METHOD AND APPARATUS FOR USING AN ULTRA-LOW DELAY MODE OF A HYPOTHETICAL REFERENCE DECODER

A method and apparatus are provided for using an ultra-low delay mode of a hypothetical reference decoder. The method is provided in a video decoder, and includes defining (320) a hypothetical reference decoder timing model to specify timing constraints based on an arrival time and a removal time of hypothetical reference decoder access units included in a video bitstream with respect to a hypothetical reference decoder buffer. The hypothetical reference decoder access units are selected from among a slice access unit and a picture access unit. The method also includes evaluating (325) the video bitstream for conformance to requirements of the hypothetical reference decoder buffer based on the hypothetical reference decoder timing model.