Patent ID: 9110849
Filing Date: 2015-08-18
Classification: G06F,H04N

Abstract:
1. A method of performing a discrete cosine transform of type II (DCT-II), the method comprising: determining, with an apparatus, whether a size of the DCT-II to perform is a multiple of two; and in response to determining that the size of the DCT-II to perform is a multiple of two, performing, with the apparatus, the DCT-II, wherein performing the DCT-II includes: computing a butterfly that includes cross-additions and cross-subtractions of inputs to the DCT-II, wherein the butterfly includes a first portion that cross-adds a first sub-set of the inputs and a second portion that cross-subtracts a second sub-set of the inputs; reversing an order of the second sub-set of cross-subtracted inputs to generate a reverse-ordered second sub-set of the inputs; computing a series of recursive subtractions that each recursively subtract the reverse-ordered second sub-set of the inputs to generate a recursively subtracted second sub-set of the inputs; computing a sub-DCT-II that receives the first sub-set of the inputs and generates a first set of outputs based on the first sub-set of the inputs; computing a full sub-DCT-III that receives the recursively subtracted second sub-set of the inputs and generates a second set of outputs based on the recursively subtracted second sub-set of the inputs; and reordering the first and second set of outputs produced by the respective sub-DCT-II and full sub-DCT-III to generate output values of the DCT-II.