Systems and methods for low complexity forward transforms using zeroed-out coefficients

A method of encoding video, the method comprising:

• storing a video block;
• determining a full power value of the video block;
• determining a reduced transform coefficient matrix, wherein the reduced transform coefficient matrix comprises an inner region of zero or non-zero values of the same inner region of a full transform coefficient matrix and an outer region of zero values, wherein the reduced transform coefficient matrix and the full transform coefficient matrix have the same size;
• determining a partial power value of the video block using the reduced transform coefficient matrix;
• transforming the video block from a pixel domain to a coefficient domain using the reduced transform coefficient matrix when the partial power is less than a product of a threshold value and the full power value;
• and
• encoding the transformed video block.

A non-transitory computer-readable medium comprising code that, when executed, causes an apparatus to:

• store a video block;
• determine a full power value of the video block;
• determine a reduced transform coefficient matrix, wherein the reduced transform coefficient matrix comprises an inner region of zero or non-zero values of the same inner region of a full transform coefficient matrix and an outer region of zero values, wherein the reduced transform coefficient matrix and the full transform coefficient matrix have the same size;
• determine a partial power value of the video block using the reduced transform coefficient matrix;
• transform the video block from a pixel domain to a coefficient domain using the reduced transform coefficient matrix when the partial power is less than a product of a threshold value and the full power value;
• and
• encode the transformed video block.

An apparatus for encoding video, comprising:

• means for storing a video block;
• means for determining a full power value of the video block;
• means for determining a reduced transform coefficient matrix, wherein the reduced transform coefficient matrix comprises an inner region of zero or non-zero values of the same inner region of a full transform coefficient matrix and an outer region of zero values, wherein the reduced transform coefficient matrix and the full transform coefficient matrix have the same size;
• means for determining a partial power value of the video block using the reduced transform coefficient matrix;
• means for transforming the video block from a pixel domain to a coefficient domain using the reduced transform coefficient matrix when the partial power is less than a product of a threshold value and the full power value;
• and
• means for encoding the transformed video block.