95 lines
3.1 KiB
C++
95 lines
3.1 KiB
C++
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// nisps/dsp/delay.hpp — static-buffer delay lines.
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//
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// Delay<N> — fixed-length feedback delay (maximilian's maxiDelayline)
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// DynamicDelay<N> — power-of-two ring with fractional-tap read + smoothed
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// delay-time (used by VerbFX's three delay lanes).
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//
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// Sample-rate is opaque to these primitives; delay sizes are in samples.
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// Convert from milliseconds at the engine layer (`samples = ms * sr / 1000`).
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#pragma once
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#include <array>
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#include <cstddef>
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#include <cstring>
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#include "../core/perf.hpp"
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namespace nisps {
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// Fixed-length feedback delay. `play()` reads the head, mixes feedback into the
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// slot, and advances. Behavior matches maxiDelayline<N>::play().
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template <std::size_t N>
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class Delay {
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public:
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Delay() noexcept { clear(); }
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void clear() noexcept {
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std::memset(memory_.data(), 0, N * sizeof(float));
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phase_ = 0u;
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}
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NISPS_HOT NISPS_FORCE_INLINE float play(float input,
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std::size_t size,
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float feedback) noexcept {
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if (size >= N) [[unlikely]] return 0.f;
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if (phase_ >= size) [[unlikely]] phase_ = 0u;
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const float out = memory_[phase_];
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memory_[phase_] = (memory_[phase_] * feedback) + input;
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++phase_;
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return out;
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}
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static constexpr std::size_t capacity() noexcept { return N; }
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private:
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alignas(16) std::array<float, N> memory_{};
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std::size_t phase_ = 0u;
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};
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// Power-of-two ring with fractional-tap read; smooths the read offset between
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// frames so changes in `target_size` glitch-freely. Mirrors maximilian's
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// `DynamicDelay<N>`.
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template <std::size_t N>
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class DynamicDelay {
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static_assert((N & (N - 1u)) == 0u, "DynamicDelay capacity must be power of two");
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static constexpr std::size_t kMask = N - 1u;
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public:
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DynamicDelay() noexcept : smoothed_size_(static_cast<float>(N)) {}
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void clear() noexcept {
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std::memset(line_.data(), 0, N * sizeof(float));
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write_index_ = 0u;
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smoothed_size_ = static_cast<float>(N);
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}
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void set_smooth_coeff(float c) noexcept { smooth_coeff_ = c; }
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NISPS_HOT NISPS_FORCE_INLINE float read(float target_size) noexcept {
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smoothed_size_ = smoothed_size_ * smooth_coeff_
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+ target_size * (1.f - smooth_coeff_);
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float read_pos = static_cast<float>(write_index_) - smoothed_size_;
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if (read_pos < 0.f) read_pos += static_cast<float>(N);
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const std::size_t i1 = static_cast<std::size_t>(read_pos);
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const float frac = read_pos - static_cast<float>(i1);
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const std::size_t i2 = (i1 + 1u) & kMask;
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return line_[i1] + frac * (line_[i2] - line_[i1]);
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}
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NISPS_HOT NISPS_FORCE_INLINE void write(float input) noexcept {
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line_[write_index_] = input;
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write_index_ = (write_index_ + 1u) & kMask;
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}
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static constexpr std::size_t capacity() noexcept { return N; }
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private:
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std::array<float, N> line_{};
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std::size_t write_index_ = 0u;
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float smoothed_size_;
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float smooth_coeff_ = 0.997f;
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};
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} // namespace nisps
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