Subramania Sudharsanan

MAJC-5200: A High Performance Microprocessor for Multimedia Computing

The newly in troduced Microprocessor Arc hitecture for Java Computing (MAJC) supports parallelism in a hierarchy of levels: multiprocessors on chip, vertical micro threading, instruction level parallelism via a very long instruction word architecture (VLIW) and SIMD. The first implemen tation, MAJC-5200, includes some key features of MAJC to realize a high performance m ultimedia processor. Two CPUs running at 500 MHz are in tegrated into the chip to provide 6.16 GFLOPS and 12.33 GOPS with high speed in terfaces providing a peak input-output (I/O) data rate of more than 4.8 G Bytes/second. The c hip is suitable for a num ber of applications including graphics/m ultimedia processing for high-end set-top boxes, digital voice processing for telecomm unications, and advanced imaging.

Entropy constrained motion estimation : Algorithm and implementation

Block-based motion estimation (ME) has been a very active area of research in the field of video signal processing and coding. Traditional ME techniques consider only the sum of the absolute differences between the current and the reference blocks to find the motion vectors (MV). Recently, several rate-constrained ME techniques have been proposed which considers the effect of encoding the MV by adding an entropy constraint to the distortion measure. Such techniques show an improved performance at low bit-rates. The displaced frame difference blocks are typically transformed using discrete cosine transform and then quantized in the transform domain. In our proposed scheme, an entropy-constrained ME algorithm is proposed which considers the number of bits allotted for coding the DFDs in addition to those used for encoding the MV and the MB mode information. Simulation results show that the proposed technique performs significantly better than the standard technique for a wide range of bit-rates. In addition, a computationally less complex scheme is also proposed, although with reduced performance improvements over the conventional scheme. The implementation aspects of the proposed schemes are also briefly discussed.

Computationally efficient lossless image coder

Lossless coding of image data has been a very active area of research in the field of medical imaging, remote sensing and document processing/delivery. While several lossless image coders such as JPEG and JBIG have been in existence for a while, their compression performance for encoding continuous-tone images were rather poor. Recently, several state of the art techniques like CALIC and LOCO were introduced with significant improvement in compression performance over traditional coders. However, these coders are very difficult to implement using dedicated hardware or in software using media processors due to their inherently serial nature of their encoding process. In this work, we propose a lossless image coding technique with a compression performance that is very close to the performance of CALIC and LOCO while being very efficient to implement both in hardware and software. Comparisons for encoding the JPEG- 2000 image set show that the compression performance of the proposed coder is within 2 - 5% of the more complex coders while being computationally very efficient. In addition, the encoder is shown to be parallelizabl at a hierarchy of levels. The execution time of the proposed encoder is smaller than what is required by LOCO while the decoder is 2 - 3 times faster that the execution time required by LOCO decoder.

Benchmarking multimedia performance

With the introduction of faster processors and special instruction sets tailored to multimedia, a number of exciting applications are now feasible on the desktops. Among these is the DVD playback consisting, among other things, of MPEG-2 video and Dolby digital audio or MPEG-2 audio. Other multimedia applications such as video conferencing and speech recognition are also becoming popular on computer systems. In view of this tremendous interest in multimedia, a group of major computer companies have formed, Multimedia Benchmarks Committee as part of Standard Performance Evaluation Corp. to address the performance issues of multimedia applications. The approach is multi-tiered with three tiers of fidelity from minimal to full compliant. In each case the fidelity of the bitstream reconstruction as well as quality of the video or audio output are measured and the system is classified accordingly. At the next step the performance of the system is measured. In many multimedia applications such as the DVD playback the application needs to be run at a specific rate. In this case the measurement of the excess processing power, makes all the difference. All these make a system level, application based, multimedia benchmark very challenging. Several ideas and methodologies for each aspect of the problems will be presented and analyzed.