Apparatus for transforming scalable video coding bitstream based on medium grained scalability to advanced video coding bitstream

PURPOSE: A conversion apparatus is provided to rewrite an MGS(Medium Grained Scalability) based SVC(Scalable Video Coding) bit stream into an AVC(Advanced Video Coding) bit stream. CONSTITUTION: An extracting unit an MGS layer of a key picture included in an MGS based SVC bit stream. A generating unit(813) creates the residual signal by adding one or more MGS layers of the key picture through a CGS-to-AVC rewriter. A computing unit(814) computes the corrected residual signal about the key picture based on the difference between the residual signal and DCD(Drift-Compensating Data). A bit stream coding unit(815) creates bit stream of single layer based on predicted data and the corrected residual signal.