Speed-up trend analysis for H.261 and model-based image coding algorithms using a parallel-pipeline model

摘要

Model-based and object-oriented coding algorithms are generally more computationally complex than current block-based image coding standards such as H.261, due primarily to the complexity of the image analysis they require. In this paper, simulations of H.261 and two model-based coding algorithms are analysed in terms of their computational complexity, and mapped onto a generalised image coder parallel-pipeline model. Example implementations of the H.261 coder and an object-oriented coder using general purpose parallel processor systems are then presented to confirm the validity of the performance trend analyses; these achieve maximum speedups of about 11 and 1.7, respectively, using up to 16 processors. The performance trends shown by the analysis indicate that the complexity of model-based coding algorithms, when combined with their reliance on coding picture differences and content-dependent algorithm execution times, interact to make it very difficult to achieve significant speed-up of sequential algorithms. Furthermore, the algorithm complexity and abstract data structures will make direct hardware implementations increasingly difficult. Overcoming these problems to achieve real-time model-based coders may require significant algorithmic compromises to be made.