Two-layer video using SNR scalability can be used to offer error resilience to video applications where channel resources are unreliable. In the event of information loss or corruption, increased priority and/or protection can be given to the base layer
bitstream in order to ensure minimum base layer picture quality. However, SNR scalability is disadvantaged by a significant increase in total bit-rate compared to an equivalent single-layer coder operating at the same quality. In this paper we identify the DCT bit allocation of the enhancement layer as the primary cause of inefficiency citing two specific areas where coding efficiency is compromised. From this, the unique probability characteristics exhibited by the enhancement layer are used to develop an alternative approach to enhancement layer DCT coding. Exploiting the conditional and adaptive coding features facilitated by arithmetic coding, four enhancement layer coding schemes are proposed and compared to the standard coder. The results show that a hybridized arithmetic coder combining run-length and base layer conditioning coding techniques emerges as the best approach, delivering up to 20–25% better compression in the enhancement layer and outperforming
even the single-layer equivalent through much of its operating range.