Stephan Mietens

New DCT Computation Technique Based on Scalable Resources

The applicability of MPEG video coding can be improved by scaling both the algorithmic complexity and resource usage, considering the desired application and device that is going to be used. This paper presents a new DCT computation technique of which both the quality and amount of computations is optimised for a limited number of operations. For halved computing resources, about 2-4 SNR dB improvement was obtained when compared to a diagonally oriented computation of coefficients, matching with the conventional MPEG scanning.

New scalable DCT computation for resource-constrained systems

The applicability of MPEG video coding can be improved by scaling the algorithmic complexity and resource usage to the desired application and device. This paper presents a new DCT computation technique of which the quality and amount of computations is maximized for a limited number of operations. For halved computing resources, about 2-4 SNR dB improvement was obtained when compared to a diagonally oriented computation of coefficients, matching with the conventional MPEG scanning.

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.

New DCT computation algorithm for video quality scaling

The application of video coding systems, such as MPEG, in portable systems like organizers and mobile phones can be scaled down to a reduced complexity that matches with the desired video quality and/or display. A new DCT computation algorithm is presented, based on an analysis for optimizing the number of computations involved at each computing stage, using existing fast DCT calculation algorithms. The analysis is used to scale down the video quality, thereby lowering the computing power and resource usage. Compared to a diagonally oriented computation of coefficients that matches with the conventional MPEG scanning, a 2 to 4 dB SNR improvement is obtained when scaling down the video quality to half the computing resources.

Flexible frame-reordering and multi-temporal motion estimation for scalable MPEG encoding in mobile consumer equipment

We present a new scalable three-stage motion estimation technique that allows scaling of the computational effort and memory bandwidth usage by a factor of 14. At full processing, our technique slightly outperforms a 128 /spl times/ 128 full search motion estimation.

Application analysis and communication aspects for future multimedia architectures

A principal challenge for reducing the cost of complex systems-on-chip is to pursue more generic systems for a broad range of products. For this purpose, we explore three new architectural concepts for state-of-the-art video applications. First, we discuss a reusable scalable hardware architecture employing a hierarchical communication network fitting with the natural hierarchy of the application. In a case study, we show that MPEG streaming in DTV occurs at high level, while subsystems communicate at lower levels. The second concept is a software design that scales over a number of processors to enable reuse over a range of VLSI process technologies. We explore this via an H.264 decoder implementation that scales nearly linearly over up to eight processors by applying data partitioning. The third concept is resource-scalability, which is required to satisfy real-time constraints in a system with a high amount of shared resources. An example complexity-scalable MPEG-2 encoder scales the required cycle budget with a factor of three, in parallel with a smooth degradation of quality.

New flexible motion estimation technique for scalable MPEG encoding using display frame order and multi-temporal references

The applicability of MPEG video coding can be improved by scaling both the algorithmic complexity and resource usage appropriately for the intended device and application. For this purpose, we present a new technique for motion estimation, based on a scalable three-stage process including frame processing in display order, approximation of motion vector fields using multiple references and optional quality refinements. Experiments show that the computational effort is scalable with a factor of 14, resulting in a global variation of 7 dB SNR in picture quality. At full processing, our technique slightly outperforms a 32/spl times/32 full search motion estimation. The technique forms a valuable contribution to mobile MPEG coding applications, following the scalability concepts introduced by Mietens, de With and Hentschel (see IEEE Int. Conf. on Image Proc. (ICIP 2001), vol.3, p.462-465, Oct. 2001).