In this paper, we focus on 2 : 1 spatial resolution downscaling transcoding from MPEG-2 to WMV. We propose two architectures (for sequences with or without B-frames respectively) that are unique in their complexity scalability and efficient control over the drifting error, which in return provide a flexible mechanism to achieve desired tradeoff between the complexity and the quality. We achieve resolution downscaling completely in the DCT domain and show that the standard IDCT (as in all the MPEG series standards) can be merged with other DCT-like transform (e.g., the integer transform in WMV) with proper one-time per-element scaling. Extensive experimental results verified the effectiveness of proposed structures against several design objectives such as complexity scalability and performance tradeoffs.