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US 8,942,505 B2Granted
Adaptive filter representation
AssigneeTelefonaktiebolaget L M Ericsson (publ)
InventorsKenneth Andersson, Richard Sjöberg
Life of this patent
Estimating the term…
Abstract
The present invention teaches a filter process used in intra or inter prediction of pixel blocks. A first, optionally interpolation, filter is applied in the first filter process to get filtered, optionally interpolated, pixel values. A differential filter and an adaptive gain are utilized in the second process for improving the prediction performance. The adaptivity of the gain can be made even on block basis, allowing a fine tuning of the pixel prediction and/or a fine tuning of pixel rotation and zooming. Alternatively, a combined one-step filter process using the interpolation filter, the differential filter and the adaptive gain is applied to the pixel values.
Claims34
A method of encoding a group of image elements in a frame of an image or video sequence, said method comprising the steps of:
- a) estimating, based on property values of said group of image elements, a parameter representation associated with a reference group of image elements in a frame, wherein the parameter representation comprises a motion vector pointing towards the reference group of image elements;
- b) providing a filter applicable to reference property values of said reference group of image elements;
- c) providing a differential filter having fixed filter coefficients;
- d) determining, based on said differential filter, said filter, said property values and said reference property values, a filter gain applicable to a filter obtainable based on said differential filter;
- e) calculating a residual error based on said property values, said parameter representation, said filter, said filter obtainable based on said differential filter and said filter gain;
- and
- f) providing a representation of said parameter representation and a representation of said residual error as an encoded representation of said group of image elements;
- wherein said determining step d) comprises determining said filter gain g by minimization of the prediction error E defined as:
- E
- 2
- =
- ∑
- n
-
- (
- S
- n
- -
- ∑
- i
-
- P
- n
- -
- i
-
- IF
- i
- +
- ∑
- j
-
- P
- n
- -
- j
-
- gDF
- j
- )
- 2
- where Sn represents the property values of image elements of group n in said frame, Pn-i is is the reference property values of image elements of reference group n−i in said frame, IF is said filter, DF is said differential filter and g is said filter gain.
39 more elements
A method of decoding a group of image elements in a frame of an encoded image or video sequence, said method comprising the steps of:
- identifying a reference group of image elements in a frame based on a parameter representation associated with said group of image elements, wherein the parameter representation comprises a motion vector pointing toward the reference group of image elements;
- providing a filter associated with said group of image elements;
- providing a filter gain and a differential filter associated with said group of image elements, said differential filter having fixed filter coefficients;
- and
- filtering reference property values of said reference group of image elements with said filter and a filter obtainable based on said filter gain and said differential filter to obtain a decoded group of image elements;
- wherein said filter gain g is determined by minimization of the prediction error E defined as:
- E
- 2
- =
- ∑
- n
-
- (
- S
- n
- -
- ∑
- i
-
- P
- n
- -
- i
-
- IF
- i
- +
- ∑
- j
-
- P
- n
- -
- j
-
- gDF
- j
- )
- 2
- where Sn represents the property values of image elements of group n in said frame, Pn-i is the reference property values of image elements of reference group n−i in said frame, IF is said filter, DF is said differential filter and g is said filter gain.
37 more elements
An encoder for encoding a group of image elements in a frame of an image or video sequence, said encoder comprising:
- a parameter representation estimator for estimating, based on property values of said group of image elements, a parameter representation associated with a reference group of image elements in a frame, wherein the parameter representation comprises a motion vector pointing toward the reference group of image elements;
- a filter provider for providing a filter applicable to reference property values of said reference group of image elements;
- a differential filter provider for providing a differential filter, said differential filter having fixed filter coefficients;
- a gain determiner for determining, based on said differential filter, said filter, said property values of said group of image elements and said reference property values, a filter gain applicable to a filter obtainable based on said differential filter;
- an error calculator for calculating a residual error based on said property values, said parameter representation, said filter, said filter obtainable based on said differential filter and said filter gain;
- and
- a group encoder for providing a representation of said parameter representation and a representation of said residual error as an encoded representation of said group of image elements;
- wherein said gain determiner determines said filter gain g by minimization of the prediction error E defined as:
- E
- 2
- =
- ∑
- n
-
- (
- S
- n
- -
- ∑
- i
-
- P
- n
- -
- i
-
- IF
- i
- +
- ∑
- j
-
- P
- n
- -
- j
-
- gDF
- j
- )
- 2
- where Sn represents the property values of image elements of group n in said frame, Pn-i is the reference property values of image elements of reference group n−i in said frame, IF is said filter, DF is said differential filter and g is said filter pain.
39 more elements
A decoder for decoding a group of image elements in a frame of an encoded image or video sequence, said decoder comprising:
- a group identifier for identifying a reference group of image elements in a frame based on a parameter representation associated with said group of image elements, wherein the parameter representation comprises a motion vector pointing toward the reference group of image elements;
- a filter provider for providing a filter, a filter gain and a differential filter associated with said group of image elements, said differential filter having fixed filter coefficients;
- and
- a filter applier for filtering reference property values of said reference group of image elements with said filter and a filter obtainable based on said filter gain and said differential filter to obtain a decoded group of image elements;
- wherein said filter gain q is determined by minimization of the prediction error E defined as:
- E
- 2
- =
- ∑
- n
-
- (
- S
- n
- -
- ∑
- i
-
- P
- n
- -
- i
-
- IF
- i
- +
- ∑
- j
-
- P
- n
- -
- j
-
- gDF
- j
- )
- 2
- where Sn represents the property values of image elements of group n in said frame, Pn-1 is the reference property values of image elements of reference group n−i in said frame, IF is said filter, DF is said differential filter and g is said filter gain.
36 more elements
Dependencies are inferred from the claim text.