INSTRUMENT design – general delay-line objects
The Odelay and Odelayi objects are used to create and use delay-lines for samples. Odelay is non-interpolating, so that requests for delays that translate into a fractional point between two samples will be ‘rounded’ to the nearest sample value. This fractional delaying can happen quite often with dynamically-changing delay lines, which makes Odelayi a better choice in those cases. Odelayi is slightly less efficient because of the interpolation math to calculate a fractional sample-point.
There are two different ways of using the Odelay/Odelayi objects. The first is based on the older RTcmix delay techniques using the delset/delput/delget/dliget approach, where delayed samples are retrieved from the delay line based upon a time- or sample-amount of delay specified in the corresponding delget or dliget function call. Samples are put ‘into’ the delay line using delput. Because the delay amount is determined when samples are retreived from the delay line, multiple taps (i.e. multiple calls to the sample-retrieving function) are allowed for each sample-generating cycle.
The second way of using the Odelay/Odelayi objects is based on approach used in the Synthesis ToolKit (STK) delay line implementation (DLineL). Samples are placed into and retrieved from the delay line simultaneously, with the length of the delay determined by a separate function call. It is prabably best not to mix the two different approaches, because the delay line pointer-updating is handled slightly differently in each case.