Report on San Francisco AES chapter’s November 2003 meeting, by Thomas Merklein and Paul Howard.

The November AESSF meeting was held at Cogswell College in Sunnyvale, California. Sami Saab, a Field Applications Engineer with Analog Devices, Inc., explained how DSP technology is applied to audio processing. He described the recent evolution of SHARC and TigerSHARC processors.

As DSPs have evolved, core processor speeds, and the number of buses and registers, have increased. Instruction multi-staging pipelines have become more complex. Compilers have matured, to allow embedded applications engineers to write software that takes advantage of improved features.

The SHARC ADSP-21262S design incorporates a programmable digital application interface (DIA), which is used to route signals through the DSP. This DSP has evolved into a system-on-a-chip (SOC).

The latest SHARC designs are targeted for many uses, including the consumer audio market.

Mr. Saab suggested the SHARC ADSP-21262S as a good candidate for audio applications due to its high speed (200 MHz) processor, peripheral set, and moderate cost.

For audio designers who require a more advanced processor than the SHARC ADSP-21262S,

the TigerSHARC ADSP-TS203S is also a cost-effective chip.

Mr. Saab discussed approximations, which come about because digital processing, with its finite precision, is used to measure an analog world.

Two demonstrations were presented. The first used a SHARC board to slow down and speed up audio, supplied by a CD player. The calculation took only 4 processor cycles, regardless of whether interpolation values were changed.

The second demo, developed for the AES convention in New York, was a sampling reverb of the La Scala Opera House, in Milan, Italy. By assigning left and right channels to two DSPs, and using 24 Mbit of on-chip memory,

the system was able to do almost a second of an impulse response without using external memory, and by using only 3% of the CPU.

A lengthy question and answer session followed, in which Mr. Saab showed some of the software used in the demonstrations.

  The presenter, Mr Sami Saab