The “4X” real-time digital signal processor

Abstract

We have realized a real-time digital signal processor for applications in real-time analysis and synthesis of sound and music. The 4X processor works as a peripheral connected to a host computer. A main feature of the 4X processor is its modularity. It consists of up to 16 elementary processors working in parallel. Each of these processors contains a data memory, an address memory, a microprogram memory, a function memory, a multiplier, and an arithmetic and logic unit. All the computations are done in 24-bit fixed point arithmetic. The 4X processor also contains 256 programmable clocks and a large dual buffer memory for recording and reproduction of signals to and from the host computer disk. The programming of the 4X, which is done in high level languages (FORTRAN and C), allows an easy programmation of the different possible structures of the machine, as oscillators, envelope generators, filters and so on. These capabilities make it possible to implement all known audio synthesis and processing techniques. The 4X processor is now used for musical composition, synthesis of aircraft noise for flight simulators, synthesis of underwater noise of submarines, audio mixing, and psychoacoustic stimulus generation.