1
2/* Stereo delay with feedback. */
3
4declare name "echo -- stereo delay effect";
5declare author "Albert Graef";
6declare version "1.0";
7
8import("music.lib");
9
10level		= hslider("level", 1, 0, 1, 0.01);
11dtime		= hslider("delay", 0.040, 0, 5, 0.001);
12feedback	= hslider("feedback", 0, 0, 1, 0.001);
13stereo		= hslider("stereo", 1, 0, 1, 0.001);
14
15/* The stereo parameter controls the amount of stereo spread. For stereo=0 you
16   get a plain delay, without crosstalk between the channels. For stereo=1 you
17   get a pure ping-pong delay where the echos from the left first appear on
18   the right channel and vice versa. Note that you'll hear the stereo effects
19   only if the input signal already has some stereo spread to begin with; if
20   necessary, you can just pan the input signal to the left or the right to
21   achieve that. */
22
23echo(dtime,level,feedback,stereo,x,y)
24		= f(x,y) // the echo loop
25		// mix
26		: (\(u,v).(x+level*(d(u)+c(v)),
27			   y+level*(d(v)+c(u))))
28		// compensate for gain level
29		: (/(1+level), /(1+level))
30with {
31	f	= g ~ (*(feedback),*(feedback));
32	g(u,v,x,y)
33		= h(x+d(u)+c(v)), h(y+d(v)+c(u));
34	h	= fdelay(1<<18, SR*dtime);
35	c(x)	= x*stereo;
36	d(x)	= x*(1-stereo);
37};
38
39process		= vgroup("echo", echo(dtime,level,feedback,stereo));
40