WO2012090286A1

WO2012090286A1 - Video image encoding method, and video image decoding method

Info

Publication number: WO2012090286A1
Application number: PCT/JP2010/073630
Authority: WO
Inventors: 太一郎塩寺; 昭行谷沢; 中條　健
Original assignee: 株式会社東芝
Priority date: 2010-12-27
Filing date: 2010-12-27
Publication date: 2012-07-05

Abstract

In the embodiment, a video image encoding method acquires reference prediction directions representing the prediction directions of an intra prediction corresponding to at least one encoded image block. A first reference prediction direction, from among the reference prediction directions, is set as the first prediction direction and a first prediction image signal is generated. A second prediction direction that is different from the first prediction direction is set and a second prediction image signal is generated. The relative distance between the reference pixels and the prediction pixels of the first and second prediction directions in a first prediction direction combination which is the combination of the set first prediction direction and second prediction direction are derived and the difference value of the relative distances is derived. A predetermined weight component is derived from the difference value. The weighted mean of the first prediction image signal and the second prediction image signal is obtained from the weight component and a third prediction image signal is generated. A prediction error signal is generated from the third prediction image signal and the prediction error signal is encoded.

Description

Video encoding method and video decoding method

Embodiments of the present invention relate to an intra-screen prediction method, a video encoding method, and a video decoding method in video encoding and decoding.

In recent years, an image coding method with greatly improved coding efficiency has been jointly developed by ITU-T and ISO / IEC. H. 26 and ISO / IEC 14496-10 (hereinafter referred to as “H.264”). H. H.264 achieves higher prediction efficiency than in-screen prediction in ISO / IEC MPEG-1, 2 and 4 (hereinafter referred to as intra prediction) by incorporating direction prediction in the spatial region (pixel region). Yes. H. As an extension of H.264, a method for further improving the coding efficiency by introducing a maximum of 34 types of prediction angles and prediction methods and performing intra prediction has been proposed.

However, in Non-Patent Document 1, since a prediction value is generated at an individual prediction angle for each of a plurality of types of prediction modes and copied in the prediction direction, a texture having a luminance gradient that smoothly changes within a pixel block. Such a video or a video with gradation cannot be predicted efficiently, and the prediction error may increase.

The problem to be solved by the present invention is to provide a moving image encoding device and a moving image decoding device including a prediction image generating device capable of improving encoding efficiency.

The moving image encoding method according to the embodiment divides an input image signal into pixel blocks expressed by hierarchical depth according to quadtree division, performs intra prediction on these divided pixel blocks, and generates a prediction error signal. And a reference prediction direction indicating a prediction direction of intra prediction corresponding to at least one encoded pixel block is acquired. Among the reference prediction directions, the first reference prediction direction is set as the first prediction direction, and a first prediction image signal is generated. A second prediction image signal is generated by setting a second prediction direction different from the first prediction direction. The relative distance between the reference pixel and the prediction pixel in each prediction direction is derived corresponding to the first prediction direction combination that is a combination of the set first prediction direction and the second prediction direction, and the difference value of the relative distance Is derived. A predetermined weight component is derived according to the difference value. According to the weight component, the first predicted image signal and the second predicted image signal are weighted and averaged to generate a third predicted image signal. A prediction error signal is generated from the third prediction image signal, and the prediction error signal is encoded.

1 is a block diagram illustrating a moving image encoding apparatus according to a first embodiment. Explanatory drawing of the prediction encoding order of a pixel block. Explanatory drawing of an example of pixel block size. Explanatory drawing of another example of pixel block size. Explanatory drawing of another example of pixel block size. Explanatory drawing of an example of the pixel block in a coding tree unit. Explanatory drawing of another example of the pixel block in a coding tree unit. Explanatory drawing of another example of the pixel block in a coding tree unit. Explanatory drawing of another example of the pixel block in a coding tree unit. Explanatory drawing which shows an example of the unidirectional intra prediction mode, prediction type, and prediction angle parameter | index based on 1st Embodiment. (A) is explanatory drawing of intra prediction mode, (b) is explanatory drawing of the reference pixel and prediction pixel of intra prediction mode, (c) is explanatory drawing of the horizontal prediction mode of intra prediction mode, ( d) Explanatory drawing of the orthogonal lower right prediction mode of intra prediction mode. The block diagram which illustrates the intra prediction part concerning a 1st embodiment. Explanatory drawing of the example of the unidirectional intra prediction number which concerns on 1st Embodiment, and a bidirectional | two-way intra prediction number. Explanatory drawing of another example of the number of unidirectional intra predictions and the number of bidirectional intra predictions which concern on 1st Embodiment. Explanatory drawing of another example of the number of unidirectional intra predictions and the number of bidirectional intra predictions which concern on 1st Embodiment. Explanatory drawing of another example of the number of unidirectional intra predictions and the number of bidirectional intra predictions which concern on 1st Embodiment. The table figure which shows an example of the relationship between prediction mode, a prediction type, bidirectional | two-way intra prediction, and unidirectional intra prediction based on 1st Embodiment. The table figure which shows another example of the relationship between prediction mode, prediction type, bidirectional | two-way intra prediction, and unidirectional intra prediction based on 1st Embodiment. The table figure which shows the continuation of FIG. 8B. The table figure which shows another example of the relationship between prediction mode, prediction type, bidirectional | two-way intra prediction, and unidirectional intra prediction based on 1st Embodiment. FIG. 8D is a table showing the continuation of FIG. 8D. The table figure which shows another example of the relationship between prediction mode, prediction type, bidirectional | two-way intra prediction, and unidirectional intra prediction based on 1st Embodiment. The table figure which shows another example of the relationship between prediction mode, prediction type, bidirectional | two-way intra prediction, and unidirectional intra prediction based on 1st Embodiment. The table figure which shows an example of the prediction mode, prediction type, bidirectional intra prediction, and unidirectional intra prediction based on 1st Embodiment. The table figure which shows another example of the relationship between prediction mode, prediction type, bidirectional | two-way intra prediction, and unidirectional intra prediction based on 1st Embodiment. The table figure which shows an example of the relationship between prediction mode, a prediction type, bidirectional | two-way intra prediction, and unidirectional intra prediction based on 1st Embodiment. The table figure which shows another example of the relationship between prediction mode, prediction type, bidirectional | two-way intra prediction, and unidirectional intra prediction based on 1st Embodiment. The table figure which illustrates a response | compatibility with the parameter | index of the prediction angle based on 1st Embodiment, and the prediction angle in the case of prediction image generation. Explanatory drawing which illustrates the prediction direction which concerns on 1st Embodiment. The block diagram of the bidirectional | two-way intra estimated image generation part based on 1st Embodiment. The table figure which illustrates a response | compatibility with bidirectional | two-way intra prediction and two unidirectional intra prediction based on 1st Embodiment. The block diagram which shows an example of the calculation method of a city area distance based on 1st Embodiment. The block diagram which shows another example of the calculation method of the city area distance based on 1st Embodiment. The block diagram which shows another example of the calculation method of the city area distance based on 1st Embodiment. The table which illustrates the relationship between the prediction mode and the distance of a prediction pixel position based on 1st Embodiment. The table which illustrates the mapping of prediction mode and a distance table based on 1st Embodiment. The table which illustrates the relationship between relative distance and a weight component based on 1st Embodiment. 6 is another table illustrating the relationship between the relative distance and the weight component according to the first embodiment. The block diagram which shows the example of the bidirectional | two-way intra prediction mode production | generation part based on 1st Embodiment. Explanatory drawing which shows an example of bidirectional | two-way intra prediction mode production | generation by a fixed table system based on 1st Embodiment. Explanatory drawing which shows an example of an adjacent block position based on 1st Embodiment. Explanatory drawing which shows an example of the conversion table from 1st prediction direction to 2nd prediction direction based on 1st Embodiment. Explanatory drawing which shows another example of the conversion table from 1st prediction direction to 2nd prediction direction based on 1st Embodiment. Explanatory drawing which shows another example of the conversion table from 1st prediction direction to 2nd prediction direction based on 1st Embodiment. The block diagram which shows another example of the bidirectional | two-way intra prediction mode production | generation part based on 1st Embodiment. Explanatory drawing which shows the example of the correspondence of the bi-directional prediction mode production | generation method from the 2nd prediction mode production | generation part to the 8th prediction mode production | generation part based on 1st Embodiment. Explanatory drawing which shows the corresponding example in case bidirectional | two-way intra prediction mode overlaps based on 1st Embodiment. Explanatory drawing which shows another corresponding example in case bidirectional | two-way intra prediction mode overlaps based on 1st Embodiment. Explanatory drawing which shows another corresponding example in case bidirectional | two-way intra prediction mode overlaps based on 1st Embodiment. Explanatory drawing which shows the example of the prediction mode structure of a color difference signal based on 1st Embodiment. The block diagram which shows another embodiment of the intra estimation part based on 1st Embodiment. Explanatory drawing of a syntax structure. Explanatory drawing of a slice header syntax. Explanatory drawing which shows an example of a prediction unit syntax. Explanatory drawing which shows another example of a prediction unit syntax. Explanatory drawing which shows another example of a prediction unit syntax. Explanatory drawing which shows another example of a prediction unit syntax. Explanatory drawing which shows another example of a prediction unit syntax. The table which shows the relationship at the time of predicting prediction mode. The table which shows an example of the encoding method of prediction mode. The table which shows another example of the encoding method of prediction mode. The table which shows another example of the encoding method of prediction mode. The table which shows another example of the encoding method of prediction mode. The block diagram which shows the 1st modification of the intra estimation part based on 1st Embodiment. Explanatory drawing which shows an example of the prediction unit syntax in the 1st modification based on 1st Embodiment. Explanatory drawing which shows another example of the prediction unit syntax in the 1st modification based on 1st Embodiment. Explanatory drawing which shows an example of the predicted value generation method of a pixel level. The block diagram which shows another example of the intra estimation part based on 1st Embodiment. The block diagram which shows another example of the intra estimation part based on 1st Embodiment. The block diagram which shows an example of the composite intra estimated image generation part based on 1st Embodiment. Explanatory drawing which shows an example according to Prediction unit syntax based on 1st Embodiment. Explanatory drawing which shows another example of the prediction unit syntax based on 1st Embodiment. The block diagram which illustrates the moving picture coding device concerning a 2nd embodiment. The block diagram which illustrates the orthogonal transformation part based on 2nd Embodiment. The block diagram which illustrates the inverse orthogonal transformation part based on 2nd Embodiment. The table figure which shows the relationship between prediction mode and a conversion index based on 2nd Embodiment. The block diagram which illustrates the coefficient order control part concerning a 2nd embodiment. The block diagram which illustrates another coefficient order control part concerning a 2nd embodiment. Explanatory drawing which shows an example of the transform unit syntax based on 2nd Embodiment. The block diagram which shows another example of the orthogonal transformation part based on 3rd Embodiment. The block diagram which shows an example of the inverse orthogonal transformation part based on 3rd Embodiment. Explanatory drawing which shows an example of the transform unit syntax based on 3rd Embodiment. The block diagram which shows an example of the moving image decoding apparatus based on 4th Embodiment. The block diagram which shows an example of the moving image decoding apparatus based on 5th Embodiment. The block diagram which illustrates the coefficient order restoration part concerning a 5th embodiment. The block diagram which shows another example of the coefficient order decompression | restoration part based on 5th Embodiment.

Hereinafter, with reference to the drawings, a video encoding device and a video decoding device according to each embodiment will be described in detail. In the following description, the term “image” can be appropriately read as terms such as “video”, “pixel”, “image signal”, and “image data”. Moreover, in the following embodiment, the same number is attached | subjected about what performs the same operation | movement, and repeated description is abbreviate | omitted.
(First embodiment)
The first embodiment relates to an image encoding device. A moving picture decoding apparatus corresponding to the picture encoding apparatus according to the present embodiment will be described in a fourth embodiment. This image encoding device can be realized by hardware such as an LSI (Large-Scale Integration) chip, a DSP (Digital Signal Processor), or an FPGA (Field Programmable Gate Array). The image encoding apparatus can also be realized by causing a computer to execute an image encoding program.

As illustrated in FIG. 1, the image encoding device 100 according to the present embodiment includes a subtraction unit 101, an orthogonal transformation unit 102, a quantization unit 103, an inverse quantization unit 104, an inverse orthogonal transformation unit 105, an addition unit 106, a loop. Filter 107, reference image memory 108, intra prediction unit 109, inter prediction unit 110, prediction selection switch 111, prediction selection unit 112, entropy encoding unit 113, output buffer 114, encoding control unit 115, and intra prediction mode memory 116 including.

The image encoding apparatus 100 in FIG. 1 divides each frame or each field constituting the input image signal 151 into a plurality of pixel blocks, performs predictive encoding on the divided pixel blocks, and generates encoded data 162. Is output. In the following description, for the sake of simplicity, it is assumed that pixel blocks are predictively encoded from the upper left to the lower right as shown in FIG. 2A. In FIG. 2A, the encoded pixel block p is located on the left side and the upper side of the encoding target pixel block c in the encoding processing target frame f.

Here, the pixel block refers to a unit for processing an image such as an M × N size block (N and M are natural numbers), a coding tree unit, a macro block, a sub block, and one pixel. In the following description, the pixel block is basically used in the meaning of the coding tree unit. However, the pixel block can be interpreted in the above-described meaning by appropriately replacing the description. The coding tree unit is typically a 16 × 16 pixel block shown in FIG. 2B, for example, but may be a 32 × 32 pixel block shown in FIG. 2C or a 64 × 64 pixel block shown in FIG. 2D, It may be an 8 × 8 pixel block (not shown) or a 4 × 4 pixel block. Also, the coding tree unit need not necessarily be square. Hereinafter, the encoding target block or coding tree unit of the input image signal 151 may be referred to as a “prediction target block”. The coding unit is not limited to a pixel block such as a coding tree unit, and a frame, a field, a slice, or a combination thereof can be used.

3A to 3D are diagrams showing specific examples of coding tree units. FIG. 3A shows an example where the size of the coding tree unit is 64 × 64 (N = 32). Here, N represents the size of the reference coding tree unit. The size when divided is defined as N, and the case where it is not divided is defined as 2N. The coding tree unit has a quadtree structure, and when divided, the four pixel blocks are indexed in the Z-scan order. FIG. 3B shows an example in which the 64 × 64 pixel block in FIG. 3A is divided into quadtrees. The numbers shown in the figure represent the Z scan order. Further, it is possible to further perform quadtree division within the index of one quadtree of the coding tree unit. The depth of division is defined by Depth. That is, FIG. 3A shows an example in which Depth = 0. FIG. 3C shows an example of a 32 × 32 (N = 16) size coding tree unit in the case of Depth = 1. A unit having the largest coding tree unit is called a large coding tree unit, and an input image signal is encoded in the order of raster scanning in this unit.

The image encoding apparatus 100 in FIG. 1 performs intra prediction (also referred to as intra prediction, intra prediction, etc.) or inter prediction (screen) for a pixel block based on the encoding parameter input from the encoding control unit 115. Inter-prediction, inter-frame prediction, motion compensation prediction, etc.) is performed to generate a predicted image signal 161. The image encoding device 100 performs orthogonal transform and quantization on the prediction error signal 152 between the pixel block (input image signal 151) and the predicted image signal 161, performs entropy encoding, and generates encoded data 162. Output.

The image encoding apparatus 100 in FIG. 1 performs encoding by selectively applying a plurality of prediction modes having different block sizes and generation methods of the predicted image signal 161. The generation method of the predicted image signal 161 can be roughly divided into two types: intra prediction in which prediction is performed within the encoding target frame and inter prediction in which prediction is performed using one or a plurality of reference frames that are temporally different. is there.

Hereinafter, each element included in the image encoding device 100 of FIG. 1 will be described.
The subtraction unit 101 subtracts the corresponding prediction image signal 161 from the encoding target block of the input image signal 151 to obtain a prediction error signal 152. The subtraction unit 101 inputs the prediction error signal 152 to the orthogonal transformation unit 102.

The orthogonal transform unit 102 performs orthogonal transform such as discrete cosine transform (DCT) on the prediction error signal 152 from the subtraction unit 101 to obtain a transform coefficient 153. The orthogonal transform unit 102 inputs the transform coefficient 153 to the quantization unit 103.

The quantization unit 103 quantizes the transform coefficient 153 from the orthogonal transform unit 102 to obtain a quantized transform coefficient 154. Specifically, the quantization unit 103 performs quantization according to quantization information such as a quantization parameter and a quantization matrix specified by the encoding control unit 115. The quantization parameter indicates the fineness of quantization. The quantization matrix is used for weighting the fineness of quantization for each component of the transform coefficient. The quantization unit 103 inputs the quantized transform coefficient 154 to the entropy encoding unit 113 and the inverse quantization unit 104.

The entropy encoding unit 113 performs various encoding parameters such as the quantized transform coefficient 154 from the quantization unit 103, the prediction information 160 from the prediction selection unit 112, and the quantization information specified by the encoding control unit 115. Entropy encoding (for example, Huffman encoding, arithmetic encoding, etc.) is performed to generate encoded data. The encoding parameter is a parameter necessary for decoding such as prediction information 160, information on transform coefficients, information on quantization, and the like. For example, the encoding control unit 115 has an internal memory (not shown), the encoding parameter is held in this memory, and the encoding parameter of an already encoded pixel block adjacent when encoding the prediction target block is stored. It is good also as a structure to use. For example, H.M. In the H.264 intra prediction, the prediction value of the prediction mode of the prediction target block can be derived from the prediction mode information of the encoded adjacent block.

The encoded data generated by the entropy encoding unit 113 is temporarily accumulated in the output buffer 114 through multiplexing, for example, and output as encoded data 162 according to an appropriate output timing managed by the encoding control unit 115. . The encoded data 162 is output to, for example, a storage system (storage medium) or a transmission system (communication line) not shown.

The inverse quantization unit 104 performs inverse quantization on the quantized transform coefficient 154 from the quantizing unit 103 to obtain a restored transform coefficient 155. Specifically, the inverse quantization unit 104 performs inverse quantization according to the quantization information used in the quantization unit 103. The quantization information used in the quantization unit 103 is loaded from the internal memory of the encoding control unit 115. The inverse quantization unit 104 inputs the restored transform coefficient 155 to the inverse orthogonal transform unit 105.

The inverse orthogonal transform unit 105 performs an inverse orthogonal transform corresponding to the orthogonal transform performed in the orthogonal transform unit 102 such as an inverse discrete cosine transform on the restored transform coefficient 155 from the inverse quantization unit 104, A restored prediction error signal 156 is obtained. The inverse orthogonal transform unit 105 inputs the restored prediction error signal 156 to the addition unit 106.

The addition unit 106 adds the restored prediction error signal 156 and the corresponding prediction image signal 161 to generate a local decoded image signal 157. The decoded image signal 157 is input to the loop filter 107. The loop filter 107 performs a deblocking filter, a Wiener filter, or the like on the input decoded image signal 157 to generate a filtered image signal 158. The generated filtered image signal 158 is input to the reference image memory 108.

The reference image memory 108 stores the filtered image signal 158 after local decoding in the memory, and when the predicted image is generated as necessary by the intra prediction unit 109 and the inter prediction unit 110, the reference image signal 159 is used. Referenced each time.

The intra prediction mode memory 116 stores the intra prediction mode information 163 applied to the prediction unit that has been encoded, and when the intra prediction unit 109 generates the bidirectional prediction mode information as necessary, It is referred to as reference intra prediction mode information 164 each time. When the unidirectional intra-prediction image generation unit 601 is applied to the intra prediction unit 109 described later, the intra prediction mode information 163 includes information on one type of unidirectional intra prediction (prediction direction or FIGS. 8A and 8B described later). Index). In addition, when the bidirectional intra prediction image generation unit 602 is applied to the intra prediction unit 109 described later, information on two types of unidirectional intra prediction (prediction direction or indexes shown in FIGS. 8A and 8B described later). Corresponds to the intra prediction mode information 163. In the following, of the two types of unidirectional intra prediction information, the first unidirectional intra prediction mode is expressed as IntraPredModeL0, and the second unidirectional intra prediction mode is expressed as IntraPredModeL1. IntraPredModeL0 includes IntraPredTypeL0 and IntraAngleIdL0. IntraPredModeL1 includes IntraPredTypeL1 and IntraAngleIdL1. As an example, when IntraPredMode [puPartIdx] = 34 is applied to the prediction unit, the intra prediction mode information 163 indicates that IntraPredTypeL0 is “Intra_Horizontal”, IntraAngleIdL0 is “0”, IntraPredTypeL1 is “Intra_Vertical”, Intra_Vertical ” Have in form. As another embodiment, the correspondence table shown in FIG. 4 may be used to change to index information. That is, IntraPredType “Intra_Horizontal” and IntraAngleId “0” are set to IntraPredMode “1”, IntraPredType “Intra_Vertical” and IntraAngleId “0” are set to IntraPredMode “0”, and intra prediction mode information 163 is also acceptable.

The intra prediction unit 109 performs intra prediction using the reference image signal 159 stored in the reference image memory 108 and the reference intra prediction mode information 164 stored in the intra prediction mode memory 116. For example, H.M. In H.264, an intra prediction image is obtained by performing pixel interpolation (copying or copying after interpolation) along a prediction direction such as a vertical direction or a horizontal direction using an encoded reference pixel value adjacent to a prediction target block. Generate. In FIG. The prediction direction of intra prediction in H.264 is shown. Further, in FIG. 2 shows an arrangement relationship between reference pixels and encoding target pixels in H.264. FIG. 5C illustrates a predicted image generation method in mode 1 (horizontal prediction), and FIG. 5D illustrates a predicted image generation method in mode 4 (diagonal lower right prediction).

In non-patent literature, H. The prediction direction of H.264 is further expanded to 34 directions to increase the number of prediction modes. A predicted pixel value is created by performing linear interpolation with 32-pixel accuracy in accordance with the predicted angle, and is copied in the predicted direction. Details of the intra prediction unit 109 used in the present embodiment will be described later.

The inter prediction unit 110 performs inter prediction using the reference image signal 159 stored in the reference image memory 108. Specifically, the inter prediction unit 110 performs block matching processing between the prediction target block and the reference image signal 159 to derive a motion shift amount (motion vector). The inter prediction unit 110 performs an interpolation process (motion compensation) based on the motion vector to generate an inter prediction image. H. With H.264, interpolation processing up to 1/4 pixel accuracy is possible. The derived motion vector is entropy encoded as part of the prediction information 160.

The prediction selection switch 111 selects the output terminal of the intra prediction unit 109 or the output terminal of the inter prediction unit 110 according to the prediction information 160 from the prediction selection unit 112, and subtracts the intra prediction image or the inter prediction image as the prediction image signal 161. 101 and the adder 106. When the prediction information 160 suggests intra prediction, the prediction selection switch 111 connects a switch to the output terminal from the intra prediction unit 109. On the other hand, when the prediction information 160 suggests inter prediction, the prediction selection switch 111 connects a switch to the output terminal from the inter prediction unit 110.

The prediction selection unit 112 has a function of setting the prediction information 160 according to the prediction mode controlled by the encoding control unit 115. As described above, intra prediction or inter prediction can be selected to generate the predicted image signal 161, but a plurality of modes can be further selected for each of intra prediction and inter prediction. The encoding control unit 115 determines one of a plurality of intra prediction modes and inter prediction modes as the optimal prediction mode, and the prediction selection unit 112 sets the prediction information 160 according to the determined optimal prediction mode. .

For example, for intra prediction, prediction mode information is specified by the encoding control unit 115 to the intra prediction unit 109, and the intra prediction unit 109 generates a predicted image signal 161 according to the prediction mode information. The encoding control unit 115 may specify a plurality of prediction mode information in order from the smallest prediction mode number, or may specify a plurality of prediction mode information in order from the largest. The encoding control unit 115 may limit the prediction mode according to the characteristics of the input image. The encoding control unit 115 does not necessarily specify all prediction modes, and may specify at least one prediction mode information for the encoding target block.

For example, the encoding control unit 115 determines an optimal prediction mode using a cost function represented by the following mathematical formula (1).

In Equation (1) (hereinafter referred to as simple encoding cost), OH indicates a code amount relating to prediction information 160 (for example, motion vector information and prediction block size information), and SAD is a prediction target block and a prediction image signal 161. The difference absolute value sum (ie, the cumulative sum of the absolute values of the prediction error signal 152) is shown. Further, λ represents a Lagrange undetermined multiplier determined based on the value of quantization information (quantization parameter), and K represents an encoding cost. When Expression (1) is used, the prediction mode that minimizes the coding cost K is determined as the optimum prediction mode from the viewpoint of the generated code amount and the prediction error. As a modification of Equation (1), the encoding cost may be estimated from OH alone or SAD alone, or the encoding cost may be estimated using a value obtained by subjecting SAD to Hadamard transform or an approximation thereof.

It is also possible to determine an optimal prediction mode by using a temporary encoding unit (not shown). For example, the encoding control unit 115 determines an optimal prediction mode using a cost function expressed by the following formula (2).

In Equation (2), D represents a sum of square errors (that is, encoding distortion) between the prediction target block and the locally decoded image, and R represents a prediction between the prediction target block and the prediction image signal 161 in the prediction mode. An error amount indicates a code amount estimated by provisional encoding, and J indicates an encoding cost. In order to derive the encoding cost J (hereinafter referred to as the detailed encoding cost) of Equation (2), provisional encoding processing and local decoding processing are required for each prediction mode, so that the circuit scale or the amount of calculation increases. . On the other hand, since the encoding cost J is derived based on more accurate encoding distortion and code amount, it is easy to determine the optimal prediction mode with high accuracy and maintain high encoding efficiency. As a modification of Equation (2), the encoding cost may be estimated from only R or D, or the encoding cost may be estimated using an approximate value of R or D. These costs may be used hierarchically. The encoding control unit 115 performs determination using Expression (1) or Expression (2) based on information obtained in advance regarding the prediction target block (prediction mode of surrounding pixel blocks, image analysis result, and the like). The number of prediction mode candidates may be narrowed down in advance.

As a modification of the present embodiment, the number of prediction mode candidates can be further reduced while maintaining encoding performance by performing two-stage mode determination combining Formula (1) and Formula (2). It becomes. Here, unlike the formula (2), the simple encoding cost represented by the formula (1) does not require a local decoding process, and can be calculated at high speed. In the moving picture coding apparatus according to the present embodiment, H.264 is used. Since the number of prediction modes is large even when compared with H.264, mode determination using the detailed coding cost is not realistic. Therefore, as a first step, mode determination using the simple coding cost is performed on the prediction modes available in the pixel block, and prediction mode candidates are derived.

Here, the number of prediction mode candidates is changed using the property that the correlation between the simple coding cost and the detailed coding cost increases as the value of the quantization parameter that determines the roughness of quantization increases.

Hereinafter, the details of the intra prediction unit 109 according to the present embodiment will be described with reference to FIG.
<Intra Prediction Unit 109>
The intra prediction unit 109 illustrated in FIG. 6 includes a unidirectional intra predicted image generation unit 601, a bidirectional intra predicted image generation unit 602, a prediction mode information setting unit 603, a selection switch 604, and a bidirectional intra prediction mode generation unit 605. . First, the reference image signal 159 is input from the reference image memory 108 to the unidirectional intra predicted image generation unit 601 and the bidirectional intra predicted image generation unit 602. Here, according to the prediction mode information controlled by the encoding control unit 115, the prediction mode information setting unit 603 determines the prediction mode generated by the unidirectional intra prediction image generation unit 601 or the bidirectional intra prediction image generation unit 602. Set and output prediction mode 651. The bidirectional intra prediction mode generation unit 605 outputs the bidirectional intra prediction mode information 652 according to the prediction mode 651 and the reference intra prediction mode information 164. The operation of the bidirectional intra prediction mode generation unit 605 will be described later. The selection switch 604 has a function of switching the output ends of the respective intra predicted image generation units in accordance with the prediction mode 651. If the input prediction mode 651 is the unidirectional intra prediction mode, the output terminal of the unidirectional intra prediction image generation unit 601 is connected to the switch, and if the prediction mode 651 is the bidirectional intra prediction mode, the bidirectional intra prediction is performed. The output terminal of the image generation unit 602 is connected. On the other hand, each of the intra predicted

image generation units

601 and 602 generates the predicted image signal 161 according to the prediction mode 651. The generated prediction image signal 161 (also referred to as a fifth prediction image signal) is output from the intra prediction unit 109. The output signal of the unidirectional intra predicted image generation unit 601 is also called a fourth predicted image signal, and the output signal of the bidirectional intra predicted image generation unit 602 is also called a third predicted image signal.

First, the prediction mode information setting unit 603 will be described in detail. 7A and 7B show the numbers of the prediction modes according to the present embodiment for each block size. PuSize indicates a pixel block (prediction unit) size to be predicted, and seven types of sizes from PU_2x2 to PU_128x128 are defined. IntraUniModeNum represents the number of prediction modes for unidirectional intra prediction, and IntraBiModeNum represents the number of prediction modes for bidirectional intra prediction. Also, Number of modes is the total number of prediction modes for each pixel block (prediction unit) size. The number of prediction modes for unidirectional intra prediction and the number of prediction modes for bidirectional intra prediction may be any values other than those shown in FIGS. 7A and 7B. Note that when the number of prediction modes for bidirectional intra prediction is 0, it means that bidirectional intra prediction is not performed with the pixel block size.

On the other hand, FIG. 8A shows the relationship between the prediction mode and the prediction method in the case of PU_4x4, PU_8x8, PU_16x16, and PU_32x32 in FIG. 7A. 10A shows the case of PU_64x64 or PU_128x128 in FIG. 7A, and FIG. 10B shows the case of PU_64x64 or PU_128x128 in FIG. 7B. Here, IntraPredMode indicates a prediction mode number, and IntraBipredFlag is a flag indicating whether or not bidirectional intra prediction. When the flag is 0, it indicates that the prediction mode is a unidirectional intra prediction mode. When the flag is 1, it indicates that the prediction mode is the bidirectional intra prediction mode. When the flag is 1, the bidirectional intra prediction mode generation unit 605 generates bidirectional intra prediction mode information 652 in accordance with IntraBipredTypeIdx that defines a bidirectional intra prediction generation method. When IntraBipredTypeIdx is 0, two types of unidirectional intra prediction modes used for bidirectional intra prediction are set in a first prediction mode generation unit 1901 described later using a predetermined table. Hereinafter, a method in which two types of unidirectional intra prediction modes used for bidirectional intra prediction are set in advance by a table is referred to as a fixed table method. FIG. 8A shows an example in which all bidirectional intra prediction modes are fixed table methods.

When IntraBipredTypeIdx is a value larger than 0, two types of unidirectional intra prediction modes used for bidirectional intra prediction are set based on the reference intra prediction mode information 164. Hereinafter, a method in which two types of unidirectional intra prediction modes used for bidirectional intra prediction based on the reference intra prediction mode information 164 are set is referred to as a direct method. IntraBipredTypeIdx has different values depending on the method of deriving two types of unidirectional intra prediction modes from the reference intra prediction mode information 164. A specific derivation method will be described later.

∙ Of the plurality of bidirectional intra prediction modes, all modes may be fixed table methods, or all modes may be direct methods. Also, some modes may be fixed table methods and the remaining modes may be direct methods. FIG. 8B shows an example in which among the eight types of bidirectional intra prediction modes, three types are the fixed table method and the remaining five types are the direct method.

IntraPredTypeLX indicates the prediction type of intra prediction. Intra_Vertical means that the vertical direction is the reference for prediction, and Intra_Horizontal means that the horizontal direction is the reference for prediction. Note that 0 or 1 is applied to X in IntraPredTypeLX. IntraPredTypeL0 indicates the first prediction mode of unidirectional intra prediction or bidirectional intra prediction. IntraPredTypeL1 indicates the second prediction mode of bidirectional intra prediction. IntraPredAngleId is an index indicating an index of a prediction angle. The prediction angle actually used in the generation of the predicted value is shown in FIG. Here, puPartIdx represents an index of the prediction unit that is divided in the quadtree division described with reference to FIG. 3B.

For example, when IntraPredMode is 4, since IntraPredTypeL0 is Intra_Vertical, it can be seen that the vertical direction is used as a reference for prediction. As can be seen from FIG. 8B, a total of 34 from IntraPredMode = 0 to 33 indicate the unidirectional intra prediction mode, and a total of 8 from IntraPredMode = 34 to 41 indicate the bidirectional intra prediction mode.

FIG. 8B shows the relationship between the prediction mode and the prediction method in the case of PU_32 × 32 in FIG. 7B. 8C shows the relationship between the prediction mode and the prediction method in the case of PU_4x4 in FIG. 7C, PU_4x4, PU_8x8, and PU_16x16 in FIG. 7D. 8D and 8E show the relationship between the prediction mode and the prediction method in the case of PU_32x32 in FIG. 7D. FIG. 8F shows the relationship between the prediction mode and the prediction method in the case of PU_4x4 in FIGS. 7A, 7B, and 7C and PU_4x4 to PU_16x16 in FIG. 7D. FIG. 8G shows the relationship between the prediction mode and the prediction method in the case of PU_32 × 32 in FIGS. 7C and 7D.

The prediction mode information setting unit 603 converts the above-described prediction information corresponding to the designated prediction mode 651 into the unidirectional intra prediction image generation unit 601 and the bidirectional intra prediction image generation unit 602 under the control of the encoding control unit 115. The prediction mode 651 is output to the selection switch 604.

Next, the unidirectional intra predicted image generation unit 601 will be described in detail. The unidirectional intra predicted image generation unit 601 has a function of generating the predicted image signal 161 for a plurality of prediction directions shown in FIG. In FIG. 12, there are 33 different prediction directions for the vertical and horizontal coordinates indicated by bold lines. H. The direction of a typical prediction angle indicated by H.264 is indicated by an arrow. In this embodiment, 33 kinds of prediction directions are prepared in the direction which pulled the line shown by the arrow from the origin. H. Similar to H.264, DC prediction for predicting with an average value of available reference pixels is added, and there are 34 prediction modes in total.

In the case of IntraPredMode = 4, since IntraPredAngleIdL0 is −4, the prediction image signal 161 is generated in the prediction direction indicated by IntraPredMode = 4 in FIG. The arrows included in the range shown in “Intra_Vertical” shown at the bottom of FIG. 12 indicate the prediction mode whose prediction type is Intra_Vertical, and are included in the range shown in “Intra_Horizontal” shown on the right side of FIG. An arrow indicates a prediction mode whose prediction type is Intra_Horizontal.

Next, a prediction image generation method of the unidirectional intra prediction image generation unit 601 will be described. Here, based on the input reference image signal 159, a predicted image value is generated, and the pixels are copied in the above-described prediction direction. The predicted image value is generated by performing interpolation with 1/32 pixel accuracy. FIG. 11 shows the relationship between IntraPredAngleIdLX and intraPredAngle used for predictive image value generation. intraPredAngle indicates a prediction angle that is actually used when a predicted value is generated. For example, when the prediction type is Intra_Vertical and intraPredAngle shown in FIG. 11 is a positive value, a predicted value generation method is expressed by a mathematical formula (3). Here, BLK_SIZE indicates the size of the pixel block (prediction unit), and ref [] indicates an array in which reference image signals are stored. Pred (k, m) indicates the generated predicted image signal 161.

Even for conditions other than the above, predicted values can be generated in the same manner according to the table of FIG. For example, the prediction value of the prediction mode indicated by IntraPredMode = 1 is H.264 shown in FIG. This is the same as H.264 horizontal prediction. The above is description of the unidirectional intra estimated image generation part 601 in this embodiment.

Next, the bidirectional intra predicted image generation unit 602 will be described in detail. FIG. 13 shows a block diagram of the bidirectional intra-predicted image generation unit 602. The bidirectional intra predicted image generation unit 602 includes a first unidirectional intra predicted image generation unit 1301, a second unidirectional intra predicted image generation unit 1302, and a weighted average unit 1303, and is based on the input reference image signal 159. Two unidirectional intra-predicted images are generated, and a function of generating a predicted image signal 161 by weighted averaging them is provided.

The functions of the first unidirectional intra predicted image generation unit 1301 and the second unidirectional intra predicted image generation unit 1302 are the same. In either case, a prediction image signal corresponding to a prediction mode given according to prediction mode information controlled by the encoding control unit 115 is generated. A first predicted image signal 1351 is output from the first unidirectional intra predicted image generation unit 1301, and a second predicted image signal 1352 is output from the second unidirectional intra predicted image generation unit 1302. Each predicted image signal is input to the weighted average unit 1303, and weighted average processing is performed. The output signal of the weighted average unit 1303 is also called a third predicted image signal.

The table in FIG. 14 is a table for deriving two unidirectional intra prediction modes from the bidirectional intra prediction mode. Here, BipredIdx is derived using Equation (4).

For example, when PuSize = PU — 8 × 8 and IntraPredMode = 34, it can be seen from FIG. 7A or 7B that IntraUniModeNum = 34, and therefore BipredIdx = 0. As a result, it is derived from FIG. 14 that the first unidirectional intra prediction mode (MappedBi2Uni (0, idx)) is 1 and the second unidirectional intra prediction mode (MappedBi2Uni (1, idx)) is 0. In other PuSize and IntraPredMode, it is possible to derive two prediction modes by the same method. Hereinafter, the first unidirectional intra prediction mode is expressed as IntraPredModeL0, and the second unidirectional intra prediction mode is expressed as IntraPredModeL1.

In this way, the first predicted image signal 1351 and the second predicted image signal 1352 generated by the first unidirectional intra predicted image generation unit 1301 and the second unidirectional intra predicted image generation unit 1302, respectively, are sent to the weighted average unit 1303. Is entered.

The weighted average unit 1303 calculates the Euclidean distance or the city area distance (Manhattan distance) based on the prediction directions of IntraPredModeL0 and IntraPredModeL1, and derives a weight component used in the weighted average process. The weight component of each pixel is represented by the Euclidean distance from the reference pixel used for prediction or the reciprocal of the urban distance, and is generalized by the following equation.

Here, when the Euclidean distance is used, ΔL is expressed by the following equation.

On the other hand, when using the city distance, ΔL is expressed by the following equation.

The weight table for each prediction mode is generalized by the following equation.

Here, ρ _L0 (n) represents the weight component of the pixel position n in IntraPredModeL0, and ρ _L1 (n) represents the weight component of the pixel position n in IntraPredModeL1. Therefore, the final prediction signal at the pixel position n is expressed by the following equation.

Here, Bipred (n) represents the predicted image signal at the pixel position n, and PredL0 (n) and PredL1 (n) are the predicted image signals of IntraPredModeL0 and IntraPredModeL1, respectively.

In this embodiment, the prediction signal is generated by selecting two prediction modes for generating the prediction pixel. However, as another embodiment, a prediction value may be generated by selecting three or more prediction modes. . In this case, the ratio of the reciprocal of the spatial distance from the reference pixel to the prediction pixel may be set as the weighting factor.

In this embodiment, the Euclidean distance from the reference pixel used in the prediction mode or the reciprocal of the urban area distance is directly used as a weight component. However, as a modification of the present embodiment, the Euclidean distance and the urban area distance from the reference pixel are variables. The weight component may be set using the distribution model. The distribution model uses at least one of a linear model, an M-order function (M ≧ 1), a nonlinear function such as a one-sided Laplace distribution or a one-sided Gaussian distribution, and a fixed value that is a fixed value regardless of the distance from the reference pixel. When a one-sided Gaussian distribution is used as a model, the weight component is expressed by the following equation.

Here, ρ (n) is a weight component at the position n of the predicted pixel, σ ² is variance, and A is a constant (A> 0).

When the one-sided Laplace distribution is used as a model, the weight component is expressed by the following equation.

Here, σ is a standard deviation, and B is a constant (B> 0).

Further, an isotropic correlation model obtained by modeling an autocorrelation function, an elliptic correlation model, a generalized Gaussian model obtained by generalizing a Laplace function or a Gaussian function may be used as the weight component model.

When the weight components represented by Equation (5), Equation (8), Equation (10), and Equation (11) are calculated each time the predicted image is generated, a plurality of multipliers are required, and the hardware scale increases. . For this reason, the circuit scale required for the said calculation can be reduced by calculating a weight component beforehand according to the relative distance for every prediction mode, and hold | maintaining in a memory. Here, a method for deriving the weight component when the city distance is used will be described.

The city area distance ΔL _L0 of IntraPredMode _L0 and the city area distance ΔL _{L1 of} IntraPredMode _L1 are calculated from Equation (7). Here, the relative distance varies depending on the prediction directions (also referred to as reference prediction directions) of the two prediction modes. As an example, typical distances in the case of PuSize = PU — 4 × 4 are shown in FIGS. 15A, 15B, and 15C. FIG. 15A shows the city distance when IntraPredModeLX = 0. FIG. 15B shows the city distance in the case of IntraPredModeLX = 1. FIG. 15C shows the city distance in the case of IntraPredModeLX = 3. Similarly, the distance can be derived using Expression (6) or Expression (7) according to each prediction mode. However, in the case of DC prediction with IntraPredModeLX = 2, the distance is 2 at all pixel positions. FIG. 16 shows a table of distances in six typical prediction modes in the case of PuSize = PU — 4 × 4. When the number of IntraPredModeLX is large, the table sizes of these distance tables may increase.

In the present embodiment, the required memory amount is reduced by sharing a distance table of several prediction modes with close prediction angles. FIG. 17 shows the mapping of IntraPredModeLX used for distance table derivation. Here, an example is shown in which a table of only the prediction mode corresponding to the prediction mode corresponding to the prediction mode and the DC prediction in 45 degrees is prepared, and other prediction angles are mapped closer to the prepared reference prediction mode. ing. When the distance from the reference prediction mode is the same, the index is mapped to the smaller one. The prediction mode shown in “MappedIntraPredMode” is referred to from FIG. 17, and a distance table can be derived.

By using the distance table, the relative distance for each pixel in the two prediction modes is calculated using the following equation.

Here, BLK_WIDTH and BLK_HEIGHT indicate the width and height of the pixel block (prediction unit), respectively, and DistDiff (n) indicates the relative distance between the two prediction modes at the pixel position n. Using Equation (12), the final prediction signal at the pixel position n is expressed by the following equation.

Here, in order to avoid an increase in hardware scale due to the use of decimal point arithmetic, when weight components are scaled in advance and converted to integer arithmetic, the following expression is obtained.

Here, for example, when the decimal part is expressed with 10-bit precision, WM = 1024, Offset = 512, and SHIFT = 10. These satisfy the following relationship.

SHIFT indicates the calculation accuracy of the decimal point calculation of the weight component, and an optimal combination may be selected by balancing the coding performance and the circuit scale at the time of hardware implementation.

18A and 18B show examples in which weight components using the one-sided Laplace distribution model in this embodiment are tabulated. FIG. 18A shows a weight component table in the case of PuSize = PU — 4 × 4. FIG. 18B shows a weight component table in the case of PuSize = PU_8 × 8. Other PuSizes can also be derived using Equation (5), Equation (8), Equation (10), and Equation (11).

As another embodiment of the weighting factor, a predetermined weighting factor is prepared for each combination of the unidirectional intra prediction modes IntraPredModeL0 and IntraPredModeL1 as a table for each pixel position and each pixel group, and the above Bired (n) is calculated. It doesn't matter. In this case, it is shown by the following formula.

ωt (n) is a weighting coefficient at the pixel position n, and has different values depending on IntraPredModeL0 and IntraPredModeL1.

<Bidirectional Intra Prediction Mode Generation Unit 605>
Next, the bidirectional intra prediction mode generation unit 605 will be described in detail.
FIG. 19 shows a block diagram of the bidirectional intra prediction mode generation unit 605. The bidirectional intra prediction mode generation unit 605 includes a first prediction mode generation unit 1901 and a second prediction mode generation unit 1902. Based on the prediction mode 651 and the reference intra prediction mode information 164, two types of unidirectional intra prediction are performed. It has a function of outputting bidirectional intra prediction mode information 652 that is a combination. One of the first prediction mode generation unit 1901 and the second prediction mode generation unit 1902 is connected to the output terminal of the selection switch 1903 in accordance with IntraBipredTypeIdx included in the prediction mode 651. The first prediction mode generation unit 1901 outputs a combination of two types of unidirectional intra predictions according to the fixed table method described above. The table in FIG. 20 is a table for deriving a combination of two types of unidirectional intra prediction corresponding to IntraPredMode, and corresponds to the prediction mode configuration in which the unidirectional intra prediction mode is excluded in FIG. 8A. BipredIdx in the figure is an index of the bidirectional intra prediction mode, and is derived using the above equation (4).

For example, in the case of PuSize = PU — 8 × 8 and IntraPredMode = 34, it can be seen from FIG. 7A or 7B that IntraUniModeNum = 34, and therefore BipredIdx = 0. Accordingly, the unidirectional first unidirectional intra prediction mode IntraPredMode = 34 and IntraPredModeL0 and the second unidirectional intra prediction mode IntraPredModeL1 are derived from the table.

The table for deriving IntraPredModeL0 and IntraPredModeL1 from BipredIdx is not limited to FIG. 20, and any one-way intra prediction mode shown in FIGS. 8A and 8B may be set as IntraPredModeL0 and IntraPredModeL1. Hereinafter, the method for deriving the bidirectional intra prediction mode by the first prediction mode generation unit 1901 is referred to as a first generation method.

The second prediction mode generation unit 1902 outputs bi-directional intra prediction mode information 652 that is a combination of two types of unidirectional intra prediction using the reference intra prediction mode information 164 according to the direct method described above.

Hereinafter, a specific method for deriving the bidirectional intra prediction mode information 652 will be described. In the following example, reference intra prediction mode information 164 corresponding to adjacent blocks A and B to which pixel positions a and b respectively belong is used as an already encoded prediction unit as shown in FIG. Hereinafter, the reference intra prediction mode information 164 corresponding to the adjacent block A is referred to as IntraPredModeA, and the reference intra prediction mode information 164 corresponding to the adjacent block B is referred to as IntraPredModeB. When bidirectional intra prediction is applied to adjacent block A, the first unidirectional intra prediction mode and the second unidirectional intra prediction mode in IntraPredModeA are referred to as IntraPredModeAL0 and IntraPredModeAL1, respectively. When unidirectional intra prediction is applied to the adjacent block A, IntraPredModeA has the same information as IntraPredModeAL0, and a predetermined fixed value (for example, minus 1) is set in IntraPredModeAL1. As with the adjacent block A, the adjacent block B is also referred to as IntraPredModeBL0 and IntraPredModeBL1.

The second prediction mode generation unit 1902 sets IntraPredModeAL0 in the first unidirectional intra prediction mode (IntraPredModeL0) and IntraPredModeB0 in the second unidirectional intra prediction mode (IntraPredModeL1) as the bidirectional intra prediction mode information 652. When bidirectional intra prediction is applied to adjacent blocks A and B, IntraPredModeAL1 may be set instead of IntraPredModeAL0, and IntraPredModeBL1 may be set instead of IntraPredModeBL0. Hereinafter, the method for deriving the bidirectional intra prediction mode by the second prediction mode generation unit 1902 is referred to as a second generation method.

As another embodiment in the second prediction mode generation unit 1902, either IntraPredModeAL0 or IntraPredModeBL1 is set as the first unidirectional intra prediction mode (IntraPredModeL0), and is modified by a method determined in advance based on IntraPredModeL0. The predicted mode may be set as the second unidirectional intra prediction mode (IntraPredModeL1). FIG. 22A shows a table for setting as a second unidirectional intra prediction mode that is an intra prediction mode in which the prediction direction is adjacent to the first unidirectional intra prediction mode. When there are two types of intra prediction modes whose prediction directions are adjacent to the first unidirectional intra prediction mode, the intra prediction mode with the small intra prediction mode index IntraPredMode is selected. By deriving IntraPredModeL1 using the table shown in FIG. 22A, bi-directional intra prediction is performed using prediction directions adjacent to each other, so that it is possible to obtain a filtering effect that removes noise in the predicted image signal. Therefore, the prediction efficiency is improved. Hereinafter, the derivation method of the bidirectional intra prediction mode by the first prediction mode generation unit 1901 is referred to as a third generation method. Moreover, you may use the table shown by FIG. 22B as a prediction direction adjacent to the opposite direction to FIG. 22A.

As yet another embodiment in the second prediction mode generation unit 1902, IntraPredModeL1 may be derived using the table shown in FIG. 22C instead of the tables shown in FIGS. 22A and 22B. IntraPredModeL0 and IntraPredModeL1 shown in FIG. 22C have a relationship in which the prediction direction is reversed. Therefore, since it is possible to perform the interpolation prediction so as to sandwich the encoded prediction unit, the prediction efficiency is improved. Hereinafter, the method for deriving the bidirectional intra prediction mode by the second prediction mode generation unit 1902 is referred to as a fourth generation method.

As yet another embodiment in the second prediction mode generation unit 1902, when bidirectional intra prediction is performed on adjacent blocks, the bidirectional intra prediction modes may be set as IntraPredModeL0 and IntraPredModeL1. When the adjacent block A is bidirectional intra prediction, IntraPredModeAL0 is set in IntraPredModeL0, and IntraPredModeAL1 is set in IntraPredModeL1. Since the same applies to the case where the adjacent block B is bidirectional intra prediction, the description thereof is omitted. Hereinafter, the method for deriving the bidirectional intra prediction mode by the second prediction mode generation unit 1902 is referred to as a fifth generation method.

As yet another embodiment in the second prediction mode generation unit 1902, IntraPredModeL1 may be derived using a predetermined table from IntraPredModeL0. Hereinafter, the method for deriving the bidirectional intra prediction mode by the second prediction mode generation unit 1902 is referred to as a sixth generation method.

<Another Embodiment of Bidirectional Intra Prediction Mode Generation Unit 605>
Another embodiment of the bidirectional intra prediction mode generation unit 605 will be described with reference to FIG. The difference is that a third prediction mode generation unit 2301 and an Nth prediction mode generation unit 2302 are added to the bidirectional intra prediction mode generation unit 605 shown in FIG. The second prediction mode generation unit 1902, the third prediction mode generation unit 2301, and the Nth prediction mode generation unit 2302 in FIG. 23 generate bidirectional intra prediction mode information 652 based on the reference intra prediction mode information 164, respectively. The derivation methods are different from each other. Note that (N−1) is the total number of prediction mode generation units that generate the bidirectional intra prediction mode information 652 based on the reference intra prediction mode information 164.

FIG. 24 illustrates an example of a method for generating each prediction mode generation unit (from the second prediction mode generation unit to the eighth prediction mode generation unit) and IntraPredModeL0 and IntraPredModeL1 at N = 8. Each prediction mode generation unit uses one of the bidirectional prediction mode generation methods (from the second generation method to the sixth generation method). When the second generation method is used and when the third generation method to the sixth generation method are used, adjacent blocks to be used are shown. Note that the correspondence relationship between the second prediction mode generation unit to the Nth prediction mode generation unit and IntraBipredTypeIdx is not limited to that in FIG. 24, and may correspond in any way.

8A and 8B show the configuration of the prediction mode according to the present embodiment. FIG. 8B shows 34 types of unidirectional intra prediction and 8 types of bidirectional intra prediction. Of the bidirectional intra predictions, IntraPredMode of 34, 35, and 36 are the first prediction mode generation unit 1901. The bidirectional intra prediction mode information 652 is generated by one generation method. When IntraPredMode is 37 to 41, both using the second prediction mode generation unit 1902, the third prediction mode generation unit 2301, the fourth prediction mode generation unit, and the fifth prediction mode generation unit (not shown) described in this embodiment. Direction intra prediction mode information 652 is generated.

As another embodiment, as shown in FIGS. 7A and 7B, the number of unidirectional intra predictions and the number of bidirectional intra predictions may be changed depending on the size of the prediction unit. In addition, among the bidirectional intra prediction modes, the number of modes using the first prediction mode generation unit 1901 and the number of modes using the prediction mode generation unit from the second prediction mode generation unit 1902 to the Nth prediction mode generation unit 2302 are Any number may be set (the number of modes may be increased for bidirectional use). FIG. 9B shows an example in which there are 17 types of unidirectional intra prediction and four types of bidirectional intra prediction, and all four types of bidirectional intra prediction use the second prediction mode generation unit 1902 and the subsequent ones.

Correspondence between IntraBipredTypeIdx and IntraPredModeL0, IntraPredModeL1 is not limited to that shown in FIGS. 8B and 9B. If the image encoding apparatus of the present embodiment and the corresponding image decoding apparatus have information indicating the same correspondence relationship in advance, the correspondence relationship can be arbitrarily set.

<Corresponding to Duplication of Bidirectional Intra Prediction Mode 1: Assigning Other Bidirectional Intra Prediction Mode>
When the bidirectional intra prediction mode generated from the second prediction mode generation unit to the Nth prediction mode generation unit overlaps with each other or the bidirectional intra prediction mode output from the first prediction mode generation unit 1901, Instead of the bidirectional intra prediction mode, another bidirectional prediction mode, for example, a bidirectional intra prediction mode derived using the first prediction mode generation unit 1901 may be used. In this case, the total number of bidirectional prediction modes is always constant. FIGS. 25A, 25B, and 25C show examples when the bidirectional intra prediction modes overlap. FIG. 25A shows that when BipredIdx (= IntraPredMode−IntraUniPredModeNum) is 5, it overlaps with the bidirectional intra prediction mode generated by another generation method. In this case, IntraBipredType in BipredIdx is reset to 0, and the bidirectional intra prediction mode is generated in the first prediction mode generation unit 1901 according to the table shown in FIG. In this example, “Intra_Vertical” and “−8” and Intra_DC are newly selected as the bidirectional intra prediction modes.

As another embodiment when the bi-directional intra prediction modes overlap, the bi-predIdx does not use the same bi-directional intra prediction mode in the first prediction mode generation unit 1901, but other bi-directional intra prediction modes shown in FIG. The prediction mode may be used. However, if BipredIdx is already assigned in the first prediction mode generation unit 1901, it is excluded from the bidirectional intra prediction modes that can be used. That is, when BipredIdx is from 0 to 2 in FIG. 25A, the bidirectional intra prediction mode is excluded. Accordingly, the bi-directional intra prediction mode in which BipredIdx shown in FIG. 20 is 3 or more can be used.

<Corresponding to Duplication of Bidirectional Intra Prediction Mode 2 ': Assigning Other Unidirectional Intra Prediction Mode>
When the bidirectional intra prediction modes generated from the second prediction mode generation unit to the Nth prediction mode generation unit overlap with each other or the bidirectional intra prediction mode output from the first prediction mode generation unit 1901, FIG. As shown in 25B, the unidirectional intra prediction mode may be replaced and used. The unidirectional intra prediction mode to be used as a replacement is preferably a unidirectional intra prediction mode having a prediction direction different from the prediction mode candidates. Specifically, in the case of a prediction unit to which the prediction mode configuration shown in FIG. 9B is applied, the unidirectional intra prediction mode is 17 modes, and therefore the above-mentioned 17 modes out of the maximum 34 modes as shown in FIG. Use a unidirectional intra prediction mode other than.

<Correspondence to Duplication of Bidirectional Intra Prediction Mode 2: Change Code Table>
Another implementation in the case where the bidirectional intra prediction modes generated from the second prediction mode generation unit to the Nth prediction mode generation unit overlap with each other or the bidirectional intra prediction mode output from the first prediction mode generation unit 1901 As a form, the bidirectional intra prediction mode information may be encoded in a state where the total number of usable bidirectional prediction modes is reduced, as shown in FIG. 25C, instead of using other bidirectional prediction modes. Absent. In the example of FIG. 25C, it is shown that the total number of bidirectional intra prediction modes is 8, and when BipredIdx is 5, it overlaps with the bidirectional intra prediction mode generated by another generation method. In this case, the bidirectional prediction mode information is encoded with the total number of bidirectional prediction modes set to 7. Accordingly, the average code amount required for the bidirectional prediction mode information is generally smaller than the total number of bidirectional prediction modes of 8. In this case, the total number of bidirectional prediction modes may change for each prediction unit.

<Correspondence to color difference signal>
Next, a color difference signal intra prediction method will be described.
FIG. 26 shows the configuration of the prediction mode for the color difference signal in this embodiment. Intra_pred_mode_chroma in FIG. 26 indicates a prediction mode index in the color difference signal. For intra_pred_mode_chroma from 0 to 3, predetermined unidirectional intra prediction (vertical, horizontal, DC, diagonal) is performed. On the other hand, when intra_pred_mode_chroma is 4, the prediction mode IntraPredMode for the luminance signal in the encoding prediction unit is applied as the prediction mode for the color difference signal. When the encoded prediction unit has the configuration of the prediction mode shown in FIG. 8B, unidirectional intra prediction whose IntraPredMode is 0 to 33 is applied, and when it is 34 or more, the above-described bidirectional intra prediction is applied.

As another embodiment regarding the intra prediction method of the color difference signal, when intra_pred_mode_chroma is 4 and bidirectional intra prediction is applied in the prediction mode IntraPredMode for the luminance signal, two types of unidirectional intra prediction modes (IntraPredModeL0 and IntraPredModeL1) are used. ) May be applied as a prediction mode for a color difference signal.

The above is the details of the intra prediction unit 109 according to this embodiment of the present invention.

<Modification of processing amount reduction on the encoding unit side of the intra prediction unit 109>
As a modification of the present embodiment, the internal configuration of the intra prediction unit 109 may be the configuration shown in FIG. In this case, compared with the configuration of the intra prediction unit 109 shown in FIG. 6, an image buffer 2701 is added, and the bidirectional intra prediction image generation unit 602 is replaced with a weighted average unit 2702. The primary image buffer 2701 has a function of temporarily storing the prediction image signal 161 for each prediction mode generated by the unidirectional intra prediction image generation unit 601 in the buffer, and the prediction controlled by the encoding control unit 115. The prediction image signal 161 corresponding to the necessary prediction mode is output to the weighted average unit 2702 according to the bidirectional intra prediction mode information 652 output from the mode and bidirectional intra prediction mode generation unit 605. This eliminates the need for the bidirectional intra predicted image generation unit 602 to hold the first unidirectional intra predicted image generation unit 1301 and the second unidirectional intra predicted image generation unit 1302, thereby reducing the hardware scale. It becomes possible.

<Syntax structure 1>
Hereinafter, the syntax used by the image coding apparatus 100 in FIG. 1 will be described.
The syntax indicates the structure of encoded data (for example, encoded data 162 in FIG. 1) when the image encoding device encodes moving image data. When decoding the encoded data, the moving picture decoding apparatus interprets the syntax with reference to the same syntax structure. FIG. 28 shows an example of syntax 2800 used by the video encoding apparatus of FIG.

The syntax 2800 includes three parts: a high level syntax 2801, a slice level syntax 2802, and a coding tree level syntax 2803. The high level syntax 2801 includes syntax information of a layer higher than the slice. A slice refers to a rectangular area or a continuous area included in a frame or a field. The slice level syntax 2802 includes information necessary for decoding each slice. The coding tree level syntax 2803 includes information necessary for decoding each coding tree (ie, each coding tree unit). Each of these parts includes more detailed syntax.

The high level syntax 2801 includes sequence and picture level syntax such as a sequence parameter set syntax 2804 and a picture parameter set syntax 2805. The slice level syntax 2802 includes a slice header syntax 2806, a slice data syntax 2807, and the like. The coding tree level syntax 2803 includes a coding tree unit syntax 2808, a prediction unit syntax 2809, and the like.

The coding tree unit syntax 2808 can have a quadtree structure. Specifically, the coding tree unit syntax 2808 can be recursively called as a syntax element of the coding tree unit syntax 2808. That is, one coding tree unit can be subdivided with a quadtree. The coding tree unit syntax 2808 includes a transform unit syntax 2810. The transform unit syntax 2810 is invoked at each coding tree unit syntax 2808 at the extreme end of the quadtree. The transform unit syntax 2810 describes information related to inverse orthogonal transformation and quantization.

FIG. 29 exemplifies slice header syntax 2806 according to the present embodiment. The slice_bipred_intra_flag shown in FIG. 29 is a syntax element indicating, for example, validity / invalidity of bidirectional intra prediction according to the present embodiment for the slice.

When slice_bipred_intra_flag is 0, the bidirectional intra according to this embodiment in the slice is invalid. Therefore, the orthogonal transform unit 102 and the inverse orthogonal transform unit 105 perform only unidirectional intra prediction. As an example of unidirectional intra prediction, prediction in which IntraBipredFlag [puPartIdx] in FIGS. 8A and 8B, 9A and 9B, and FIG. Intra prediction specified in H.264 may be performed.

As an example, when slice_bipred_intra_flag is 1, the bidirectional intra prediction according to the present embodiment is effective in the entire area in the slice.

As another example, when slice_bipred_intra_flag is 1, in the syntax of a lower layer (coding tree unit, transform unit, etc.), the prediction validity / efficiency according to the present embodiment is determined for each local region in the slice. Invalidity may be specified.

FIG. 30A shows an example of the prediction unit syntax. Pred_mode in the figure indicates the prediction type of the prediction unit. MODE_INTRA indicates that the prediction type is intra prediction. intra_split_flag is a flag indicating whether or not the prediction unit is further divided into four prediction units. When intra_split_flag is 1, a prediction unit is obtained by dividing a prediction unit into four in half in the vertical and horizontal sizes. When intra_split_flag is 0, the prediction unit is not divided.

Intra_luma_bipred_flag [i] is a flag indicating whether the prediction mode IntraPredMode applied to the prediction unit is a unidirectional intra prediction mode or a bidirectional intra prediction mode. i indicates the position of the divided prediction unit, and 0 is set when the intra_split_flag is 0, and 0 to 3 when the intra_split_flag is 1. In this flag, the value of IntraBipredFlag of the prediction unit shown in FIGS. 8A and 8B, 9A and 9B, and 10 is set.

When intra_luma_bipred_flag [i] is 1, this indicates that the prediction unit is bi-directional intra prediction, and is information that identifies the used bi-directional intra prediction mode among a plurality of prepared bi-directional intra prediction modes. Intra_luma_bipred_mode [i] is encoded. intra_luma_bipred_mode [i] may be encoded with the isometric length according to the bidirectional intra prediction mode number IntraBiModeNum shown in FIGS. 7A to 7D, or may be encoded using a predetermined code table. Further, as described above, when the total number of bidirectional intra prediction modes is different for each prediction unit, it is encoded using a code table that switches according to the total number of bidirectional intra prediction modes indicated for each prediction unit. Also good. When intra_luma_bipred_flag [i] is 0, it indicates that the prediction unit is unidirectional intra prediction, and predictive encoding is performed from adjacent blocks.

prev_intra_luma_unipred_flag [i] is a flag indicating whether or not the prediction value MostProbable of the prediction mode calculated from the adjacent block and the intra prediction mode of the prediction unit are the same. Details of the MostProbable calculation method will be described later. When prev_intra_luma_unipred_flag [i] is 1, it indicates that the MostProbable and the intra prediction mode IntraPredMode are equal. When prev_intra_luma_unipred_flag [i] is 0, it indicates that the MostProbable and the intra prediction mode IntraPredMode are different, and the information rem_intraiprecoded_code that specifies whether the intra prediction mode IntraPredMode is a mode other than MostProbable. . The rem_intra_luma_unipred_mode [i] may be encoded in the same length according to the bidirectional intra prediction mode number IntraUniModeNum shown in FIGS. 7A and 7B, or may be encoded using a predetermined code table. From the intra prediction mode IntraPredMode, rem_intra_luma_unipred_mode [i] is calculated using the following equation.

Next, a method for calculating MostProbable that is a predicted value in the prediction mode will be described. MostProbable is calculated according to the following equation.

Min (x, y) is a parameter for outputting the smaller one of the inputs x and y.

Also, intraPredModeAL0 and intraPredModeBL0 respectively indicate the first unidirectional intra prediction modes of the prediction units adjacent to the left and above the encoded prediction unit as described above. When an adjacent prediction unit cannot be referenced outside the screen or before encoding, the first unidirectional intra prediction mode of the referable prediction unit is MostProbable. In addition, when both adjacent prediction units cannot be referred to, Intra_DC is set in MostProbable.

Further, when MostProbable is larger than the number of unidirectional intra prediction modes IntraUniPredModeNum of the encoded prediction unit, MostProbable is recalculated using the following equation.

“MappedProbable ()” is a table for converting MostProbable, and an example is shown in FIG. 31.

<Syntax structure 2>
Next, another example of the prediction unit syntax is shown in FIG. 30C. Since pred_mode and intra_split_flag are the same as the syntax example described above, description thereof is omitted. luma_pred_mode_code_type [i] indicates the type of prediction mode IntraPredMode applied to the prediction unit, 0 (IntraUnifiedMostProb) indicates unidirectional intra prediction, and intra prediction mode is the same as MostProbable. Intra prediction indicates that the intra prediction mode is different from MostProbable, and 2 (IntraBipred) indicates that it is a bidirectional intra prediction mode. 32A, B, C, and D show an example of assignment of the number of modes according to the meaning corresponding to luma_pred_mode_code_type and the mode configuration shown in bin, FIG. 7A or FIG. 7B, FIG. 7C, and FIG. 7D. When luma_pred_mode_code_type [i] is 0, the intra prediction mode is the MostProbable mode, so no further information encoding is necessary. When luma_pred_mode_code_type [i] is 1, information rem_intra_luma_unipred_mode [i] that specifies which mode other than MostProbable is the intra prediction mode IntraPredMode is encoded. rem_intra_luma_unipred_mode [i] may be encoded with the isometric length according to the number of bidirectional intra prediction modes IntraUniModeNum shown in FIG. 7A, FIG. 7B, FIG. 7C, or FIG. May be. From the intra prediction mode IntraPredMode, rem_intra_luma_unipred_mode [i] is calculated using Equation (16). Further, when luma_pred_mode_code_type [i] is 2, it indicates that the prediction unit is bidirectional intra prediction, and information that identifies the used bidirectional intra prediction mode among the prepared bidirectional intra prediction modes. Intra_luma_bipred_mode [i] is encoded. intra_luma_bipred_mode [i] may be encoded in equal length according to the bidirectional intra prediction mode number IntraBiModeNum shown in FIG. 7A, FIG. 7B, FIG. 7C, or FIG. 7D, or encoded using a predetermined code table. May be. Further, as described above, when the total number of bidirectional intra prediction modes is different for each prediction unit, it is encoded using a code table that switches according to the total number of bidirectional intra prediction modes indicated for each prediction unit. Also good.

The above is the syntax configuration according to the present embodiment.

<Syntax structure 3>
FIG. 30D shows still another example relating to the prediction unit syntax. In this example, based on the prediction unit syntax shown in FIG. 30A, whether bidirectional intra prediction can be used or whether conventional intra-unidirectional prediction can be used with bidirectional intra prediction disabled. Shows the syntax for switching within the encoding prediction unit. In the case where the bidirectional intra prediction cannot be used and only the conventional unidirectional intra prediction can be used, the table shown in FIG. 4 may be used instead of FIG. 8A and FIG. 8B, or FIG. 8A or FIG. IntraPredMode of 33 or more may be ignored. FIG. 4 is obtained by deleting IntraPredTypeL1 and IntraPredAngleIdL1 indicating information related to the second prediction mode at the time of bidirectional intra prediction from FIG. 8A or FIG. 8B, and deleting a table in which unnecessary IntraPredMode is 33 or more. A similar configuration with respect to FIG. 4 and FIG. 8A or FIG. 8B may be applied with respect to FIG. 9A, FIG. 9B, or FIG. 10 corresponding to FIG. 8A or FIG.
Note that pred_mode and intra_split_flag are the same as the syntax example described above, and thus description thereof is omitted.

Intra_bipred_flag is a flag indicating whether or not bi-directional intra prediction can be used in the encoded prediction unit. When intra_bipred_flag is 0, it indicates that bi-directional intra prediction is not used in the encoded prediction unit. Even when intra_split_flag is 1, that is, when the encoded prediction unit is further divided into four, bi-directional intra prediction is not used in all prediction units, and only uni-directional intra prediction is effective.

When intra_bipred_flag is 1, it indicates that bi-directional intra prediction can be used in the encoded prediction unit. Even when intra_split_flag is 1, that is, when the encoded prediction unit is further divided into four, in all prediction units, bidirectional intra prediction can be selected in addition to unidirectional intra prediction.

In a region where bi-directional intra prediction is not necessary (for example, a flat region), intra_bipred_flag is encoded as 0 to disable bi-directional intra prediction. Since the amount of codes necessary for encoding can be reduced, encoding efficiency is improved.

<Syntax structure 4>
FIG. 30E shows still another example relating to the prediction unit syntax. In this example, based on the prediction unit syntax shown in FIG. 30C, whether bidirectional intra prediction can be used or whether only conventional unidirectional intra prediction can be used with bidirectional intra prediction disabled. Shows the syntax for switching within the encoding prediction unit. intra_bipred_flag is a flag indicating whether or not bi-directional intra prediction can be used in the encoding prediction unit, and is the same as the above-described intra_bipred_flag, and thus the description thereof is omitted.

(First modification)
<First Modification of Intra Prediction Unit>
As a first modification related to the intra prediction unit 109, in combination with adaptive reference pixel filtering shown in JCTVC-B205_draft002, section 5.2.1 “Intra prediction process for luma samples”, JCT-VC 2nd Meeting Geneva, July, 2010 It doesn't matter. FIG. 33 shows the intra prediction unit 109 when adaptive reference pixel filtering is used. 6 is different from the intra prediction unit 109 shown in FIG. 6 in that a reference pixel filter unit 3301 is added. The reference pixel filter unit 3301 receives the reference image signal 159 and the prediction mode 651, performs adaptive filter processing described later, and outputs a filtered reference image signal 3351. The filtered reference image signal 3351 is input to the unidirectional intra predicted image generation unit 601 and the bidirectional intra predicted image generation unit 602. The configuration and processing other than the reference pixel filter unit 3301 are the same as those of the intra prediction unit 109 shown in FIG.

Next, the reference pixel filter unit 3301 will be described. The reference pixel filter unit 3301 determines whether to filter reference pixels used for intra prediction according to the reference pixel filter flag and the intra prediction mode included in the prediction mode 651. The reference pixel filter flag is a flag indicating whether or not to filter the reference pixel when the intra prediction mode IntraPredMode is a value other than “Intra_DC”. When the reference pixel filter flag is 1, the reference pixel is filtered. In the case of the reference pixel filter flag 0, the reference pixel is not filtered. When IntraPredMode is “Intra_DC”, the reference pixel is not filtered and the reference pixel filter flag is set to 0. When the reference pixel filter flag is 1, a filtered reference image signal 3351 is calculated by the following filtering. Note that p [x, y] indicates a reference pixel before filtering, and pf [x, y] indicates a reference pixel in filter terms. Further, x and y indicate relative positions of the reference pixels when the upper left pixel position in the prediction unit is x = 0 and y = 0. PuPartSize indicates the size (pixel) of the prediction unit.

<Syntax structure 5>
34A and 34B show a prediction unit syntax structure when performing adaptive reference pixel filtering. FIG. 34A adds the syntax intra_luma_filter_flag [i] related to the adaptive reference pixel filter to FIG. 30A. FIG. 34B adds syntax intra_luma_filter_flag [i] related to the adaptive reference pixel filter to FIG. 30C. intra_luma_filter_flag [i] is further encoded when the intra prediction mode IntraPredMode [i] is other than Intra_DC. When the flag is 0, it indicates that the reference pixel is not filtered. Further, when intra_luma_filter_flag [i] is 1, it indicates that the reference pixel filtering is applied.

In the above example, intra_luma_filter_flag [i] is encoded when the intra prediction mode IntraPredMode [i] is other than Intra_DC. As another example, when IntraPredMode [i] is 0 to 2, intra_luma_filter_flag [ i] need not be encoded. In this case, intra_luma_filter_flag [i] is set to 0.

In addition, for the other syntax structures shown in FIGS. 30B, 30D, and 30E, the intra_luma_filter_flag [i] described above may be added in the same meaning.

(Second modification)
<Second Modification of Intra Prediction Unit>
As a second modification of the intra prediction unit 109, it may be used in combination with the composite intra prediction shown in JCTVC-B205_draft002, section 9.6 “Combined Intra Prediction”, JCT-VC 2nd Meeting Geneva, July, 2010 . In the decoded intra prediction in this document, a prediction value is obtained by performing weighted averaging of the result of the above-described unidirectional intra prediction and the average value of pixels adjacent to the left, top, and top left with respect to the prediction pixel. When a decoded image signal 157 is calculated in a moving picture decoding apparatus 5000 or an image encoding apparatus 100 described later, decoded pixels can be used as pixels adjacent to the left, upper, and upper left. On the other hand, since it is impossible to use decoded pixels before the decoded image signal 157 is calculated in the image encoding device 100, the input image signal 151 is used as a pixel adjacent to the left, upper, and upper left. FIG. 35 shows positions of adjacent decoded pixels A (left), B (upper), and C (upper left) used for prediction of the prediction target pixel X. Therefore, composite intra prediction is a so-called open-loop prediction method in which prediction values differ between the image encoding device 100 and the moving image decoding device 5100.

FIG. 37 shows a block diagram of the intra prediction unit 109 when combined with composite intra prediction. A difference is that a composite intra predicted image generation unit 3601, a selection switch 3602, and a decoded image buffer 3701 are added to the intra prediction unit 109 shown in FIG.

When the bidirectional intra prediction and the composite intra prediction are combined, first, in the selection switch 604, the unidirectional intra prediction image generation unit 601 or the bidirectional intra prediction image generation unit according to the prediction mode information controlled by the encoding control unit 115. The output terminal of 602 is switched. Hereinafter, the output predicted image signal 161 is referred to as a direction predicted image signal 161.

Thereafter, the direction prediction image signal 161 is input to the composite intra prediction image generation unit 3601, and the prediction image signal 161 in the composite intra prediction is generated. The description of the composite intra predicted image generation unit 3601 will be described later. Thereafter, the selection switch 3602 switches between using the prediction image signal 161 and the direction prediction image signal in the composite intra prediction according to the composite intra prediction application flag in the prediction mode information controlled by the encoding control unit 115. The final prediction image signal 161 in the intra prediction unit 109 is output. When the composite intra prediction application flag is 1, the predicted image signal 161 output from the composite intra predicted image generation unit 3601 becomes the final predicted image signal 161. On the other hand, when the composite intra prediction application flag is 0, the direction prediction image signal 161 is the prediction image signal 161 that is finally output. The predicted image signal output from the composite intra predicted image generation unit 3601 is also called a sixth predicted image signal.

When the prediction image signal 161 is generated from the composite intra prediction image generation unit 3601, the addition unit 106 adds the decoded prediction error signal 156 separately decoded and the pixel unit to generate a decoded image signal 157 for each pixel. And stored in the decoded image buffer 3701. The stored decoded image signal 157 in units of pixels is input to the composite intra predicted image generation unit 3601 as a reference pixel 3751, and is used for pixel level prediction described later as an adjacent pixel 3751 shown in FIG.

Next, the composite intra prediction image generation unit 3601 will be described with reference to FIG. The composite intra prediction image generation unit 3601 includes a pixel level prediction signal generation unit 3801 and a composite intra prediction calculation unit 3802. The pixel level prediction signal generation unit 3801 inputs the reference pixel 3751 as the adjacent pixel 3751 and outputs the pixel level prediction signal 3851 by predicting the prediction target pixel X from the adjacent pixel. Specifically, the pixel level prediction signal 3851 (X) of the prediction target pixel is calculated from A, B, and C indicating the adjacent pixel 3751 using Equation (21).

Note that the coefficients related to A, B, and C may be other values.

The composite intra prediction calculation unit 3802 performs a weighted average of the direction prediction image signal 161 (X ′) and the pixel level prediction signal 3851 (X), and outputs a final prediction image signal 161 (P). Specifically, the following formula is used.

Note that W is a weighted average weight coefficient (an integer value between W = 0 and 32) of the direction prediction image signal 161 (X ′) and the pixel level prediction signal 3851 (X).

When the prediction image signal 161 is generated using the composite intra prediction, and the prediction error signal 152 and the decoded image signal 157 are further generated, the decoded image signal 157 may have different values in encoding and decoding. Therefore, after all the decoded image signals 157 in the encoded prediction syntax are generated, the above-described combined intra prediction is executed again using the decoded image signal 157 as an adjacent pixel, so that the predicted image signal 161 that is the same as that in the decoding is obtained. Is further added to the prediction error signal 152 to generate a decoded image signal 157 identical to the decoding.

The above is an embodiment when combined with composite intra prediction.

(Third Modification)
<Third Modification of Intra Prediction Unit>
The weighting factor W may be switched according to the position of the prediction pixel in the prediction unit. In general, a prediction image signal generated using unidirectional intra prediction and bidirectional intra prediction generates a prediction value from spatially adjacent reference pixels positioned on the left or above already encoded. The absolute value of the prediction error tends to increase as the distance from the reference pixel increases. Therefore, by increasing the weighting coefficient of the direction prediction image signal 161 and the pixel level prediction signal 3851 when the distance is close to the reference pixel, the weighting coefficient of the direction prediction image signal 161 is increased, and when it is far away, the weighting coefficient is decreased. It becomes possible.

On the other hand, in the complex intra prediction, a prediction error signal is generated using an input image signal at the time of encoding. At this time, since the pixel level prediction signal 3851 becomes an input image signal, even when the spatial distance between the reference pixel position and the prediction pixel position is increased, the prediction of the pixel level prediction signal 3851 is compared with the direction prediction image signal 161. High accuracy. However, the weighting coefficient of the direction prediction image signal 161 and the pixel level prediction signal 3851 is simply increased when the weight coefficient of the direction prediction image signal 161 is close to the reference pixel, and is decreased when the distance is small. Although the prediction error is reduced, there is a problem that the prediction accuracy at the time of encoding and the prediction value at the time of local decoding are different and the prediction accuracy is lowered. Therefore, especially when the value of the quantization parameter is large, as the spatial distance between the reference pixel position and the predicted pixel position becomes large, the difference generated in the case of such an open loop is set by setting the value of W small. A decrease in coding efficiency due to the phenomenon can be suppressed.

<Syntax structure 6>
39A and 39B show the prediction unit syntax structure when performing composite intra prediction. FIG. 39A is different from FIG. 30A in that a syntax combined_intra_pred_flag for switching presence / absence of composite intra prediction is added. This is equivalent to the above-described composite intra prediction application flag. In addition, FIG. 39B adds a syntax combined_intra_pred_flag for switching presence / absence of composite intra prediction to FIG. 30C. When combined_intra_pred_flag is 1, the selection switch 3602 shown in FIG. 37 is connected to the output terminal of the composite intra predicted image generation unit 3601. When combined_intra_pred_flag is 0, the selection switch 3602 shown in FIG. 37 is connected to the output terminal of either the unidirectional intra prediction image generation unit 601 or the bidirectional intra prediction image generation unit 602 to which the selection switch 604 is connected. .

Furthermore, you may combine with the 2nd modification of an intra estimation part. The above is the description regarding another embodiment of the intra prediction unit 109.

According to the first embodiment described above, highly efficient intra prediction can be realized. Therefore, the coding efficiency is improved, and the subjective image quality is also improved.

(Second Embodiment)
<Moving Image Encoding Device—Second Embodiment>
The video encoding apparatus according to the second embodiment differs from the image encoding apparatus according to the first embodiment in details of orthogonal transform and inverse orthogonal transform. In the following description, in the present embodiment, the same parts as those in the first embodiment are denoted by the same indexes, and different parts will be mainly described. A moving picture decoding apparatus corresponding to the picture encoding apparatus according to the present embodiment will be described in a fifth embodiment.

FIG. 40 is a block diagram showing a video encoding apparatus according to the second embodiment. The change from the moving picture encoding apparatus according to the first embodiment is that a transformation selection unit 4001 and a coefficient order control unit 4002 are added. Also, the internal structures of the orthogonal transform unit 102 and the inverse orthogonal transform unit 105 are different. Hereinafter, processing performed by the moving image encoding apparatus in FIG. 40 will be described.

First, the orthogonal transform unit 102 and the inverse orthogonal transform unit 105 will be described with reference to FIGS. 41 and 42, respectively.

<Orthogonal transform unit 102>
The orthogonal transform unit 102 in FIG. 41 includes a first orthogonal transform unit 4101, a second orthogonal transform unit 4102, an Nth orthogonal transform unit 4103, and a transform selection switch 4104. Although an example having N types of orthogonal transform units is shown here, there may be a plurality of transform sizes using the same orthogonal transform method, or there may be a plurality of orthogonal transform units performing different orthogonal transform methods. . Moreover, each may be mixed. For example, the first orthogonal transform unit 4101 can be set to 4 × 4 size DCT, the second orthogonal transform unit 4102 can be set to 8 × 8 size DCT, and the Nth orthogonal transform unit 4103 can be set to 16 × 16 size DCT. The first orthogonal transform unit 4101 is 4 × 4 size DCT, the second orthogonal transform unit 4102 is 4 × 4 size DST (discrete sine transform), and the Nth orthogonal transform unit 4103 is 8 × 8 size KLT (Karunen-Labe transform). ) Can also be set. In addition, it is possible to select a transform that is not orthogonal transform, or a single transform. In this case, N = 1 is considered.

First, the conversion selection switch 4104 will be described. The conversion selection switch 4104 has a function of selecting the output terminal of the subtraction unit 101 according to the conversion selection information 4051. The conversion selection information 4051 is one piece of information controlled by the encoding control unit 115, and is set by the conversion selection unit 4001 according to the prediction information 160. For example, H.M. In H.264, 4 × 4 DCT is set for intra prediction of a 4 × 4 pixel block (prediction unit), and 8 × 8 DCT is set for intra prediction of an 8 × 8 pixel block (prediction unit). In the present embodiment, when the transformation selection information 4051 indicates the first orthogonal transformation, the output terminal of the switch is connected to the first orthogonal transformation unit 4101. On the other hand, when the transformation selection information 4051 is the second orthogonal transformation, the output end is connected to the second orthogonal transformation unit 4102.

Next, processing from the first orthogonal transform unit 4101 to the Nth orthogonal transform unit 4103 will be described. In the present embodiment, an example in which one of the N orthogonal transform units is DCT and the other is KLT (Karunen-Loeve transform) will be described. Here, the first orthogonal transform unit 4101 performs DCT, and the other

orthogonal transform units

4102 and 4103 perform KLT (Carhunen-Labe transform).

<Inverse orthogonal transform unit 105>
The inverse orthogonal transform unit 105 in FIG. 42 includes a first inverse orthogonal transform unit 4201, a second inverse orthogonal transform unit 4202, an Nth inverse orthogonal transform unit 4203, and a transform selection switch 4204. First, the conversion selection switch 4204 will be described. The transformation selection switch 4204 has a function of selecting the output terminal of the inverse quantization unit 104 according to the inputted transformation selection information 4051. The conversion selection information 4051 is one piece of information controlled by the encoding control unit 115, and is set by the conversion selection unit 4001 according to the prediction information 160.

When the transformation selection information 4051 is the first orthogonal transformation, the output terminal of the switch is connected to the first inverse orthogonal transformation unit 4201. On the other hand, when the transformation selection information 4051 is the second orthogonal transformation, the output end is connected to the second inverse orthogonal transformation unit 4202. Similarly, when the transform selection information 4051 is the Nth orthogonal transform, the output terminal is connected to the Nth inverse orthogonal transform unit 4203. Here, the transform selection information 4051 set in the orthogonal transform unit 102 and the transform selection information 4051 set in the inverse orthogonal transform unit 105 are the same, and the inverse orthogonal transform corresponding to the transform performed in the orthogonal transform unit 102 is performed. This is performed synchronously by the inverse orthogonal transform unit 105. That is, the first inverse orthogonal transform unit 4201 performs inverse discrete cosine transform (hereinafter referred to as IDCT), and the second inverse orthogonal transform unit 4202 and the Nth inverse orthogonal transform unit 4203 are based on KLT (Karunen-Labe transform). Inverse transformation is performed. Although an example using IDCT or the like is shown here as an example, orthogonal transformation such as Hadamard transformation or discrete sine transformation may be used, or non-orthogonal transformation may be used. In any case, the corresponding inverse conversion is performed in conjunction with the conversion unit 102.

<Conversion selection unit 4001>
Next, the conversion selection unit 4001 shown in FIG. 40 will be described. The transformation selection unit 4001 receives prediction information 160 that is controlled by the encoding control unit 115 and includes the prediction mode set by the prediction selection unit 112 and the like. Based on the prediction information 160, the transform selection unit 4001 has a function of setting MapdTransformIdx information indicating which orthogonal transform is used for which prediction mode. FIG. 43 shows conversion selection information 4051 (MappedTransformIdx) in intra prediction. Here, an example of N = 9 is shown. Note that the first orthogonal transform unit 4101 and the corresponding first inverse orthogonal transform unit 4201 are selected during DC prediction corresponding to IntraPredModeLX = 2. By mapping to the reference prediction mode with a close prediction angle in this way, compared to the case of preparing an orthogonal transformer and an inverse orthogonal transformer for all prediction modes, orthogonal transformation and inverse orthogonal transformation at the time of hardware implementation It is possible to reduce the circuit scale. When bi-directional intra prediction is selected, after two IntraPredModeL0 and IntraPredModeL1 are derived, MapTransformIdx is derived from FIG. 43 using a prediction mode corresponding to IntraPredModeL0. In the present embodiment, an example of N = 9 has been shown, but the value of N may be selected in an optimal combination by balancing the coding performance and the circuit scale at the time of hardware implementation.

<Coefficient order controller 4002>
Next, the coefficient order control unit 4002 will be described. FIG. 44 shows a block diagram of the coefficient order control unit 4002. The coefficient order control unit 4002 includes a coefficient order selection switch 4404, a first coefficient order conversion unit 4401, a second coefficient order conversion unit 4402, and an Nth coefficient order conversion unit 4403. For example, the coefficient order selection switch 4404 has a function of switching between the output terminal of the switch and the coefficient order conversion units 4401 to 4403 in accordance with the MappedTransformIdx shown in FIG. The N types of coefficient order conversion units 4401 to 4403 have a function of converting the two-dimensional data of the quantization conversion coefficient 154 quantized by the quantization unit 103 into one-dimensional data. For example, H.M. In H.264, two-dimensional data is converted into one-dimensional data using a zigzag scan.

When orthogonal transform in consideration of the intra prediction direction is used, the quantized transform coefficient 154 obtained by performing the quantization process on the transform coefficient 153 subjected to orthogonal transform has a characteristic that the tendency of generating non-zero transform coefficients in the block is biased. have. The tendency of occurrence of this non-zero transform coefficient has different properties for each prediction direction of intra prediction. However, when different videos are encoded, the generation tendency of non-zero transform coefficients in the same prediction direction has a similar property. Therefore, when transforming two-dimensional data into one-dimensional data (2D-1D conversion), entropy coding is performed preferentially from transform coefficients at positions where the occurrence probability of non-zero transform coefficients is high, thereby encoding transform coefficients. It is possible to reduce information. Therefore, by learning the generation probability of the non-zero conversion coefficient in advance based on information indicating the prediction direction such as the prediction mode included in the prediction information 160, for example, H.264. Compared with H.264, it is possible to reduce the code amount of the transform coefficient without causing an increase in the calculation amount.

As yet another example, the coefficient order control unit 4002 may dynamically update the scan order in 2D-1D conversion. The coefficient order control unit 4002 that performs such an operation is illustrated in FIG. The coefficient order control unit 4002 includes an occurrence frequency counting unit 4501 and an updating unit 4502 in addition to the configuration of FIG. The coefficient order conversion units 4401 to 4403 are the same except that the scan order is updated by the update unit 4502.

The occurrence frequency counting unit 4501 creates a histogram 4552 of the number of occurrences of non-zero coefficients in each element of the quantized transform coefficient sequence 4052 for each prediction mode. The occurrence frequency counting unit 4501 inputs the created histogram 4552 to the updating unit 4502.

The update unit 4502 updates the coefficient order based on the histogram 4552 at a predetermined timing. The timing is, for example, the timing when the coding process of the coding tree unit is finished, the timing when the coding process for one line in the coding tree unit is finished, or the like.

Specifically, the update unit 4502 refers to the histogram 4552 and updates the coefficient order with respect to the prediction mode having an element in which the number of occurrences of non-zero coefficients is counted more than a threshold. For example, the update unit 4502 updates the prediction mode having an element in which the occurrence of a non-zero coefficient is counted 16 times or more. By providing a threshold value for the number of occurrences, the coefficient order is updated globally, so that it is difficult to converge to a local optimum solution.

The update unit 4502 sorts the elements in the descending order of the occurrence frequency of the non-zero coefficient regarding the prediction mode to be updated. Sorting can be realized by existing algorithms such as bubble sort and quick sort. Then, the update unit 4502 inputs the update coefficient order 4551 indicating the order of the sorted elements to the coefficient order conversion parts 4401 to 4403 corresponding to the prediction mode to be updated.

When the update coefficient order 4551 is input, each conversion unit performs 2D-1D conversion according to the updated scan order. When the scan order is dynamically updated, the initial scan order of each 2D-1D conversion unit needs to be determined in advance. As described above, by dynamically updating the scan order, the tendency of occurrence of non-zero coefficients in the quantized transform coefficients 154 changes according to the influence of the properties of the predicted image, quantization information (quantization parameters), and the like. Even in this case, high encoding efficiency can be expected stably. Specifically, the generated code amount of run-length encoding in the entropy encoding unit 113 can be suppressed.
Note that the syntax configuration in the present embodiment is the same as in the first embodiment.

As a modification of the present embodiment, the conversion selection unit 4001 can select the mapped transform IDx separately from the prediction information 160. In this case, information indicating which nine types of orthogonal transforms or inverse orthogonal transforms are used is set in the entropy encoding unit 113 and encoded together with the quantized transform coefficient sequence 4052. FIG. 46 shows an example of syntax in this modification. Directional_transform_idx indicated in the syntax indicates information indicating which of N orthogonal transforms has been selected.

According to the second embodiment described above, highly efficient orthogonal transformation and inverse orthogonal transformation can be realized while alleviating the difficulty in hardware implementation and software implementation. Therefore, the coding efficiency is improved, and the subjective image quality is also improved.

(Third embodiment)
<Moving Image Encoding Device—Third Embodiment>
As an embodiment related to the orthogonal transformation unit 102, it may be combined with the rotation transformation shown in JCTVC-B205_draft002, section 5.3.5.2 “Rotational transformation process”, JCT-VC 2nd Meeting Geneva, July, 2010. Rotational transformation is a technique for further increasing the coefficient density of transformation coefficients by further performing rotational transformation after orthogonal transformation using DCT.

<Orthogonal transform unit 102>
FIG. 47 is a block diagram of the orthogonal transform unit 102 according to this embodiment. The orthogonal transform unit 102 includes new processing units such as a first rotation transform unit 4701, a second rotation transform unit 4702, an Nth rotation transform unit 4703, and a discrete cosine transform unit 4704, and includes an existing transform selection switch 4104. The discrete cosine transform unit 4704 performs DCT, for example. The conversion coefficient after DCT is input to the conversion selection switch 4104. Here, the conversion selection switch 4104 connects the output end of the switch to any of the first rotation conversion unit 4701, the second rotation conversion unit 4702, and the Nth rotation conversion unit 4703 according to the conversion selection information 4051. For example, the switches are sequentially switched according to the control of the encoding control unit 115. The rotation conversion units 4701 to 4703 perform rotation conversion on each conversion coefficient using a predetermined rotation matrix. A conversion coefficient 153 after rotation conversion is output. This conversion is a reversible conversion.

Here, it may be determined which rotation matrix is used by using the encoding cost as shown in the above formulas (1) and (2). Also, a table in which the prediction mode and the conversion number as shown in FIG. 43 are associated in advance may be prepared and selected. Here, an example in which the rotation conversion unit is applied before the quantization unit 103 is shown, but the rotation conversion unit may be applied to the quantization conversion coefficient 154 after the quantization process. In this case, the orthogonal transform unit 102 performs only DCT.

<Inverse orthogonal transform unit 105>
FIG. 48 is a block diagram of the inverse orthogonal transform unit 105 according to the present embodiment. The inverse orthogonal transform unit 105 includes new processing units such as a first inverse rotation transform unit 4801, a second inverse rotation transform unit 4802, an Nth inverse rotation transform unit 4803, and an inverse discrete cosine transform unit 4804, and an existing transform selection switch 4204. Have The restored transform coefficient 155 input after the inverse quantization process is input to the transform selection switch 4204. Here, the conversion selection switch 4204 connects the output terminal of the switch to one of the first reverse rotation conversion unit 4801, the second reverse rotation conversion unit 4802, and the Nth reverse rotation conversion unit 4803 according to the conversion selection information 4051. After that, the reverse rotation conversion processing is performed in any one of the reverse rotation conversion units 4801 to 4803, which is the same as the rotation conversion used in the orthogonal conversion unit 102, and the result is output to the inverse discrete cosine conversion unit 4804. The inverse discrete cosine transform unit 4804 performs, for example, IDCT on the input signal to restore the restored prediction error signal 156. Although an example using IDCT is shown here as an example, orthogonal transform such as Hadamard transform or discrete sine transform may be used, or non-orthogonal transform may be used. In any case, the corresponding inverse conversion is performed in conjunction with the conversion unit 102.

The syntax in this embodiment is shown in FIG. The rotation_transform_idx shown in the syntax means the number of the rotation matrix to be used.

According to the third embodiment described above, highly efficient orthogonal transformation and inverse orthogonal transformation can be realized while alleviating the difficulty in hardware implementation and software implementation. Therefore, the coding efficiency is improved, and the subjective image quality is also improved.

(Fourth embodiment)
The fourth embodiment relates to a moving picture decoding apparatus. The video encoding device corresponding to the video decoding device according to the present embodiment is as described in the first embodiment. That is, the moving picture decoding apparatus according to the present embodiment decodes encoded data generated by, for example, the moving picture encoding apparatus according to the first embodiment.

As shown in FIG. 50, the moving picture decoding apparatus according to this embodiment includes an input buffer 5001, an entropy decoding unit 5002, an inverse quantization unit 5003, an inverse orthogonal transform unit 5004, an addition unit 5005, and a loop filter 5006. An image memory 5007, an intra prediction unit 5008, an inter prediction unit 5009, a prediction selection switch 5010, an output buffer 5011, a decoding control unit 5012, and an intra prediction mode memory 5013 are included.

50 decodes the encoded data 5051 stored in the input buffer 5001, stores the decoded image 5060 in the output buffer 5011, and outputs it as an output image. The encoded data 5051 is output from, for example, the moving image encoding apparatus shown in FIG. 1 or the like, and is temporarily stored in the input buffer 5001 through a storage system or transmission system (not shown).

The entropy decoding unit 5002 performs decoding based on the syntax for each frame or field for decoding the encoded data 5051. The entropy decoding unit 5002 sequentially entropy-decodes the code string of each syntax, and reproduces the encoding parameters of the encoding target block such as prediction information 5059 including the prediction mode information and the quantization transform coefficient 5052. The encoding parameter is a parameter necessary for decoding, such as prediction information 5059, information on transform coefficients, information on quantization, and the like.

The inverse quantization unit 5003 performs inverse quantization on the quantized transform coefficient 5052 from the entropy decoding unit 5002 to obtain a restored transform coefficient 5053. Specifically, the inverse quantization unit 5003 performs inverse quantization according to the information on the quantization decoded by the entropy decoding unit 5002. The inverse quantization unit 5003 inputs the restored transform coefficient 5053 to the inverse orthogonal transform unit 5004.

The inverse orthogonal transform unit 5004 performs inverse orthogonal transform corresponding to the orthogonal transform performed on the encoding side, on the reconstruction transform coefficient 5053 from the inverse quantization unit 5003, and obtains a reconstruction prediction error signal 5054. The inverse orthogonal transform unit 5004 inputs the restored prediction error signal 5054 to the addition unit 5005.

The addition unit 5005 adds the restored prediction error signal 5054 and the corresponding predicted image signal 5058 to generate a decoded image signal 5055. The decoded image signal 5055 is input to the loop filter 5006. The loop filter 5006 performs a deblocking filter, a Wiener filter, or the like on the input decoded image signal 5055 to generate a filtered image signal 5056. The generated filtered image signal 5056 is temporarily stored in the output buffer 5011 for the output image, and is also stored in the reference image memory 5007 for the reference image signal 5057. The filtered image signal 5056 stored in the reference image memory 5007 is referred to by the intra prediction unit 5008 and the inter prediction unit 5009 as a reference image signal 5057 in units of frames or fields as necessary. The filtered image signal 5056 temporarily accumulated in the output buffer 5011 is output according to the output timing managed by the decoding control unit 5012.

The intra prediction mode memory 5013 has the same function as the intra prediction mode memory 116 shown in FIG. 1 and stores intra prediction mode information 5061 applied to the prediction unit for which decoding has been completed. When the unit 5008 generates bidirectional prediction mode information as necessary, it is referred to as reference intra prediction mode information 5062 each time.
The intra prediction unit 5008, the inter prediction unit 5009, and the selection switch 5010 are substantially the same or similar elements as the intra prediction unit 109, the inter prediction unit 110, and the selection switch 111 in FIG. The intra prediction unit 5008 and the intra prediction unit 109 use the reference intra prediction mode information 5062 stored in the intra prediction mode memory 5013 and the reference intra prediction mode information 164 stored in the intra prediction mode memory 116, respectively. Make a prediction. For example, H.M. In H.264, an intra prediction image is obtained by performing pixel interpolation (copying or copying after interpolation) along a prediction direction such as a vertical direction or a horizontal direction using an encoded reference pixel value adjacent to a prediction target block. Generate. In FIG. The prediction direction of intra prediction in H.264 is shown. Further, in FIG. The arrangement | positioning relationship between the reference pixel and encoding object pixel in H.264 is shown. FIG. 5C illustrates a predicted image generation method in mode 1 (horizontal prediction), and FIG. 5D illustrates a predicted image generation method in mode 4 (diagonal lower right prediction).

Also, Jung-Hye Min, “Unification of the Directional Intra Prediction Methods in TMuC”, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11-VCB , July 2010. The prediction direction of H.264 is further expanded to 34 directions to increase the number of prediction modes. A predicted pixel value is created by performing linear interpolation with 32-pixel accuracy in accordance with the predicted angle, and is copied in the predicted direction. Details of the intra prediction unit 5008 used in this embodiment will be described later.

The inter prediction unit 5009 performs inter prediction using the reference image signal 5057 stored in the reference image memory 5007. Specifically, the inter prediction unit 5009 obtains a motion shift amount (motion vector) between the prediction target block and the reference image signal 5057 from the entropy decoding unit 5002, and performs an interpolation process ( Motion prediction) is performed to generate an inter prediction image. H. With H.264, interpolation processing up to 1/4 pixel accuracy is possible.

The prediction selection switch 5010 selects the output terminal of the intra prediction unit 5008 or the output terminal of the inter prediction unit 5009 according to the decoded prediction information 5059, and inputs the intra prediction image or the inter prediction image to the adding unit 5005 as the prediction image signal 5058. To do. When the prediction information 5059 indicates intra prediction, the prediction selection switch 5010 connects a switch to the output terminal from the intra prediction unit 5008. On the other hand, when the prediction information 5059 indicates inter prediction, the prediction selection switch 5010 connects a switch to the output terminal from the inter prediction unit 5009.

The decoding control unit 5012 controls each element of the moving picture decoding apparatus in FIG. Specifically, the decoding control unit 5012 performs various controls for decoding processing including the above-described operation.

50 uses the same or similar syntax as that described with reference to FIGS. 28, 29, 30A to 30E, 34A to 34B, and 39A to 39B. Detailed description thereof is omitted.

Hereinafter, the details of the intra prediction unit 5008 will be described with reference to FIG.
In the present embodiment, the intra prediction unit 5008 has the same configuration and processing content as the intra prediction unit 109 described in the first embodiment.

An intra prediction unit 5008 (109 in FIG. 6) illustrated in FIG. 6 includes a unidirectional intra prediction image generation unit 601, a bidirectional intra prediction image generation unit 602, a prediction mode information setting unit 603, a selection switch 604, and bidirectional intra prediction. A mode generation unit 605 is included. First, a reference image signal 5057 (159 in FIG. 6) is input from the reference image memory 5007 to the unidirectional intra prediction image generation unit 601 and the bidirectional intra prediction image generation unit 602. Here, according to the prediction mode information controlled by the decoding control unit 5012, the prediction mode information setting unit 603 determines the prediction mode generated by the unidirectional intra prediction image generation unit 601 or the bidirectional intra prediction image generation unit 602. Set and output prediction mode 651. The bidirectional intra prediction mode generation unit 605 outputs the bidirectional intra prediction mode information 652 according to the prediction mode 651 and the reference intra prediction mode information 164. The selection switch 604 has a function of switching the output ends of the respective intra predicted image generation units in accordance with the prediction mode 651. If the input prediction mode 651 is the unidirectional intra prediction mode, the output terminal of the unidirectional intra prediction image generation unit 601 is connected to the switch, and if the prediction mode 651 is the bidirectional intra prediction mode, the bidirectional intra prediction is performed. The output terminal of the image generation unit 602 is connected. On the other hand, each of the intra predicted

image generation units

601 and 602 generates a predicted image signal 5058 (161 in FIG. 6) according to the prediction mode 651. The generated predicted image signal 5058 is output from the intra prediction unit 109.

First, the prediction mode information setting unit 603 will be described in detail. 7A and 7B show the numbers of the prediction modes according to the present embodiment for each block size. PuSize indicates a pixel block (prediction unit) size to be predicted, and seven types of sizes from PU_2x2 to PU_128x128 are defined. IntraUniModeNum represents the number of prediction modes for unidirectional intra prediction, and IntraBiModeNum represents the number of prediction modes for bidirectional intra prediction. Also, Number of modes is the total number of prediction modes for each pixel block (prediction unit) size.

On the other hand, FIGS. 8A and 8B show the relationship between the prediction mode and the prediction method when PuSize is PU_8x8, PU_16x16, and PU_32x32. 9A and 9B show a case where PuSize is PU_4x4, and FIG. 10 shows a case where PU_64x64 or PU_128x128. Here, IntraPredMode indicates a prediction mode number, and IntraBipredFlag is a flag indicating whether or not bidirectional intra prediction. When the flag is 0, it indicates that the prediction mode is a unidirectional intra prediction mode. When the flag is 1, it indicates that the prediction mode is the bidirectional intra prediction mode. When the flag is 1, the bidirectional intra prediction mode generation unit 605 generates bidirectional intra prediction mode information 652 in accordance with IntraBipredTypeIdx that defines a bidirectional intra prediction generation method. When IntraBipredTypeIdx is 0, two types of unidirectional intra prediction modes used for bidirectional intra prediction are set in a first prediction mode generation unit 1901 described later using a predetermined table. Hereinafter, a method in which two types of unidirectional intra prediction modes used for bidirectional intra prediction are preliminarily tabled is referred to as a fixed table method. FIG. 8A shows an example in which all bidirectional intra prediction modes are fixed table methods.

When IntraBipredTypeIdx is a value larger than 0, two types of unidirectional intra prediction modes used for bidirectional intra prediction are set based on the reference intra prediction mode information 164. Hereinafter, a method in which two types of unidirectional intra prediction modes used for bidirectional intra prediction based on the reference intra prediction mode information 164 are set is referred to as a direct method. IntraBipredTypeIdx has different values depending on the method of deriving two types of unidirectional intra prediction modes from the reference intra prediction mode information 164.

IntraPredTypeLX indicates the prediction type of intra prediction. Intra_Vertical means that the vertical direction is the reference for prediction, and Intra_Horizontal means that the horizontal direction is the reference for prediction. Note that 0 or 1 is applied to X in IntraPredTypeLX. IntraPredTypeL0 indicates the first prediction mode of unidirectional intra prediction or bidirectional intra prediction. IntraPredTypeL1 indicates the second prediction mode of bidirectional intra prediction. IntraPredAngleId is an index indicating an index of a prediction angle. The prediction angle actually used in the generation of the predicted value is shown in FIG. Here, puPartIdx represents the index of the divided block in the quadtree division described with reference to FIG. 3B.

The prediction mode information setting unit 603 converts the above-described prediction information corresponding to the designated prediction mode 651 to the unidirectional intra prediction image generation unit 601 and the bidirectional intra prediction image generation unit 602 under the control of the decoding control unit 5012. And the prediction mode 651 is output to the selection switch.

Next, the unidirectional intra predicted image generation unit 601 will be described in detail. The unidirectional intra predicted image generation unit 601 has a function of generating a predicted image signal 5058 (161 in FIG. 6) for a plurality of prediction directions shown in FIG. In FIG. 12, there are 33 different prediction directions for the vertical and horizontal coordinates indicated by bold lines. H. The direction of a typical prediction angle indicated by H.264 is indicated by an arrow. In this embodiment, 33 kinds of prediction directions are prepared in the direction which pulled the line shown by the arrow from the origin. H. Similar to H.264, DC prediction for predicting with an average value of available reference pixels is added, and there are 34 prediction modes in total.

When IntraPredMode = 4, because IntraPredAngleIdL0 is −4, a prediction image signal 5058 (161 in FIG. 6) is generated in the prediction direction indicated by IntraPredMode = 4 in FIG. The arrows included in the range shown in “Intra_Vertical” shown at the bottom of FIG. 12 indicate the prediction mode whose prediction type is Intra_Vertical, and are included in the range shown in “Intra_Horizontal” shown on the right side of FIG. An arrow indicates a prediction mode whose prediction type is Intra_Horizontal.

<Intra Prediction Unit 5008>
Next, a prediction image generation method of the unidirectional intra prediction image generation unit 601 will be described. Here, based on the input reference image signal 5057 (159 in FIG. 6), a predicted image value is generated, and the pixels are copied in the above-described prediction direction. The predicted image value is generated by performing interpolation with 1/32 pixel accuracy. FIG. 11 shows the relationship between IntraPredAngleIdLX and intraPredAngle used for predictive image value generation. intraPredAngle indicates a prediction angle that is actually used when a predicted value is generated. For example, when the prediction type is Intra_Vertical and intraPredAngle shown in FIG. 11 is a positive value, the prediction value generation method is expressed by the above equation (3). Here, BLK_SIZE indicates the size of the pixel block (prediction unit), and ref [] indicates an array in which reference image signals are stored. Also, pred (k, m) indicates the generated predicted image signal 5058 (161 in FIG. 6).

Next, the bidirectional intra predicted image generation unit 602 will be described in detail. FIG. 13 shows a block diagram of the bidirectional intra-predicted image generation unit 602. The bidirectional intra predicted image generation unit 602 includes a first unidirectional intra predicted image generation unit 1301, a second unidirectional intra predicted image generation unit 1302, and a weighted average unit 1303. An input reference image signal 5057 (FIG. 13 has a function of generating two unidirectional intra-predicted images based on 159) and generating a predicted image signal 5058 (161 in FIG. 13) by weighted averaging them.

The functions of the first unidirectional intra predicted image generation unit 1301 and the second unidirectional intra predicted image generation unit 1302 are the same. In either case, a prediction image signal corresponding to a prediction mode given according to prediction mode information controlled by the encoding control unit 115 is generated. A first predicted image signal 1351 is output from the first unidirectional intra predicted image generation unit 1301, and a second predicted image signal 1352 is output from the second unidirectional intra predicted image generation unit 1302. Each predicted image signal is input to the weighted average unit 1303, and weighted average processing is performed.

For example, in the case of PuSize = PU — 8 × 8 and IntraPredMode = 34, it can be seen from FIG. 7A or 7B that IntraUniModeNum = 34, and therefore BipredIdx = 0. As a result, it is derived from FIG. 14 that the first unidirectional intra prediction mode (MappedBi2Uni (0, idx)) is 1 and the second unidirectional intra prediction mode (MappedBi2Uni (1, idx)) is 0. In other PuSize and IntraPredMode, it is possible to derive two prediction modes by the same method. Hereinafter, the first unidirectional intra prediction mode is expressed as IntraPredModeL0, and the second unidirectional intra prediction mode is expressed as IntraPredModeL1.

Thus, the first predicted image signal 1351 and the second predicted image signal 1352 generated by the first unidirectional intra predicted image generation unit 1301 and the second unidirectional intra predicted image generation unit 1302 are sent to the weighted average unit 1303. Entered.

The weighted average unit 1303 calculates a Euclidean distance or a city area distance (Manhattan distance) based on the prediction directions of IntraPredModeL0 and IntraPredModeL1, and derives a weight component used in the weighted average process. The weight component of each pixel is represented by the reciprocal of the Euclidean distance or the city distance from the reference pixel used for prediction, and is generalized by Expression (5). Here, when using the Euclidean distance, ΔL is expressed by Equation (6). On the other hand, when using the city distance, ΔL is expressed by Equation (7). The weight table for each prediction mode is generalized to Equation (8). Therefore, the final prediction signal at the pixel position n is expressed by Equation (9).

In this embodiment, the Euclidean distance from the reference pixel used in the prediction mode or the reciprocal of the urban area distance is used as a weight component as it is, but as another embodiment, the Euclidean distance from the reference pixel and the urban area distance are variables. The weight component may be set using the distributed model. The distribution model uses at least one of a linear model, an M-order function (M ≧ 1), a nonlinear function such as a one-sided Laplace distribution or a one-sided Gaussian distribution, or a fixed value that is a fixed value regardless of the distance from the reference pixel. When the one-sided Gaussian distribution is used as a model, the weight component is expressed by Equation (10). Further, when the one-sided Laplace distribution is used as a model, the weight component is expressed by Expression (11).

The city area distance ΔL _L0 of IntraPredMode _L0 and the city area distance ΔL _{L1 of} IntraPredMode _L1 are calculated from Equation (7). Here, the relative distance varies depending on the prediction direction of the two prediction modes. As an example, typical distances in the case of PuSize = PU — 4 × 4 are shown in FIGS. FIG. 15A shows the city distance when IntraPredModeLX = 0. FIG. 15B shows the city distance in the case of IntraPredModeLX = 1. FIG. 15C shows the city distance in the case of IntraPredModeLX = 3. Similarly, the distance can be derived using Expression (6) or Expression (7) according to each prediction mode. However, in the case of DC prediction with IntraPredModeLX = 2, the distance is 2 at all pixel positions. FIG. 16 shows a table of distances in six typical prediction modes in the case of PuSize = PU — 4 × 4. When the number of IntraPredModeLX is large, the table sizes of these distance tables may increase.

By using the distance table, the relative distance for each pixel in the two prediction modes is calculated using Equation (12). Using Equation (12), the final prediction signal at the pixel position n is represented by Equation (13). Here, in order to avoid an increase in hardware scale due to the use of decimal point arithmetic, the weight component is scaled in advance and converted to integer arithmetic, it can be expressed by Equation (14). Here, for example, when the decimal part is expressed with 10-bit precision, WM = 1024, Offset = 512, and SHIFT = 10. These satisfy the relationship of Expression (15).

An example in which the weight components using the one-sided Laplace distribution model in this embodiment are tabulated is shown in FIGS. 18A and 18B. FIG. 18A shows a weight component table in the case of PuSize = PU — 4 × 4. FIG. 18B shows a weight component table in the case of PuSize = PU_8 × 8. Other PuSizes can also be derived using Equation (5), Equation (8), Equation (10), and Equation (11).
<Bidirectional Intra Prediction Mode Generation Unit 605>
Since the bidirectional intra prediction mode generation unit 605 is the same as the bidirectional intra prediction mode generation unit 605 described in the first embodiment, description thereof is omitted.

The above is the details of the intra prediction unit 5008 according to the present embodiment.

<Syntax structure 1>
Hereinafter, the syntax used by the video decoding device 5000 in FIG. 50 will be described.
The syntax indicates the structure of encoded data (for example, encoded data 162 in FIG. 1) when the moving image decoding apparatus 5000 decodes moving image data. The image encoding apparatus represented by the first embodiment encodes this encoded data using the same syntax structure. FIG. 28 illustrates a syntax 2800 used by the video decoding device 5000 in FIG. Since the syntax 2800 is the same as that of the first embodiment, a detailed description thereof will be omitted.

Next, an example of the prediction unit syntax according to this embodiment will be described.

When intra_luma_bipred_flag [i] is 1, this indicates that the prediction unit is bi-directional intra prediction, and is information that identifies the used bi-directional intra prediction mode among a plurality of prepared bi-directional intra prediction modes. Intra_luma_bipred_mode [i] is decoded. intra_luma_bipred_mode [i] may be decoded in equal length according to the bidirectional intra prediction mode number IntraBiModeNum shown in FIG. 7, or may be decoded using a predetermined code table. Further, as described above, when the total number of bidirectional intra prediction modes is different for each prediction unit, it is decoded using a code table that switches according to the total number of bidirectional intra prediction modes indicated for each prediction unit. Also good. When intra_luma_bipred_flag [i] is 0, it indicates that the prediction unit is unidirectional intra prediction, and predictive decoding is performed from adjacent blocks.

Prev_intra_luma_unipred_flag [i] is a flag indicating whether or not the prediction value MostProbable of the prediction mode calculated from the adjacent block and the intra prediction mode of the prediction unit are the same. Details of the MostProbable calculation method will be described later. When prev_intra_luma_unipred_flag [i] is 1, it indicates that the MostProbable and the intra prediction mode IntraPredMode are equal. When prev_intra_luma_unipred_flag [i] is 0, it indicates that the MostProbable and the intra prediction mode IntraPredMode are different, and the information rem_intraprelum decoding that further specifies the intra prediction mode IntraPredMode other than MostProbable. . rem_intra_luma_unipred_mode [i] may be decoded in equal length according to the bidirectional intra prediction mode number IntraUniModeNum shown in FIGS. 7A and 7B, or may be decoded using a predetermined code table. From the intra prediction mode IntraPredMode, rem_intra_luma_unipred_mode [i] is calculated using Equation (17).

Next, a method for calculating MostProbable, which is a predicted value in the prediction mode, will be described. MostProbable is calculated according to Equation (18). Min (x, y) is a parameter for outputting the smaller one of the inputs x and y.

Also, intraPredModeAL0 and intraPredModeBL0 respectively indicate the first unidirectional intra prediction modes of the prediction units adjacent to the left and above the decoded prediction unit as described above. When the adjacent prediction unit cannot be referred to outside the screen or before decoding, the first unidirectional intra prediction mode of the referable prediction unit is MostProbable. In addition, when both adjacent prediction units cannot be referred to, Intra_DC is set in MostProbable.

Also, when MostProbable is larger than the unidirectional intra prediction mode number IntraUniPredModeNum of the decoding prediction unit, the MostProbable is recalculated using Equation (19). “MappedProbable ()” is a table for converting MostProbable, and an example is shown in FIG. 31.

<Syntax structure 2>
Next, another example of the prediction unit syntax is shown in FIG. 30C. Since pred_mode and intra_split_flag are the same as the syntax example described above, description thereof is omitted. luma_pred_mode_code_type [i] indicates the type of the prediction mode IntraPredMode applied to the prediction unit, where 0 (IntraUnifiedMostProb) is unidirectional intra prediction and the intra prediction mode is the same as MostProbable, 1 (IntraUnipre intrareprediction) The intra prediction mode is different from MostProbable, and 2 (IntraBipred) indicates a bidirectional intra prediction mode. FIG. 32A to FIG. 32D show an example of assignment of the number of modes according to the meaning corresponding to luma_pred_mode_code_type, and the mode configuration shown in FIG. 7A to FIG. 7D. When luma_pred_mode_code_type [i] is 0, the intra prediction mode is the MostProbable mode, so no further information decoding is necessary. When luma_pred_mode_code_type [i] is 1, information rem_intra_luma_unipred_mode [i] that specifies which mode other than MostProbable is the intra prediction mode IntraPredMode is decoded. The rem_intra_luma_unipred_mode [i] may be decoded in equal length according to the bidirectional intra prediction mode number IntraUniModeNum shown in FIGS. 7A to 7D, or may be decoded using a predetermined code table. From the intra prediction mode IntraPredMode, rem_intra_luma_unipred_mode [i] is calculated using Equation (16). Further, when luma_pred_mode_code_type [i] is 2, it indicates that the prediction unit is bidirectional intra prediction, and information that identifies the used bidirectional intra prediction mode among the prepared bidirectional intra prediction modes. Intra_luma_bipred_mode [i] is decoded. intra_luma_bipred_mode [i] may be decoded in equal length according to the bidirectional intra prediction mode number IntraBiModeNum shown in FIGS. 7A to 7D, or may be decoded using a predetermined code table. Further, as described above, when the total number of bidirectional intra prediction modes is different for each prediction unit, it is decoded using a code table that switches according to the total number of bidirectional intra prediction modes indicated for each prediction unit. Also good.

The above is the syntax configuration according to the present embodiment.

<Syntax structure 3>
FIG. 30D shows still another example relating to the prediction unit syntax. In this example, based on the prediction unit syntax shown in FIG. 30A, whether bidirectional intra prediction can be used or whether conventional intra-unidirectional prediction can be used with bidirectional intra prediction disabled. Shows the syntax for switching within the prediction unit to be decoded.
Note that pred_mode and intra_split_flag are the same as the syntax example described above, and thus description thereof is omitted.

Intra_bipred_flag is a flag indicating whether or not bidirectional intra prediction can be used in the decoding prediction unit. When intra_bipred_flag is 0, it indicates that bi-directional intra prediction is not used in the decoding prediction unit. Even when intra_split_flag is 1, that is, when the decoded prediction unit is further divided into four, bi-directional intra prediction is not used in all prediction units, and only uni-directional intra prediction is effective.

When intra_bipred_flag is 1, it indicates that bidirectional intra prediction can be used in the decoding prediction unit. Even when intra_split_flag is 1, that is, when the decoded prediction unit is further divided into four, in all prediction units, bidirectional intra prediction can be selected in addition to unidirectional intra prediction.

In a region where bi-directional intra prediction is unnecessary (for example, a flat region), the intra-bipred_flag is decoded as 0 to disable bi-directional intra prediction. Since the amount of code required for decoding can be reduced, the coding efficiency is improved.

<Syntax structure 4>
FIG. 30E shows still another example relating to the prediction unit syntax. In this example, based on the prediction unit syntax shown in FIG. 30C, whether bidirectional intra prediction can be used or whether only conventional unidirectional intra prediction can be used with bidirectional intra prediction disabled. Shows the syntax for switching in the decoding prediction unit. intra_bipred_flag is a flag indicating whether or not bi-directional intra prediction can be used in the decoding prediction unit, and is the same as the above-described intra_bipred_flag, and thus the description thereof is omitted.

(First modification)
<Intra prediction unit first modification>
As a first modification related to the intra prediction unit 5008, in combination with adaptive reference pixel filtering shown in JCTVC-B205_draft002, section 5.2.1 “Intra prediction process for luma samples”, JCT-VC 2nd Meeting Geneva, July, 2010 It doesn't matter. FIG. 33 shows an intra prediction unit 5008 (109 in FIG. 33) when adaptive reference pixel filtering is used. 6 is different from the intra prediction unit 5008 shown in FIG. 6 (109 in FIG. 6) in that a reference pixel filter unit 3301 is added. The reference pixel filter unit 3301 inputs a reference image signal 5057 (159 in FIG. 33) and a prediction mode 651, performs adaptive filter processing described later, and outputs a filtered reference image signal 3351. The filtered reference image signal 3351 is input to the unidirectional intra predicted image generation unit 601 and the bidirectional intra predicted image generation unit 602. The configuration and processing other than the reference pixel filter unit 3301 are the same as those of the intra prediction unit 5008 shown in FIG.

Next, the reference pixel filter unit 3301 will be described. The reference pixel filter unit 3301 determines whether to filter reference pixels used for intra prediction according to the reference pixel filter flag and the intra prediction mode included in the prediction mode 651. The reference pixel filter flag is a flag indicating whether or not to filter the reference pixel when the intra prediction mode IntraPredMode is a value other than “Intra_DC”. When the reference pixel filter flag is 1, the reference pixel is filtered. In the case of the reference pixel filter flag 0, the reference pixel is not filtered. When IntraPredMode is “Intra_DC”, the reference pixel is not filtered and the reference pixel filter flag is set to 0. When the reference pixel filter flag is 1, a filtered reference image signal 3351 is calculated by filtering shown in Expression (20). Note that p [x, y] indicates a reference pixel before filtering, and pf [x, y] indicates a reference pixel in filter terms. Further, x and y indicate relative positions of the reference pixels when the upper left pixel position in the prediction unit is x = 0 and y = 0. PuPartSize indicates the size (pixel) of the prediction unit.

<Syntax structure 5>
34A and 34B show a prediction unit syntax structure when performing adaptive reference pixel filtering. FIG. 34A adds the syntax intra_luma_filter_flag [i] related to the adaptive reference pixel filter to FIG. 30A. FIG. 34B adds syntax intra_luma_filter_flag [i] related to the adaptive reference pixel filter to FIG. 30C. intra_luma_filter_flag [i] is further decoded when the intra prediction mode IntraPredMode [i] is other than Intra_DC. When the flag is 0, it indicates that the reference pixel is not filtered. Further, when intra_luma_filter_flag [i] is 1, it indicates that the reference pixel filtering is applied.

In the above example, intra_luma_filter_flag [i] is decoded when the intra prediction mode IntraPredMode [i] is other than Intra_DC. As another example, when IntraPredMode [i] is 0 to 2, intra_luma_filter_flag [ i] may not be decrypted. In this case, intra_luma_filter_flag [i] is set to 0.

(Second modification)
<Intra Prediction Unit Second Modification>
As a second modification related to the intra prediction unit 5008, it may be used in combination with the composite intra prediction shown in JCTVC-B205_draft002, section 9.6 “Combined Intra Prediction”, JCT-VC 2nd Meeting Geneva, July, 2010. . In the decoded intra prediction in this document, a prediction value is obtained by performing weighted averaging of the result of the above-described unidirectional intra prediction and the average value of pixels adjacent to the left, top, and top left with respect to the prediction pixel. When the decoded image signal 5055 is calculated in the moving image decoding device 5000 or the image encoding device 100, it is possible to use decoded pixels as pixels adjacent to the left, upper, and upper left.

FIG. 37 shows a block diagram of the intra prediction unit 5008 (109 in FIG. 37) when combined with composite intra prediction. The difference is that a composite intra predicted image generation unit 3601, a selection switch 3602 and a decoded image buffer 3701 are added to the intra prediction unit 5008 shown in FIG.

When the bidirectional intra prediction and the composite intra prediction are combined, first, in the selection switch 604, the unidirectional intra prediction image generation unit 601 or the bidirectional intra prediction image generation unit according to the prediction mode information controlled by the decoding control unit 5012. The output terminal of 602 is switched. Hereinafter, the output predicted image signal 5058 (161 in FIG. 37) is referred to as a direction predicted image signal 5058.

Thereafter, the direction prediction image signal is input to the composite intra prediction image generation unit 3601, and a prediction image signal 5058 in the composite intra prediction is generated. After that, the selection switch 3602 switches between using the prediction image signal 5058 and the direction prediction image signal in the composite intra prediction according to the composite intra prediction application flag in the prediction mode information controlled by the decoding control unit 5012. The final prediction image signal 5058 in the intra prediction unit 5008 is output. When the composite intra prediction application flag is 1, the predicted image signal 5058 output from the composite intra predicted image generation unit 3601 becomes the final predicted image signal 5058. On the other hand, when the composite intra prediction application flag is 0, the direction prediction image signal 5058 is the prediction image signal 5058 that is finally output.

Next, the composite intra prediction image generation unit 3601 will be described with reference to FIG. The composite intra prediction image generation unit 3601 includes a pixel level prediction signal generation unit 3801 and a composite intra prediction calculation unit 3802. The pixel level prediction signal generation unit 3801 predicts the prediction target pixel X from adjacent pixels and outputs a pixel level prediction signal 3851. As described above, the adjacent pixel indicates the decoded image signal 5055. Specifically, the pixel level prediction signal 3851 (X) of the prediction target pixel is calculated using Expression (21). The coefficients related to A, B, and C may be other values.

The composite intra prediction calculation unit 3802 performs a weighted average of the direction prediction image signal 5058 (161 in FIG. 38) (X ′) and the pixel level prediction signal 3851 (X), and outputs a final prediction image signal 5058 (P). To do. Specifically, Formula (22) is used.

Note that W is a weighted average weight coefficient (an integer value between W = 0 and 32) of the direction prediction image signal 5058 (X ′) and the pixel level prediction signal 3851 (X). The above is an embodiment when combined with composite intra prediction.

(Third Modification)
<Intra Prediction Unit Third Modification>
The weighting factor W may be switched according to the position of the prediction pixel in the prediction unit. In general, a prediction image signal generated using unidirectional intra prediction and bidirectional intra prediction generates a prediction value from spatially adjacent reference pixels positioned on the left or above already encoded. The absolute value of the prediction error tends to increase as the distance from the reference pixel increases. Therefore, the weighting coefficient of the direction prediction image signal 5058 and the pixel level prediction signal 3851 is increased when the weight coefficient of the direction prediction image signal 161 is close to the reference pixel, and is decreased when the distance is far away, thereby improving the prediction accuracy. It becomes possible.

On the other hand, in the complex intra prediction, a prediction error signal is generated using an input image signal at the time of encoding. At this time, since the pixel level prediction signal 3851 becomes an input image signal, even if the spatial distance between the reference pixel position and the prediction pixel position is increased, the prediction of the pixel level prediction signal 3851 is compared with the direction prediction image signal 5058. High accuracy. However, the weight coefficient of the direction prediction image signal 5058 and the pixel level prediction signal 3851 is simply increased when the weight coefficient of the direction prediction image signal 5058 is close to the reference pixel, and the weight coefficient of the direction prediction image signal 5058 is small when it is far away. Although the prediction error is reduced, there is a problem that the prediction accuracy at the time of encoding and the prediction value at the time of local decoding are different and the prediction accuracy is lowered. Therefore, especially when the value of the quantization parameter is large, as the spatial distance between the reference pixel position and the predicted pixel position becomes large, the difference generated in the case of such an open loop is set by setting the value of W small. A decrease in coding efficiency due to the phenomenon can be suppressed.

<Syntax structure 6>
39A and 39B show the prediction unit syntax structure when performing composite intra prediction. FIG. 39A is different from FIG. 30A in that a syntax combined_intra_pred_flag for switching presence / absence of composite intra prediction is added. This is equivalent to the above-described composite intra prediction application flag. In addition, FIG. 39B adds a syntax combined_intra_pred_flag for switching presence / absence of composite intra prediction to FIG. 30C. When combined_intra_pred_flag is 1, the selection switch 3602 shown in FIG. 37 is connected to the output terminal of the composite intra predicted image generation unit 3601. When combined_intra_pred_flag is 0, the selection switch 3602 shown in FIG. 36 is connected to the output terminal of either the unidirectional intra prediction image generation unit 601 or the bidirectional intra prediction image generation unit 602 to which the selection switch 604 is connected. .

In addition, for the other syntax structures shown in FIGS. 30B, 30D, and 30E, the intra_luma_filter_flag [i] described above may be added in the same meaning.
Furthermore, you may combine with the 2nd modification of an intra estimation part.

This completes the description of another embodiment of the intra prediction unit 5008.

According to the fourth embodiment described above, since the same or similar intra prediction unit as that of the video encoding device according to the first embodiment is included, the same or the same as the video encoding device according to the first embodiment or Similar effects can be obtained.

(Fifth embodiment)
<Video Decoding Device—Fifth Embodiment>
The video decoding device according to the fifth embodiment differs from the video decoding device according to the above-described fourth embodiment in the details of inverse orthogonal transform. In the following description, in this embodiment, the same parts as those in the fourth embodiment are denoted by the same reference numerals, and different parts will be mainly described. The moving picture coding apparatus corresponding to the moving picture decoding apparatus according to the present embodiment is as described in the second embodiment.

FIG. 51 is a block diagram showing a moving picture decoding apparatus according to the fifth embodiment. A change from the video decoding apparatus according to the fourth embodiment is that a transformation selection unit 5102 and a coefficient order restoration unit 5101 are added. Also, the internal structure of the inverse orthogonal transform unit 5004 is different.

<Inverse orthogonal transform unit 5004>
First, the inverse orthogonal transform unit 5004 will be described with reference to FIG. Note that the inverse orthogonal transform unit 5004 has the same configuration as the inverse orthogonal transform unit 105 according to the second embodiment. Therefore, in this embodiment, the conversion selection information 4051 in FIG. 42 is replaced with the conversion selection information 5151, the restored conversion coefficient 155 is replaced with the restored conversion coefficient 5053, and the restored prediction error signal 156 is replaced with the restored prediction error signal 5054. explain.

42 includes a first inverse orthogonal transform unit 4201, a second inverse orthogonal transform unit 4202, an Nth inverse orthogonal transform unit 4203, and a transform selection switch 4204. The inverse orthogonal transform unit 5004 (105 in FIG. 42) in FIG. First, the conversion selection switch 4204 will be described. The conversion selection switch 4204 has a function of selecting the output terminal of the inverse quantization unit 5003 according to the input conversion selection information 5151. The conversion selection information 5151 is one piece of information controlled by the decoding control unit 5012 and is set by the conversion selection unit 5102 according to the prediction information 5059.

When the conversion selection information 5151 is the first orthogonal transform, the output terminal of the switch is connected to the first inverse orthogonal transform unit 4201. On the other hand, when the transformation selection information 5151 is the second orthogonal transformation, the output end is connected to the second inverse orthogonal transformation unit 4202. Similarly, when the transform selection information 5151 is the Nth orthogonal transform, the output terminal is connected to the Nth inverse orthogonal transform unit 4203.

<Conversion selection unit 5102>
Next, the conversion selection unit 5102 shown in FIG. 51 will be described. Prediction information 5059 controlled by the decoding control unit 5012 and decoded by the entropy decoding unit 5002 is input to the transformation selection unit 5102. Based on the prediction information 5059, the transform selection unit 5102 has a function of setting MapdTransformIdx information indicating which inverse orthogonal transform is used for which prediction mode. FIG. 43 shows conversion selection information 5151 (MappedTransformIdx) in intra prediction. Here, an example of N = 9 is shown. Note that the first inverse orthogonal transform unit 4201 is selected during DC prediction corresponding to IntraPredModeLX = 2. By mapping to the reference prediction mode with a close prediction angle in this way, compared to the case of preparing an orthogonal transformer and an inverse orthogonal transformer for all prediction modes, orthogonal transformation and inverse orthogonal transformation at the time of hardware implementation It is possible to reduce the circuit scale. When bi-directional intra prediction is selected, after two IntraPredModeL0 and IntraPredModeL1 are derived, the mapped transformIdx is derived from FIG. 43 using the prediction mode corresponding to IntraPredModeL0. In the present embodiment, an example of N = 9 has been shown, but the value of N may be selected in an optimal combination by balancing the coding performance and the circuit scale at the time of hardware implementation.

<Coefficient order restoration unit 5101>
Next, the coefficient order restoration unit 5101 will be described. FIG. 52 shows a block diagram of the coefficient order restoration unit 5101. The coefficient order restoration unit 5101 has a function of performing reverse scan order conversion with the coefficient order control unit 4002 according to the second embodiment.

The coefficient order restoration unit 5101 includes a coefficient order selection switch 5204, a first coefficient forward / reverse transform unit 5201, a second coefficient forward / reverse transform unit 5202, and an Nth coefficient forward / reverse transform unit 5203. For example, the coefficient order selection switch 5204 has a function of switching between the output terminal of the switch and the coefficient order inverse conversion units 5201 to 5203 in accordance with the mapped transform idx shown in FIG. The N types of coefficient forward / inverse transform units 5201 to 5203 have a function of inversely transforming one-dimensional data into two-dimensional data with respect to the quantized transform coefficient sequence 5152 decoded by the entropy decoding unit 5002. For example, H.M. In H.264, two-dimensional data is converted into one-dimensional data using a zigzag scan. Here, for example, it means that conversion from a zigzag scan to a raster scan is performed.

When using orthogonal transform in consideration of the prediction direction of intra prediction, the quantized transform coefficient obtained by performing quantization processing on the transform coefficient that has been subjected to orthogonal transform has the property that the tendency of generating non-zero transform coefficients in the block is biased. Have. The tendency of occurrence of this non-zero transform coefficient has different properties for each prediction direction of intra prediction. However, when different videos are encoded, the generation tendency of non-zero transform coefficients in the same prediction direction has a similar property. Therefore, when transforming two-dimensional data into one-dimensional data (2D-1D conversion), entropy coding is performed preferentially from transform coefficients at positions where the occurrence probability of non-zero transform coefficients is high, thereby encoding transform coefficients. It is possible to reduce information. Conversely, on the decoding side, it is necessary to restore the one-dimensional data to the two-dimensional data. Here, the raster scan is restored as a one-dimensional reference scan.

As yet another example, the coefficient order restoration unit 5101 may dynamically update the scan order in the 1D-2D conversion. The configuration of the coefficient order restoration unit 5101 that performs such an operation is illustrated in FIG. The coefficient order restoration unit 5101 includes an occurrence frequency counting unit 5301 and an updating unit 5302 in addition to the configuration of FIG. The coefficient order reverse conversion units 5201,..., 5203 are the same except that the 1D-2D scan order is updated by the update unit 5302.

The occurrence frequency counting unit 5301 creates a histogram 5351 of the number of occurrences of non-zero coefficients in each element of the quantized transform coefficient sequence 5152 for each prediction mode. The occurrence frequency counting unit 5301 inputs the created histogram 5351 to the update unit 5302.

The update unit 5302 updates the coefficient order based on the histogram 5351 at a predetermined timing. The timing is, for example, the timing when the coding process of the coding tree unit is finished, the timing when the coding process for one line in the coding tree unit is finished, or the like.

Specifically, the update unit 5302 refers to the histogram 5351 and updates the coefficient order with respect to the prediction mode having an element in which the number of occurrences of non-zero coefficients is counted more than a threshold. For example, the update unit 5302 updates the prediction mode having an element in which the occurrence of a non-zero coefficient is counted 16 times or more. By providing a threshold value for the number of occurrences, the coefficient order is updated globally, so that it is difficult to converge to a local optimum solution.

The update unit 5302 sorts the elements in descending order of the occurrence frequency of the non-zero coefficient regarding the prediction mode to be updated. Sorting can be realized by existing algorithms such as bubble sort and quick sort. Then, the update unit 5302 inputs the update coefficient order 5352 indicating the order of the sorted elements to the coefficient order inverse transform units 5201 to 5203 corresponding to the prediction mode to be updated.

When the update coefficient order 5352 is input, each inverse conversion unit performs 1D-2D conversion according to the updated scan order. When the scan order is dynamically updated, the initial scan order of each 1D-2D conversion unit needs to be determined in advance. The initial scan order is the same as that of the coefficient order control unit 4002 of the moving picture coding apparatus shown in FIG. In this way, when the scan order is dynamically updated, the tendency of occurrence of non-zero coefficients in the quantized transform coefficients changes according to the effect of the predicted image properties, quantization information (quantization parameters), etc. In addition, stable and high encoding efficiency can be expected. Specifically, the generated code amount of run-length encoding in the entropy encoding unit 113 can be suppressed.

Note that the syntax configuration in this embodiment is the same as that in the fourth embodiment.

As a modification of the present embodiment, the conversion selection unit 5102 can select the mapped transform IDx separately from the prediction information 5059. In this case, information indicating which nine types of orthogonal transforms or inverse orthogonal transforms are used is set in the decoding control unit 5012 and used by the inverse orthogonal transform unit 5004. FIG. 46 shows an example of syntax in this embodiment. Directional_transform_idx indicated in the syntax indicates information indicating which of N orthogonal transforms has been selected.

According to the fifth embodiment described above, the same or similar inverse orthogonal transform unit as that of the video encoding device according to the second embodiment is included, and thus the same as the video encoding device according to the second embodiment. Or a similar effect can be obtained.

(Sixth embodiment)
<Video Decoding Device—Sixth Embodiment>
The video decoding device according to the sixth embodiment differs from the video decoding device according to the above-described fourth embodiment in the details of inverse orthogonal transform. In the following description, in this embodiment, the same parts as those in the fourth embodiment are denoted by the same reference numerals, and different parts will be mainly described. The moving picture encoding apparatus corresponding to the moving picture decoding apparatus according to the present embodiment is as described in the third embodiment.

As an embodiment related to the inverse orthogonal transform unit 5004, it may be combined with the rotation transformation shown in JCTVC-B205_draft002, 5.3.5.2 “Rotational transformation process”, JCT-VC 2nd Meeting Geneva, July, 2010.

<Inverse orthogonal transform unit 5004>
FIG. 48 is a block diagram of the inverse orthogonal transform unit 5004 (105 in FIG. 48) according to the present embodiment. The inverse orthogonal transform unit 5004 includes new processing units, a first inverse rotation transform unit 4801, a second inverse rotation transform unit 4802, an Nth inverse rotation transform unit 4803, and an inverse discrete cosine transform unit 4804, and an existing transform selection switch 4204. Have The restored transform coefficient 5053 (155 in FIG. 48) input after the inverse quantization process is input to the transform selection switch 4204. Here, according to the conversion selection information 5151 (4051 in FIG. 48), the conversion selection switch 4204 sets the output end of the switch to the first reverse rotation conversion unit 4801, the second reverse rotation conversion unit 4802, and the Nth reverse rotation conversion unit 4803. Connect to one. Thereafter, the reverse rotation conversion processing is performed in any one of the reverse rotation conversion units 4801 to 4803, which is the same as the rotation conversion used in the orthogonal conversion unit 102 shown in FIG. 47, and is output to the inverse discrete cosine conversion unit 4804. . The inverse discrete cosine transform unit 4804 performs, for example, IDCT on the input signal to restore the restored prediction error signal 5054 (156 in FIG. 48). Although an example using IDCT is shown here as an example, orthogonal transform such as Hadamard transform or discrete sine transform may be used, or non-orthogonal transform may be used. In any case, corresponding inverse transformation is performed in conjunction with the orthogonal transformation unit 102 shown in FIG.

According to the sixth embodiment described above, the same or similar inverse orthogonal transform unit as that of the image encoding device according to the third embodiment is included, and therefore the same or similar as that of the image encoding device according to the third embodiment. The effect of can be obtained.

Hereinafter, modifications of each embodiment will be listed and introduced.
In the first to sixth embodiments, an example is described in which a frame is divided into rectangular blocks having a size of 16 × 16 pixels, and encoding / decoding is sequentially performed from the upper left block to the lower right side of the screen. (See FIG. 2A). However, the encoding order and the decoding order are not limited to this example. For example, encoding and decoding may be performed sequentially from the lower right to the upper left, or encoding and decoding may be performed so as to draw a spiral from the center of the screen toward the screen end. Furthermore, encoding and decoding may be performed in order from the upper right to the lower left, or encoding and decoding may be performed so as to draw a spiral from the screen edge toward the center of the screen.

In the first to sixth embodiments, the description has been given by exemplifying the prediction target block sizes such as the 4 × 4 pixel block, the 8 × 8 pixel block, and the 16 × 16 pixel block, but the prediction target block is uniform. It does not have to be a block shape. For example, the prediction target block (prediction unit) size may be a 16 × 8 pixel block, an 8 × 16 pixel block, an 8 × 4 pixel block, a 4 × 8 pixel block, or the like. Also, it is not necessary to unify all the block sizes within one coding tree unit, and a plurality of different block sizes may be mixed. When a plurality of different block sizes are mixed in one coding tree unit, the amount of codes for encoding or decoding the division information increases as the number of divisions increases. Therefore, it is desirable to select the block size in consideration of the balance between the code amount of the division information and the quality of the locally decoded image or the decoded image.

In the first to sixth embodiments, for the sake of simplicity, a comprehensive description of the color signal component is described without distinguishing between the luminance signal and the color difference signal. However, when the prediction process is different between the luminance signal and the color difference signal, the same or different prediction methods may be used. If different prediction methods are used between the luminance signal and the chrominance signal, the prediction method selected for the chrominance signal can be encoded or decoded in the same manner as the luminance signal.

In the first to sixth embodiments, for the sake of simplicity, a comprehensive description of the color signal component is described without distinguishing between the luminance signal and the color difference signal. However, when the orthogonal transformation process is different between the luminance signal and the color difference signal, the same or different orthogonal transformation methods may be used. If different orthogonal transformation methods are used between the luminance signal and the color difference signal, the orthogonal transformation method selected for the color difference signal can be encoded or decoded in the same manner as the luminance signal.

In the first to sixth embodiments, syntax elements not defined in the embodiment can be inserted between the rows of the table shown in the syntax configuration, and other conditional branch descriptions are included. It does not matter. Alternatively, the syntax table can be divided and integrated into a plurality of tables. Moreover, it is not always necessary to use the same term, and it may be arbitrarily changed depending on the form to be used.

As described above, each embodiment can realize highly efficient orthogonal transformation and inverse orthogonal transformation while alleviating the difficulty in hardware implementation and software implementation. Therefore, according to each embodiment, the encoding efficiency is improved, and the subjective image quality is also improved.

The instructions shown in the processing procedure shown in the above embodiment can be executed based on a program that is software. A general-purpose computer system stores this program in advance, and by reading this program, it is also possible to obtain the same effects as those obtained by the video encoding device and video decoding device of the above-described embodiment. is there. The instructions described in the above-described embodiments are, as programs that can be executed by a computer, magnetic disks (flexible disks, hard disks, etc.), optical disks (CD-ROM, CD-R, CD-RW, DVD-ROM, DVD). ± R, DVD ± RW, etc.), semiconductor memory, or a similar recording medium. As long as the recording medium is readable by the computer or the embedded system, the storage format may be any form. If the computer reads the program from the recording medium and causes the CPU to execute instructions described in the program based on the program, the computer is similar to the video encoding device and video decoding device of the above-described embodiment. Operation can be realized. Of course, when the computer acquires or reads the program, it may be acquired or read through a network.
In addition, the OS (operating system), database management software, MW (middleware) such as a network, etc. running on the computer based on the instructions of the program installed in the computer or embedded system from the recording medium implement this embodiment. A part of each process for performing may be executed.
Furthermore, the recording medium in the present invention is not limited to a medium independent of a computer or an embedded system, but also includes a recording medium in which a program transmitted via a LAN or the Internet is downloaded and stored or temporarily stored. Further, the program for realizing the processing of each of the above embodiments may be stored on a computer (server) connected to a network such as the Internet and downloaded to the computer (client) via the network.
Further, the number of recording media is not limited to one, and when the processing in the present embodiment is executed from a plurality of media, it is included in the recording media in the present invention, and the configuration of the media may be any configuration.

The computer or the embedded system in the present invention is for executing each process in the present embodiment based on a program stored in a recording medium, and includes a single device such as a personal computer or a microcomputer, Any configuration such as a system in which apparatuses are connected to a network may be used.
Further, the computer in the embodiment of the present invention is not limited to a personal computer, but includes an arithmetic processing device, a microcomputer, and the like included in an information processing device, and a device capable of realizing the functions in the embodiment of the present invention by a program, The device is a general term.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 100 ... Image coding apparatus, 101 ... Subtraction part, 102 ... Orthogonal transformation part, 103 ... Quantization part, 104 ... Inverse quantization part, 105 ... Inverse orthogonal transformation part, 106 ... Adder, 107 ... Loop filter, 108 ... Reference image memory 109 ... Intra prediction unit 110 ... Inter prediction unit 111 ... Prediction selection switch 112 ... Prediction selection unit 113 ... Entropy coding unit 114 ... Output buffer 115 ... Coding control unit 116 ... Intra Prediction mode memory 151 ... Input image signal 152 ... Prediction error signal 153 ... Conversion coefficient 154 ... Quantization conversion coefficient 155 ... Reconstruction conversion coefficient 156 ... Reconstruction prediction error signal 157 ... Decoded image signal 158 ... Covered Filter image signal, 159 ... Reference image signal, 160 ... Prediction information, 161 ... Prediction image signal, Direction prediction image signal, 162 ... Coding data 163 ... Intra prediction mode information, 164 ... Reference intra prediction mode information, 601 ... Unidirectional intra prediction image generation unit, 602 ... Bidirectional intra prediction image generation unit, 603 ... Prediction mode information setting unit, 604 ... Selection switch, 605 ... Bidirectional intra prediction mode generation unit, 651 ... Prediction mode, 652 ... Bidirectional intra prediction mode information, 1301 ... First unidirectional intra prediction image generation unit, 1302 ... Second unidirectional intra prediction image generation unit, 1303 ... Weighted average unit, 1351 ... first prediction image signal, 1352 ... second prediction image signal, 1901 ... first prediction mode generation unit, 1902 ... second prediction mode generation unit, 1903 ... selection switch, 2301 ... third prediction mode Generation unit 2302 ... Prediction mode generation unit 2701 ... Primary image buffer 2702 ... Weighted plane 2800 ... Syntax, 2801 ... High level syntax, 2802 ... Slice level syntax, 2803 ... Coding tree level syntax, 2804 ... Sequence parameter set syntax, 2805 ... Picture parameter set syntax, 2806 ... Slice header syntax, 2807 ... Slice data syntax 2808 ... Coding tree unit syntax, 2809 ... Prediction unit syntax, 2810 ... Transform unit syntax, 3301 ... Reference pixel filter unit, 3351 ... Filtered reference image signal, 3601 ... Composite intra prediction image generation unit, 3602 ... Selection switch 3701, decoded pixel buffer, 3701 ... decoded image buffer, 3751 ... reference pixel, adjacent pixel, 380 DESCRIPTION OF SYMBOLS 1 ... Pixel level prediction signal production | generation part, 3802 ... Composite intra prediction calculation part, 3851 ... Pixel level prediction signal, 4001 ... Conversion selection part, 4002 ... Coefficient order control part, 4051 ... Conversion selection information, 4052 ... Quantization conversion coefficient sequence 4101: First orthogonal transform unit, 4102 ... Second orthogonal transform unit, 4103 ... Orthogonal transform unit, 4104 ... Transformation selection switch, 4201 ... First inverse orthogonal transform unit, 4202 ... Second inverse orthogonal transform unit, 4203 ... Inverse orthogonal transformation unit, 4204 ... transformation selection switch, 4401 ... coefficient forward transformation unit, 4401 ... first coefficient forward transformation unit, 4402 ... second coefficient forward transformation unit, 4403 ... coefficient forward transformation unit, 4404 ... coefficient order selection switch, 4501 ... Occurrence frequency counting unit, 4502 ... Update unit, 4551 ... Update coefficient order, 4552 ... Histogram, 4701 ... Rotation conversion unit, 4701 ... First Conversion unit, 4702 ... second rotation conversion unit, 4703 ... rotation conversion unit, 4704 ... discrete cosine conversion unit, 4801 ... reverse rotation conversion unit, 4801 ... first reverse rotation conversion unit, 4802 ... second reverse rotation conversion unit, 4803: inverse rotation transform unit, 4804 ... inverse discrete cosine transform unit, 5000 ... moving picture decoding device, 5001 ... input buffer, 5002 ... entropy decoding unit, 5003 ... inverse quantization unit, 5004 ... inverse orthogonal transform unit, 5005 ... adder, 5006 ... loop filter, 5007 ... reference image memory, 5008 ... intra predictor, 5009 ... inter predictor, 5010 ... prediction selection switch, 5011 ... output buffer, 5012 ... decoding controller, 5013 ... intra prediction mode Memory, 5051... Encoded data, 5052... Quantization transform coefficient, 5053. 54 ... Restored prediction error signal, 5055 ... Decoded image signal, 5056 ... Filtered image signal, 5057 ... Reference image signal, 5058 ... Predicted image signal, Direction predicted image signal, 5059 ... Prediction information, 5060 ... Decoded image, 5061 ... Intra Prediction mode information, 5062 ... Reference intra prediction mode information, 5100 ... Video decoding device, 5101 ... Coefficient order restoration unit, 5102 ... Transformation selection unit, 5151 ... Transformation selection information, 5152 ... Quantized transformation coefficient sequence, 5201 ... Coefficient Forward / reverse conversion unit, 5201 ... first coefficient forward / reverse conversion unit, 5202 ... second coefficient forward / reverse conversion unit, 5203 ... coefficient forward / reverse conversion unit, 5204 ... coefficient order selection switch, 5301 ... occurrence frequency counting unit, 5302 ... update unit, 5351 ... Histogram, 5352... Update coefficient order.

Claims

The input image signal is divided into pixel blocks expressed by hierarchical depth according to quadtree division, intra prediction is performed on these divided pixel blocks, a prediction error signal is generated, and transform coefficients are encoded. In the video encoding method,
Obtaining a reference prediction direction indicating a prediction direction of the intra prediction corresponding to at least one encoded pixel block;
Among the reference prediction directions, the first reference prediction direction is set as the first prediction direction, and a first prediction image signal is generated,
Generating a second predicted image signal by setting a second prediction direction different from the first prediction direction;
According to the weight component, the first predicted image signal and the second predicted image signal are weighted averaged to generate a third predicted image signal,
Generating a prediction error signal from the third predicted image signal;
Encoding the prediction error signal;
A moving picture encoding method comprising:
Generating the second predicted image signal comprises:
(A) a second reference prediction direction that is the reference prediction direction in the encoded pixel block different from the encoded pixel block corresponding to the first reference prediction direction;
(B) an adjacent prediction direction with respect to the first prediction direction;
(C) a prediction direction obtained by inverting the first prediction direction; and
(D) a prediction direction obtained by converting the first prediction direction by a predetermined method;
The moving picture coding method according to claim 1, wherein any one of the above is set in the second prediction direction.
Select one selected first prediction direction combination from the plurality of first prediction direction combination candidates,
Generating the third predicted image signal using the first prediction direction and the second prediction direction corresponding to the selected first prediction direction combination;
The video encoding method according to claim 2, further comprising:
Fourth prediction by setting a second prediction direction combination that is a combination of a predetermined prediction direction and a combination of a fourth prediction direction and a fifth prediction direction from among a plurality of predetermined prediction directions. Generating an image signal and a fifth predicted image signal;
Deriving the relative distance between the reference pixel and the prediction pixel in each prediction direction corresponding to the set second prediction direction combination, deriving a difference value of the relative distance,
In accordance with the difference value, a predetermined weight component is derived,
According to the weight component, the fourth predicted image signal and the fifth predicted image signal are weighted averaged to generate a sixth predicted image signal,
Selecting one of the third predicted image signal and the sixth predicted image signal as a seventh predicted image signal;
Generating a prediction error signal from the seventh predicted image signal;
Encode the prediction error signal;
The video encoding method according to claim 3, further comprising:
When bidirectional intra prediction is applied to the encoded pixel block, one of the first prediction direction combination and the second prediction direction combination included in the bidirectional intra prediction is set as the reference prediction direction. The moving picture encoding method according to claim 4, further comprising:
When the selected first prediction direction combination included in the sixth predicted image signal is the same as another first prediction direction combination candidate or the second prediction direction combination,
An eighth prediction image signal and a ninth prediction direction are set by setting an eighth prediction direction and a ninth prediction direction, which are third prediction direction combinations different from the other first prediction direction combination candidates and the second prediction direction combination, respectively. Nine predicted image signals are generated,
Deriving the relative distance between the reference pixel and the prediction pixel in each prediction direction corresponding to the set third prediction direction combination, deriving a difference value of the relative distance,
In accordance with the difference value, a predetermined weight component is derived,
According to the weight component, the eighth predicted image signal and the ninth predicted image signal are weighted and averaged to generate a tenth predicted image signal and replace the sixth predicted image signal.
The moving picture encoding method according to claim 5, further comprising:
Obtain the total number of the first prediction direction combination and the second prediction direction combination that are combinations of different prediction directions,
Encoding prediction mode information for specifying the seventh predicted image signal with reference to a predetermined code table according to the total number,
The moving picture encoding method according to claim 5, further comprising:
An eleventh prediction image signal is generated by setting an eleventh prediction direction from the plurality of predetermined prediction directions,
Selecting one of the seventh predicted image signal and the eleventh predicted image signal as a twelfth predicted image signal;
Generating a prediction error signal from the twelfth prediction image signal;
Encoding the prediction error signal;
The moving picture coding method according to claim 6 or 7, further comprising:
When the selected first prediction direction combination included in the sixth predicted image signal is the same as another first prediction direction combination candidate or the second prediction direction combination,
Generating a twelfth prediction image signal by setting a twelfth prediction direction different from the eleventh prediction direction from the plurality of predetermined prediction directions;
The video encoding method according to claim 8, further comprising:
When the prediction mode of the luminance signal in the pixel block specifies the seventh prediction image signal as the ninth prediction image signal, the fourth prediction direction and the fifth prediction direction included in the seventh prediction image signal Is set to the color difference signal of the same pixel block, and a color difference prediction image signal is generated,
When the prediction mode of the luminance signal specifies the eighth prediction image signal as the ninth prediction image signal, the eighth prediction direction included in the eighth prediction image signal is set to a color difference signal of the same pixel block And generating a color difference prediction image signal,
The video encoding method according to claim 9, further comprising:
The input image signal is divided into pixel blocks expressed by hierarchical depth according to quadtree division, intra prediction is performed on these divided pixel blocks, a prediction error signal is generated, and transform coefficients are decoded. In the video decoding method,
Obtaining a reference prediction direction indicating a prediction direction of the intra prediction corresponding to at least one decoded pixel block;
Among the reference prediction directions, a first reference prediction direction is set as a first prediction direction to generate a first prediction image signal,
Generating a second predicted image signal by setting a second prediction direction different from the first prediction direction;
According to the weight component, the first predicted image signal and the second predicted image signal are weighted averaged to generate a third predicted image signal,
Generating a prediction error signal from the third predicted image signal;
Decoding the prediction error signal;
A moving picture decoding method.
Generating the second predicted image signal comprises:
(A) a second reference prediction direction that is the reference prediction direction in the decoded pixel block different from the decoded pixel block corresponding to the first reference prediction direction;
(B) an adjacent prediction direction with respect to the first prediction direction;
(C) a prediction direction obtained by inverting the first prediction direction; and
(D) a prediction direction obtained by converting the first prediction direction by a predetermined method;
The moving picture decoding method according to claim 11, wherein any one of the above is set in the second prediction direction.
Select one selected first prediction direction combination from the plurality of first prediction direction combination candidates,
Generating the third predicted image signal using the first prediction direction and the second prediction direction corresponding to the selected first prediction direction combination;
The moving picture decoding method according to claim 12, further comprising:
A fourth prediction image signal is set by setting a second prediction direction combination which is a combination of a predetermined prediction direction and a combination of a fourth prediction direction and a fifth prediction direction from among the predetermined prediction directions. And a fifth predicted image signal,
Deriving the relative distance between the reference pixel and the prediction pixel in each prediction direction corresponding to the set second prediction direction combination, deriving a difference value of the relative distance,
In accordance with the difference value, a predetermined weight component is derived,
According to the weight component, the fourth predicted image signal and the fifth predicted image signal are weighted averaged to generate a sixth predicted image signal,
Selecting one of the third predicted image signal and the sixth predicted image signal as a seventh predicted image signal;
Generating a prediction error signal from the seventh predicted image signal;
Decoding the prediction error signal;
The video decoding method according to claim 13, further comprising:
When bidirectional intra prediction is applied to the decoded pixel block, one of the first prediction direction combination and the second prediction direction combination included in the bidirectional intra prediction is set as the reference prediction direction. 15. The moving picture decoding method according to claim 14, further comprising:
When the selected first prediction direction combination included in the sixth predicted image signal is the same as another first prediction direction combination candidate or the second prediction direction combination,
An eighth prediction image signal and a ninth prediction direction are set by setting an eighth prediction direction and a ninth prediction direction, which are third prediction direction combinations different from the other first prediction direction combination candidates and the second prediction direction combination, respectively. Nine predicted image signals are generated,
Deriving the relative distance between the reference pixel and the prediction pixel in each prediction direction corresponding to the set third prediction direction combination, deriving a difference value of the relative distance,
In accordance with the difference value, a predetermined weight component is derived,
According to the weight component, the eighth predicted image signal and the ninth predicted image signal are weighted and averaged to generate a tenth predicted image signal and replace the sixth predicted image signal.
The video decoding method according to claim 15, further comprising:
Obtain the total number of the first prediction direction combination and the second prediction direction combination that are combinations of different prediction directions,
Decoding prediction mode information identifying the seventh predicted image signal with reference to a code table determined in advance according to the total number,
The video decoding method according to claim 15, further comprising:
An eleventh prediction image signal is generated by setting an eleventh prediction direction from the plurality of predetermined prediction directions,
Selecting one of the seventh predicted image signal and the eleventh predicted image signal as a twelfth predicted image signal;
Generating a prediction error signal from the twelfth prediction image signal;
Decoding the prediction error signal;
The video decoding method according to claim 16 or 17, further comprising:
When the selected first prediction direction combination included in the sixth predicted image signal is the same as another first prediction direction combination candidate or the second prediction direction combination,
Generating a twelfth prediction image signal by setting a twelfth prediction direction different from the eleventh prediction direction from the plurality of predetermined prediction directions;
The video decoding method according to claim 18, further comprising:
When the prediction mode of the luminance signal in the pixel block specifies the seventh prediction image signal as the ninth prediction image signal, the fourth prediction direction and the fifth prediction direction included in the seventh prediction image signal Is set to the color difference signal of the same pixel block, and a color difference prediction image signal is generated,
When the prediction mode of the luminance signal specifies the eighth prediction image signal as the ninth prediction image signal, the eighth prediction direction included in the eighth prediction image signal is set to a color difference signal of the same pixel block And generating a color difference prediction image signal,
The video decoding method according to claim 19, further comprising: