Filter banks for enhancing signals using oversampled subband transforms

A filter bank for reconstruction of an output signal from a number K of processed subband components, comprising a filtering module for generating the output signal from 2d components obtained from the K subband components, including a low-frequency component and 2d−1 higher-frequency components, d being an integer at least equal to 1 representing a dimension of the output signal,

• wherein said 2d−1 higher-frequency components are oversampled compared to said low-frequency component,
• wherein each filtering module is made of 2d−1 filtering units arranged in a binary tree having d levels, wherein, for 1 ≦i ≦d, the i-th level in the tree has 2d−i filtering units each receiving a respective input low-frequency signal and a respective input high-frequency signal oversampled compared to said respective input low-frequency signal and producing a respective output signal,
• wherein the 2d respective input components supplied to said filtering module are distributed as respective input low-frequency and high-frequency signals to the 2d−1 filtering units of the first level in the tree, wherein, for any i>1, the respective input low-frequency and high-frequency signals of the 2d−i filtering units of the i-th level in the tree are the respective output signals from the 2d−i+1 filtering units of the (i−1)-th level in the tree, and wherein the output signal of said filtering module is the output signal of the filtering unit of the d-th level in the tree,
• and wherein at least one of the filtering units has:
• a first branch for filtering an upsampled version of the respective input low-frequency signal of the filtering unit to form a first component signal;
• a second branch for filtering a first modified version of the respective input high-frequency signal of the filtering unit, in which the odd samples are replaced by zeroes, to form a second component signal;
• a first adder to form a first partially reconstructed signal as a sum of the first and second component signals;
• a third branch for filtering the partially reconstructed signal to form a third component signal;
• a fourth branch for filtering a second modified version of the respective input high-frequency signal of the filtering unit, in which the even samples are replaced by zeroes, to form a fourth component signal;
• a second adder to form a second partially reconstructed signal as a sum of the third and fourth component signals;
• and
• a combiner to produce the respective output signal of the filtering unit as a combination of the first and second partially reconstructed signals.

A filter bank for reconstruction of an output signal from a number K of processed subband components, comprising a filtering module for generating the output signal from 2d components obtained from the K subband components, including a low-frequency component and 2d−1 higher-frequency components, d being an integer at least equal to 1 representing a dimension of the output signal,

• wherein said 2d−1 higher-frequency components are oversampled compared to said low-frequency component,
• wherein each filtering module is made of 2d−1 filtering units arranged in a binary tree having d levels, wherein, for 1 ≦i ≦d, the i-th level in the tree has 2d−i filtering units each receiving a respective input low-frequency signal and a respective input high-frequency signal oversampled compared to said respective input low-frequency signal and producing a respective output signal,
• wherein the 2d respective input components supplied to said filtering module are distributed as respective input low-frequency and high-frequency signals to the 2d−1 filtering units of the first level in the tree, wherein, for any i >1, the respective input low-frequency and high-frequency signals of the 2d−i filtering units of the i-th level in the tree are the respective output signals from the 2d−i+1 filtering units of the (i−1)-th level in the tree, and wherein the output signal of said filtering module is the output signal of the filtering unit of the d-th level in the tree
• and wherein at least one of the filtering units has:
• a first filter for generating a first even sub-component from the respective input low-frequency signal of the filtering unit;
• a second filter for generating a first odd sub-component from the respective input low-frequency signal of the filtering unit;
• a third filter for generating a second even sub-component from a first downsampled version of the respective input high-frequency signal of the filtering unit;
• a fourth filter for generating a second odd sub-component from said first downsampled version of the input high-frequency signal;
• a fifth filter for generating a third even sub-component from a second downsampled version of the respective input high-frequency signal of the filtering unit;
• a sixth filter for generating a third odd sub-component from said second downsampled version of the input high-frequency signal;
• a combiner to produce the respective output signal of the filtering unit having even components respectively obtained as a sum of the first, second and third even sub-components and as a sum of the first, second and third odd sub-components.

An enhancement system for two-dimensional signals, comprising:

• a first filter bank for subband decomposition of an input two-dimensional image signal into a number K of subband components;
• a subband enhancement module for processing the K subband components from the first filter bank and forming K enhanced subband components;
• and
• a second filter bank for reconstruction of an output two-dimensional image signal from the K enhanced subband components,
• wherein the first filter bank comprises a first filtering module for transforming the input two-dimensional image signal into four components including a first low-frequency component and three first higher-frequency components oversampled compared to said first low-frequency component, and wherein the second filter bank comprises a second filtering module for generating the output two-dimensional image signal from four components obtained from the K enhanced subband components, including a second low-frequency component and three second higher-frequency components oversampled compared to said second low-frequency component.

An enhancement system for three-dimensional signals, comprising:

• a first filter bank for subband decomposition of an input three-dimensional video signal into a number K of subband components;
• a subband enhancement module for processing the K subband components from the first filter bank and forming K enhanced subband components;
• and
• a second filter bank for reconstruction of an output three-dimensional video signal from the K enhanced subband components,
• wherein the first filter bank comprises a first filtering module for transforming the input signal into eight components including a first low-frequency component and seven first higher-frequency components oversampled compared to said first low-frequency component,
• and wherein the second filter bank comprises a second filtering module for generating the output three-dimensional video signal from eight components obtained from the K enhanced subband components, including a second low-frequency component and seven second higher-frequency components oversampled compared to said second low-frequency component.

An enhancement system for d-dimensional signals, d being an integer at least equal to 1, comprising:

• a first filter bank for subband decomposition of an input signal into a number K of subband components, wherein the subband decomposition is based on wavelet transforms;
• a subband enhancement module for processing the K subband components from the first filter bank and forming K enhanced subband components;
• and
• a second filter bank for reconstruction of an output signal from the K enhanced subband components,
• wherein the first filter bank comprises a first filtering module for transforming the input signal into 2d components including a first low-frequency component and 2d−1 first higher-frequency components oversampled compared to said first low-frequency component,
• and wherein the second filter bank comprises a second filtering module for generating the output signal from 2d components obtained from the K enhanced subband components, including a second low-frequency component and 2d−1 second higher-frequency components oversampled compared to said second low-frequency component.