METHOD OF FILTERING A SIGNAL AND OF OBTAINING FILTER COEFFICIENTS

1 . Method of filtering a signal, including:

determining a class of a section ( 23 ; 39 ) of the signal obtained as input, wherein the determination of the class includes calculating a signal section ( 28 ; 41 ) comprising at least a component representative of a derivative of at least a first order of the input signal section ( 23 ; 39 ) and applying a quantisation operation to the calculated signal section ( 28 ; 41 ), wherein, in the quantisation operation, a quantisation step is adapted to a dynamite range of the calculated signal section ( 28 ; 41 ); and

selecting a digital filter associated with the class from a plurality of available filters.

2 . Method according to claim 1 , wherein the quantisation operation comprises an n-bit adaptive dynamic range coding.

3 . Method according to claim 1 , wherein the input signal section ( 28 ; 41 ) is obtained from an array of pixel data encoding a digital image ( 38 ).

4 . Method according to claim 3 , wherein the plurality of filters comprise isotropic filters.

5 . Method according to claim 3 , wherein the digital image is comprised in a sequence ( 19 ) of images and data representative of the sequence of images ( 19 ) is obtained, and wherein the input signal section ( 23 ; 39 ) is obtained by, for each of at least one pixel ( 24 ′; 24 ″) of the digital image, estimating a direction of motion of a region of the image comprising the pixel ( 24 ′; 24 ″) over a plurality of the sequence ( 19 ) of images and selecting values of pixels ( 26 ′ a - h; 26 ″ a - h ) positioned relative to the pixel ( 24 ′; 24 ″) along the direction of motion.

6 . Method according to claim 5 ; including determining a magnitude of the motion of the region of the image comprising the pixel ( 24 ′; 24 ″) and selecting a certain number of pixels ( 26 ′ a - h; 26 ″ a - h ) at mutual intervals dependent in size on the magnitude of the motion.

7 . Device for filtering a signal, including:

an input ( 8 ) for receiving the signal;

a device component for determining a class of a section ( 23 ; 39 ) of the signal obtained as input, the device component including a signal processing component ( 9 ) for calculating a signal section ( 28 ; 41 ) comprising at least a component representative of a derivative of at least a first order of the input signal section ( 23 ; 39 ) and a signal processing component ( 9 ) for applying a quantisation operation to the calculated signal section ( 28 ; 41 ), wherein the device is configured to implement the quantisation operation such that a quantisation step is adapted to a dynamic range of the calculated signal section ( 28 ; 41 ); and

a switch for switching between a plurality of available digital filters.

8 . Device according to claim 7 , configured to carry out a method according to any one of claims 1 - 6 .

9 . Device for rendering at least one image on a display, comprising an interface ( 2 , 4 ) for receiving a signal encoding at least one image and a filter device ( 7 ) for filtering a digital signal representative of the at least one image, wherein the filter device ( 7 ) is constituted according to claim 8 .

10 . Method of obtaining filter coefficients of a plurality of filters, including:

obtaining a plurality of test signal sections ( 55 a - n ) and associated target signal values ( 60 a - n ), each test signal section ( 55 a - n ) associated with one of a plurality of classes;

for each class, optimising a set of filter coefficients of an associated filter such that filtered versions of the test signal sections ( 55 a - n ) associated with that class best approximate their associated target signal values ( 60 a - n ); and

associating each optimised set of filter coefficients with a class code ( 59 ) obtainable by:

for any test signal section ( 55 ) associated with the class associated with the optimised set of filter coefficients, calculating a signal section ( 57 ) comprising at least a component representative of a derivative of at least a first order the test signal section ( 55 ) and applying a quantisation operation to the calculated signal section ( 57 ), wherein, in the quantisation operation, a quantisation step is adapted to a dynamic range of the calculated signal section ( 57 ).

11 . Method according to claim 10 , wherein the quantisation operation comprises an n-bit adaptive dynamic range coding.

12 . Method according to claim 10 , wherein the each test signal section ( 55 ) is obtained from an array of pixel data encoding a digital image ( 50 ).

13 . Method according to claim 12 , wherein the plurality of filters comprise isotropic filters.

14 . Method according to claim 12 , wherein the digital image ( 50 ) is comprised in a sequence of images and data representative of the sequence of images is obtained, and wherein a test signal section ( 55 ) is obtained by, for each of at least one pixel of the digital image ( 50 ), obtaining data representative of a direction of motion of a region of the image ( 50 ) comprising the pixel over a plurality of the sequence of images and selecting values of pixels positioned relative to the pixel along the direction of motion.

15 . Computer program including a set of instructions capable, when incorporated in a machine-readable medium, of causing a system having information processing capabilities to perform a method according to claim 1 .