1. A video signal processing method, comprising: obtaining a current macroblock type; obtaining a boundary coding flag depending upon the current macroblock type; when the boundary intra coding flag indicates that the current macroblock is coded in an intra prediction mode by using boundary intra coding, obtaining boundary coding information; deriving a boundary within the current macroblock based upon the boundary coding information; and coding regions divided based upon the boundary in the intra prediction mode, wherein the boundary refers to a boundary of a region having a pixel value relatively different from a pixel value of a neighboring region within the current macroblock.