Optimal intra prediction in block-based video coding to calculate minimal activity direction based on texture gradient distribution

• US 9,451,266 B2
• Filed: 01/14/2014
• Issued: 09/20/2016
• Est. Priority Date: 11/16/2011
• Status: Active Grant

• Current Assignee: Beamr Imaging Ltd.
• Original Assignee: Vanguard Video LLC (Beamr Ltd.)
• Inventors: Zheludkov, Alexander C., Martemyanov, Alexey, Terterov, Nikolay
• Primary Examiner(s): LEE, Y YOUNG
• Application Number:
  US14/154,709
• Publication Number:
  US 20140126635A1
• Time in Patent Office: 980 Days
• US Class Current: 1/1
• CPC Class Codes: H04N 19/11 among a plurality of spatial predictive coding modes
• CPC Class Codes: H04N 19/119 Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/19 using optimisation based on Lagrange multipliers
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/52 by predictive encoding
• CPC Class Codes: H04N 19/521 for estimating the reliability of the determined motion vectors or motion vector field, e.g. for smoothing the motion vector field or for correcting motion vectors
• CPC Class Codes: H04N 19/523 with sub-pixel accuracy
• CPC Class Codes: H04N 19/53 Multi-resolution motion estimation; Hierarchical motion estimation
• CPC Class Codes: H04N 19/533 Motion estimation using multistep search, e.g. 2D-log search or one-at-a-time search [OTS]
• CPC Class Codes: H04N 19/567 Motion estimation based on rate distortion criteria
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/65 using error resilience

Abstract

Simplified selection of optimal intra prediction in block-based video coding based on texture gradient distribution and minimal activity direction. The minimal activity direction is defined by a vector (α(B, W), β(B, W)) indicating minimal variation of a discrete function P(x, y) inside a spatial aria of block B with weights W.

Claims

1. A video codec comprising a control circuit configured and arranged to calculate minimal activity direction based on texture gradient distribution, the minimal activity direction being defined by a vector (α

(B, W), β

(B, W)) indicating minimal variation of a discrete function P(x, y) inside a spatial area of block B with weights W;

the vector (α

(B, W), β

(B, W)) being a solution of a minimization problem;

2. A video codec of claim 1, wherein the control circuit further configured and arranged to provide simplified selection of an optimal intra prediction by:

choosing a texture block B of size L×

L starting with coordinates (x, y);

choosing a spatial area S including the texture block B;

choosing a weight matrix for S, wherein in a simplest case all weights w(j, k)=1;

calculating the minimal activity direction (α

, β

) and a corresponding angular intra prediction mode;

defining a set Q of intra predictions for selecting an optimal intra prediction mode P_k, the set Q including at least a plurality of angular intra predictions for angles γ

₀, γ

₁ . . . γ

<sub>T−

1</sub>, and a plurality of non-angular intra predictions;

calculating minimal activity direction strengths for the block B with weights W;

constructing a reduced set of intra predictions Q₁ by excluding from the set Q at least one plurality of intra predictions; and

selecting the optimal intra prediction P_k from the reduced set Q₁ of intra predictions.

3. The video codec of claim 2, wherein the control circuit further configured and arranged to calculate the minimal activity direction strengths for block B with weights W:

4. The video codec of claim 3, wherein the control circuit is further configured and arranged to construct the reduced set of intra predictions Q₁ by excluding at least one plurality of intra predictions from the set Q based on the following:

if C₁ ({tilde over (B)},W)<

X₁, excluding the plurality of angular intra predictions for the angles γ

₀, γ

₁ . . . γ

<sub>T−

1</sub>;

if C₁ ({tilde over (B)},W)>

X₂ and C₂ ({tilde over (B)},W)<

X₃ excluding the plurality of non-angular predictions;

wherein X₁, X₂, X₃ are constants for parameters defined by desired speed and quality of encoding.