Random Access Region of Interest in Backward Coding of Wavelet Trees

Random access to high quality regions of interest (ROI) from compressed bit streams of large images is becoming a necessary feature in many applications, particularly in viewing important areas within larger images. We have developed a completely new multi-rate image subband coding scheme using backward coding of wavelet trees (BCWT), which is fast, memory-efficient and resolution-scalable, while offering much less complexity than many other codecs, including block-based ones, e.g. JPEG2000. Although the focus of this paper is the inclusion of random access ROI decoding capabilities in BCWT, the method can also be modified in order to accommodate conventional ROI schemes in which the selected region is decoded with higher fidelity than the rest of the image. Experimental results compare the original BCWT bitstream size against that of the resulting ROI.