A method for executing video encoding operations. The method includes encoding an incoming video stream into a plurality of macro blocks by using a video encoder and receiving a foreground-background slice map specification for the plurality of macro blocks. A plurality of critical coordinates are calculated for each rectangle comprising the foreground background slice map specification. Each of the plurality of critical coordinates are examined to assign group membership for their respective macro blocks. The furthest macro block of the respective macro blocks from a raster origination is designated as a last macro block of a group. The data comprising the group is transmitted out from the encoder once the last macro block has been processed.