A digital media content (e.g., image, video, audio, etc.) encoder/decoder employs a spatially varying parameter to condition the application of an overlap pre-process and post-process to adjacent transform block edges for the spatial-domain lapped transform. This conditional application of the lapped transform to sub-blocks of the digital media can be signaled on an edge, block, macro-block or other granularity. Further, a restriction on use of the conditional lapped transform based on a frame-level quantization or other bit-rate related parameter minimizes the signaling overhead impact at low bit-rates of coding.