Tutorials and Topics - Peabody Computer Music

Tutorial 13Sampling:Recording and playbackThe index~ object receives a signal as its input, which represents a sample number. It looksup that sample in its associated buffer~, and sends the value of that sample out its outlet asa signal. The count~ object just sends out a signal value that increases by one with eachsample. So, if you send the output of count~—a steady stream of increasing numbers—tothe input of index~—which will treat them as sample numbers—index~ will read straightthrough the buffer~, playing it back at the current sampling rate.Play the sound in a buffer~ by looking up each sample and sending it to the dac~• Click on the button marked “Play” to play the sound in the buffer~. You can changethe starting sample number by sending a different starting number into count~.This combination of count~ and index~ lets you specify a precise sample number in thebuffer~ where you want to start playback. However, if you want to specify starting andending points in the buffer~ in terms of milliseconds, and/or you want to play the soundback at a different speed—or even backward—then the play~ object is more appropriate.Variable speed playback: play~The play~ object receives a signal in its inlet which indicates a position, in milliseconds, inits associated buffer~; play~ sends out the signal value it finds at that point in the buffer~.Unlike index~, though, when play~ receives a position that falls between two samples inthe buffer~ it interpolates between those two values. For this reason, you can read througha buffer~ at any speed by sending an increasing or decreasing signal to play~, and it willinterpolate between samples as necessary. (Theoretically, you could use index~ in a similarmanner, but it does not interpolate between samples so the sound fidelity would beconsiderably worse.)127