Method for sub-pixel value interpolation

A method of interpolation in video coding in which an image comprising pixels arranged in rows and columns and represented by values having a specified dynamic range, the pixels in the rows residing at unit horizontal locations and the pixels in the columns residing at unit vertical locations, is interpolated to generate values for sub-pixels at fractional horizontal and vertical locations, the method comprising:

• a) when values for sub-pixels at half unit horizontal and unit vertical locations, and unit horizontal and half unit vertical locations are required, interpolating such values directly using weighted sums of pixels residing at unit horizontal and unit vertical locations;
• b) when values for sub-pixels at half unit horizontal and half unit vertical locations are required, interpolating such values directly using a weighted sum of values for sub-pixels residing at half unit horizontal and unit vertical locations calculated according to step (a);
• and
• c) when values for sub-pixels at quarter unit horizontal and quarter unit vertical locations are required, interpolating such values by taking the average of at least one pair of a first pair of values of a sub-pixel located at a half unit horizontal and unit vertical location, and a sub-pixel located at a unit horizontal and half unit vertical location and a second pair of values of a pixel located at a unit horizontal and unit vertical location, and a sub-pixel located at a half unit horizontal and half unit vertical location.

A video coder for coding an image comprising pixels arranged in rows and columns and represented by values having a specified dynamic range, the pixels in the rows residing at unit horizontal locations and the pixels in the columns residing at unit vertical locations, the video coder comprising an interpolator adapted to generate values for sub-pixels at fractional horizontal and vertical locations, the fractional horizontal and vertical locations being defined according to ½x, where x is a positive integer having a maximum value N, the interpolator being adapted to:

• a) interpolate values for sub-pixels at ½N−1 unit horizontal and unit vertical locations, and unit horizontal and ½N−1 unit vertical locations directly using weighted sums of pixels residing at unit horizontal and unit vertical locations;
• b) interpolate values for sub-pixels at ½N−1 unit horizontal and ½N−1 unit vertical locations directly using a choice of a first weighted sum of values for sub-pixels residing at ½N−1 unit horizontal and unit vertical locations and a second weighted sum of values for sub-pixels residing at unit horizontal and ½N−1 unit vertical locations, the first and second weighted sums of values being calculated according to step (a);
• and
• c) interpolate a value for a sub-pixel situated at a ½N unit horizontal and ½N unit vertical location by taking a weighted average of the value of a first sub-pixel or pixel situated at a ½N−m unit horizontal and ½N−n unit vertical location and the value of a second sub-pixel or pixel located at a ½N−p unit horizontal and ½N−q unit vertical location, variables m, n, p and q taking integer values in the range 1 to N such that the first and second sub-pixels or pixels are located diagonally with respect to the sub-pixel at ½N unit horizontal and ½N vertical location.

A communications terminal comprising a video coder for coding an image comprising pixels arranged in rows and columns and represented by values having a specified dynamic range, the pixels in the rows residing at unit horizontal locations and the pixels in the columns residing at unit vertical locations, the video coder comprising an interpolator adapted to generate values for sub-pixels at fractional horizontal and vertical locations, the fractional horizontal and vertical locations being defined according to ½x, where x is a positive integer having a maximum value N, the interpolator being adapted to:

• a) interpolate values for sub-pixels at ½N−1 unit horizontal and unit vertical locations, and unit horizontal and ½N−1 unit vertical locations directly using weighted sums of pixels residing at unit horizontal and unit vertical locations;
• b) interpolate values for sub-pixels at ½N−1 unit horizontal and ½N−1 unit vertical locations directly using a choice of a first weighted sum of values for sub-pixels residing at ½N−1 unit horizontal and unit vertical locations and a second weighted sum of values for sub-pixels residing at unit horizontal and ½N−1 unit vertical locations, the first and second weighted sums of values being calculated according to step (a);
• and
• c) interpolate a value for a sub-pixel situated at a ½N unit horizontal and ½N unit vertical location by taking a weighted average of the value of a first sub-pixel or pixel situated at a ½N−m unit horizontal and ½N−n unit vertical location and the value of a second sub-pixel or pixel located at a ½N−p unit horizontal and ½N−q unit vertical location, variables m, n, p and q taking integer values in the range 1 to N such that the first and second sub-pixels or pixels are located diagonally with respect to the sub-pixel at ½N unit horizontal and ½N vertical location.

A telecommunications system comprising a communications terminal and a network, the telecommunications network and the communications terminal being connected by a communications link over which coded video can be transmitted, the communications terminal comprising a video coder for coding for coding an image comprising pixels arranged in rows and columns and represented by values having a specified dynamic range, the pixels in the rows residing at unit horizontal locations and the pixels in the columns residing at unit vertical locations, the video coder comprising an interpolator adapted to generate values for sub-pixels at fractional horizontal and vertical locations, the fractional horizontal and vertical locations being defined according to ½x, where x is a positive integer having a maximum value N, the interpolator being adapted to:

• a) interpolate values for sub-pixels at ½N−1 unit horizontal and unit vertical locations, and unit horizontal and ½N−1 unit vertical locations directly using weighted sums of pixels residing at unit horizontal and unit vertical locations;
• b) interpolate values for sub-pixels at ½N−1 unit horizontal and ½N−1 unit vertical locations directly using a choice of a first weighted sum of values for sub-pixels residing at ½N−1 unit horizontal and unit vertical locations and a second weighted sum of values for sub-pixels residing at unit horizontal and ½N−1 unit vertical locations, the first and second weighted sums of values being calculated according to step (a);
• and
• c) interpolate a value for a sub-pixel situated at a ½N unit horizontal and ½N unit vertical location by taking a weighted average of the value of a first sub-pixel or pixel situated at a ½N−m unit horizontal and ½N−n unit vertical location and the value of a second sub-pixel or pixel located at a ½N−p unit horizontal and ½N−q unit vertical location, variables m, n, p and q taking integer values in the range 1 to N such that the first and second sub-pixels or pixels are located diagonally with respect to the sub-pixel at ½N unit horizontal and ½N vertical location.

A telecommunications system comprising a communications terminal and a network, the telecommunications network and the communications terminal being connected by a communications link over which coded video can be transmitted, the network comprising a video coder for coding for coding an image comprising pixels arranged in rows and columns and represented by values having a specified dynamic range, the pixels in the rows residing at unit horizontal locations and the pixels in the columns residing at unit vertical locations, the video coder comprising an interpolator adapted to generate values for sub-pixels at fractional horizontal and vertical locations, the fractional horizontal and vertical locations being defined according to ½x, where x is a positive integer having a maximum value N, the interpolator being adapted to:

• a) interpolate values for sub-pixels at ½N−1 unit horizontal and unit vertical locations, and unit horizontal and ½N−1 unit vertical locations directly using weighted sums of pixels residing at unit horizontal and unit vertical locations;
• b) interpolate values for sub-pixels at ½N−1 unit horizontal and ½N−1 unit vertical locations directly using a choice of a first weighted sum of values for sub-pixels residing at ½N−1 unit horizontal and unit vertical locations and a second weighted sum of values for sub-pixels residing at unit horizontal and ½N−1 unit vertical locations, the first and second weighted sums of values being calculated according to step (a);
• and
• c) interpolate a value for a sub-pixel situated at a ½N unit horizontal and ½N unit vertical location by taking a weighted average of the value of a first sub-pixel or pixel situated at a ½N−m unit horizontal and ½N−n unit vertical location and the value of a second sub-pixel or pixel located at a ½N−p unit horizontal and ½N−q unit vertical location, variables m, n, p and q taking integer values in the range 1 to N such that the first and second sub-pixels or pixels are located diagonally with respect to the sub-pixel at ½N unit horizontal and ½N vertical location.

A telecommunications system comprising a communications terminal and a network, the telecommunications network and the communications terminal being connected by a communications link over which coded video can be transmitted, the communications terminal comprising a video coder for coding an image comprising pixels arranged in rows and columns and represented by values having a specified dynamic range, the pixels in the rows residing at unit horizontal locations and the pixels in the columns residing at unit vertical locations, the coder comprising an interpolator adapted to generate values for sub-pixels at fractional horizontal and vertical locations, the resolution of the sub-pixels being determined by a positive integer N, the interpolator being adapted to:

• a) interpolate values for sub-pixels at ½N−1 unit horizontal and unit vertical locations, and unit horizontal and ½N−1 unit vertical locations directly using weighted sums of pixels residing at unit horizontal and unit vertical locations;
• b) interpolate a value for a sub-pixel at a sub-pixel horizontal and sub-pixel vertical location is required directly using a choice of a first weighted sum of values for sub-pixels located at a vertical location corresponding to that of the sub-pixel being calculated and a second weighted sum of values for sub-pixels located at a horizontal location corresponding to that of the sub-pixel being calculated.

A telecommunications system comprising a communications terminal and a network, the telecommunications network and the communications terminal being connected by a communications link over which coded video can be transmitted, the network comprising a video coder for coding for coding an image comprising pixels arranged in rows and columns and represented by values having a specified dynamic range, the pixels in the rows residing at unit horizontal locations and the pixels in the columns residing at unit vertical locations, the coder comprising an interpolator adapted to generate values for sub-pixels at fractional horizontal and vertical locations, the resolution of the sub-pixels being determined by a positive integer N, the interpolator being adapted to:

• a) interpolate values for sub-pixels at ½N−1 unit horizontal and unit vertical locations, and unit horizontal and ½N−1 unit vertical locations directly using weighted sums of pixels residing at unit horizontal and unit vertical locations;
• b) interpolate a value for a sub-pixel at a sub-pixel horizontal and sub-pixel vertical location is required directly using a choice of a first weighted sum of values for sub-pixels located at a vertical location corresponding to that of the sub-pixel being calculated and a second weighted sum of values for sub-pixels located at a horizontal location corresponding to that of the sub-pixel being calculated.