
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [xx + xPos [i]] [yy + yPos [i]] * fltCoeff [i]
Third Embodiment
The third embodiment differs from the first embodiment in that the position in a picture is calculated.

A specific flow of correction of the position of the reference pixel by the adaptive filter 305_2 of the loop filter 305 according to the third embodiment will be described.
(Step S3-1) The same processing as the above (step S1-1) is performed.
(Step S3-2) Subsequently, the target pixel setting unit 035_2a multiplies the CTU size by the value obtained by dividing the coordinates (xx, yy) based on the upper left of the picture by the CTU size, thereby setting the upper left coordinate of the CTU of the target picture. Calculate (xCTU, yCTU).
(Step S3-3) The same processing as the above (step S1-2) is performed.
(Step S3-4) The reference region setting unit 305_2b sets values obtained by adding horPos [i] and verPos [i] as xxPos [i] and yPos [i], and xx and yy. .
(Step S3-5) Subsequently, the reference area setting unit 305_2b substitutes a value obtained by subtracting the reference restriction boundary variable K1 from the x coordinate yCTU in the picture into the reference restriction line vbLine1. The reference area setting unit 305_2b adds the CTU size to the CTU coordinates yCTU, and substitutes a value obtained by subtracting the reference restriction boundary variable K2 into the reference restriction line vbLine2. The reference area setting unit 305_2b adds the CTU size to the CTU coordinates yCTU, and substitutes a value obtained by adding the reference restriction boundary variable K2 to the reference restriction line vbLine3.
(Step S3-6) Subsequently, when the y coordinate yy of the target pixel is less than the reference limit line vbLine2, the reference area setting unit 305_2b substitutes the reference limit line vbLine1 for the lower limit yMin of the reference area, and the upper limit of the reference area. Substitute the value obtained by subtracting 1 from the reference restriction line vbLine2 into yMax. On the other hand, when the y coordinate yy of the target pixel is equal to or more than the reference restriction line vbLine2, the reference area setting unit 305_2b substitutes the reference restriction line vbLine2 for the lower limit yMin of the reference area, and the reference restriction line vbLine3 for the upper limit yMax of the reference area. Substitute 1 minus the value.
(Step S3-7) Subsequently, the reference area setting unit 305_2b corrects the reference position by any of the following methods.
(A) The reference area setting unit 305_2b clips a value obtained by clipping the Y coordinate yPos [i] of the reference pixel between the lower limit yMin of the reference area and the upper limit yMax of the reference area, and the Y coordinate yPos [i] of the reference pixel. (Refer to (a) of FIG. 16).
(B) The reference area setting unit 305_2b refers to the case where the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference area or the Y coordinate yPos [i] of the reference pixel exceeds the upper limit yMax of the reference area. The position xx of the target pixel is substituted into the X coordinate xPos [i] of the pixel, and the position yy of the target pixel is substituted into the position yPos [i] of the reference pixel in the y direction (see (b) in FIG. 16).
(C) The reference area setting unit 305_2b refers to the case where the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference area or the Y coordinate yPos [i] of the reference pixel exceeds the upper limit yMax of the reference area. Yy is substituted for the Y coordinate yPos [i] of the pixel (see (c) in FIG. 16).
(D) The reference area setting unit 305_2b subtracts the Y coordinate yPos [i] of the reference pixel from twice the lower limit yMin of the reference area if the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference area. A value is substituted into the Y coordinate yPos [i] of the reference pixel. Further, when the Y coordinate yPos [i] of the reference pixel exceeds the upper limit yMax of the reference region, the reference region setting unit 305_2b subtracts the Y coordinate yPos [i] of the reference pixel from twice the upper limit yMax of the reference region. Is substituted into the Y coordinate yPos [i] of the reference pixel (see (d) in FIG. 16).
(Step S3-8) The same processing as the above (step S1-8) is performed.

The above process flow is as follows, using pseudo code as an example.
// For each i = 0..NALF_FLT_TAP-1, derive the position xPos [i], yPos [i] of the reference pixel
// CTU position calculation
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCB, yCB) of CU
xx = xCB + x, yy = yCB + y
xCTU = (x / CtuSize) * CtuSize // = (x >> log2CtuSize) << log2CtuSize
yCTU = (y / CtuSize) * CtuSize // = (y >> log2CtuSize) << log2CtuSize
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = xx + horPos [i]
yPos [i] = yy + verPos [i]
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = yCTU-K1
vbLine2 = yCTU + CtuSize-K2
vbLine3 = yCTU + CtuSize + K2
// Set reference range according to target pixel position
if (yy <vbLine2) {yMin = vbLine1, yMax = vbLine2-1} // target pixel position is top partif (yy> = vbLine2) {yMin = vbLine2, yMax = vbLine3-1} // target pixel position is bottom part
// Reference position correction (any one of (a), (b), (c) and (d) below can be used)
yPos [i] = Clip3 (yMin, yMax, yPos [i]) // (a) In the case of using boundary pixels
if (yPos [i] <yMin | | yPos [i]> yMax) {xPos [i] = xx, yPos [i] = yy} // (b) When using central pixel
if (yPos [i] <yMin | | yPos [i]> yMax) {yPos [i] = yy} // (c) When using center line
if (yPos [i] <yMin) {yPos [i] = 2 * yMin-yPos [i]}
if (yPos [i]> yMax) {yPos [i] = 2 * yMax-yPos [i]} // (d) In the case of using mirror pixels
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [xPos [i]] [yPos [i]] * fltCoeff [i]
Fourth Embodiment
The fourth embodiment differs from the first embodiment in that the boundary distance is calculated. Boundary distance refers to the distance from a certain y coordinate to a reference restriction line.

A specific flow of correction of the position of the reference pixel by the adaptive filter 305_2 of the loop filter 305 according to the fourth embodiment will be described.
(Step S4-1) A process similar to the above (step S1-1) is performed.
(Step S4-2) The same processing as the above (Step S1-2) is performed.
(Step S4-3) The reference area setting unit 305_2b sets values obtained by adding xInCTU and yInCTU to horPos [i] and verPos [i] as xPos [i] and yPos [i]. .
(Step S4-4) The same processing as the above (step S1-4) is performed.
(Step S4-5) The same processing as the above (step S1-5) is performed.
(Step S4-6) Subsequently, the reference area setting unit 305_2b substitutes a value obtained by subtracting the reference restriction line vbLine2 from the remainder obtained by dividing y calculated in step S4-1 by the CTU size into the boundary distance dist2VB.
(Step S4-7) Subsequently, when the boundary distance dist2VB is less than 0, the reference area setting unit 305_2b substitutes the reference restriction line vbLine1 into the lower limit yMin of the reference area, and the reference restriction line vbLine2 into the upper limit yMax of the reference area. Substitute 1 minus the value. On the other hand, when the boundary distance dist2VB is 0 or more, the reference area setting unit 305_2b substitutes the reference restriction line vbLine2 for the lower limit yMin of the reference area, and substitutes the value obtained by subtracting 1 from the reference restriction line vbLine3 for the upper limit yMax of the reference area. .

Alternatively, when the boundary distance dist2VB is less than 0, the reference region setting unit 305_2b substitutes the reference restriction line vbLine1 into the lower limit yMin of the reference region, and adds 1 to the value obtained by adding 1 to the upper limit yMax of the reference region. Assign the multiplied value. On the other hand, when the boundary distance dist2VB is 0 or more, the reference region setting unit 305_2b substitutes the boundary distance dist2VB for the lower limit yMin of the reference region, and substitutes a value obtained by subtracting 1 from the reference limit line vbLine3 for the upper limit yMax of the reference region.
(Step S4-8) Subsequently, the reference area setting unit 305_2b corrects the reference position by any one of the following methods.
(A) The reference area setting unit 305_2b uses a value obtained by clipping the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel between the lower limit yMin of the reference area and the upper limit yMax of the reference area. The value obtained by subtracting the Y coordinate yInCTU of the target pixel is substituted into the Y coordinate yPos [i] of the reference pixel (see (a) in FIG. 16).
(B) If the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference region, the reference region setting unit 305_2b, or the Y coordinate yInCTU of the target pixel and the reference pixel
If the sum with the Y coordinate yPos [i] exceeds the upper limit yMax of the reference area, 0 is substituted for the X coordinate xPos [i] and the Y coordinate yPos [i] of the reference pixel (see (b) in FIG. 16).
(C) If the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference region, the reference region setting unit 305_2b, or the Y coordinate yInCTU of the target pixel and the reference pixel If the sum with the Y coordinate yPos [i] exceeds the upper limit yMax of the reference area, 0 is substituted for the Y coordinate yPos [i] of the reference pixel (see (c) in FIG. 16).
(D) If the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference region, the reference region setting unit 305_2b determines that the reference pixel is twice as large as the lower limit yMin of the reference region. The value obtained by subtracting the Y coordinate yPos [i] of is assigned to the Y coordinate yPos [i] of the reference pixel. Further, when the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel exceeds the upper limit yMax of the reference region, the reference region setting unit 305_2b starts at twice the upper limit yMax of the reference region The value obtained by subtracting the Y coordinate yPos [i] is substituted for the Y coordinate yPos [i] of the reference pixel (see (d) in FIG. 16).
(Step S4-9) The same processing as the above (step S1-8) is performed.

The above process flow is as follows, using pseudo code as an example.
// For each i = 0..NALF_FLT_TAP-1, derive the position xPos [i], yPos [i] of the reference pixel
// CTU position calculation
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCB, yCB) of CU
xx = xCB + x, yy = yCB + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = horPos [i] + xInCTU
yPos [i] = verPos [i] + yInCTU
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = -K1
vbLine2 = CtuSize-K2
vbLine3 = CtuSize + K2
// Boundary distance calculation
dist2VB = yInCTU-vbLine2
// Reference range setting according to boundary distance
if (dist2VB <0) {yMin = vbLine1, yMax = vbLine2-1} // Target pixel position is top partif (dist2VB> = 0) {yMin = vbLine2, yMax = vbLine3-1} // Target pixel position is bottom part
The following expressions are also possible
if (dist2VB <0) {yMin = vbLine1, yMax =-dist2VB-1} // top part
if (dist2VB> = 0) {yMin = dist2VB, yMax = vbLine3-1} // bottom part (otherwise)
// Reference position correction (any one of (a), (b), (c) and (d) below can be used)
yPos [i] = Clip3 (yMin, yMax, yPos [i]) // (a) In the case of using boundary pixels
if (yPos [i] <yMin | | yPos [i]> yMax) {xPos [i] = 0, yPos [i] = 0} // (b) When using central pixel
if (yPos [i] <yMin || yPos [i]> yMax) {yPos [i] = 0} // (c) When using center line
if (yPos [i] <yMin) {yPos [i] = 2 * yMin-yPos [i]}
if (yPos [i]> yMax) {yPos [i] = 2 * yMax-yPos [i]} // (d) In the case of using mirror pixels
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [(xx / CtuSize) * CtuSize + xPos [i]] [(yy / CtuSize) * CtuSize + yPos [i]] * fltCoeff [i]
Fifth Embodiment
The fifth embodiment differs from the first embodiment in that a table determined according to the boundary distance is referred to.

FIG. 14 is an example of a table referred to by the reference region setting unit 305_2b of the loop filter 305 according to the present embodiment. The table shown in FIG. 14 is determined according to the boundary distance dist2VB.

A specific flow of correction of the position of the reference pixel by the adaptive filter 305_2 of the loop filter 305 according to the fifth embodiment will be described.
(Step S5-1) The same processing as the above (step S1-1) is performed.
(Step S5-2) The same processing as the above (step S1-2) is performed.
(Step S5-3) The same processing as the above (Step S1-4) is performed.
(Step S5-4) The same processing as the above (step S1-5) is performed.
(Step S5-5) The same processing as the above (step S4-6) is performed.
(Step S5-6) Subsequently, the reference area setting unit 305_2b refers to the horizontal position horPos [i] corresponding to i (i = 0..NALF_FLT_TAP-1) with reference to the table shown in FIG. Substitute into the X coordinate xPos [i] of the reference pixel. Further, the reference region setting unit 305_2b refers to the position verPos [i] in the vertical direction corresponding to i (i = 0..NALF_FLT_TAP-1) with reference to the table shown in FIG. Assign to i].
(Step S5-7) The same processing as the above (step S1-8) is performed.

The above process flow is as follows, using pseudo code as an example.
// For each i = 0..NALF_FLT_TAP-1, derive the position xPos [i], yPos [i] of the reference pixel
// CTU position calculation
// (x, y) is the coordinate based on the upper left coordinate (xCb, yCb) of CU
xx = xCb + x, yy = yCb + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = -K1
vbLine2 = CtuSize-K2
vbLine3 = CtuSize + K2
// Boundary distance dist2VB calculation
dist2VB = yInCTU-vbLine2
// Reference position setting according to the table determined according to boundary distance dist2VB
if (dist2VB <-3 || dist2VB> 2) k = 0
else if (dist2VB ==-3 || dist2VB == 2) k = 1
else if (dist2VB == -2 || dist2VB == 1) k = 2
else k = 3 // dist2VB ==-1 || dist2VB == 0
xPos [i] = horPos [i]
yPos [i] = verPos [k] [i]
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [xx + xPos [i]] [yy + yPos [i]] * fltCoeff [i]
Here, refSamples [xPos] [yPos] is a reference pixel of coordinates (xPos, yPos) based on the pixel to be filtered (xx, yy). Note that (x, y) is (xInCTU, yInCTU) in the in-screen position of the target pixel or in the CTU. The reference pixel uses the input pixel of the adaptive filter.

Sixth Embodiment
The sixth embodiment differs from the above embodiments in that the reference area is limited in the horizontal direction.

FIG. 15 is a diagram illustrating another example of the reference restriction line set by the reference region setting unit 305_2b of the loop filter 305 according to the sixth embodiment.

(A) of FIG. 15 shows the reference area in the case where the target pixel is located at the left part. When the target pixel lp is in the left part, it is between the reference restriction line vbCol1 located apart from the CTU boundary on the left by L1 pixels and the reference restriction line vbCol2 located apart from the CTU boundary on the right by L2 pixels on the left Is the reference area.

(B) of FIG. 15 shows a reference area when the target pixel is located in the right part. When the target pixel rp is in the right part, the reference restriction line vbCol2 located on the left side from the CTU boundary on the right side by L2 pixels and the reference restriction line vbCol3 located on the right side from the CTU boundary on the right side by L2 pixels Is the reference area.

A specific flow of correction of the position of the reference pixel by the adaptive filter 305_2 of the loop filter 305 according to the sixth embodiment will be described.
(Step S6-1) A process similar to the above (step S1-1) is performed.
(Step S6-2) The same processing as the above (Step S1-2) is performed.
(Step S6-3) The same processing as the above (step S4-3) is performed.
(Step S6-4) The same processing as the above (Step S1-4) is performed.
(Step S6-5) The same processing as the above (Step S1-5) is performed.
(Step S6-6) Subsequently, the reference area setting unit 305_2b substitutes 0 for the reference restriction boundary variable L1 when the process of the deblock filter is off with respect to the left CTU boundary, and the process is ON. The NDF is substituted for the reference restriction boundary variable L1. When the deblocking filter process is off for the right CTU boundary, 0 is substituted into the reference restriction boundary variable L2, and when the process is on, NDF is substituted into the reference restriction boundary variable L2.
(Step S6-7) Subsequently, the reference area setting unit 305_2b substitutes a value obtained by adding a minus sign to the reference restriction boundary variable L1 to the reference restriction line vbCol1. In addition, the reference area setting unit 305_2b substitutes a value obtained by subtracting the reference restriction boundary variable L2 from the CTU size into the reference restriction line vbCol2. The reference area setting unit 305_2b substitutes a value obtained by adding the reference restriction boundary variable L2 to the CTU size, to the reference restriction line vbCol3.
(Step S6-8) The same processing as the above (Step S1-6) is performed.
(Step S6-9) Subsequently, when the X coordinate xInCTU of the target pixel is less than the reference restriction line vbCol2, the reference area setting unit 305_2b substitutes the reference restriction line vbCol1 for the left end xMin of the reference area, and the reference area The value obtained by subtracting 1 from the reference restriction line vbCol2 is assigned to the right end xMax of. On the other hand, when the X coordinate xInCTU of the target pixel is equal to or more than the reference restriction line vbCol2, the reference area setting unit 305_2b substitutes the reference restriction line vbCol2 for the left end xMin of the reference area and refers to the end xMax for the right side of the reference area. Substitute the value obtained by subtracting 1 from the limit line vbCol3.
(Step S6-10) Subsequently, the reference area setting unit 305_2b corrects the reference position by any of the following methods.
(A) The reference area setting unit 305_2b adds the sum of the X coordinate xInCTU of the target pixel and the X coordinate xPos [i] of the reference pixel to the left end xMin of the reference area and the right end xMax of the reference area. A value obtained by subtracting the X coordinate xInCTU of the target pixel from the clipped value is substituted for the X coordinate xPos [i] of the reference pixel.

In addition, the reference area setting unit 305_2b is a target based on a value obtained by clipping the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel between the lower limit yMin of the reference area and the upper limit yMax of the reference area. The value obtained by subtracting the Y coordinate yInCTU of the pixel is substituted for the Y coordinate yPos [i] of the reference pixel (see (a) in FIG. 16).
(B) If the sum of the X coordinate xInCTU of the target pixel and the X coordinate xPos [i] of the reference pixel is less than the left end xMin of the reference region, the reference region setting unit 305_2b determines the X coordinate xInCTU of the target pixel and the reference pixel If the sum of the x coordinate xPos [i] of the x exceeds the upper limit xMax on the right side of the reference area, the sum of the Y coordinate yInCTU of the target pixel and the y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference area Or when the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel exceeds the upper limit yMax of the reference area, 0 in the X coordinate xPos [i] and the Y coordinate yPos [i] of the reference pixel Is substituted (see (b) in FIG. 16).
(C) If the sum of the X coordinate xInCTU of the target pixel and the X coordinate xPos [i] of the reference pixel is less than the left end xMin of the reference region, the reference region setting unit 305_2b determines the X coordinate xInCTU of the target pixel and the reference pixel The sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference area, when the sum of the X coordinate xPos [i] of x exceeds the right end xMax of the reference area Or, if the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel exceeds the upper limit yMax of the reference area, 0 is substituted for the Y coordinate yPos [i] of the reference pixel (see FIG. c) see
(D) If the sum of the X coordinate xInCTU of the target pixel and the X coordinate xPos [i] of the reference pixel is less than the left end xMin of the reference area, the reference area setting unit 305_2b 2 of the left end xMin of the reference area A value obtained by subtracting the double of the X coordinate xInCTU of the target pixel and the X coordinate xPos [i] of the reference pixel from the double is substituted for the X coordinate xPos [i] of the reference pixel. Further, when the sum of the X coordinate xInCTU of the target pixel and the X coordinate xPos [i] of the reference pixel exceeds the right end xMax of the reference area, the reference area setting unit 305_2b doubles the right end xMax of the reference area. A value obtained by subtracting twice the X coordinate xInCTU of the target pixel and the X coordinate xPos [i] of the reference pixel from is substituted into the X coordinate xPos [i] of the reference pixel.

Further, when the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel is less than the lower limit yMin of the reference region, the reference region setting unit 305_2b determines that the target pixel is twice the lower limit yMin of the reference region. A value obtained by subtracting twice the Y coordinate yInCTU and the Y coordinate yPos [i] of the reference pixel is substituted for the Y coordinate yPos [i] of the reference pixel. In addition, when the sum of the Y coordinate yInCTU of the target pixel and the Y coordinate yPos [i] of the reference pixel exceeds the upper limit yMax of the reference region, the reference region setting unit 305_2b calculates twice the upper limit yMax of the reference region to the target pixel A value obtained by subtracting twice the Y coordinate yInCTU and the Y coordinate yPos [i] of the reference pixel is substituted for the Y coordinate yPos [i] of the reference pixel (see (d) in FIG. 16).
(Step S6-11) The same processing as the above (step S1-8) is performed.

The above process flow is as follows, using pseudo code as an example.
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCb, yCb) of the CU
xx = xCb + x, yy = yCb + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = horPos [i] + xInCTU
yPos [i] = verPos [i] + yInCTU
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = -K1
vbLine2 = CtuSize-K2
vbLine3 = CtuSize + K2
L1 = left deblocking filter off? 0: NDF
L2 = Right deblocking filter off? 0: NDF
vbCol1 = -L1
vbCol2 = CtuSize-L2
vbCol3 = CtuSize + L2
// Set reference range according to target pixel position
if (yInCTU <vbLine2) {yMin = vbLine1, yMax = vbLine2-1}
if (yInCTU> = vbLine2) {yMin = vbLine2, yMax = vbLine3-1}
if (xInCTU <vbCol2) {xMin = vbCol1, xMax = vbCol2-1}
if (xInCTU> = vbCol2) {xMin = vbCol2, xMax = vbCol3-1}
// Reference position correction (any one of (a), (b), (c) and (d) below can be used)
xPos [i] = Clip3 (xMin, xMax, xPos [i]) // (a)
yPos [i] = Clip3 (yMin, yMax, yPos [i]) // (a)
yPos [i]> xMax | | yPos [i] <yMin | | yPos [i]> yMax) {xPos [i] = xInCTU, yPos [i] = yInCTU} // (b)
if (xPos [i] <xMin || xPos [i]> xMax) {xPos [i] = xInCTU} // (c)
if (yPos [i] <yMin || yPos [i]> yMax) {yPos [i] = yInCTU} // (c)
if (xPos [i] <xMin) {xPos [i] = 2 * xMin-xPos [i]} if (xPos [i]> xMax) {xPos [i] = 2 * xMax-xPos [i]} // (d)
if (yPos [i] <yMin) {yPos [i] = 2 * yMin-yPos [i]} if (yPos [i]> yMax) {yPos [i] = 2 * yMax-yPos [i]} // (d)
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [xPos [i]] [yPos [i]] * fltCoeff [i]
The above is equivalent to the following.
// For each i = 0..NALF_FLT_TAP-1, derive the position xPos [i], yPos [i] of the reference pixel
// CTU position calculation
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCB, yCB) of CU
xx = xCB + x, yy = yCB + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = horPos [i] + xInCTU
yPos [i] = verPos [i] + yInCTU
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = -K1
vbLine2 = CtuSize-K2
vbLine3 = CtuSize + K2
L1 = left deblocking filter off? 0: NDF
L2 = Right deblocking filter off? 0: NDF
vbCol1 = -L1
vbCol2 = CtuSize-L2
vbCol3 = CtuSize + L2
// Set reference range according to target pixel position
if (yInCTU <vbLine2) {yMin = vbLine1, yMax = vbLine2-1}
if (yInCTU> = vbLine2) {yMin = vbLine2, yMax = vbLine3-1}
if (xInCTU <vbCol2) {xMin = vbCol1, xMax = vbCol2-1}
if (xInCTU> = vbCol2) {xMin = vbCol2, xMax = vbCol3-1}
// Reference position correction (any one of (a), (b), (c) and (d) below can be used)
xPos [i] = Clip3 (xMin, xMax, xInCTU + xPos [i])-xInCTU // (a)
yPos [i] = Clip3 (yMin, yMax, yInCTU + yPos [i])-yInCTU // (a)
if (xInCTU + xPos [i] <xMin || xInCTU + xPos [i]> xMax || yInCTU + yPos [i] <yMin || yInCTU + yPos [i]> yMax) {xPos [i] = 0, yPos [i] = 0} // (b)
if (xInCTU + xPos [i] <xMin || xInCTU + xPos [i]> xMax) {xPos [i] = 0} // (c)
if (yInCTU + yPos [i] <yMin || yInCTU + yPos [i]> yMax) {yPos [i] = 0} // (c)
if (xInCTU + xPos [i] <xMin) {xPos [i] = 2 * (xMin-x InCTU)-xPos [i]} if (xInCTU + xPos [i]> xMax) {xPos [i] = 2 * ( xMax-xInCTU)-xPos [i]} // (d)
if (yInCTU + yPos [i] <yMin) {yPos [i] = 2 * (yMin-yInCTU)-yPos [i]} if (yInCTU + yPos [i]> yMax) {yPos [i] = 2 * ( yMax-yInCTU)-yPos [i]} // (d)
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [(xx / CtuSize) * CtuSize + xPos [i]] [(yy / CtuSize) * CtuSize + yPos [i]] * fltCoeff [i]
Seventh Embodiment
The seventh embodiment differs from the sixth embodiment in that a reference restriction line for restricting the x direction is set without restricting the position of the target pixel.

A specific flow of correction of the position of the reference pixel by the adaptive filter 305_2 of the loop filter 305 according to the seventh embodiment will be described.
(Step S7-1) The same processing as the above (step S6-1) is performed.
(Step S7-2) The same processing as the above (step S6-2) is performed.
(Step S7-3) The same processing as the above (step S6-3) is performed.
(Step S7-4) The same processing as the above (step S6-4) is performed.
(Step S7-5) The same processing as the above (Step S6-5) is performed.
(Step S7-6) The same processing as the above (Step S6-6) is performed.
(Step S7-7) The same processing as the above (Step S6-7) is performed.
(Step S7-8) The same processing as the above (Step S6-8) is performed.
(Step S7-9) Subsequently, the reference area setting unit 305_2b substitutes the reference restriction line vbCol1 into the left end xMin of the reference area, and subtracts 1 from the reference restriction line vbCol3 into the right end xMax of the reference area. substitute.
(Step S7-10) The same processing as the above (Step S6-10) is performed.
(Step S7-11) A process similar to the above (step S6-11) is performed.

The above process flow is as follows, using pseudo code as an example.
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCb, yCb) of the CU
xx = xCb + x, yy = yCb + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = horPos [i] + xInCTU
yPos [i] = verPos [i] + yInCTU
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = -K1
vbLine2 = CtuSize-K2
vbLine3 = CtuSize + K2
L1 = left deblocking filter off? 0: NDF
L2 = Right deblocking filter off? 0: NDF
vbCol1 = -L1
vbCol2 = CtuSize-L2
vbCol3 = CtuSize + L2
// Set reference range according to target pixel position
if (yInCTU <vbLine2) {yMin = vbLine1, yMax = vbLine2-1}
if (yInCTU> = vbLine2) {yMin = vbLine2, yMax = vbLine3-1}
// The reference range may be set in the X direction regardless of the target pixel position
xMin = vbCol1, xMax = vbCol3-1
// Reference position correction (any of the following (a), (b), (c), (d) can be used, (d) is omitted)
xPos [i] = Clip3 (xMin, xMax, xPos [i]) // (a)
yPos [i] = Clip3 (yMin, yMax, yPos [i]) // (a)
xPos [i]> xMax | | yPos [i] <yMin | | yPos [i]> yMax) {xPos [i] = xInCTU, yPos [i] = yInCTU} // (b)
if (xPos [i] <xMin || xPos [i]> xMax) {xPos [i] = xInCTU} // (c)
if (yPos [i] <yMin || yPos [i]> yMax) {yPos [i] = yInCTU} // (c)
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [x] [y] = ref refSamples [xPos [i]] [yPos [i]] * fltCoeff [i]
The above is equivalent to the following processing.
// For each i = 0..NALF_FLT_TAP-1, derive the position xPos [i], yPos [i] of the reference pixel
// CTU position calculation
// (x, y) is the coordinate of the target pixel based on the upper left coordinate (xCb, yCb) of the CU
xx = xCb + x, yy = yCb + y
xInCTU = xx% CtuSize
yInCTU = yy% CtuSize
// Reference position setting
xPos [i] = horPos [i]
yPos [i] = verPos [i]
// Reference restriction line setting
K1 = upper deblocking filter off? 0: NDF
K2 = lower deblocking filter off? 0: NDF
vbLine1 = -K1
vbLine2 = CtuSize-K2
vbLine3 = CtuSize + K2
L1 = left deblocking filter off? 0: NDF
L2 = Right deblocking filter off? 0: NDF
vbCol1 = -L1
vbCol2 = CtuSize-L2
vbCol3 = CtuSize + L2
// Set reference range according to target pixel position
if (yInCTU <vbLine2) {yMin = vbLine1, yMax = vbLine2-1}
if (yInCTU> = vbLine2) {yMin = vbLine2, yMax = vbLine3-1}
// The reference range may be set in the X direction regardless of the target pixel position
xMin = vbCol1, xMax = vbCol3-1
// Reference position correction (any of the following (a), (b), (c), (d) can be used, (d) is omitted)
xPos [i] = Clip3 (xMin, xMax, xPos [i])-xInCTU // (a)
yPos [i] = Clip3 (yMin, yMax, yPos [i])-yInCTU // (a)
if (xInCTU + xPos [i] <xMin || xInCTU + xPos [i]> xMax || yInCTU + yPos [i] <yMin || yInCTU + yPos [i]> yMax) {xPos [i] = 0, yPos [i] = 0} // (b)
if (xInCTU + xPos [i] <xMin || xInCTU + xPos [i]> xMax) {xPos [i] = 0} // (c)
if (yInCTU + yPos [i] <yMin || yInCTU + yPos [i]> yMax) {yPos [i] = 0} // (c)
// Filter based on the derived reference position xPos [i], yPos [i] and the filter coefficient fltCoef [i]
fltSamples [xx] [yy] = ref refSamples [xx + xPos [i]] [yy + yPos [i]] * fltCoeff [i]
(Comparative example 1)
FIG. 17 is a diagram illustrating a reference region in the first comparative example.

As a first comparative example, a virtual boundary technique will be described in which referring to pixels outside the boundary as reference pixels with a virtual boundary line (VB line) several pixels away from the boundary of the target CTU as the boundary is used.

In the virtual boundary technology, the adaptive filter ALF is applied to pixels that have been filtered (also referred to as DF-completed) by the deblocking filter DF. For this reason, it is necessary to know the range of the DF completed area. Here, at the time of applying the adaptive filter ALF to the target CTU, the entire target CTU is not necessarily DF-completed. For example, the top of the CTU may be DFed and the bottom may not yet be DFed. Therefore, the “lower VB line” is set at the boundary of the range of the DF-completed area in the target CTU. When waiting for DF processing of the area below the lower VB line, access to the area below the lower VB line is also possible. However, in this case, (1) processing delay increases, (2) reading back to the frame buffer becomes necessary, and a memory band becomes large.

On the other hand, although the area above the upper CTU boundary is DF-completed, the area above the certain boundary (referred to as "written area") has already been written to the frame buffer, so There is no pixel information in the line memory. For this reason, reference to the pixels in this area is possible by (1) transferring again from the frame buffer, but the memory band becomes large, and (2) it is possible by loading in the line memory, but the line memory Need to increase the size. Therefore, "upper VB line" is set at the boundary with the written area.

As shown in FIG. 17, the area between the upper VB line and the lower VB line is a DF-finished area. In the virtual boundary technology, processing delay, memory band and line memory can be reduced by providing the VB line.

(Comparative example 2)
FIG. 18 is a diagram illustrating a reference region in the second comparative example.

As Comparative Example 2, a technique of changing the setting method of the reference area according to on / off of the filtering process by the deblocking filter will be mentioned. FIG. 18 is a diagram showing a reference region according to on or off of the deblocking filter in the second comparative example.

(A) of FIG. 18 shows the reference area when the deblocking filter is on. When filtering by the deblocking filter is on, the upper VB line is set to a line K above the CTU line, and the area below the upper VB line is set as the reference area of the adaptive filter.

(B) of FIG. 18 shows the reference area when the deblocking filter is off. When filtering by the deblocking filter is off, the upper VB line is set to the CTU line, and the area below the upper VB line is set as the reference area of the adaptive filter. Here, when the deblocking filter is off and the slice in the region above the CTU is different from the slice in the region in the CTU, the region above the CTU can not be referenced in the filtering process by the adaptive filter. Therefore, the area that can be referred to in the filtering process by the adaptive filter is limited to the upper CTU boundary or less.

Eighth Embodiment
Another embodiment of the present invention is described below with reference to FIG. In addition, the description is abbreviate | omitted about the member which has the same function as the member demonstrated in the said embodiment for convenience of explanation.

(Loop filter 305a)
FIG. 19 is a block diagram showing the configuration of the loop filter 305a. As shown in FIG. 19, the loop filter 305a includes a deblocking filter 305_1, an adaptive filter 305a_2, and an internal memory 305_3.

(Adaptive filter 305a_2)
As shown in FIG. 19, the adaptive filter 305a_2 includes a target pixel setting unit 305_2a, a reference area setting unit 305_2b, and a filter processing unit 305a_2c.

(Filtering unit 305a_2c)
The filter processing unit 305a_2c multiplies each of the target pixel in the input image P, the pixels around the target pixel, and the activity calculated by referring to at least a part of the peripheral pixels, by a weighting factor. The point is different from the above embodiment.

The pixel value of the target pixel is s (N / 2), and the pixel values of its peripheral pixels are (s (0) to s (N / 2-1), s (N / 2 + 1) to s (N) In the case of), the filtering process can be expressed by the following equation.

sflt = (Σa (i) * (s (i) + s (Ni)) + a (N / 2) * s (N / 2) + o) >> shift
Here, Σ is the sum of i = 0 to N / 2, a (i) is a filter coefficient, o is an offset, and shift is a coefficient for normalization. As shown in FIG. 20, in the case of N = 24, the above equation can be expressed by the following equation.

sflt = (a0 * (s0 + s24) + a1 * (s1 + s23) + ... + a11 * (s11 + s13) + a12 * s12 + o) >> shift
In the above equation, the filter coefficients are described as a0... A12, and the pixel values are described as s0.

prodFlt = a0 * (s0 + s24) + a1 * (s1 + s23) +... + a11 * (s11 + s13) + a12 * s12
Expressed as, sflt can be expressed by the following equation.

sflt = (prodFlt + o) >> shift
The activity is, for example, SAD (Sum of Absolute Difference, difference absolute value sum) shown by the following equation, and in a region surrounded by a thick line shown in FIG. 20, the pixel value of the target pixel (s12) and pixels around the target pixel Can be calculated by the sum of the absolute values of the difference between each of the pixel values of at least a part of (s7, s11, s13, s17, and also referred to as a set S of pixels).

act (s7, s11, s13, s17) = | s7-s12 | + | s11-s12 | + | s13-s12 | + | s17-s12 |
In general, act () can be represented by the following formula.

act (s (0), s (1), ... s (N)) = = abs (s (i)-s (N / 2))
Here, Σ is the sum of i = 0 to N, N is the number of peripheral pixels, and s (N / 2) is the target pixel.

In the present embodiment, the concept of "intermediate value d" is introduced. The intermediate value d is derived from the sum of the pixel values of the pixels around the target pixel, the pixel value of the target pixel, the activity act (x) of the pixel set S, and the predetermined constant KACT, as shown by the following equation can do.

d = (s0 + s1 + s2 + s3 + ... + s11 + s13 + ... s24-24 * s12) / (KACT + act (s0, s1, s2, ..., s24))
Here, the division can be implemented by combining multiplication processing of the table value table [i] for the divisor i and the dividend, and shift processing. For example, when dividing the dividend xxx by the divisor yyy, it can be processed as the following equation.

xxx / yyy = (xxx * table [yyy] + round) >> tblshift
here,
round = 1 << (tblshift-1)
And table [i] is derived, for example, by the following equation.

table [i] = (1 << tblshift) / i
The adaptive filter 305a_2 uses the intermediate value d as one of the terms of the adaptive filter ALF, for example, as shown in the following equation.

sflt = (prodFlt + b0 * d + o) >> shift
That is, in the filter processing units 305a_2c, processing for right bit shifting the result obtained by multiplying the weighting factor to the intermediate value derived from the activity is added.

Also, the adaptive filter 305a_2 can adopt a set S of various pixels. An example of the pixel set S will be described with reference to FIGS.

The adaptive filter 305a_2 can adopt, as a set S of pixels, pixels adjacent to the upper, lower, left, and right of the target pixel s12, as shown in FIG. In the case shown in FIG. 20, the intermediate value dN1 can be expressed by the following equation.

dN1 = {(s7 + s11 + s13 + s17)-4 * s12} / (KACT + act (s7, s11, s12, s13, s17))
Further, the adaptive filter 305a_2 can use the intermediate value dN1 as one of the terms of the adaptive filter ALF, as shown by the following equation.

slft = (prodFlt + b0 * dN1 + o) >> shift
The adaptive filter 305a_2 can adopt, as the set S of pixels, pixels adjacent to the upper, lower, left, and right of the target pixel s12 and diagonally as shown in FIG. In the case shown in FIG. 21, the intermediate value dN2 can be expressed by the following equation.

dN2 = {(s6 + s7 + s8 + s11 + s13 + s16 + s17 + s18)-8 * s12} / (KACT + act (s6, s7, s8, s11, s11, s12, s13, s16, s17, s18))
In addition, the adaptive filter 305a_2 can use the intermediate value dN2 as one of the terms of the adaptive filter ALF, as shown by the following equation.

slft = (prodFlt + b0 * dN2 + o) >> shift
As shown in FIG. 22, the adaptive filter 305a_2 can adopt, as the set S of pixels, pixels adjacent to each other with a gap of one pixel above, below, to the left, and to the right of the target pixel s12. In the case shown in FIG. 22, the intermediate value dN3 can be expressed by the following equation.

dN3 = {(s0 + s1 + s2 + s3 + s4 + s5 + s9 + s10 + s14 + s15 + s19 + s20 + s21 + s22 + s23 + s24)-16 * s12} / (KACT + act (s0, s1) , s2, s3, ..., s24))
Also, the adaptive filter 305a_2 can use the intermediate value dN3 as one of the terms of the adaptive filter ALF, as shown by the following equation.

slft = (prodFlt + b0 * dN3 + o) >> shift
Furthermore, the adaptive filter 305a_2 can use a plurality of different intermediate values d as a term of the adaptive filter ALF as indicated by the following equation. In the following equation, an intermediate value dN1 in the case of adopting the pixel set S shown in FIG. 20 and an intermediate value dN2 in the case of adopting the pixel group S shown in FIG. 21 are used.

slft = (prodFlt + b0 * dN1 + b1 * dN2 + o) >> shift
That is, the filter processing units 305a_2c process the sum of the terms obtained by multiplying the weighting factor to the intermediate value derived from the activity. Furthermore, the filter processing units 305a_2c performs a process of right bit shifting the result obtained by taking the sum.

In addition, the adaptive filter 305a_2 may include pixels aligned in the horizontal direction, the vertical direction, and the diagonal direction in the set S of pixels (that is, the pixels referred to for calculating the activity).

The adaptive filter 305a_2 can adopt, as the set S of pixels, pixels aligned in the horizontal direction with the target pixel s12 in the CTU, as shown in FIG. In the case shown in FIG. 23, the intermediate value dH can be expressed by the following equation.

dH = {(s10 + s11 + s13 + s14)-4 * s12} / (KACT + act (s10, s11, s12, s13, s14))
Further, when the adaptive filter 305a_2 adopts, as the pixel set S, pixels aligned in the vertical direction with the target pixel s12 in the CTU, the intermediate value dV can be expressed by the following equation.

dV = {(s2 + s7 + s17 + s22)-4 * s12} / (KACT + act (s2, s7, s12, s17, s22))
Further, the adaptive filter 305a_2 can use the intermediate values dH and dV as the terms of the adaptive filter ALF, as shown by the following equation.

sflt = (prodFlt + b0 * dH + b1 * dV + o) >> shift
As shown in FIG. 24, the adaptive filter 305a_2 can adopt, as a set S of pixels, pixels that are diagonally aligned with the target pixel s12 in the CTU. In the case shown in FIG. 24, the intermediate value dD1 can be expressed by the following equation.

dD1 = {(s0 + s6 + s18 + s24)-4 * s12} / (KACT + act (s0, s6, s12, s18, s24))
When the adaptive filter 305a_2 adopts, in the CTU, pixels aligned in the vertical direction symmetrical to the target pixel s12 in the direction shown in FIG. 24 as the pixel set S, the intermediate value dD2 can be expressed by the following equation.

dD2 = {(s4 + s8 + s16 + s20)-4 * s12} / (KACT + act (s4, s8, s12, s16, s20))
Further, the adaptive filter 305a_2 can use the intermediate values dD1 and dD2 as the terms of the adaptive filter ALF, as shown by the following equation.

sflt = (prodFlt + b0 * dD1 + b1 * dD2 + o) >> shift
Furthermore, when adaptive filter 305a_2 adopts pixels aligned in a direction different from the direction shown in FIG. 24 together with target pixel s12 in CTU as pixel set S, intermediate values dD23, dD21, dD19, dD15 expressed by the following equations are obtained. It can be derived.

dD23 = {(s1 + s23)-2 * s12} / (KACT + act (s1, s12, s23))
dD21 = {(s3 + s21)-2 * s12} / (KACT + act (s3, s12, s21))
dD19 = {(s5 + s19)-2 * s12} / (KACT + act (s5, s12, s19))
dD15 = {(s9 + s15)-2 * s12} / (KACT + act (s9, s15, s21))
In addition, the adaptive filter 305a_2 can use the intermediate values dD23, dD21, dD19, and dD15 as the terms of the adaptive filter ALF, as indicated by the following equation.

sflt = (prodFlt + b0 * dD23 + b1 * dD21 + b2 * dD19 + b3 * dD15 + o) >> shift
Further, the adaptive filter 305a_2 has an intermediate value dH derived from the set S of pixels horizontally aligned with the target pixel s12, an intermediate value dV derived derived from the set S of pixels vertically aligned with the target pixel s12, and Intermediate values dD1 and dD2 derived from a set S of pixels of pixels aligned in a diagonal direction with the target pixel s12 can be used as a term of the adaptive filter ALF as shown by the following equation.

sflt = (prodFlt + b0 * dH + b1 * dV + b2 * dD1 + b3 * dD2 + o) >> shift
The following equation is an intermediate value dN1 derived from the set S of pixels adjacent to the target pixel s12 above and below, and an intermediate value dH derived from the set S of pixels horizontally aligned with the target pixel s12, the target pixel s12 And the intermediate values dD1 and dD2 derived from the pixel set S as the terms of the adaptive filter ALF. Indicates the case.

sflt = (prodFlt + b0 * dN1 + b1 * dH + b2 * dV + b3 * dD1 + b4 * dD2 + o) >> shift
According to this embodiment, the adaptive filter ALF has a term obtained by multiplying each of the activities calculated by referring to at least a part of surrounding pixels by a weighting factor. Thus, the filter strength of the adaptive filter ALF can be adjusted in pixel units. Also, the filter strength of the adaptive filter ALF can be changed according to the sequence or block.

(Configuration of image coding apparatus)
Next, the configuration of the image coding apparatus 11 according to the present embodiment will be described. FIG. 4 is a block diagram showing the configuration of the image coding apparatus 11 according to the present embodiment. The image coding device 11 includes a predicted image generation unit 101, a subtraction unit 102, a DCT / quantization unit 103, an entropy coding unit 104, an inverse quantization / inverse DCT unit 105, an addition unit 106, a loop filter 107, a prediction parameter memory (Prediction parameter storage unit, frame memory) 108, reference picture memory (reference image storage unit, frame memory) 109, coding parameter determination unit 110, and prediction parameter coding unit 111 are configured. The prediction parameter coding unit 111 includes an inter prediction parameter coding unit 112 and an intra prediction parameter coding unit 113.

The prediction image generation unit 101 generates, for each picture of the image T, the prediction image P of the prediction unit PU for each coding unit CU, which is an area obtained by dividing the picture. Here, the predicted image generation unit 101 reads a decoded block from the reference picture memory 109 based on the prediction parameter input from the prediction parameter coding unit 111. The prediction parameter input from the prediction parameter coding unit 111 is, for example, a motion vector in the case of inter prediction. The predicted image generation unit 101 reads a block at a position on the reference image indicated by the motion vector starting from the target PU. In the case of intra prediction, the prediction parameter is, for example, an intra prediction mode. The pixel value of the adjacent PU used in the intra prediction mode is read from the reference picture memory 109, and a PU predicted image P is generated. The prediction image generation unit 101 generates a PU prediction image P using one of a plurality of prediction methods for the read reference picture block. The prediction image generation unit 101 outputs the generated prediction image P of PU to the subtraction unit 102.

The predicted image generation unit 101 performs the same operation as the predicted image generation unit 308 described above. For example, FIG. 6 is a schematic diagram showing a configuration of the inter predicted image generation unit 1011 included in the predicted image generation unit 101. The inter prediction image generation unit 1011 includes a motion compensation unit 10111 and a weight prediction unit 10112. The motion compensation unit 10111 and the weight prediction unit 10112 have the same configuration as that of the above-described motion compensation unit 3091 and weight prediction unit 3094, and therefore the description thereof is omitted here.

The prediction image generation unit 101 generates a PU prediction image P based on the pixel value of the reference block read from the reference picture memory, using the parameter input from the prediction parameter coding unit. The predicted image generated by the predicted image generation unit 101 is output to the subtraction unit 102 and the addition unit 106.

The subtraction unit 102 subtracts the signal value of the predicted image P of the PU input from the predicted image generation unit 101 from the pixel value of the corresponding PU of the image T to generate a residual signal. The subtraction unit 102 outputs the generated residual signal to the DCT / quantization unit 103.

The DCT / quantization unit 103 performs DCT on the residual signal input from the subtraction unit 102 to calculate DCT coefficients. The DCT / quantization unit 103 quantizes the calculated DCT coefficient to obtain a quantization coefficient. The DCT / quantization unit 103 outputs the obtained quantization coefficient to the entropy coding unit 104 and the inverse quantization / inverse DCT unit 105.

The entropy coding unit 104 receives the quantization coefficient from the DCT / quantization unit 103, and receives the coding parameter from the prediction parameter coding unit 111. The coding parameters to be input include, for example, codes such as a reference picture index refIdxLX, a prediction vector index mvp_LX_idx, a difference vector mvdLX, a prediction mode predMode, and a merge index merge_idx.

The entropy coding unit 104 entropy-codes the input quantization coefficient and coding parameters to generate a coded stream Te, and outputs the generated coded stream Te to the outside.

The inverse quantization / inverse DCT unit 105 inversely quantizes the quantization coefficient input from the DCT / quantization unit 103 to obtain a DCT coefficient. The inverse quantization / inverse DCT unit 105 performs inverse DCT on the obtained DCT coefficients to calculate a residual signal. The inverse quantization / inverse DCT unit 105 outputs the calculated residual signal to the addition unit 106.

The addition unit 106 adds, for each pixel, the signal value of the predicted image P of the PU input from the prediction image generation unit 101 and the signal value of the residual signal input from the inverse quantization / inverse DCT unit 105 for decoding. Generate an image. The addition unit 106 stores the generated decoded image in the reference picture memory 109.

The loop filter 107 applies a deblocking filter, a sample adaptive offset (SAO), and an adaptive filter (ALF) to the decoded image generated by the adding unit 106.

The prediction parameter memory 108 stores the prediction parameter generated by the coding parameter determination unit 110 in a predetermined position for each picture and CU to be coded.

The reference picture memory 109 stores the decoded image generated by the loop filter 107 in a predetermined position for each picture and CU to be encoded.

The coding parameter determination unit 110 selects one of a plurality of sets of coding parameters. The coding parameter is a prediction parameter described above or a parameter to be coded that is generated in association with the prediction parameter. The prediction image generation unit 101 generates a PU prediction image P using each of these sets of coding parameters.

The coding parameter determination unit 110 calculates, for each of the plurality of sets, a cost value indicating the size of the information amount and the coding error. The cost value is, for example, the sum of the code amount and a value obtained by multiplying the square error by the coefficient λ. The code amount is the information amount of the coded stream Te obtained by entropy coding the quantization error and the coding parameter. The squared error is a sum between pixels with respect to the square value of the residual value of the residual signal calculated by the subtraction unit 102. The factor λ is a real number greater than a preset zero. The coding parameter determination unit 110 selects a set of coding parameters that minimize the calculated cost value. Thereby, the entropy coding unit 104 externally outputs the set of selected coding parameters as the coded stream Te, and does not output the set of non-selected coding parameters. The coding parameter determination unit 110 stores the determined coding parameters in the prediction parameter memory 108.

The prediction parameter coding unit 111 derives a format for coding from the parameters input from the coding parameter determination unit 110, and outputs the format to the entropy coding unit 104. Derivation of a form for encoding is, for example, derivation of a difference vector from a motion vector and a prediction vector. Further, the prediction parameter coding unit 111 derives parameters necessary to generate a prediction image from the parameters input from the coding parameter determination unit 110, and outputs the parameters to the prediction image generation unit 101. The parameters required to generate a predicted image are, for example, motion vectors in units of subblocks.

The inter prediction parameter coding unit 112 derives inter prediction parameters such as a difference vector based on the prediction parameters input from the coding parameter determination unit 110. The inter prediction parameter coding unit 112 derives the inter prediction parameter by the inter prediction parameter decoding unit 303 (refer to FIG. 5 and the like) as a configuration for deriving the parameters necessary for generating the prediction image to be output to the prediction image generation unit 101. Partially include the same configuration as the configuration. The configuration of the inter prediction parameter coding unit 112 will be described later.

The intra prediction parameter coding unit 113 derives a format (for example, MPM_idx, rem_intra_luma_pred_mode, etc.) for coding from the intra prediction mode IntraPredMode input from the coding parameter determination unit 110.

(Loop filter 107)
The loop filter 107 has the same function as the loop filter 305 included in the image decoding device 31 described above. More specifically, an adaptive filter using a reference restriction line may be used. Also, the term of the adaptive loop filter may be changed on a pixel basis based on the activity.

Ninth Embodiment
The adaptive filter 305 _ 2 may classify small classes (eg, 2 × 2 or 4 × 4) into classes having the same property, and apply different filter coefficients to the classified classes. For example, an identifier classid indicating a class may be derived from the directionality DIR of the small block and the activity ACT according to the following equation.

classid = DIR * N + ACT
For example, if DIR = 0-4, ACT = 0-4 and N = max (ACT) + 1 = 5, the small blocks are classified into classes 0-24.

FIG. 25 is a diagram visualizing the values of the filter coefficients derived by the adaptive filter 305_2 in units of classes. Although FIG. 25 is plotted as a binary image, gradation is not represented, but it is actually a smooth figure. Two-dimensional values of filter coefficients (hereinafter, filter coefficient shapes) can be expressed for 25 classes corresponding to each DIR and ACT. In addition, it is possible to evaluate how much the filter coefficient shape differs depending on the class. As a result of the inventor's evaluation, it has been confirmed that the shape of the filter coefficient is greatly different for each sequence, each class, each frame, and each quantization step.

(A) of FIG. 26 is a diagram showing the residual amount (residual reduction amount gain) which has changed before and after application of the filter coefficient derived by the adaptive filter 305_2 in units of classes.

gain [classid] = residual before adaptive filtering-residual after adaptive filtering = || fltin (x, y)-org (x, y) | ^ 2-|| fltout (x, y )-org (x, y) | ^ 2
Here, fltin, fltout, and org are the pixel value before the filter, the pixel value after the filter, and the pixel value of the original image, respectively, and (x, y) are the positions of the pixels belonging to the class classid. When the difference gain is large, the residual largely decreases before and after the adaptive filter. By calculating gain [classid] for 25 classes classid corresponding to each DIR and ACT, it can be known in which class the residual reduction amount (effect) of the adaptive filter is large.

(B) of FIG. 26 shows the appearance frequency of the class classified by the adaptive filter 305_2. It is a value obtained by dividing the number classified into each class by the total number of blocks when classifying into small blocks. It can be obtained by counting the classid at each position (x, y) as follows.

count [classid (x, y)] + = 1
According to the inventor's evaluation, it can be understood that (1) the amount of residual reduction in a medium to large class of activity ACT is large, and (2) the image is blurred when QP increases, so that ACT decreases. .

The adaptive filter 305 _ 2 is a filter coefficient based on the evaluation of the filter coefficient on a class basis, the residual reduction amount on a class basis, and the occurrence frequency on a class basis shown in FIG. 25 and FIGS. You may design.

For example, the adaptive filter 305 _ 2 may turn off the adaptive filtering of the class “classid” when the residual reduction amount in units of classes is less than a predetermined threshold. Whether to turn off the adaptive filter processing may encode syntax alf_class_flag [classidx] indicating whether the adaptive filter is turned on or off in the class classid. The syntax alf_class_flag [classid] indicating whether the adaptive filter is turned on or off may be further encoded in an image area or in units of blocks (for example, in units of CUs). For example, alf_cu_flag [x] [y] indicates on / off.

When the number of actual classes is NumActualClass, the image decoding apparatus 31 may decode alf_class_flag [classid] of classid = 0..NumActualClass-1 and perform filter processing as follows, when the actual number of classes is NumActualClass.

If alf_class_flag [classid] is 1, the loop filter 305 performs adaptive filter processing on the pixel of the class indicated by the classid of the target pixel using the filter coefficient indicated by the classid. Otherwise, adaptive filter processing is not performed.

The image decoding device 31 further decodes alf_cu_flag [x] [y] from the slice header, and the loop filter 305 determines that alf_cu_flag [x] [y] of the position (x, y) of the target pixel is 1. And if alf_class_flag [classid] is 1 for the classid of the position (x, y) of the target pixel, adaptive filter processing is performed on the target pixel using the filter coefficient indicated by the classid. Otherwise, adaptive filter processing is not performed.

Note that the image encoding device 11 and a part of the image decoding device 31 in the embodiment described above, for example, the entropy decoding unit 301, the prediction parameter decoding unit 302, the loop filter 305, the prediction image generation unit 308, the inverse quantization / inverse DCT Unit 311, addition unit 312, predicted image generation unit 101, subtraction unit 102, DCT / quantization unit 103, entropy coding unit 104, inverse quantization / inverse DCT unit 105, loop filter 107, coding parameter determination unit 110, The prediction parameter coding unit 111 may be realized by a computer. In that case, a program for realizing the control function may be recorded in a computer readable recording medium, and the computer system may read and execute the program recorded in the recording medium. Here, the “computer system” is a computer system built in any of the image encoding device 11 and the image decoding device 31, and includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” means a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built in a computer system. Furthermore, the “computer-readable recording medium” is one that holds a program dynamically for a short time, like a communication line in the case of transmitting a program via a network such as the Internet or a communication line such as a telephone line. In such a case, a volatile memory in a computer system serving as a server or a client may be included, which holds a program for a predetermined time. The program may be for realizing a part of the functions described above, or may be realized in combination with the program already recorded in the computer system.

In addition, part or all of the image encoding device 11 and the image decoding device 31 in the above-described embodiment may be realized as an integrated circuit such as a large scale integration (LSI). Each functional block of the image encoding device 11 and the image decoding device 31 may be individually processorized, or part or all may be integrated and processorized. Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. In the case where an integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology, integrated circuits based on such technology may also be used.

As mentioned above, although one embodiment of this invention was described in detail with reference to drawings, a specific structure is not restricted to the above-mentioned thing, Various design changes etc. in the range which does not deviate from the summary of this invention It is possible to

[Application example]
The image encoding device 11 and the image decoding device 31 described above can be mounted and used in various devices that transmit, receive, record, and reproduce moving images. The moving image may be a natural moving image captured by a camera or the like, or an artificial moving image (including CG and GUI) generated by a computer or the like.

First, the fact that the image encoding device 11 and the image decoding device 31 described above can be used for transmission and reception of a moving image will be described with reference to FIG.

(A) of FIG. 27 is a block diagram showing a configuration of a transmission device PROD_A on which the image coding device 11 is mounted. As shown in (a) of FIG. 27, the transmission device PROD_A modulates a carrier wave with the coding unit PROD_A1 for obtaining coded data by coding a moving image, and the coding data obtained by the coding unit PROD_A1. A modulation unit PROD_A2 for obtaining a modulation signal thereby, and a transmission unit PROD_A3 for transmitting the modulation signal obtained by the modulation unit PROD_A2. The image coding apparatus 11 described above is used as the coding unit PROD_A1.

The transmission device PROD_A is a camera PROD_A4 for capturing a moving image, a recording medium PROD_A5 for recording the moving image, an input terminal PROD_A6 for externally inputting the moving image, and a transmission source of the moving image input to the encoding unit PROD_A1. , And may further include an image processing unit A7 that generates or processes an image. In (a) of FIG. 27, although the configuration in which the transmission device PROD_A includes all of these is illustrated, a part of the configuration may be omitted.

Note that the recording medium PROD_A5 may be a recording of a non-coded moving image, or a moving image encoded by a recording encoding method different from the transmission encoding method. It may be one. In the latter case, it is preferable to interpose, between the recording medium PROD_A5 and the encoding unit PROD_A1, a decoding unit (not shown) that decodes the encoded data read from the recording medium PROD_A5 according to the encoding scheme for recording.

(B) of FIG. 27 is a block diagram showing a configuration of a reception device PROD_B on which the image decoding device 31 is mounted. As shown in (b) of FIG. 27, the receiver PROD_B demodulates the modulated signal received by the receiver PROD_B1, which receives the modulated signal, and the demodulator PROD_B2, which obtains encoded data by demodulating the modulated signal received by the receiver PROD_B1, and And a decoding unit PROD_B3 for obtaining a moving image by decoding encoded data obtained by the unit PROD_B2. The image decoding device 31 described above is used as the decoding unit PROD_B3.

The receiving device PROD_B is a display PROD_B4 for displaying a moving image, a recording medium PROD_B5 for recording the moving image, and an output terminal for outputting the moving image to the outside as a supply destination of the moving image output by the decoding unit PROD_B3. It may further comprise PROD_B6. Although (b) of FIG. 27 illustrates the configuration in which the reception device PROD_B includes all of these, a part may be omitted.

Incidentally, the recording medium PROD_B5 may be for recording a moving image which has not been encoded, or is encoded by a recording encoding method different from the transmission encoding method. May be In the latter case, an encoding unit (not shown) may be interposed between the decoding unit PROD_B3 and the recording medium PROD_B5 to encode the moving image acquired from the decoding unit PROD_B3 according to the encoding method for recording.

The transmission medium for transmitting the modulation signal may be wireless or wired. Further, the transmission mode for transmitting the modulation signal may be broadcast (here, a transmission mode in which the transmission destination is not specified in advance), or communication (in this case, transmission in which the transmission destination is specified in advance) (Refer to an aspect). That is, transmission of the modulation signal may be realized by any of wireless broadcast, wired broadcast, wireless communication, and wired communication.

For example, a broadcasting station (broadcasting facility etc.) / Receiving station (television receiver etc.) of terrestrial digital broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B which transmits and receives a modulated signal by wireless broadcasting. A cable television broadcast station (broadcasting facility or the like) / receiving station (television receiver or the like) is an example of a transmitting device PROD_A / receiving device PROD_B which transmits and receives a modulated signal by cable broadcasting.

In addition, a server (such as a workstation) / client (television receiver, personal computer, smart phone, etc.) such as a VOD (Video On Demand) service or a video sharing service using the Internet is a transmitting device that transmits and receives modulated signals by communication. This is an example of PROD_A / receiving device PROD_B (Normally, in a LAN, either wireless or wired is used as a transmission medium, and in WAN, wired is used as a transmission medium). Here, the personal computer includes a desktop PC, a laptop PC, and a tablet PC. The smartphone also includes a multifunctional mobile phone terminal.

In addition to the function of decoding the encoded data downloaded from the server and displaying it on the display, the client of the moving image sharing service has a function of encoding a moving image captured by a camera and uploading it to the server. That is, the client of the moving image sharing service functions as both the transmitting device PROD_A and the receiving device PROD_B.

Next, the fact that the image encoding device 11 and the image decoding device 31 described above can be used for recording and reproduction of a moving image will be described with reference to FIG.

(A) of FIG. 28 is a block diagram showing a configuration of a recording device PROD_C on which the image coding device 11 described above is mounted. As shown in (a) of FIG. 28, the recording device PROD_C uses the encoding unit PROD_C1, which obtains encoded data by encoding a moving image, and the encoded data obtained by the encoding unit PROD_C1, to the recording medium PROD_M. And a writing unit PROD_C2 for writing. The image coding device 11 described above is used as the coding unit PROD_C1.

The recording medium PROD_M may be (1) a type incorporated in the recording device PROD_C, such as a hard disk drive (HDD) or a solid state drive (SSD), or (2) an SD memory. It may be of a type connected to the recording device PROD_C, such as a card or a Universal Serial Bus (USB) flash memory, or (3) a DVD (Digital Versatile Disc) or a BD (Blu-ray Disc: Registration It may be loaded into a drive device (not shown) built in the recording device PROD_C, such as a trademark).

In addition, the recording device PROD_C is a camera PROD_C3 for capturing a moving image as a supply source of the moving image input to the encoding unit PROD_C1, an input terminal PROD_C4 for inputting the moving image from the outside, and a reception for receiving the moving image The image processing unit PROD_C5 may further include an image processing unit PROD_C6 that generates or processes an image. Although (a) of FIG. 28 exemplifies a configuration in which the recording apparatus PROD_C includes all of these, a part may be omitted.

Note that the receiving unit PROD_C5 may receive an uncoded moving image, and receives encoded data encoded by a transmission encoding scheme different from the recording encoding scheme. It may be In the latter case, it is preferable to interpose a transmission decoding unit (not shown) that decodes encoded data encoded by the transmission encoding scheme between the reception unit PROD_C5 and the encoding unit PROD_C1.

Examples of such a recording device PROD_C include a DVD recorder, a BD recorder, an HDD (Hard Disk Drive) recorder, etc. (In this case, the input terminal PROD_C4 or the receiving unit PROD_C5 is a main supply source of moving images). . In addition, a camcorder (in this case, the camera PROD_C3 is the main supply source of moving images), a personal computer (in this case, the receiving unit PROD_C5 or the image processing unit C6 is the main supply source of moving images), a smartphone (this In this case, the camera PROD_C3 or the receiving unit PROD_C5 is a main supply source of moving images) and the like are also examples of such a recording device PROD_C.

(B) of FIG. 28 is a block showing the configuration of the playback device PROD_D on which the image decoding device 31 described above is mounted. As shown in (b) of FIG. 28, the playback device PROD_D decodes the moving image by decoding the encoded data read by the reading unit PROD_D1 that reads the encoded data written to the recording medium PROD_M and the reading unit PROD_D1. And a decryption unit PROD_D2 to be obtained. The image decoding device 31 described above is used as the decoding unit PROD_D2.

The recording medium PROD_M may be (1) a type incorporated in the playback device PROD_D such as an HDD or an SSD, or (2) such as an SD memory card or a USB flash memory. It may be of a type connected to the playback device PROD_D, or (3) it may be loaded into a drive device (not shown) built in the playback device PROD_D, such as DVD or BD. Good.

In addition, the playback device PROD_D is a display PROD_D3 that displays a moving image as a supply destination of the moving image output by the decoding unit PROD_D2, an output terminal PROD_D4 that outputs the moving image to the outside, and a transmission unit that transmits the moving image. It may further comprise PROD_D5. Although (b) of FIG. 28 exemplifies a configuration in which the playback device PROD_D includes all of these, a part may be omitted.

The transmission unit PROD_D5 may transmit a non-encoded moving image, or transmit encoded data encoded by a transmission encoding method different from the recording encoding method. It may be In the latter case, an encoding unit (not shown) may be interposed between the decoding unit PROD_D2 and the transmission unit PROD_D5 for encoding moving pictures according to a transmission encoding scheme.

As such a playback device PROD_D, for example, a DVD player, a BD player, an HDD player, etc. may be mentioned (in this case, the output terminal PROD_D4 to which a television receiver etc. is connected is the main supply destination of moving images) . In addition, television receivers (in this case, the display PROD_D3 is the main supply destination of moving images), digital signage (also referred to as an electronic signboard or electronic bulletin board, etc.), the display PROD_D3 or the transmission unit PROD_D5 is the main supply of moving images. First, desktop type PC (in this case, output terminal PROD_D4 or transmission unit PROD_D5 is the main supply destination of moving images), laptop type or tablet type PC (in this case, display PROD_D3 or transmission unit PROD_D5 is moving image) The main supply destination of the image), the smartphone (in this case, the display PROD_D3 or the transmission unit PROD_D5 is the main supply destination of the moving image), and the like are also examples of such a reproduction device PROD_D.

(Hardware realization and software realization)
In addition, each block of the image decoding device 31 and the image encoding device 11 described above may be realized as hardware by a logic circuit formed on an integrated circuit (IC chip), or a CPU (Central Processing Unit) It may be realized as software using

In the latter case, each of the devices described above includes a CPU that executes instructions of a program that implements each function, a ROM (Read Only Memory) that stores the program, a RAM (Random Access Memory) that expands the program, the program, and various other methods. A storage device (recording medium) such as a memory for storing data is provided. The object of the embodiment of the present invention is to record computer program readable program codes (execution format program, intermediate code program, source program) of control programs of the above-mentioned respective devices which are software for realizing the functions described above. The present invention can also be achieved by supplying a medium to each of the above-described devices, and a computer (or a CPU or an MPU) reading and executing a program code recorded on a recording medium.

Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, CDs (Compact Disc Read-Only Memory) / MO disks (Magneto-Optical disc). ) Disks including optical disks such as MD (Mini Disc) / DVD (Digital Versatile Disc) / CD-R (CD Recordable) / Blu-ray Disc (registered trademark), IC cards (including memory cards) Cards such as optical cards, mask ROMs / erasable programmable read-only memories (EPROMs) / electrically erasable and programmable read-only memories (EEPROMs) / semiconductor memories such as flash ROMs, or programmable logic devices (PLDs) And logic circuits such as FPGA (Field Programmable Gate Array) can be used.

Further, each device may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. This communication network is not particularly limited as long as the program code can be transmitted. For example, the Internet, intranet, extranet, LAN (Local Area Network), ISDN (Integrated Services Digital Network), VAN (Value-Added Network), CATV (Community Antenna television / Cable Television) communication network, virtual private network (Virtual Private) Network), telephone network, mobile communication network, satellite communication network, etc. can be used. Also, the transmission medium that constitutes this communication network may be any medium that can transmit the program code, and is not limited to a specific configuration or type. For example, even if wired such as IEEE (Institute of Electrical and Electronic Engineers) 1394, USB, power line carrier, cable TV line, telephone line, ADSL (Asymmetric Digital Subscriber Line) line, infrared rays such as IrDA (Infrared Data Association) or remote control , BlueTooth (registered trademark), IEEE 802.11 wireless, HDR (High Data Rate), NFC (Near Field Communication), DLNA (Digital Living Network Alliance (registered trademark), mobile phone network, satellite link, terrestrial digital broadcast network, etc. It can also be used wirelessly. The embodiment of the present invention may also be realized in the form of a computer data signal embedded in a carrier wave, in which the program code is embodied by electronic transmission.

Embodiments of the present invention are not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. That is, an embodiment obtained by combining technical means appropriately modified within the scope of the claims is also included in the technical scope of the present invention.

[Summary]
An image filter device (loop filter 107, 305) according to aspect 1 of the present invention is an image filter device that generates an output image by acting on an input image composed of a plurality of basic unit areas, and the basic unit A boundary filter unit (deblocking filter 305_1) acting on a block boundary including a boundary of a region and an adaptive filter unit (adaptive filter 305_2) are provided, and the boundary filter unit turns on / off the boundary filter of slice boundaries or tile boundaries. The adaptive filter unit sets virtual boundaries different in position depending on whether the filtering process by the boundary filter unit is on or off at a slice boundary or a tile boundary, and the virtual boundary The filter processing is performed with reference to the pixel value located inside.

According to the above configuration, the adaptive filter unit sets virtual boundaries different in position depending on whether the filtering process by the boundary filter unit is on or off at the slice boundary or tile boundary, so that the virtual boundary The pixel values located inside can be referred to, and filtering can be performed efficiently.

In the image filter device (loop filter 107, 305) according to aspect 2 of the present invention, in the above aspect 1, when the boundary filter unit refers to the pixel value of the pixel outside the virtual boundary, the pixel value is The pixel value of the pixel within the virtual boundary and adjacent to the virtual boundary may be replaced.

According to the above configuration, more similar pixel values can be substituted.

In the image filter device (loop filter 107, 305) according to aspect 3 of the present invention, in the above aspect 1, when the boundary filter unit refers to the pixel value of the pixel outside the virtual boundary, the pixel value is It may be replaced with the pixel value of the central pixel of the filter reference area that is the pixel within the virtual boundary.

According to the above configuration, the average pixel value in the filter reference area can be replaced.

An image filter device (loop filter 305a) according to aspect 4 of the present invention includes a filter unit (filter processing units 305a_2c) that generates an output image by acting on an input image, and the filter processing by the filter unit A process of multiplying each of the target pixel in the input image, the pixels around the target pixel, and the activity calculated by referring to at least a part of the peripheral pixels may be included by multiplying the weighting factor .

According to the above configuration, since the activity calculated by referring to at least a part of the surrounding pixels is referred to, a filter according to the image characteristic can be applied to the input image data.

In the image filter device (loop filter 305 a) according to aspect 5 of the present invention, in the above aspect 4, pixels to which reference is made to calculate the activity include pixels lined in the horizontal direction, vertical direction, and diagonal direction. May be included.

According to the above configuration, it is possible to refer to surrounding pixels corresponding to the target pixel.

In the image filter device (loop filter 305a) according to aspect 6 of the present invention, in the

above aspect

4 or 5, processing for taking the sum of each term obtained by multiplying the weighting coefficient in the above-mentioned filter processing; A process of right bit shifting the result obtained by taking the above sum may be included.

[Cross-reference to related applications]
This application claims the benefit of priority to Japanese Patent Application filed on Dec. 26, 2017: Japanese Patent Application No. 2017-250223, the entire contents of which are hereby incorporated by reference. Included in this book.

An embodiment of the present invention is suitably applied to an image decoding apparatus that decodes encoded data obtained by encoding image data, and an image encoding apparatus that generates encoded data obtained by encoding image data. it can. Further, the present invention can be suitably applied to the data structure of encoded data generated by the image encoding device and referenced by the image decoding device.

11 Image Coding Device 31

Image Decoding Device

107, 305, 305a Loop Filter (Image Filter Device)
305_1 Deblocking filter (boundary filter part)
305_2 Adaptive filter (Adaptive filter section)
305a_2c Filter processing unit (filter unit)

Claims

An image filter apparatus that generates an output image by acting on an input image composed of a plurality of basic unit areas, comprising:
A boundary filter unit acting on a block boundary including the boundary of the basic unit region;
And an adaptive filter unit,
The boundary filter unit is capable of turning on or off a boundary filter of slice boundaries or tile boundaries, and
The above adaptive filter unit
Setting virtual boundaries different in position depending on whether the filtering process by the boundary filter unit is on or off at slice boundaries or tile boundaries;
An image filter apparatus that performs filter processing with reference to pixel values located within the virtual boundary.
The boundary filter unit is
When referring to the pixel value of a pixel outside the virtual boundary, the pixel value is replaced with the pixel value of a pixel within the virtual boundary that is adjacent to the virtual boundary. The image filter apparatus of claim 1.
The boundary filter unit is
When referring to the pixel value of the pixel outside the virtual boundary, the pixel value is replaced with the pixel value of the central pixel of the filter reference area that is the pixel within the virtual boundary. Image filter device according to claim 1.
A filter unit that generates an output image by acting on the input image;
For filter processing by the above filter unit,
Target pixel in the input image,
Pixels around the target pixel, and
An image filter apparatus comprising: a process of multiplying each of activities calculated by referring to at least a part of the surrounding pixels by a weighting factor.
5. The image filter device according to claim 4, wherein the pixels referred to for calculating the activity include pixels arranged in the horizontal direction, the vertical direction, and the diagonal direction.
The above filter process
A process of taking the sum of each term obtained by multiplying the weighting factor, and
The image filter apparatus according to claim 4 or 5, further comprising a process of right bit shifting the result obtained by taking the sum.
The image decoding apparatus which decodes an image, Comprising: The image decoding apparatus provided with the image filter apparatus in any one of Claims 1-6 as a filter made to act on a decoded image.
An image coding apparatus for coding an image, comprising: the image filter apparatus according to any one of claims 1 to 6 as a filter for acting on a locally decoded image.