Resource-aware complexity scalability for mobile MPEG encoding

Complexity scalability attempts to scale the required resources of an algorithm with the chose quality settings, in order to broaden the application range. In this paper, we present complexity-scalable MPEG encoding of which the core processing modules are modified for scalability. Scalability is basically achieved for the computational complexity by varying the number of computed DCT coefficients and the number of evaluated motion vectors, while other modules are designed such that they scale with the previous parameters. Resource usage such as power-consuming memory accesses scale accordingly. The interdependencies of the scalable modules and the system performance are evaluated. Experimental results show scalability giving a smooth change in complexity and coresponding video quality. The elapsed execution time of the scalable encoder, reflecting the computational complexity, can be gradually reduced to roughly 50% of its execution time when operating at high quality. The video quality scaled betwee 21.5 dB and 38.5 dB PSNR for different sequences targeting 1500 kbps. The implemented encoder and the scalability techniques can be successfully applied in mobile systems based on MPEG video compression, and also has advantages in multi-tasking environments like high-end TV sets. The obtained scalability techniques can be applied to other coding standards like MPEG-4 and H.264 as well.