This paper proposes a novel multilayer video transcoding approach for multicasting pre-encoded video to heterogeneous end-systems via diverse grouping of networks. Multilayer transcoding is first addressed by means of multi-quality or SNR scalability of the MPEG-2 standard. Frequency domain transcoding and drift-compensated transcoding are derived from the closed-loop and multi-loop SNR scalabilities respectively. The proposed transcoding architectures are verified in terms of eliminating picture drift whilst preserving compatibility with the MPEG-2 SNR decoder. Multilayer transcoding is then addressed by means of multi-resolution or spatial scalability of the MPEG-2 standard that supports different video formats. The transcoder retains the full resolution of the incoming video stream in its enhancement layer whilst generating a low spatio-temporal resolution base-layer compatible with the H.263 video format. Hence providing both multilayer transcoding and video format portability. The resultant video layers are shown to be free from drift with PSNR results comparable to those of the respective scalable encoders.