Patent ID: 9747255
Date: 2017-08-29
CPC Classifications: G06F,H04N

Claim:
1. A method for decoding an encoded video bit stream in a video decoder, the method comprising: decoding a pruned transform flag in the encoded video bit stream, wherein the pruned transform flag indicates that a subset region of a transform block contains all non-zero coefficients of the transform block, wherein the subset region consists of M rows and N columns of the transform block; inverse scanning only quantized transform coefficients of the subset region decoded from the encoded video bit stream to generate the transform block; and performing one dimensional (1D) inverse discrete cosine transformation (IDCT) computations on the transform block to generate a residual block, wherein one of a value of M or N of the subset region signaled by the pruned transform flag is used to determine pruning of the 1D IDCT computations, wherein performing the 1D IDCT computations includes: receiving a transform coefficient and a corresponding IDCT coefficient; setting a prune flag to indicate pruning when a value of the transform coefficient is zero; setting the prune flag to indicate no pruning when the value of the transform coefficient is non-zero; disabling latching of the transform coefficient for multiplication with the IDCT coefficient during a clock cycle and outputting a zero when the prune flag is set to indicate pruning; and enabling latching of the transform coefficient for multiplication with the IDCT coefficient during a clock cycle and outputting a product of the transform coefficient and the IDCT coefficient when the pruning flag is set to indicate no pruning.