Methods and apparatus for adaptive coupled pre-processing and post-processing filters for video encoding and decoding

In a video encoder, a method, comprising:

• encoding input data for a picture into a resultant bitstream, wherein said video encoder comprises a pre-filter and a post-filter coupled to the pre-filter, wherein said pre-filter filters the input data for the picture and the post-filter filters in-loop reconstructed data for the picture,
• wherein at least one of filter coefficients and filter parameters for at least one of the pre-filter and the post-filter are selected responsive to at least one of a resolution, a local gradient, and a gradient direction, wherein gradient is a difference between pixels being pre-filtered, and adaptation is made discrete by partitioning a gradient strength, gradient direction and gradient variance into disjoint ranges and applying fixed filters for different ranges, and
• wherein a Lagrangian parameter for luminance and chrominance in the video encoder's rate-distortion optimizer is a function of the coding efficiency of the pre-filter and the post-filter;
• and
• wherein the pre-filter and post-filter are implemented with a lifting scheme and adaptation is embedded therein by changing values of a diagonal matrix, obtained by performing singular value decomposition on a fixed pre-filter transform matrix, such that values of the diagonal matrix can be reversed at a decoder.

An apparatus, comprising:

• a video decoder for decoding residual image data for a picture, wherein said video decoder comprises a pre-filter and a post-filter coupled to the pre-filter, wherein said pre-filter filters a reference picture for use in decoding the residual image data and the post-filter filters in-loop reconstructed data for the picture,
• wherein at least one of filter coefficients and filter parameters for at least one of the pre-filter and the post-filter are selected responsive to at least one of a resolution, a local gradient, and a gradient direction, wherein gradient is a difference between pixels being pre-filtered, and adaptation is made discrete by partitioning a gradient strength, gradient direction and gradient variance into disjoint ranges and applying fixed filters for different ranges, and
• wherein a Lagrangian parameter for luminance and chrominance in the video decoder's rate-distortion optimizer is a function of the coding efficiency of the pre-filter and the post-filter;
• and
• wherein the pre-filter and post-filter are implemented with a lifting scheme and adaptation is embedded therein by changing values of a diagonal matrix, obtained by performing singular value decomposition on a fixed pre-filter transform matrix, such that values of the diagonal matrix can be reversed from those of an encoder.

In a video decoder, a method comprising:

• decoding residual image data for a picture, wherein said video decoder comprises a pre-filter and a post-filter coupled to the pre-filter, wherein said pre-filter filters a reference picture for use in decoding the residual image data and the post-filter filters in-loop reconstructed data for the picture,
• wherein at least one of filter coefficients and filter parameters for at least one of the pre-filter and the post-filter are selected responsive to at least one of a resolution, a local gradient, and a gradient direction, wherein gradient is a difference between pixels being pre-filtered, and adaptation is made discrete by partitioning a gradient strength, gradient direction and gradient variance into disjoint ranges and applying fixed filters for different ranges, and
• wherein a Lagrangian parameter for luminance and chrominance in the video decoder's rate-distortion optimizer is a function of the coding efficiency of the pre-filter and the post-filter;
• and
• wherein the pre-filter and post-filter are implemented with a lifting scheme and adaptation is embedded therein by changing values of a diagonal matrix, obtained by performing singular value decomposition on a fixed pre-filter transform matrix, such that values of the diagonal matrix can be reversed from those of an encoder.

A non-transitory computer readable storage media having video signal data encoded thereupon, comprising:

• input data for a picture encoded, wherein the input data for the picture, when encoded, was pre-filtered using a pre-filter, and in-loop reconstructed data for the picture, when encoded, was post-filtered using a post-filter directly coupled to the pre-filter,
• wherein at least one of filter coefficients and filter parameters for at least one of the pre-filter and the post-filter are selected responsive to at least one of a resolution, a local gradient, and a gradient direction, wherein gradient is a difference between pixels being pre-filtered, and adaptation is made discrete by partitioning a gradient strength, gradient direction and gradient variance into disjoint ranges and applying fixed filters for different ranges, and
• wherein a Lagrangian parameter for luminance and chrominance in the encoded video's rate-distortion optimizer is a function of the coding efficiency of the pre-filter and the post-filter;
• and
• wherein the pre-filter and post-filter are implemented with a lifting scheme and adaptation is embedded therein by changing values of a diagonal matrix, obtained by performing singular value decomposition on a fixed pre-filter transform matrix, such that values of the diagonal matrix can be reversed from those of an encoder.