mirror of
https://github.com/cookiengineer/audacity
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55 lines
2.1 KiB
Plaintext
55 lines
2.1 KiB
Plaintext
(BUZZ-ALG
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(NAME "buzz")
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(ARGUMENTS ("long" "n") ("rate_type" "sr") ("double" "hz")
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("time_type" "t0") ("sound_type" "s_fm"))
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(SUPPORT-FUNCTIONS "
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#include \"sine.h\"
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")
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(STATE ("double" "ph_incr" "0")
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("float" "n_2_r" "1.0F / (n * 2)")
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("float" "n_2_p1" "(n * 2) + 1")
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;; note: hz * 0.5 because this formula generates tones an octave up,
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;; we also have to correct for the modulation s_fm. If hz != 0, then
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;; ph_incr is the increment per hz, so ph_incr/hz is the right scale
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;; factor. If hz == 0, then the ph_incr/hz is SINE_TABLE_LEN * 0.5 / sr.
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("double" "phase" "compute_phase(PI*0.5, 69.0, SINE_TABLE_LEN,
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SINE_TABLE_LEN * 440.0, sr, hz * 0.5, &susp->ph_incr);
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s_fm->scale *= hz != 0 ? (sample_type) (susp->ph_incr / hz)
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: (sample_type) (SINE_TABLE_LEN * 0.5 / sr)")) ;cancel 0/0
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(ALWAYS-SCALE s_fm)
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(INLINE-INTERPOLATION T) ; so that modulation can be low frequency
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(STEP-FUNCTION s_fm)
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(TERMINATE (MIN s_fm))
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(LOGICAL-STOP (MIN s_fm))
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(INNER-LOOP-LOCALS " long table_index;
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double x1;
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sample_type num, denom, samp;
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")
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(INNER-LOOP "
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table_index = (long) phase;
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x1 = sine_table[table_index];
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denom = (sample_type) (x1 + (phase - table_index) *
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(sine_table[table_index + 1] - x1));
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if (denom < 0.001 && denom > -0.005) {
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samp = 1.0F;
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} else {
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double phn2p1 = phase * n_2_p1 * (1.0/SINE_TABLE_LEN);
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phn2p1 = (phn2p1 - (long) phn2p1) * SINE_TABLE_LEN;
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table_index = (long) phn2p1;
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x1 = sine_table[table_index];
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num = (sample_type) (x1 + (phn2p1 - table_index) *
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(sine_table[table_index + 1] - x1));
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samp = ((num / denom) - 1.0F) * n_2_r;
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}
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output = samp;
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phase += ph_incr + s_fm;
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while (phase > SINE_TABLE_LEN) phase -= SINE_TABLE_LEN;
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/* watch out for negative frequencies! */
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while (phase < 0) phase += SINE_TABLE_LEN")
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(CONSTANT "ph_incr" "n_2_p1" "n_2_r")
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(SAMPLE-RATE "sr")
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)
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