Temporal scalability using P-pictures for low-latency applications

Many of the newer video coding/compression standards, including MPEG-4 and H.263+ support some form of temporal scalability as part of their layered codec concept. This is generally realized by using bi-directionally predicted pictures (B-pictures), which use both an earlier and a subsequent P-picture as reference (anchor) pictures. This paper introduces a new form of temporal scalability employing only P-pictures. This mechanism results in improved real-time behavior (particularly lower latency) and a more flexible layering structure, at the cost of less efficient coding. The P-picture based temporal scalability mechanism is particularly useful for interactive multimedia communication on networks that offer several independent transport streams (possibly with different quality of service), but have sub-optimal real-time characteristics. Typical applications include both the Internet and some forms of mobile communication. The 1998 version of H.263 (known as H.263+ in both academia and industry) offers a mechanism to support P-picture scalability within the bit-stream through the reference picture selection mode. Other video coding standards, including those of the MPEG family, require slight modifications to the decoder in order to support the proposed mechanism.