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(TAPV-ALG
(NAME "tapv")
(ARGUMENTS ("sound_type" "s1") ("double" "offset") ("sound_type" "vardelay")
("double" "maxdelay"))
(INLINE-INTERPOLATION T)
(INTERNAL-SCALING vardelay)
(ALWAYS-SCALE s1)
(START (MAX s1 vardelay))
(TERMINATE (MIN s1 vardelay))
(LOGICAL-STOP (MIN s1))
(STATE ("double" "offset" "offset * s1->sr")
("double" "vdscale" "vardelay->scale * s1->sr")
("double" "maxdelay" "maxdelay * s1->sr")
("long" "bufflen" "MAX(2, (long) (susp->maxdelay + 1.5))")
("long" "index" "susp->bufflen")
("sample_type *" "buffer"
"(sample_type *) calloc(susp->bufflen + 1, sizeof(sample_type))"))
(SAMPLE-RATE (MAX s1))
(CONSTANT "maxdelay" "offset" "vdscale" "buffer")
(INNER-LOOP-LOCALS " double phase;
long i;
")
(INNER-LOOP " phase = vardelay * vdscale + offset;
/* now phase should give number of samples of delay */
if (phase < 0) phase = 0;
else if (phase > maxdelay) phase = maxdelay;
phase = (double) index - phase;
/* now phase is a location in the buffer (before modulo) */
/* Time out to update the buffer:
* this is a tricky buffer: buffer[0] == buffer[bufflen]
* the logical length is bufflen, but the actual length
* is bufflen + 1 to allow for a repeated sample at the
* end. This allows for efficient interpolation.
*/
buffer[index++] = s1;
if (index > bufflen) {
buffer[0] = buffer[bufflen];
index = 1;
}
/* back to the phase calculation:
* use conditional instead of modulo
*/
if (phase < 0) phase += bufflen;
i = (long) phase; /* put integer part in i */
phase -= (double) i; /* put fractional part in phase */
output = (sample_type) (buffer[i] * (1.0 - phase) +
buffer[i + 1] * phase);")
(FINALIZATION " free(susp->buffer);
")
)
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