Smoothed directional and DC intra prediction

An image decoding method, comprising:

• deriving a prediction pixel block for use in predictive coding based on a direction of a prediction vector assigned to the prediction pixel block in which a prediction value for a prediction location in the prediction pixel block is derived from a combination of reference values at two locations of previously-decoded pixel data according to according to:
• when the direction of the prediction vector and its opposite direction both point toward previously decoded pixel data, deriving the prediction value from references values two locations of previously-decoded pixel data intercepted by extending the prediction vector in the direction and its opposite through the prediction location,
• when the direction of the prediction vector and its opposite direction do not both point toward previously-decoded pixel data, deriving the pixel location's value from a combination of a reference value at a third location of previously-decoded pixel data intercepted by extending the prediction vector through the prediction location, and a reference value at a fourth location of previously-decoded pixel data intercepted by a vector that passes through the prediction location and is orthogonal to the direction of the prediction vector;
• and
• decoding coded pixel block differentially with reference to the prediction pixel block.

A computer readable medium storing program instruction that, when executed by a processing device, cause the processing device to execute an image decoding method, comprising:

• deriving a prediction pixel block for use in predictive coding based on a direction of a prediction vector assigned to the prediction pixel block in which a prediction value for a prediction location in the prediction pixel block is derived from a combination of reference values at two locations of previously-decoded pixel data according to according to:
• when the direction of the prediction vector and its opposite direction both point toward previously decoded pixel data, deriving the prediction value from references values at two locations of previously-decoded pixel data intercepted by extending the prediction vector in the direction and its opposite through the prediction location,
• when the direction of the prediction vector and its opposite direction do not both point toward previously-decoded pixel data, deriving the pixel location's value from a combination of a reference values at a third location of previously-decoded pixel data intercepted by extending the prediction vector through the prediction location, and a reference value at a fourth location of previously-decoded pixel data intercepted by a vector that passes through the prediction location and is orthogonal to the direction of the prediction vector;
• and
• decoding coded pixel block differentially with reference to the prediction pixel block.

A decoding system, comprising:

• a video decoder, having an input for coded pixel blocks, an input for a prediction pixel block, and an output for decoded pixel blocks,
• a reference picture buffer to store decoded data assembled from the decoded pixel blocks, and
• a predictor that, for pixel blocks to be coded by intra-coding, generates a prediction pixel block, based on a direction of a prediction vector assigned to the prediction pixel block in which a prediction value for a prediction location of the prediction pixel block is derived from a combination of reference values at two locations of previously-decoded pixel data according to:
• when the direction of the prediction vector and its opposite direction both point toward previously decoded pixel data, deriving the prediction value from references values two locations of previously-decoded pixel data intercepted by extending the prediction vector in the direction and its opposite through the prediction location,
• when the direction of the prediction vector and its opposite direction do not both point toward previously-decoded pixel data, deriving the pixel location's value from a combination of a reference value at a third location of previously-decoded pixel data intercepted by extending the prediction vector through the prediction location, and a reference value at a fourth location of previously-decoded pixel data intercepted by a vector that passes through the prediction location and is orthogonal to the direction of the prediction vector.

A system for image coding comprising a processing device and a computer readable medium storing instructions that, when executed by the processing device cause:

• deriving a prediction pixel block for use in predictive coding based on a direction of a prediction vector assigned to the prediction pixel block in which a prediction value for a prediction location in the prediction pixel block is derived from a combination of reference values at two locations of previously-decoded pixel data according to according to:
• when the direction of the prediction vector and its opposite direction both point toward previously decoded pixel data, deriving the prediction value from references values at two locations of previously-decoded pixel data intercepted by extending the prediction vector in the direction and its opposite through the prediction location,
• when the direction of the prediction vector and its opposite direction do not both point toward previously-decoded pixel data, deriving the pixel location's value from a combination of a reference value at a third location of previously-decoded pixel data intercepted by extending the prediction vector through the prediction location and a reference value at a fourth location of previously-decoded pixel data intercepted by a vector that passes through the prediction location and is orthogonal to the direction of the prediction vector;
• and
• coding an input pixel block differentially with reference to the prediction pixel block.

A computer readable medium storing program instruction that, when executed by a processing device, cause the processing device to execute an image coding method, comprising:

• deriving a prediction pixel block for use in predictive coding based on a direction of a prediction vector assigned to the prediction pixel block in which a prediction value for a prediction location in the prediction pixel block is derived from a combination of reference values at two locations of previously-decoded pixel data according to:
• when the direction of the prediction vector and its opposite direction both point toward previously decoded pixel data, deriving the prediction value from references values at two locations of previously-decoded pixel data intercepted by extending the prediction vector in the direction and its opposite through the prediction location,
• when the direction of the prediction vector and its opposite direction do not both point toward previously-decoded pixel data, deriving the pixel location's value from a combination of a reference value at a third location of previously-decoded pixel data intercepted by extending the prediction vector through the prediction location and a reference value at a fourth location of previously-decoded pixel data intercepted by a vector that passes through the prediction location and is orthogonal to the direction of the prediction vector;
• and
• coding an input pixel block differentially with reference to the prediction pixel block.