1. A method for transcoding regions of interests ROI in video surveillance system with a camera with a HD sensor for recording the observed scene in high resolution, a hierarchical encoder, a buffer for potential later ROI extraction and an extractor characterized in that: first to extract an image in moderate resolution from a hierarchical coded datastream, second to extract the coefficients of the higher resolution levels from said coded datastream, and third to add the coefficients to said already decoded image, so that said image region of said ROI will be of higher resolution and a hierarchical transcoding of spatial scalable regions of interest ROI was made.