TEnv

Overview

Triggerable linear envelope generator with attack, hold, and release. Ported from Soundpipe.

This is a bit of a mess at the moment.

Top Files

<<tenv.h>>=

#ifndef SK_TENV_H
#define SK_TENV_H

#ifndef SKFLT
#define SKFLT float
#endif

<<typedefs>>

#ifdef SK_TENV_PRIV
<<structs>>
#endif

<<funcdefs>>

#endif

<<tenv.c>>=

#define SK_TENV_PRIV
#include "tenv.h"
<<funcs>>

Struct and Initialization

<<typedefs>>=

typedef struct sk_tenv sk_tenv;

<<structs>>=

struct sk_tenv {
    unsigned long pos, atk_end, rel_start, totaldur;
    SKFLT atk, rel, hold;
    SKFLT atk_slp, rel_slp;
    SKFLT last;
    int sigmode;
    SKFLT input;
    int started;
    int sr;
};

<<funcdefs>>=

void sk_tenv_init(sk_tenv *te, int sr);

<<funcs>>=

void sk_tenv_init(sk_tenv *te, int sr)
{
    te->pos = 0;
    te->last = 0;
    te->atk = 0.1;
    te->hold = 0.3;
    te->rel = 0.2;
    te->sigmode = 0;
    te->input = 0;

    te->sr = sr;
    te->atk_end = te->sr * te->atk;
    te->rel_start = te->sr * (te->atk + te->hold);
    te->atk_slp = 1.0 / te->atk_end;
    te->rel_slp = -1.0 / (te->sr * te->rel);
    te->totaldur = sr * (te->atk + te->hold + te->rel);

    te->started = 0;
}

Compute

<<funcdefs>>=

SKFLT sk_tenv_tick(sk_tenv *te, SKFLT trig);

<<funcs>>=

<<reinit>>
<<envelope>>
SKFLT sk_tenv_tick(sk_tenv *te, SKFLT trig)
{
    SKFLT out;
    out = 0;

    if (trig != 0) {
        reinit(te);
        te->started = 1;
    }

    if (te->started) out = envelope(te);

    return out;
}

<<envelope>>=

static SKFLT envelope(sk_tenv *env)
{
    SKFLT sig;
    unsigned long pos;
    SKFLT out;

    out = 0;
    sig = 0;
    pos = env->pos;

    if (pos < env->atk_end) {
        sig = env->last + env->atk_slp;
    } else if (pos < env->rel_start) {
        sig = 1.0;
    } else if (pos < env->totaldur) {
        sig = env->last + env->rel_slp;
    } else{
        sig = 0.0;
    }

    sig = (sig > 1.0) ? 1.0 : sig;
    sig = (sig < 0.0) ? 0.0 : sig;

    /* Internal input signal mode */
    if (env->sigmode) {
        out = env->input * sig;
    } else {
        out = sig;
    }

    env->pos++;
    env->last = sig;

    return out;
}

<<reinit>>=

static void reinit(sk_tenv *te)
{
    te->pos = 0;
    te->atk_end = te->sr * te->atk;
    te->rel_start = te->sr * (te->atk + te->hold);
    te->atk_slp = 1.0 / te->atk_end;
    te->rel_slp = -1.0 / (te->sr * te->rel);
    te->totaldur = te->sr * (te->atk + te->hold + te->rel);
}

Parameters

<<funcdefs>>=

void sk_tenv_attack(sk_tenv *te, SKFLT atk);

<<funcs>>=

void sk_tenv_attack(sk_tenv *te, SKFLT atk)
{
    te->atk = atk;
}

<<funcdefs>>=

void sk_tenv_hold(sk_tenv *te, SKFLT hold);

<<funcs>>=

void sk_tenv_hold(sk_tenv *te, SKFLT hold)
{
    te->hold = hold;
}

<<funcdefs>>=

void sk_tenv_release(sk_tenv *te, SKFLT rel);

<<funcs>>=

void sk_tenv_release(sk_tenv *te, SKFLT rel)
{
    te->rel = rel;
}