A　novel　fast　variable　block　size　selection　method　for　an　inter-MB　in　a　video-downsizing　transcoder　for　H.264　is　proposed,　which　uses　the　spatial　homogeneity　based　on　moving　edge　detection　and　temporal　stationary　characteristics　by　measuring　activity　magnitude.　Based　on　the　homogeneity　and　stationary　of　macro-blocks,　only　a　few　inter-modes　are　operated　with　the　RDO　process.　In　addition,　adaptive　motion　vector　re-construction　and　refinement　scheme　are　proposed　based　on　region　of　interest　(ROI),　besides　of　using　variance　and　DCT　coefficient　for　the　definition　of　diversity　and　importance,　respectively.　Experimental　results　show　that　the　new　method　is　more　robust　and　achieves　good　performance　in　both　quality　and　complexity.