Abstract
This work discusses two approaches to incorporating error resiliency in the Simple Scalable Profile SSP of the ISO/IEC MPEG-4 14496-2 visual standard. As such scalable MPEG-4 is made suitable for deployment in a mobile communication environment. When it was defined in 2000, the syntax of the Simple Scalable Profile (SSP) prohibited the use of the error resiliency tools which were available in the base layer of the MPEG-4 codec. GPRS simulations are employed to illustrate the need for error resiliency in the SSP profile. Two solutions are then proposed based on whether or not bitstream syntax modifications are employed. The first solution is syntax friendly and emulates the use of the Video Packet resiliency tool whilst remaining compliant with standardized decoders. The limitations and constraints of such an approach are then elaborated upon. It is shown that syntax modifications are inevitable. Thus, the second solution proposes the syntax modifications to incorporate the error resiliency tools of the base layer into the enhancement layers of the SSP profile. The new syntax is verified through subjective testing using Multi Media Double Stimulus Continuous Quality Evaluation (MMDSCQE). Subsequently, the new syntax was approved by the ISO/IEC MPEG-4 committee and resulted in a new profile known as the Error Resilient Simple Scalable Profile (ER-SSP). It is shown that minor modifications are required in the Header Extension tool to synchronize the decoding process between the enhancement and the base layer. Thus, it is shown that base layer error resilience tools are equally applicable to the enhancement layer with nominal syntax changes.
