Originally Posted by

**PaulStoffregen**
That's the one I have been using for FM, the early experiment I made used the multiply block with envelope and the waveform mod output to compare that results of that vs just running the waveformmod block into the envelope:

https://forum.pjrc.com/threads/58984...t=synthesis"].

Now I am trying to use a wavetable as a carrier for the modulation source. I had already hit upon the

Code:

// Pre-compute the phase angle for every output sample of this update
ph = phase_accumulator;
priorphase = phasedata[AUDIO_BLOCK_SAMPLES-1];
if (moddata && modulation_type == 0) {
// Frequency Modulation
bp = moddata->data;
for (i=0; i < AUDIO_BLOCK_SAMPLES; i++) {
int32_t n = (*bp++) * modulation_factor; // n is # of octaves to mod
int32_t ipart = n >> 27; // 4 integer bits
n &= 0x7FFFFFF; // 27 fractional bits
#ifdef IMPROVE_EXPONENTIAL_ACCURACY
// exp2 polynomial suggested by Stefan Stenzel on "music-dsp"
// mail list, Wed, 3 Sep 2014 10:08:55 +0200
int32_t x = n << 3;
n = multiply_accumulate_32x32_rshift32_rounded(536870912, x, 1494202713);
int32_t sq = multiply_32x32_rshift32_rounded(x, x);
n = multiply_accumulate_32x32_rshift32_rounded(n, sq, 1934101615);
n = n + (multiply_32x32_rshift32_rounded(sq,
multiply_32x32_rshift32_rounded(x, 1358044250)) << 1);
n = n << 1;
#else
// exp2 algorithm by Laurent de Soras
// https://www.musicdsp.org/en/latest/Other/106-fast-exp2-approximation.html
n = (n + 134217728) << 3;
n = multiply_32x32_rshift32_rounded(n, n);
n = multiply_32x32_rshift32_rounded(n, 715827883) << 3;
n = n + 715827882;
#endif
uint32_t scale = n >> (14 - ipart);
uint64_t phstep = (uint64_t)inc * scale;
uint32_t phstep_msw = phstep >> 32;
if (phstep_msw < 0x7FFE) {
ph += phstep >> 16;
} else {
ph += 0x7FFE0000;
}
phasedata[i] = ph;
}
release(moddata);
} else if (moddata) {
// Phase Modulation
bp = moddata->data;
for (i=0; i < AUDIO_BLOCK_SAMPLES; i++) {
// more than +/- 180 deg shift by 32 bit overflow of "n"
uint32_t n = (uint16_t)(*bp++) * modulation_factor;
phasedata[i] = ph + n;
ph += inc;
}
release(moddata);

as the bit I need I just don't fully understand the magic yet. Any suggestions as to routing the audio from a wavetable to be the carrier source?