ACTS project AC105

The main objective of EMPHASIS is to produce real time optimised MPEG-4 software to run on current and future European developed microprocessors. The experience we learn from the first software implementation will be fed into the architectural definition component of our work so that future processor architectures will be able to deliver even more performance. This is essential to satisfy the insatiable demands that applications require (historically for the last twenty years computer applications have outgrown the CPU's ability to process them every three years!).

We complete our project with a demonstrator of MPEG-4 technology running on a high performance microprocessor. We will demonstrate the benefits of content based interactivity that MPEG-4 delivers to the applications development community.

Contributing to MPEG-4 Standardisation

Initially though EMPHASIS is providing valuable expertise and effort to assist the standardisation effort of MPEG-4. The main areas we have been active in so far include:

It is essential that MPEG-4 can meet both market demands as well as compression efficiency requirements. The ability to map MPEG-4 functionality onto the highly programmable platforms demanded by MPEG-4 is crucial for its success. EMPHASIS is uniquely positioned to provide this advice to the MPEG community. Indeed the project manager of EMPHASIS chairs the Implementation Studies Group within MPEG-4. Currently we are performing an implementation complexity analysis on the Video Verification model and NBC (Non Backwards Compatible) Audio.

One of the areas we have looked at and proposed, is the concept of graceful degradation whereby a decoder armed with the knowledge of which objects are most important can make informed decisions as to how to degrade performance under conditions of heavy processor loading (not necessarily caused by MPEG-4 applications).

The Implementation Studies Group is now also responsible for investigating the feasibility of downloading MPEG-4 Tools and algorithms in a platform independent way (flex-2 functionality). EMPHASIS is able to draw upon its expertise in the fields of processor architectures, operating systems technologies and virtual machine implementations to analyse the problem and provide recommendations back to MPEG.

Real Time Software

Writing real time software is not for the feint hearted. In order to lower the cost of silicon implementation, the provision of highly efficient low level software that extracts the maximum performance from the processor is essential. Careful attention paid to key software modules that are called many thousands of times per second can yield a very significant improvement in performance. The system can then either exploit this extra performance to increase functionality or else the clock speed of the processor could be reduced thereby saving power. Techniques applied to this challenging problem include:- cycle counting, instruction issue rate, cache memory utilisation, register allocation, memory system bandwidth, data locality of reference, latency etc.

Syntactically speaking...

The syntax area of MPEG-4 is a key component of its architecture. The ability to composite objects together in a flexible manner dictates that a flexible syntax be developed. This permits individually compressed objects to be combined and composited for display (Video & Audio). Significant technical contributions and active participation in MSDL (MPEG-4 Syntactic Description Layer) have come from EMPHASIS. EMPHASIS will continue to influence this component of MPEG-4.

Technology Trial.

The focus of our activity is to be able to demonstrate the content based interactivity of MPEG-4 when running on a low cost terminal that will eventually be suitable for mass market deployment. You can be sure that demonstration will be an excellent advertisement for both MPEG-4 and European developed Architecture, Software and Hardware!

Paul Fellows
SGS-THOMSON Microelectronics Ltd.
MPEG-4 Implementation Studies Group Chairman
E-mail: paulf@bristol.st.com