Intra-prediction apparatus for removing a directional intra-prediction mode from a set of predetermined directional intra-prediction modes

Abstract

An intra-prediction method includes: determining, by an intra-prediction apparatus, a directional intra-prediction mode for a rectangular video coding block from an extended set of directional intra-prediction modes, wherein the extended set of directional intra-prediction modes includes extended directional intra-prediction modes and conventional directional intra-prediction modes and determining, by the intra-prediction apparatus, a plurality of available reference samples based on a direction of the directional intra-prediction mode. The method further includes: intra-predicting, by the intra-prediction apparatus, pixel values of pixels of the rectangular video coding block based on the plurality of available reference samples.

Claims

1. An intra-prediction method, comprising: determining, by an intra-prediction apparatus, a directional intra-prediction mode for a rectangular video coding block from an extended set of directional intra-prediction modes, wherein the extended set of directional intra-prediction modes includes conventional directional intra-prediction modes and extended directional intra-prediction modes, wherein the rectangular video coding block has a first side and a second side, and wherein a length of the first side is greater than a length of the second side; determining, by the intra-prediction apparatus, a plurality of available reference samples based on a direction of the directional intra-prediction mode; and intra-predicting, by the intra-prediction apparatus, pixel values of pixels of the rectangular video coding block based on the plurality of available reference samples; wherein the conventional directional intra-prediction modes are applicable to both square video coding blocks and non-square rectangular video coding blocks, and wherein the extended directional intra-prediction modes are applicable to non-square rectangular video coding blocks and are not applicable to square video coding blocks.

2. The intra-prediction method of claim 1, wherein determining the directional intra-prediction mode for the rectangular video coding block is based on an aspect ratio of the rectangular video coding block, and wherein the aspect ratio of the rectangular video coding block is $R_{asp} = \frac{L_{shorter}}{L_{longer}},$ where L.sub.shorter and L.sub.longer are the lengths of the second and first sides of the rectangular video coding block, respectively.

3. The intra-prediction method of claim 2, wherein a number of the extended directional intra-prediction modes of the extended set of directional intra-prediction modes is based on an angle α, wherein: $α = \frac{π}{4} - \arctan (\frac{L_{shorter}}{L_{longer}}) .$

4. The intra-prediction method of claim 1, wherein the rectangular video coding block is a coding unit, a prediction unit, or a transform unit.

5. An intra-prediction apparatus, comprising a processor and a non-transitory memory having instructions stored thereon, wherein the instructions, when executed by the processor, facilitate: determining a directional intra-prediction mode for a rectangular video coding block from an extended set of directional intra-prediction modes, wherein the extended set of directional intra-prediction modes includes conventional directional intra-prediction modes and extended directional intra-prediction modes, wherein the rectangular video coding block has a first side and a second side, and wherein a length of the first side is greater than a length of the second side; determining a plurality of available reference samples based on a direction of the directional intra-prediction mode; and intra-predicting pixel values of pixels of the rectangular video coding block based on the plurality of available reference samples; wherein the conventional directional intra-prediction modes are applicable to both square video coding blocks and non-square rectangular video coding blocks, and wherein the extended directional intra-prediction modes are applicable to non-square rectangular video coding blocks and are not applicable to square video coding blocks.

6. The intra-prediction apparatus of claim 5, wherein the instructions, when executed by the processor, further facilitate: removing a directional intra-prediction mode from a set of predetermined directional intra-prediction modes in response to a length associated with the plurality of available reference samples being smaller than a multiple of the length of the first side.

7. The intra-prediction apparatus of claim 5, wherein the rectangular video coding block is a coding unit, a prediction unit, or a transform unit.

8. The intra-prediction apparatus of claim 5, wherein the apparatus is an encoder or a decoder.

9. A non-transitory computer readable medium having processor-executable instructions stored thereon for intra-prediction, wherein the processor-executable instructions, when executed, facilitate: determining a directional intra-prediction mode for a rectangular video coding block from an extended set of directional intra-prediction modes, wherein the extended set of directional intra-prediction modes includes conventional directional intra-prediction modes and extended directional intra-prediction modes, wherein the rectangular video coding block has a first side and a second side, and wherein a length of the first side is greater than a length of the second side; determining a plurality of available reference samples based on a direction of the directional intra-prediction mode; and intra-predicting pixel values of pixels of the rectangular video coding block based on the plurality of available reference samples; wherein the conventional directional intra-prediction modes are applicable to both square video coding blocks and non-square rectangular video coding blocks, and wherein the extended directional intra-prediction modes are applicable to non-square rectangular video coding blocks and are not applicable to square video coding blocks.

10. The non-transitory computer readable medium of claim 9, wherein the processor-executable instructions, when executed, further facilitate: determining a non-prediction area within the rectangular video coding block based on the length of the second side and a predetermined direction of the directional intra-prediction mode.

11. The non-transitory computer readable medium of claim 9, wherein determining the directional intra-prediction mode for the rectangular video coding block is based on an aspect ratio of the rectangular video coding block, and wherein the aspect ratio of the rectangular video coding block is $R_{asp} = \frac{L_{shorter}}{L_{longer}},$ where L.sub.shorter and L.sub.longer are the lengths of the second and first sides of the rectangular video coding block, respectively.

12. The non-transitory computer readable medium of claim 11, wherein a number of the extended directional intra-prediction modes of the extended set of directional intra-prediction modes is based on an angle α, wherein: $α = \frac{π}{4} - \arctan (\frac{L_{shorter}}{L_{longer}}) .$

13. The non-transitory computer readable medium of claim 9, wherein the rectangular video coding block is a coding unit, a prediction unit, or a transform unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further embodiments of the invention will be described with respect to the following figures, wherein:

(2) FIG. 1 shows a schematic diagram of an intra-prediction apparatus for removing a directional intra-prediction mode of a rectangular video coding block from a set of predetermined directional intra-prediction modes;

(3) FIG. 2 shows a schematic diagram of an encoding apparatus for encoding a rectangular video coding block;

(4) FIG. 3 shows a schematic diagram of a decoding apparatus for decoding an encoded rectangular video coding block;

(5) FIG. 4 shows a schematic diagram of an intra-prediction method for removing a directional intra-prediction mode of a rectangular video coding block from a set of predetermined directional intra-prediction modes;

(6) FIG. 5 shows a schematic diagram of a video coding block illustrating different directional intra-prediction modes;

(7) FIGS. 6(a) and 6(b) illustrate an example of block partitioning and a corresponding tree structure by using quad-tree plus binary-tree (QTBT);

(8) FIGS. 7(a) and 7(b) illustrate implementations of a directional intra-prediction mechanism in quad-tree (QT) and quad-tree plus binary-tree (QTBT) frameworks, respectively;

(9) FIGS. 8(a) and 8(b) illustrate an extension of a set of directional intra-prediction modes subject to an aspect ratio of a given rectangular video coding block;

(10) FIG. 9 shows a schematic diagram illustrating an extension of a set of directional intra-prediction modes subject to an aspect ratio of a given rectangular video coding block;

(11) FIG. 10 shows a schematic diagram illustrating a preservation of a cardinality of directional intra-prediction modes subject to an aspect ratio of a given rectangular video coding block;

(12) FIG. 11 illustrates an example of block partitioning and a corresponding tree structure by using quad-tree plus binary-tree (QTBT), wherein the number of available reference samples along a longer side is less than its double length in a rectangular video coding block;

(13) FIG. 12 illustrates enabling or disabling a set of directional intra-prediction modes subject to an availability of reference samples of a given rectangular video coding block;

(14) FIG. 13 illustrates a first step of a signaling mechanism for extension of directional intra-prediction modes;

(15) FIG. 14 illustrates a second step of a signaling mechanism for extension of directional intra-prediction modes;

(16) FIG. 15 illustrates a decoding process for a directional intra mode index by applying a signaling mechanism;

(17) FIG. 16 shows a schematic diagram illustrating an implementation of a signaling mechanism applied in an encoding apparatus;

(18) FIG. 17 shows a schematic diagram illustrating an implementation of a signaling mechanism applied in a decoding apparatus;

(19) FIGS. 18(a) and 18(b) show schematic diagrams illustrating implementations of a signaling mechanism applied to the Enhanced Intra-Prediction (EIP) mechanism; and

(20) FIG. 19 shows a schematic diagram of an encoding apparatus for encoding a rectangular video coding block comprising an intra-prediction apparatus.

(21) In the various figures, identical reference signs will be used for identical or at least functionally equivalent features.

DETAILED DESCRIPTION OF EMBODIMENTS

(22) In the following description, reference is made to the accompanying drawings, which form part of the disclosure, and in which are shown, by way of illustration, exemplary aspects of embodiments of the present invention. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, as the scope of the present invention is defined be the appended claims.

(23) For instance, it is understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

(24) FIG. 1 shows a schematic diagram of an intra-prediction apparatus 100 for removing a directional intra-prediction mode of a rectangular video coding block from a set of predetermined directional intra-prediction modes. Each predetermined directional intra-prediction mode of the set of predetermined directional intra-prediction modes is associated with a predetermined direction, the rectangular video coding block having a first side and a second side, a length (L.sub.longer) of the first side being greater than a length (L.sub.shorter) of the second side. The intra-prediction apparatus 100 comprises a reference sample determining unit 101 configured to select the directional intra-prediction mode from the set of predetermined directional intra-prediction modes, to determine a plurality of available reference samples on the basis of a predetermined direction of the directional intra-prediction mode, the available reference samples extending along the first side of the rectangular video coding block, and to determine a length (L.sub.RSlonger) associated with the plurality of available reference samples, a directional intra-prediction mode removing unit 103 configured to compare the length (L.sub.longer) of the first side with the length (L.sub.RSlonger) associated with the plurality of available reference samples, and to remove the directional intra-prediction mode from the set of predetermined directional intra-prediction modes if the length (L.sub.RSlonger) associated with the plurality of available reference samples is smaller than a multiple of the length (L.sub.longer) of the first side for obtaining a reduced set of predetermined directional intra-prediction modes, and an intra-prediction unit 105 configured to intra-predict pixel values of pixels of the rectangular video coding block on the basis of the reduced set of predetermined directional intra-prediction modes. The intra-prediction apparatus 100 further comprises an area determining unit 107 configured to determine a non-prediction area (S.sub.uncov) within the rectangular video coding block upon the basis of the length (L.sub.shorter) of the second side and the predetermined direction of the directional intra-prediction mode.

(25) FIG. 2 shows a schematic diagram of an encoding apparatus 200 for encoding a rectangular video coding block. The encoding apparatus 200 comprises an intra-prediction apparatus 100 for providing a predicted rectangular video coding block, and an encoding unit 201 configured to encode the rectangular video coding block on the basis of the predicted rectangular video coding block.

(26) FIG. 3 shows a schematic diagram of a decoding apparatus 300 for decoding an encoded rectangular video coding block. The decoding apparatus 300 comprises an intra-prediction apparatus 100 for providing a predicted rectangular video coding block, and a restoration unit 301 configured to restore a rectangular video coding block on the basis of an encoded rectangular video coding block and the predicted rectangular video coding block.

(27) FIG. 4 shows a schematic diagram of an intra-prediction method 400 for removing a directional intra-prediction mode of a rectangular video coding block from a set of predetermined directional intra-prediction modes. Each predetermined directional intra-prediction mode of the set of predetermined directional intra-prediction modes is associated with a predetermined direction, the rectangular video coding block having a first side and a second side, a length (L.sub.longer) of the first side being greater than a length (L.sub.shorter) of the second side. The intra-prediction method 400 comprises selecting 401 the directional intra-prediction mode from the set of predetermined directional intra-prediction modes, determining 403 a plurality of available reference samples on the basis of a predetermined direction of the directional intra-prediction mode, the available reference samples extending along the first side of the rectangular video coding block, determining 405 a length (L.sub.RSlonger) associated with the plurality of available reference samples, comparing 407 the length (L.sub.longer) of the first side with the length (L.sub.RSlonger) associated with the plurality of available reference samples, removing 409 the directional intra-prediction mode from the set of predetermined directional intra-prediction modes if the length (L.sub.RSlonger) associated with the plurality of available reference samples is smaller than a multiple of the length (L.sub.longer) of the first side for obtaining a reduced set of predetermined directional intra-prediction modes, and intra-predicting 411 pixel values of pixels of the rectangular video coding block on the basis of the reduced set of predetermined directional intra-prediction modes.

(28) FIG. 5 shows a schematic diagram of a video coding block illustrating different directional intra-prediction modes. The intra prediction modes as shown in FIG. 5 include a planar mode (the intra-prediction mode index is 0), DC mode (the intra-prediction mode index is 1), and 33 directional modes (the intra-prediction mode index ranges from 2 to 34, indicated by the solid lines). The set of directional intra-prediction modes was extended up to 65 modes (almost doubled) by decreasing a step angle between directional intra-prediction modes by a factor of 2. The dotted lines in FIG. 5 denote the angular modes, which are introduced in the JEM software.

(29) FIGS. 6(a) and 6(b) illustrate an example of block partitioning and a corresponding tree structure by using quad-tree plus binary-tree (QTBT), wherein solid lines denote quad-tree partitioning and dashed lines denote binary-tree partitioning. In each partitioning node of the binary-tree, the partitioning type is indicated by 0 (horizontal partitioning) or 1 (vertical partitioning).

(30) FIGS. 7(a) and 7(b) illustrate implementations of a directional intra-prediction mechanism in quad-tree (QT) and quad-tree plus binary-tree (QTBT) frameworks, respectively. Here, the same number of reference samples are used along both shorter and longer sides of rectangular blocks. Therefore, the number of directional intra-prediction modes depends on neither aspect ratio of blocks nor actual availability of reference samples in the current implementation of the QTBT framework.

(31) FIGS. 8(a) and 8(b) illustrate an extension of a set of directional intra-prediction modes subject to an aspect ratio of a given rectangular video coding block. As shown in FIG. 8(a), an aspect ratio of a square video coding block is 1:1 and a set of conventional directional intra-prediction modes is used for predicting values of a video coding block being reconstructed. On the other hand, a rectangular video coding block comprises shorter and longer sides, and such asymmetry can be used to improve the current directional intra-prediction mechanism by increasing its prediction accuracy. As illustrated in FIG. 8(b), the number of available directional intra-prediction modes can be increased along a long side.

(32) FIG. 9 shows a schematic diagram illustrating an extension of a set of directional intra-prediction modes subject to an aspect ratio of a given rectangular video coding block. The corresponding processing steps may be implemented by the intra-prediction apparatus 100 and/or the intra-prediction method 400. In FIG. 9, square pixels represent reference samples for intra-prediction, wherein the order of probabilities that the reference samples are available is: reference pixel with dots>reference pixel with stripes>reference pixel with diagonal stripes.

(33) The number of the newly introduced directional intra-prediction modes may depend on the aspect ratio of the rectangular video coding block. The angle that encompasses these new modes is defined by the following formula:

(34) $α = \frac{π}{4} - \arctan (\frac{L_{shorter}}{L_{longer}})$
wherein L.sub.shorter and L.sub.longer are the lengths of the shorter and longer sides of the rectangular video coding block, respectively. As illustrated in FIG. 9, L.sub.shorter=width and L.sub.longer=height for a vertical orientation of the rectangular video coding block. The actual number of these modes may depend on the angle between neighbor directional modes and the angle α defined by the above formula.

(35) In the up-to-date version of the JEM software (version JEM-4.0), the average angle step between neighbor directional modes defined by an intra-prediction interpolation filter does not depend on the block size and equals:

(36) $s = \frac{π}{64}$

(37) Thus, in the case of uniformly spaced directional intra-prediction modes, the number N of the newly introduced modes equals:

(38) $N = .Math. \frac{α}{s} .Math. = 16 - .Math. \frac{64}{π} \arctan (\frac{L_{shorter}}{L_{longer}}) .Math.$
wherein custom character is a floor operation.

(39) In the embodiment shown in FIG. 9, the number of reference samples is extended along the longer side, and it is not reduced for the shorter side. Therefore, the amount of intra-prediction modes that are available along the longer side (the angle that encompasses these modes is marked by a solid line) is increased, but the number of intra-prediction modes that are available along the shorter side (the angle that encompasses these modes is marked by a dashed line) is not decreased. Hence, the cardinality of the intra-prediction mode set is only increased while the aspect ratio

(40) $R_{asp} = \frac{L_{shorter}}{L_{longer}}$
is decreasing. On the other hand, another approach to preserve the original number of directional intra-prediction modes is also possible according to another embodiment.

(41) FIG. 10 shows a schematic diagram illustrating a preservation of a cardinality of directional intra-prediction modes subject to an aspect ratio of a given rectangular video coding block. As shown in FIG. 10, the amount of the directional intra-prediction modes added along the longer side (the angle that encompasses these modes is marked by a solid line) may be equal to the amount of the directional intra-prediction modes removed along the shorter side (the angle that encompasses these modes is marked by a dashed lines). Thus, the cardinality of the intra-prediction mode set remains the same as for square blocks.

(42) According to an embodiment, whether to extend a set of available intra-prediction modes or not can also depend on the availability of reference samples because they are needed to generate an intra-predictor.

(43) FIG. 11 illustrates an example of block partitioning and a corresponding tree structure by using quad-tree plus binary-tree (QTBT), wherein the number of available reference samples along a longer side is less than its double length in a rectangular video coding block. As shown in FIG. 11, the quad-tree plus binary-tree (QTBT) partitioning framework produces a partitioning, wherein the actual number of available reference samples along a longer side is less than its double length as assumed in the above examples in FIGS. 9 and 10. Therefore, the approach for increasing the number of the directional intra-prediction modes in the above examples may need to be adjusted according to an availability of reference samples for the case of FIG. 11.

(44) FIG. 12 illustrates enabling or disabling a set of directional intra-prediction modes subject to an availability of reference samples of a given rectangular video coding block within the quad-tree plus binary-tree (QTBT) partitioning framework, wherein a grey rectangle area represents a currently processed video coding block, square pixels with diagonal stripes indicate available reference samples, and square pixels with dots indicate unavailable reference samples. Disabling can e.g. be achieved by removing a respective directional intra-prediction mode from the set.

(45) A fractional non-prediction area P of a rectangular video coding block generated using interpolated reference samples may be calculated as follows:

(46) $\begin{matrix} P_{a r e a} = \frac{S_{u n c o v}}{S_{block}} = \frac{S_{u n c o v}}{L_{s h o r t e r} .Math. L_{longer}} = \frac{L_{s h o r t e r}^{2} .Math. \tan γ}{2 .Math. L_{s h o r t e r} .Math. L_{longer}} \\ = \frac{L_{s h o r t e r} .Math. \tan γ}{2 .Math. L_{longer}} = \frac{L_{s h o r t e r}}{L_{longer}} .Math. \frac{\tan γ}{2} = R_{a s p} .Math. \frac{\tan γ}{2} \end{matrix}$
wherein L.sub.longer and L.sub.shorter are the lengths of the longer and shorted sides of a rectangular video coding block, respectively, γ is the angle of a given directional intra-prediction mode belonging to the extended set, S.sub.block=L.sub.shorter L.sub.longer is the area of a rectangular video coding block to be predicted,

(47) $S_{uncov} = \frac{L_{shorter}^{2} .Math. \tan γ}{2}$
is the non-prediction area, i.e. the area of the video coding block that may not be predicted using non-interpolated reference samples, as marked by stripes.

(48) Therefore, the closer an intra-prediction direction is located to the diagonal marked by a dashed line, the larger part of an area that remains may not be predicted using non-interpolated reference samples. In an example, the set of directional intra-prediction modes is not extended if the length L.sub.RSlonger of non-interpolated reference samples along the longer side is less than the double length of the longer side:
L.sub.RSlonger<2L.sub.longer.

(49) If a set of directional intra-prediction modes is extended, it is desirable to signal the newly extended modes, which may not be accomplished using existing conventional mechanisms. For this purpose, a 2-step signaling mechanism for the extension of directional intra-prediction modes is set forth and explained in FIGS. 13 and 14.

(50) FIG. 13 illustrates a first step of a signaling mechanism for extension of directional intra-prediction modes, wherein a set of extended modes is mapped to a conventional set of intra-prediction modes using a mirroring procedure.

(51) FIG. 14 illustrates a second step of a signaling mechanism for extension of directional intra-prediction modes, wherein a one-bit flag is used to distinguish between conventional and extended directional modes. The flag is assigned a value “0” for a conventional mode and “1” for an extended mode. Furthermore, the flag in the signaling mechanism is used only for those directional modes that are reflections of extended ones.

(52) FIG. 15 illustrates a decoding process for a directional intra mode index by applying a signaling mechanism. As shown in FIG. 15, the extended modes of the directional intra-prediction are flagged with “1”, the conventional modes having a mapped mode are flagged with “0”, and the other modes have no additional signaling value.

(53) FIG. 16 shows a schematic diagram illustrating an implementation of a signaling mechanism applied in an encoding apparatus. In a first processing step 1601 the index of the intra-prediction mode I.sub.IPM is parsed from the bitstream. Thereafter, in processing step 1603 a decision is taken depending on whether the decoded intra-prediction mode is a directional intra prediction mode. In the case the signaling scheme is applied in the context of HEVC video coding, the intra-prediction mode is directional when I.sub.IPM is greater than 1. If the intra-prediction mode is directional, in processing step 1605 a decision is taken depending on whether the decoded intra-prediction mode is extended. The decoded intra-prediction mode is extended when I.sub.IPM is greater than Q[π/2+arctan(Width/Height)] and smaller than VDIAG_IDX, wherein Width and Height are the lengths of short and long sides of a rectangular video coding block being decoded, and VDIAG_IDX is equal to 66 according to embodiments of the invention. Then, the flag “ext_dir_mode_flag” is assigned to a value of 0 for the conventional modes which can have mapped extended code (see processing steps 1607, 1609). A rate-distortion cost (RD-cost) is estimated for the conventional modes in processing step 1611. The flag “ext_dir_mode_flag” is assigned to a value of 1 for the extended modes (see processing steps 1613, 1615). A rate-distortion cost (RD-cost) for the conventional modes is estimated in processing step 1617. The flag “ext_dir_mode_flag” is determined by finding the lowest rate-distortion cost (RD-cost) between the conventional modes and extended modes in processing step 1619.

(54) FIG. 17 shows a schematic diagram illustrating an implementation of a signaling mechanism applied in a decoding apparatus. In a first processing step 1701 the index of the intra-prediction mode I.sub.IPM is parsed from the bitstream. Thereafter, in processing step 1703 a decision is taken depending on whether the decoded intra prediction mode is a directional intra prediction mode. In the case the signaling scheme is applied in the context of HEVC video coding, the intra prediction mode is directional when I.sub.IPM is greater than 1. If the intra-prediction mode is directional, in processing step 1705 a decision is taken depending on whether the decoded intra-prediction mode is extended. The decoded intra-prediction mode is extended when I.sub.IPM is greater than Q[π/2+arctan(Width/Height)] and smaller than VDIAG_IDX, wherein Width and Height are the lengths of short and long sides of a rectangular block being decoded, and VDIAG_IDX is equal to 66 according to embodiments of the invention. For extended directional intra-prediction modes the value of the flag “ext_dir_mode_flag” is parsed from the bitstream in processing step 1707. According to embodiments of the invention this flag is introduced into the bitstream to code whether to apply the disclosed mechanism to the prediction unit. In processing step 1709, a decision is taken to use either the extended prediction scheme if ext_dir_mode_flag is equal to 1 (processing step 1711a) or the conventional prediction if ext_dir_mode_flag is not equal to 1 (processing step 1711b), as provided by embodiments of the invention, for obtaining the predicted signal. The decision in processing step 1709 is taken on the basis of the value of the flag “ext_dir_mode_flag”, which has been determined in processing step 1707.

(55) The signaling mechanism is applicable to a wider spectrum of cases according to embodiments of the invention. For example, it can be used to reduce a signaling overhead caused by an extended set of directional intra-prediction modes used in Enhanced Intra-Prediction (EIP) technique proposed by Google for its VPX codec family. This EIP technique is needed to improve the compression efficiency of intra-predicted blocks within inter-predicted pictures. EIP is a two-pass mechanism for increasing the number of available prediction directions, wherein blocks with good inter-prediction modes are initially encoded, and then intra blocks with access to more boundaries are filled in.

(56) FIGS. 18(a) and 18(b) show schematic diagrams illustrating implementations of a signaling mechanism applied to the Enhanced Intra-Prediction (EIP) mechanism. In the cases shown in FIGS. 18(a) and 18(b), 4 (2π) and 3 (3π/2) sides of a video coding block are available for directional intra-prediction, respectively. Solid lines denote directions from a main angle and dashed lines denote directions from a complimentary angle. In both cases, the set of available intra-prediction modes is more than for a conventional case.

(57) As described above, the same 2-step signaling mechanism can be conducted to signal what angle the selected directional intra-prediction mode belongs to by using a one-bit flag. Firstly, a directional mode can be mapped onto the main angle if the directional mode is selected from the complementary angle. Secondly, the one-bit flag can be set to “ON” if the direction is selected from the complementary angle; otherwise, the flag can be set to “OFF”.

(58) FIG. 19 shows a schematic diagram of an encoding apparatus 200 for encoding a rectangular video coding block comprising an intra-prediction apparatus 100. A decoding apparatus 300 can be implemented analogously.

(59) While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations or embodiments, such a feature or aspect may be combined with one or more further features or aspects of the other implementations or embodiments as may be desired or advantageous for any given or particular application. Furthermore, to the extent that the terms “include”, “have”, “with”, or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprise”. Also, the terms “exemplary”, “for example” and “e.g.” are merely meant as an example, rather than the best or optimal. The terms “coupled” and “connected”, along with derivatives thereof may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

(60) Although exemplary aspects have been illustrated and described herein, it will be appreciated that a variety of alternate and/or equivalent implementations may be substituted for the exemplary aspects shown and described without departing from the scope of the present disclosure. This application may cover any adaptations or variations of the exemplary aspects discussed herein.

(61) Although elements in the following claims may be recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

(62) Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present disclosure has been described with reference to one or more exemplary embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, embodiments of the invention may be practiced otherwise than as specifically described herein.

Intra-prediction apparatus for removing a directional intra-prediction mode from a set of predetermined directional intra-prediction modes

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Abstract

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Description