This paper presents a fully software-based MPEG-2 encoder architecture, which uses scene-change detection to optimize the Group-of-Picture (GOP) structure for the actual video sequence. This feature enables easy, lossless edit cuts at scene-change positions and it also improves overall picture quality by providing good reference frames for motion prediction. Another favourable aspect is the high coding speed obtained, because the encoder is based on a novel concept for parallel MPEG coding on SMP machines. This concept allows the use of advanced frame-based coding algorithms for motion estimation and adaptive quantization, thereby enabling high-quality software encoding in real-time. Our proposal can be combined with the conventional parallel computing approach on slice basis, to further improve parallelization efficiency. The concepts in the current SAMPEG implementation for MPEG-2 are directly applicable to MPEG-4 encoders.