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102 lines
3.7 KiB
C++
102 lines
3.7 KiB
C++
#include "enhance.h"
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#include "fastmath.h"
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#include "numeric.h"
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#include "tables.h"
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namespace halfrate::core {
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namespace {
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constexpr float kResponseScale = 0x1.8209f6p+1f; // 3.01592898
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constexpr float kLog2Floor = 0x1.197998p-40f; // 1e-12, keeps log2 finite
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constexpr float kTiltStart = -0x1.4cccccp-1f; // tilt starts at harmonic 0.65 L ...
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constexpr float kTiltWidth = 0x1.666668p-2f; // ... reaches full at 0.65 L + 0.35 L
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constexpr float kTiltLog2Gain = 0x1.19999ap-1f; // full tilt: 2^0.55
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// cos(2 pi f l) from the table, f in cycles per sample
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inline float harmonic_cosine(float fundamental, float harmonic) {
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float phase = fundamental * harmonic;
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phase = phase * 8192.0f;
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phase = phase + 0.5f;
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return tables::kCosine[to_int64_sat(phase) & 8191];
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}
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} // namespace
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void enhance_formants(const EnhanceOptions& options, float fundamental, float omega, int harmonic_count,
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float* amplitude) {
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if (options.mode != 1) return;
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int count = harmonic_count;
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if (count < 1) return;
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float r0 = 0.0f, r1 = 0.0f;
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for (int l = 1; l <= count; l++) {
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float power = amplitude[l] * amplitude[l];
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r0 = r0 + power;
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r1 = r1 + power * harmonic_cosine(fundamental, static_cast<float>(static_cast<unsigned>(l)));
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}
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if (r0 <= 0.0f) return;
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float r0_squared = r0 * r0, r1_squared = r1 * r1;
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float squares = r1_squared + r0_squared;
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float twice_product = r1 * (r0 + r0);
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float difference = r0_squared - r1_squared;
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float weight[kMaxHarmonics + 8];
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int32_t every = options.bypass_divisor;
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uint32_t bypass_limit = static_cast<uint32_t>(every); // l * every, wrapping like a 32-bit counter
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for (int l = 1; l <= count; l++, bypass_limit += static_cast<uint32_t>(every)) {
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float w = 1.0f;
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float denominator = difference * (r0 * omega);
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float harmonic = static_cast<float>(static_cast<unsigned>(l));
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float numerator;
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if (denominator <= 0.0f) goto store;
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numerator = squares - twice_product * harmonic_cosine(fundamental, harmonic);
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numerator = numerator * kResponseScale;
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if (numerator <= 0.0f) goto store;
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if (amplitude[l] <= 0.0f) goto store;
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{
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float log2_amplitude = fast_log2(amplitude[l]);
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float log2_response = fast_log2(numerator / denominator);
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log2_response = log2_response * 0.5f;
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float raw = fast_exp2(options.strength * (log2_amplitude + log2_response));
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if (every >= 1 && static_cast<int32_t>(bypass_limit) <= count)
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w = 1.0f;
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else
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w = raw > options.max_weight ? options.max_weight : (raw < options.min_weight ? options.min_weight : raw);
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float exponent = fundamental * harmonic < options.split_frequency ? options.power_low : options.power_high;
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if (exponent != 1.0f) w = fast_exp2(exponent * fast_log2(w));
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}
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store:
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weight[l] = w;
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}
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float energy = 0.0f;
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for (int l = 1; l <= count; l++) {
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float v = amplitude[l] * weight[l];
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amplitude[l] = v;
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energy = energy + v * v;
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}
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float scale = 1.0f;
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if (energy > 0.0f) scale = fast_sqrt(r0 / energy);
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for (int l = 1; l <= count; l++) amplitude[l] = scale * amplitude[l];
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}
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void shape_log2(const FrameParams& frame, bool tilt, float* out) {
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int count = frame.harmonic_count;
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float amplitude[kMaxHarmonics + 8];
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amplitude[0] = 0.0f;
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for (int i = 0; i < count; i++) amplitude[1 + i] = fast_exp2(frame.log2_amplitude[i]);
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enhance_formants(EnhanceOptions{}, frame.fundamental, frame.omega, count, amplitude);
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if (tilt) {
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for (int l = 1; l <= count; l++) {
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float x = static_cast<float>(static_cast<unsigned>(l)) / static_cast<float>(count);
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x = x + kTiltStart;
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x = x / kTiltWidth;
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if (!(x > 0.0f)) continue;
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float a = amplitude[l];
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x = x > 1.0f ? 1.0f : x;
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x = x * kTiltLog2Gain;
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amplitude[l] = a * fast_exp2(x);
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}
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}
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for (int i = 0; i < count; i++) out[1 + i] = fast_log2(amplitude[1 + i] + kLog2Floor);
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}
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} // namespace halfrate::core
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