sndloop — A sound looper with pitch control.


This opcode records input audio and plays it back in a loop with user-defined duration and crossfade time. It also allows the pitch of the loop to be controlled, including reversed playback.


asig, krec sndloop ain, kpitch, ktrig, idur, ifad


idur -- loop duration in seconds

ifad -- crossfade duration in seconds


asig -- output sig

krec -- 'rec on' signal, 1 when recording, 0 otherwise

kpitch -- pitch control (transposition ratio); negative values play the loop back in reverse

ktrig -- trigger signal: when 0, processing is bypassed. When switched on (ktrig >= 1), the opcode starts recording until the loop memory is full. It then plays the looped sound until it is switched off again (ktrig = 0). Another recording can start again with ktrig >= 1.


Here is an example of the sndloop opcode. It uses the file sndloop.csd.

Example 1007. Example of the sndloop opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

; Select audio/midi flags here according to platform
-odac      ;;;realtime audio out
;-iadc    ;;;uncomment -iadc if realtime audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o sndloop.wav -W  ;;; for file output any platform

sr = 44100 
ksmps = 32 
0dbfs  = 1 
nchnls = 2

instr 1

itrig  = p4
asig   diskin2 "drumsMlp.wav", 1, 0, 1		;get the signal in, loop it
ktrig  line 0, itrig, 1				;when to trigger signal = p4
kpitch line 1.2, p3, .5				;vary pitch of recorded signal
aout,krec sndloop asig, kpitch, ktrig, .4, 0.05	;rec starts at p4 sec, for .4 secs and 0.05 crossfade
       printk2 krec               	  	; prints the recording signal
       outs    aout, aout



i1 0 5 .5	;trigger in seconds (=p4)
i1 + 5 .8
i1 + 10 1.2


The example above shows the basic operation of sndloop. Pitch can be controlled at the k-rate, recording is started as soon as the trigger value is >= 1. Recording can be restarted by making the trigger 0 and then 1 again.

See also

Sample Playback


Author: Victor Lazzarini
April 2005

New in Version 5.00