MPEG-4 makes move into silicon

MPEG-4 makes move into siliconRoy Rubenstein For an audio visual standard that is still to be completed, MPEG-4 is spurring significant ICdesign activity. The interest in the object oriented MPEG-4 standard – whose first phase will be completed early next year – stems from the fact that it’s the first true multimedia standard. “Until now if you wanted to process content in addition to video, how would you do it?” said Dr Jan Borman of IMEC, the Belgium electronics research institute. “MPEG-4 provides such a multimedia framework. It is also scalable – for different platforms, and for different bandwidths.” The flexibility of MPEG-4 is something that Hans Schwendner, v-p of Siemens Semiconductors for image and video ICs, also highlights. “MPEG-4 can be partitioned into several levels and profiles. The profiles define the maximum number of [video, graphics] objects you can process as well as the kind of audio support that is provided.” This scalability – while a strength of the standard – makes the design of cores for its execution taxing. “We are developing a complete architecture for MPEG-4,” said IMEC’s Borman, who stressed that care is required when comparing MPEG-4 cores. IMECis working with six industrial partners to address two key MPEG-4 application areas: mobile video phones and desktop PCs. “For each application, the methodology is the same; what differs is the cost factor,” said Borman. He cites the example of an MPEG-4 design for PCs. “Here a graphics pipeline is already available and it makes sense to use it.” For a portable device, this is not the case. IMEC argues that a key element in the design of an MPEG-4 core is to tailor the memory around the on-chip processing units, what Borman calls a ‘dedicated memory hierarchy’. This not only reduces overall power consumption – important for a portable design – but also benefits processing performance. For its video phone IC, IMEC is talking in terms of a general purpose CPU- either a 16-bit or 32-bit Risc core – coupled to four dedicated hardware units for such tasks as video decoding and motion compensation. Siemens Semiconductors is also developing ‘multiple MPEG-4 cores’ for applications ranging from mobile video phones to object retrieval via the Internet. According to Schwendner, the scalable nature of MPEG-4 equates to a processing requirement ranging from 50Mips to several Bops.
Siemens is investigating coupling dedicated hardware units to its TriCore and Carmel DSP cores for mobile video phone applications. For high end ‘billion ops’ MPEG-4 applications, Siemens has produced a multiple instruction, scalable parallel processor design.

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