A generalized hypothetical reference decoder for H.264/AVC

In video coding standards, a compliant bit stream must be decoded by a hypothetical decoder that is conceptually connected to the output of an encoder and consists of a decoder buffer, a decoder, and a display unit. This virtual decoder is known as the hypothetical reference decoder (HRD) in H.263 and the video buffering verifier in MPEG. The encoder must create a bit stream so that the hypothetical decoder buffer does not overflow or underflow. These previous decoder models assume that a given bit stream will be transmitted through a channel of a known bit rate and will be decoded (after a given buffering delay) by a device of some given buffer size. Therefore, these models are quite rigid and do not address the requirements of many of today´s important video applications such as broadcasting video live or streaming pre-encoded video on demand over network paths with various peak bit rates to devices with various buffer sizes. In this paper, we present a new HRD for H.264/AVC that is more general and flexible than those defined in prior standards and provides significant additional benefits.