Playback Controllers:

IMPORTANT: This specialised component is intended for use in conjunction with a Controllable Input Audio File (refer to the corresponding on-line help for for a detailed description of WaveWarp's controllable playback functionality). In order to implement the controllable granular playback, the following connections must be implemented on the DrawingBoard:

• the 6 input control signals for this component can be arbitrarily time-varying control signals (containing the desired time-histories of playback rate factors and durations, as specified in the table below).
• the output control signal from this component must be connected to the control input of a Controllable Input Audio file.
• the input audio signal for this component must originate from the audio ouput of the same Controllable Input Audio file used above.
• the output audio signal from this component (and not from the Controllable Input Audio file) is the desired "granularized" signal to be routed to the output soundcard (or to other downstream components for further processing).

NOTE: This component is identical in function to the Granular Playback Controller except that the grain manipulation parameters are selected dynamically via the control inputs, rather than via the Parameter Window.

The file playback is organised as follows:

1. A "grain" (buffer) is filled by reading from the file at a specified rate. During this filling process, the successive samples which are being stored in the grain, are simultaneously sent to the output. When the grain is full, the file reading is de-activated.
2. The grain is then played back at a specified rate and for a specified number of repititions. During this time, the file is not being read, so no original samples are lost.
3. After the total number of grain playback repititions have been executed, samples are then read from the file, at a specified rate and for a specified duration, and simultaneously sent to the output. This is known as the "hop" phase.
4. After the hop phase has been executed, the grain is re-filled, and the entire process is repeated, starting from Step 1.

Control Input Index	Purpose
1	Controls the "instantaneous" grain size (expressed in numbers of samples).
2	Sets the number of times the grain is played after it has been filled.
3	Sets the "instantaneous" hop size (expressed in numbers of samples).
4	Controls the rate (expressed as a multiplication factor applied to the file's sample rate) at which the samples are read from the file when filling the grain.
5	Sets the rate (expressed as an effective step-size) at which the samples are read from the grain when it is played.
6	Sets the rate (expressed as a multiplication factor applied to the file's sample rate) at which the samples are read from the file when it is being played during the "hop" (i.e. between grains).

Algorithm

In order to suppress discontinuities at grain boundaries, a built-in search mechanism ensures that each grain starts on a zero-crossing upwards transition (the grain length therefore varies by a few samples from grain-to-grain, in order to satisfy this criterion).

See [Roa] p.180-184 for an introduction to granular playback methods.

Signal Implementations