Provided are systems and methods for adjusting quantization parameters of blocks of video data to be encoded, in order to reduce visual artifacts between slices of video data. Each slice includes one or more blocks organized in one or more lines, and can be coded independently without information from any other slices of video data. A complexity value of a current block corresponding to a last block of the slice on a particular line is determined and used to determine whether the current block includes a transition from a complex region to a flat region, wherein complex regions are characterized as having higher complexity in comparison to flat regions. In response to a determination that the current block includes such a transition, the QP for coding the current block may be decreased.