A General Filter Design Language with Real-time Parameter Control in Pd, Max/MSP, and jMax
Shahrokh Yadegari · 2003
Most signal processing environments for computer music, such as Pd, Max/MSP, and jMax, transfer audio data among their objects by vectors (blocks). In such environments, to implement Infinite Impulse Response (IIR) filters one either has to set the block-size to 1 or to write an external object which embeds the filter operations. Neither of these solutions are simple or trivial. In this paper we present the fexpr ∼ object which provides a general and flexible language for designing filters by simply entering the filter expressions at object creation time and controlling their parameters in real-time within the host environment. Fexpr ∼ also allows for multiple interdependent filters to be defined in a single object, and thus, it can be used for finding numerical solutions to differential equations (difference equations). The implementation and the filter definition syntax of the object are discussed along with a number of examples. 1