Low Bit-Rate Video Systems

In this paper, the importance of including small image features at the initial levels of a progressive second generation video coding scheme is presented. It is shown that a number of meaningful small features called details should be coded, even at very low data bit-rates, in order to match their perceptual significance to the human visual system. We propose a method for extracting, perceptually selecting and coding of visual details in a video sequence using morphological techniques. Its application in the framework of a multiresolution segmentation-based coding algorithm yields better results than pure segmentation techniques at higher compression ratios, if the selection step fits some main subjective requirements. Details are extracted and coded separately from the region structure and included in the reconstrutted images in a later stage. The fact of considering the local background of a given detail for its perceptual selection breaks the concept of “partition” in the segmentation scheme. As long as details are not considered as adjacent regions but isolated features spread over the image, “detail coding” can be seen as one step towards the so called feature-based video coding techniques.