52 lines
2.7 KiB
C++
52 lines
2.7 KiB
C++
// trigger_seam.h — PURE Trigger-mode frames↔fraction converter for the S-VIEW-3 envelope seam.
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// NO VST3, NO REAPER, NO SWELL/LICE types at the boundary.
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//
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// The TRIGGER SEAM (documented in envelope_overlay.h) converts between the two representations
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// of Trigger fade lengths:
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//
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// ENGINE domain (TriggerParams / sampler_core): SOURCE FRAMES — int64_t absolute frame counts
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// that anchor directly to the voice's source-timeline read pointer.
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//
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// OVERLAY domain (AmpEnvelope / envelope_overlay): FRACTIONS — doubles in [0,1] of the played
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// span, where the played span is:
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// playLengthFrames = round(lengthFraction * (frameCount - startFrame))
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// The overlay stores fractions so the drawn shape stays invariant across sample-rate changes;
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// the engine stores frames so the voice advances correctly at the live rate.
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//
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// This module owns the one shared formula so the pack (frames->fractions) and unpack
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// (fractions->frames) paths are provably consistent and unit-tested independently of the shell.
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// The shell (reasampler_editor.cpp) calls these two functions from packEnvelope / unpackEnvelope.
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//
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// S-VIEW-F2 safety: the fractions produced here are in [0,1] by construction; a caller that
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// clamps the fractions to [0,1] before writing the AmpEnvelope preserves the slider-range
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// invariant (a drag can never produce a value a slider couldn't reach).
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#pragma once
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#include <cstdint>
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namespace reasampler::instrument::map {
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// The source-frame length of the Trigger played span:
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// postStart = max(0, frameCount - startFrame)
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// playLength = round(lengthFraction * postStart)
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// `frameCount` is the total decoded sample length in source frames.
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// `startFrame` is the effective start point (zone.startPoint, or 0 when absent).
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// `lengthFraction` is TriggerParams::lengthFraction — (0,1], the fraction of the post-start span.
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// Returns 0 when postStart == 0 or lengthFraction <= 0.
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std::int64_t triggerPlayLength(double lengthFraction,
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std::int64_t frameCount,
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std::int64_t startFrame);
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// Convert a source-frame fade count to a fraction of the play span (PACK direction, draw path).
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// Returns 0.0 when playLength == 0 (degenerate sample or zero %-length); the fraction is
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// NOT clamped — the caller clamps to [0,1] when filling AmpEnvelope so the overlay clamp logic
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// stays in envelope_edit, not here.
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double framesToFadeFraction(std::int64_t fadeFrames, std::int64_t playLength);
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// Convert a fade fraction to a source-frame count (UNPACK direction, commit path).
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// Rounds to nearest integer frame. Returns 0 when playLength == 0.
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std::int64_t fadeFractionToFrames(double fadeFraction, std::int64_t playLength);
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} // namespace reasampler::instrument::map
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