Angular table for improving intra prediction

Patent metadata

Field	Value
Publication number	US-9344715-B2
Application number	US-201213670382-A
Country	US
Kind code	B2
Filing date	Nov 6, 2012
Priority date	Nov 7, 2011
Publication date	May 17, 2016
Grant date	May 17, 2016

Abstract

A method of intra prediction comprising computing a prediction block for a luma block, wherein computing the prediction block includes using a plurality of directional intra prediction modes and an angular table (angTable) comprising a plurality of entries, and wherein a value of each entry is determined via a mathematical derivation. An apparatus comprising a memory configured to store an angTable comprising a plurality of entries, wherein a value of each entry is determined via a mathematical derivation, and a processor configured to compute a prediction block for a luma block using a plurality of directional intra prediction modes and the angTable.

First claim

What is claimed is:

1. A method of intra prediction comprising computing a prediction block for a luma block, wherein computing the prediction block includes using a plurality of directional intra prediction modes and an angular table (angTable) comprising a plurality of entries, wherein a value of each entry is determined via a mathematical derivation, wherein determining at least one of the entry values comprises computing ln(sin(θ 1 ))−ln(sin(θ 0 )), wherein θ 0 denotes a lower boundary angle of an angular interval, and wherein θ 1 denotes an upper boundary angle of the angular interval, and wherein the angular interval is part of an angular range covered by the plurality of directional intra prediction modes.

2. The method of claim 1 , wherein the mathematical derivation comprises calculating a weighting factor for the angular interval, wherein calculating the weighting factor comprises averaging weighting factors for a plurality of sub-intervals included in the angular interval.

3. method of claim 1 , wherein the luma block is part of a video frame, wherein the prediction block is subtracted from the luma block to generate a residual block, wherein the residual block is transformed, quantized, and entropy encoded to generate an output bit stream.

4. The method of claim 1 , further comprising:
computing a difference between the prediction block and the luma block to generate a residual block;
transforming the residual block to generate a plurality of transform coefficients;
quantizing the plurality of transform coefficients to generate a plurality of quantized transform coefficients; and
entropy encoding at least part of the plurality of quantized transform coefficients to generate an encoded bit stream.

5. The method of claim wherein determining at least one of the entry values comprises:
determining a lower boundary angle of the angular interval;
determining an upper boundary angle of the angular interval;
obtaining an equivalent averaging prediction angle (EAPA) in the angular interval, wherein the angular interval is part of an angular range covered by the plurality of directional intra prediction modes; and
computing at least one of the entry values based on the EAPA.

6. The method of claim 5 , wherein the lower boundary angle is based on a pre-configured angular width greater than zero and smaller than π/4, the upper boundary angle is based on a pre-configured angular width greater than zero and smaller than π/4, and the EAPA is in an i-th angular interval of the angular range [π/4+Δstep, π/2], wherein i =0, 1, 2, 3, 4, 5, 6.

7. The method of claim 1 , wherein determining at least one of the entry values further comprises:
computing an angular width of the angular interval; and
integer dividing ln(sin(θ 1 )−ln(sin(θ 0 )) by the angular width.

8. The method of claim 7 , wherein a number of the directional intra prediction modes is 33.

9. The method of claim 7 , wherein the angular range comprises a number of angular intervals including the angular interval.

10. The method of claim 9 , wherein each angular interval is equal in the angular width.

11. A method of intra prediction comprising computing a prediction block for a luma block, wherein computing the prediction block includes using a plurality of directional intra prediction modes and an angular table (angTable) comprising a plurality of entries, wherein a value of each entry is determined via a mathematical derivation,
wherein determining K entry values comprises computing
for integer i=0, 1, . . . , K−1,

θ
0

=

(

π
/
4

+

i
*

(

π
/
4

-
Δstep

)

)

/
K

,

⁢

θ
1

=

(

π
/
4

+

(

i
+
1

)

*

(

π
/
4

-
Δstep

)

)

/
K

,

⁢
and

cot
⁡

(

θ

equ
,
i

)

=

ln
⁡

(

sin
⁡

(

θ
1

)

)

-

ln
⁡

(

sin
⁡

(

θ
0

)

)

Assignees

• Futurewei Technologies Inc

Inventors

• Liu Lingzhi

Classifications

• H04N19/00018 Primary

  Electricity · mapped topic

• H04N19/593

  involving spatial prediction techniques · CPC title

• H04N19/136

  Incoming video signal characteristics or properties · CPC title

• H04N19/103 Primary

  Selection of coding mode or of prediction mode · CPC title

• H04N19/176 Primary

  the region being a block, e.g. a macroblock · CPC title