daniel
1e1d6bddbb
Per-zone play params on SampleData; hand-rolled pure pitch_shift OLA for Preserve (WDL drags windows.h); zone-payload v3 tail; RT-safe pre-warmed shifters + Preserve voice cap.
89 lines
5.0 KiB
C++
89 lines
5.0 KiB
C++
#pragma once
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// pitch_shift — a PURE, per-voice, duration-preserving pitch shifter: the S16 "Preserve"
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// engine's DSP core. Time-domain overlap-add (OLA) with two half-window-offset read taps
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// crossfaded to hide the ring-wrap seam. Source is consumed 1:1 and output produced 1:1
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// (duration held); only the PITCH changes — an octave up plays the same wall-clock length
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// as the root note, unlike the Varispeed `readPos_ += ratio_` resample path.
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//
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// WHY A HAND-ROLLED PURE MODULE, NOT WDL (S16-F2, decided at build). The spec's lean was
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// route (a) `WDL_SimplePitchShifter`. But its include chain
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// (simple_pitchshift.h -> queue.h -> heapbuf.h -> wdltypes.h) does `#ifdef _WIN32 ->
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// #include <windows.h>` unconditionally, which CANNOT enter the pure sampler_core module
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// (CLAUDE.md load-bearing split: NO vendor/host/SDK types; sampler_core_tests links neither
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// SDK and compiles outside the DAW). So the Preserve DSP lands as route (b): a house-native
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// pure module alongside peaks / wav_trim, CTest-testable, RT-disciplined. Same
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// PitchEngine::Preserve contract behind the seam — if WDL is ever preferred it swaps in at
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// the SHELL, never in the pure core.
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//
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// PURE MODULE: NO VST3, NO REAPER, NO SWELL, NO vendor/ includes. Standard library only.
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// Shares the `AudioSample` float alias from peaks (the one house precedent — sampler_core /
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// wav_trim do the same).
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//
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// RT DISCIPLINE (S16 hard constraint). `configure()` sizes the ring ONCE (off the audio
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// thread, at voice allocation). `warm()` pre-fills the ring with silence so steady-state
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// latency is reached before the first real sample (no cold-start click). `process()` does
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// NO allocation and NO locks — it reads/writes the pre-sized ring only. All state is plain
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// value fields, so a voice owning one by value costs a fixed ring buffer per channel.
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#include <cstddef>
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#include <cstdint>
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#include <vector>
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#include "peaks.h" // AudioSample (float)
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namespace reasampler {
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// A per-channel time-domain OLA pitch shifter. One instance transposes ONE channel; a stereo
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// voice owns two (or a stereo-aware wrapper) — the algorithm is per-sample and channel-count
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// agnostic, matching the S7 "one read head, per-channel value" idiom of the core.
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//
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// The default-constructed shifter is INERT: with no configure() it passes input through
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// unchanged (shift ratio 1.0, empty ring), so a Varispeed voice that never touches it is
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// byte-identical to the pre-S16 engine.
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class PitchShifter {
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public:
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// Size the delay ring for `windowFrames` (the OLA grain length) and prepare the two
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// read taps a half-window apart. `windowFrames` <= 1 degrades to pass-through (no ring),
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// so a degenerate configure never divides by zero or wraps a zero span. Called OFF the
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// audio thread (allocates). Resets all running state. A larger window = smoother on large
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// transpositions but more latency; the shell picks it from the Preserve quality setting.
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void configure(std::int64_t windowFrames);
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// Pre-fill the ring with silence (one full window of zero writes) so the read taps reach
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// steady state before the first real sample. Removes the cold-start seam (the S16 "onset
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// click absent" requirement) — call once at voice allocation after configure(). No-op when
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// unconfigured (pass-through needs no warm-up).
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void warm();
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// The pitch shift ratio: 2^((note - root)/12) plus any per-frame pitch-envelope bias.
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// 1.0 = no shift (pass-through-equivalent output). Set per frame is fine (cheap); the tap
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// advance simply uses the current value. Values <= 0 are ignored (kept at the last valid
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// ratio) so a bad input never runs the taps backward or stalls them.
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void setShiftRatio(double ratio);
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// Transform ONE input frame into ONE output frame (duration-preserving: 1 in, 1 out).
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// RT-safe: reads/writes the pre-sized ring only, no allocation, no lock. When unconfigured
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// (window <= 1) returns `in` unchanged (pass-through). Otherwise writes `in` at the write
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// head, reads the two half-window-offset taps advancing at the shift ratio, crossfades
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// them by the write-head-relative distance (equal-power), and advances both heads by one.
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AudioSample process(AudioSample in);
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// Reset running state to a freshly-warmed-equivalent silence (ring zeroed, heads re-seeded)
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// WITHOUT reallocating — for voice reuse without a re-configure. Keeps the current window.
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void reset();
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// True once configure() sized a real ring (window > 1). A pass-through shifter is false.
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bool configured() const { return window_ > 1; }
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std::int64_t window() const { return window_; }
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private:
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std::vector<AudioSample> ring_; // delay line, length `window_` (channel-local)
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std::int64_t window_ = 0; // OLA grain length in frames; <= 1 = pass-through
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std::int64_t writePos_ = 0; // integer write head into the ring (source rate)
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double readPos_ = 0.0; // fractional read head (advances at shift ratio)
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double ratio_ = 1.0; // current shift ratio (>0)
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};
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} // namespace reasampler
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