Methods and apparatus for transcoding digital video data are disclosed. In an embodiment, a transcoder (300) decodes a digital video block (304) using a first coding scheme, such as 8×8 MPEG-2/4, to produce domain transformed data (306) and a motion vector (308). The transcoder (300) then estimates an energy level of each sub-block in the digital video block (304) in the frequency domain (as opposed to the spatial domain), thereby reducing or eliminating the need for motion compensation. For each sub-block with an estimated energy level below a desired threshold (e.g., likely an all-zero sub-block), the transcoder (300) transcodes the sub-block by converting the motion vector (308) from the first coding scheme (e.g., MPEG-2/4) to the second coding scheme (e.g., H.264) (e.g., convert 8×8 MPEG-2/4 vector to 4×4 H.264 vector or reuse the MPEG-2/4 vector if all four sub-blocks are AZB and coding in H.264 as an 8×8 block). The transcoded sub-block may then be used (e.g., stored or transmitted).