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reasampler/tests/test_sampler_core.cpp
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// Standalone tests for reasampler::sampler_core — no VST3, no REAPER, no test
// framework. Same fast build/run loop as bank_model_tests / peaks_tests: feed known
// inputs, assert the engine's behavior.
//
// Covers (PLAN.md S3 / CONTEXT.md §Phase S pure core):
// 1. polyphonic allocation — N notes -> N voices; note-off releases the right voice.
// 2. voice stealing at the bound — deterministic policy (release-first, then oldest).
// 3. ADSR envelope shape vs a known signal, incl. release-before-sustain.
// 4. repitch ratio correctness across +/-1 octave from root incl. unity, asserted on
// the observed period of a synthesized sine.
// 5. loop-point sustain — held note past sample end loops [start,end) seamlessly;
// zero-length loop and absent-loop behavior.
// 6. keymap: chromatic-from-single-root; zoned ranges with boundary notes; velocity
// -> volume; out-of-zone note -> defined no-play.
//
// The plain-data boundary (no VST3/REAPER types in the core) is enforced STRUCTURALLY
// by the CMake target linking neither SDK — this file includes only sampler_core.h +
// the standard library, which is itself the compile-time proof.
#include "../src/vst/sampler_core.h"
#include <cmath>
#include <cstdio>
#include <vector>
using namespace reasampler;
static int g_fail = 0;
#define CHECK(cond) do { if(!(cond)) { \
std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
static bool approx(double a, double b, double tol) { return std::fabs(a - b) <= tol; }
constexpr double kPi = 3.14159265358979323846;
// A silent (all-1.0) sample so a rendered voice's output tracks the envelope * velocity
// directly (DC of amplitude 1). Root at note 60 by default.
static SampleData dcSample(std::size_t frames, int rootNote = 60) {
SampleData s;
s.frames.assign(frames, 1.0f);
s.rootNote = rootNote;
return s;
}
// A mono sine of `cycles` periods over `frames` frames — used to observe repitch by
// measuring the played-back period.
static SampleData sineSample(std::size_t frames, double cycles, int rootNote = 60) {
SampleData s;
s.frames.resize(frames);
for (std::size_t i = 0; i < frames; ++i) {
s.frames[i] = static_cast<float>(std::sin(2.0 * kPi * cycles *
static_cast<double>(i) / static_cast<double>(frames)));
}
s.rootNote = rootNote;
return s;
}
// An ADSR that stays fully open (level 1) forever while held, so voice output equals
// velocity gain — isolates allocation/repitch/loop tests from envelope shaping.
static AdsrParams flatAdsr() {
AdsrParams a;
a.attackFrames = 0;
a.decayFrames = 0;
a.sustainLevel = 1.0;
a.releaseFrames = 0; // note-off -> instant silence.
return a;
}
// ---------------------------------------------------------------------------
// 6. Keymap resolution.
// ---------------------------------------------------------------------------
static void testChromaticSingleRoot() {
Keymap km = Keymap::singleSampleChromatic(dcSample(100, 60));
CHECK(km.zones.size() == 1);
// Every note in 0..127 resolves to the single zone.
for (int n = 0; n <= 127; ++n) {
ZoneResolution r = km.resolve(n, 100);
CHECK(r.matched);
CHECK(r.zoneIndex == 0);
}
}
static void testZonedRangesBoundaries() {
Keymap km;
km.samples.push_back(dcSample(100, 48)); // low sample
km.samples.push_back(dcSample(100, 72)); // high sample
// Two adjacent zones: [36,59] and [60,83]. Boundary notes 59/60 must land in the
// correct zone; a first-match order test would catch an off-by-one.
km.zones.push_back(KeyZone{36, 59, 48, 0});
km.zones.push_back(KeyZone{60, 83, 72, 1});
CHECK(km.resolve(36, 100).matched);
CHECK(km.resolve(36, 100).zoneIndex == 0);
CHECK(km.resolve(59, 100).zoneIndex == 0); // last note of zone 0
CHECK(km.resolve(60, 100).zoneIndex == 1); // first note of zone 1
CHECK(km.resolve(83, 100).zoneIndex == 1); // last note of zone 1
// Out of every zone -> defined no-play (not a match, not zone 0).
CHECK(!km.resolve(35, 100).matched);
CHECK(!km.resolve(84, 100).matched);
CHECK(!km.resolve(127, 100).matched);
}
static void testFirstMatchOnOverlap() {
// Overlapping zones: the earlier zone wins (documented deterministic rule).
Keymap km;
km.samples.push_back(dcSample(10, 60));
km.samples.push_back(dcSample(10, 60));
km.zones.push_back(KeyZone{0, 127, 60, 0}); // catch-all first
km.zones.push_back(KeyZone{60, 60, 60, 1}); // shadowed by the catch-all
CHECK(km.resolve(60, 100).zoneIndex == 0);
}
// ---------------------------------------------------------------------------
// 4. Repitch ratio correctness.
// ---------------------------------------------------------------------------
static void testPitchRatioMath() {
CHECK(approx(pitchRatio(60, 60), 1.0, 1e-9)); // unity at root
CHECK(approx(pitchRatio(72, 60), 2.0, 1e-9)); // +1 octave
CHECK(approx(pitchRatio(48, 60), 0.5, 1e-9)); // -1 octave
CHECK(approx(pitchRatio(61, 60), std::pow(2.0, 1.0 / 12.0), 1e-9)); // +1 semitone
}
// Observe repitch on the rendered signal: a voice played an octave above root should
// advance through the sample twice as fast, so a sine's observed period halves. We
// measure the period by counting the interval between positive-going zero crossings.
static double observedPeriodFrames(const std::vector<AudioSample>& out) {
std::vector<std::size_t> upCrossings;
for (std::size_t i = 1; i < out.size(); ++i) {
if (out[i - 1] <= 0.0f && out[i] > 0.0f) upCrossings.push_back(i);
}
if (upCrossings.size() < 2) return 0.0;
// Average spacing between crossings.
double sum = 0.0;
for (std::size_t i = 1; i < upCrossings.size(); ++i) {
sum += static_cast<double>(upCrossings[i] - upCrossings[i - 1]);
}
return sum / static_cast<double>(upCrossings.size() - 1);
}
static void testRepitchObservedPeriod() {
// A sine of 20 cycles over 8000 frames -> native period 400 frames at unity.
const std::size_t frames = 8000;
const double cycles = 20.0;
const double nativePeriod = static_cast<double>(frames) / cycles; // 400
// Unity: played at root, observed period ~= native.
{
Keymap km = Keymap::singleSampleChromatic(sineSample(frames, cycles, 60));
VoiceEngine eng(4, km, flatAdsr());
eng.noteOn(60, 127);
std::vector<AudioSample> out;
eng.render(out, frames);
double p = observedPeriodFrames(out);
CHECK(approx(p, nativePeriod, 2.0));
}
// +1 octave: advances 2x, observed period halves.
{
Keymap km = Keymap::singleSampleChromatic(sineSample(frames, cycles, 60));
VoiceEngine eng(4, km, flatAdsr());
eng.noteOn(72, 127);
std::vector<AudioSample> out;
eng.render(out, frames / 2); // half as many frames covers the whole sample
double p = observedPeriodFrames(out);
CHECK(approx(p, nativePeriod / 2.0, 2.0));
}
// -1 octave: advances 0.5x, observed period doubles.
{
Keymap km = Keymap::singleSampleChromatic(sineSample(frames, cycles, 60));
VoiceEngine eng(4, km, flatAdsr());
eng.noteOn(48, 127);
std::vector<AudioSample> out;
eng.render(out, frames);
double p = observedPeriodFrames(out);
CHECK(approx(p, nativePeriod * 2.0, 4.0));
}
}
// ---------------------------------------------------------------------------
// 3. ADSR envelope shape vs a known signal.
// ---------------------------------------------------------------------------
static void testAdsrShape() {
AdsrParams p;
p.attackFrames = 10;
p.decayFrames = 10;
p.sustainLevel = 0.5;
p.releaseFrames = 10;
AdsrEnvelope env;
env.configure(p);
env.noteOn();
// Attack: 0 -> ramps up. Frame 0 == 0, rising each frame.
double prev = -1.0;
for (int i = 0; i < 10; ++i) {
double v = env.tick();
CHECK(v >= prev); // monotonic non-decreasing through attack
CHECK(v >= 0.0 && v <= 1.0);
prev = v;
}
// Decay: from 1.0 down toward sustain 0.5, monotonic non-increasing.
prev = 2.0;
for (int i = 0; i < 10; ++i) {
double v = env.tick();
CHECK(v <= prev + 1e-9); // non-increasing through decay
CHECK(v >= 0.5 - 1e-9); // never below sustain during decay
prev = v;
}
// Sustain: holds 0.5 indefinitely.
for (int i = 0; i < 100; ++i) {
CHECK(approx(env.tick(), 0.5, 1e-9));
}
CHECK(env.stage() == AdsrEnvelope::Stage::Sustain);
// Release: 0.5 -> 0 over 10 frames, then Finished + latched at 0.
env.noteOff();
prev = 1.0;
for (int i = 0; i < 10; ++i) {
double v = env.tick();
CHECK(v <= prev + 1e-9); // non-increasing through release
prev = v;
}
CHECK(env.finished());
for (int i = 0; i < 10; ++i) CHECK(approx(env.tick(), 0.0, 1e-12));
}
static void testAdsrReleaseBeforeSustain() {
// noteOff during the attack ramp releases from the PARTIAL level, not sustain.
AdsrParams p;
p.attackFrames = 100;
p.decayFrames = 10;
p.sustainLevel = 0.8;
p.releaseFrames = 20;
AdsrEnvelope env;
env.configure(p);
env.noteOn();
// Advance 50 frames into a 100-frame attack -> partial level ~0.5.
double last = 0.0;
for (int i = 0; i < 50; ++i) last = env.tick();
CHECK(last > 0.3 && last < 0.7); // partway up the attack ramp
CHECK(env.stage() == AdsrEnvelope::Stage::Attack);
env.noteOff();
CHECK(env.stage() == AdsrEnvelope::Stage::Release);
// First release frame must be at or below the partial level we left off at —
// NOT jump up to sustain 0.8. This is the release-before-sustain guarantee.
double firstRelease = env.tick();
CHECK(firstRelease <= last + 1e-9);
CHECK(firstRelease < p.sustainLevel); // proves it did not snap to sustain
// Decays to zero.
double prev = firstRelease;
for (int i = 0; i < 20; ++i) {
double v = env.tick();
CHECK(v <= prev + 1e-9);
prev = v;
}
CHECK(env.finished());
}
static void testAdsrZeroAttackDecay() {
// Zero attack + zero decay -> jumps straight to sustain on the first ticks.
AdsrParams p;
p.attackFrames = 0;
p.decayFrames = 0;
p.sustainLevel = 0.7;
p.releaseFrames = 5;
AdsrEnvelope env;
env.configure(p);
env.noteOn();
// Zero attack emits the attack peak (1.0) on frame 0 and immediately transitions
// through the (also zero-length) decay, so by frame 1 the envelope is holding
// sustain. The peak-at-boundary is the documented single-frame edge, not a bug.
CHECK(approx(env.tick(), 1.0, 1e-9)); // frame 0: attack peak
CHECK(approx(env.tick(), 0.7, 1e-9)); // frame 1: sustain
CHECK(approx(env.tick(), 0.7, 1e-9));
CHECK(env.stage() == AdsrEnvelope::Stage::Sustain);
}
// ---------------------------------------------------------------------------
// 1. Polyphonic allocation + note-off routing.
// ---------------------------------------------------------------------------
static void testPolyphonicAllocation() {
Keymap km = Keymap::singleSampleChromatic(dcSample(1000, 60));
VoiceEngine eng(8, km, flatAdsr());
// Four simultaneous notes -> four active voices, each on a distinct voice.
std::size_t v60 = eng.noteOn(60, 100);
std::size_t v64 = eng.noteOn(64, 100);
std::size_t v67 = eng.noteOn(67, 100);
std::size_t v72 = eng.noteOn(72, 100);
CHECK(v60 != VoiceEngine::kNoVoice);
CHECK(eng.activeVoiceCount() == 4);
CHECK(v60 != v64 && v64 != v67 && v67 != v72 && v60 != v72);
// Note-off on 64 releases exactly one voice; with instant release it goes idle
// after the next render frame.
eng.noteOff(64);
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(eng.activeVoiceCount() == 3);
// The still-held notes keep sounding.
eng.render(out, 1);
CHECK(eng.activeVoiceCount() == 3);
}
static void testNoteOffReleasesNewestSameNote() {
// Prove that noteOff releases the NEWEST (highest startOrder) instance of a
// re-triggered note, leaving the older voice in sustain.
//
// Two voices at distinct velocities so their output is distinguishable:
// "first" (older) -> velocity 64 -> gain ~0.504 (G_old)
// "second" (newer) -> velocity 127 -> gain 1.0 (G_new)
//
// With a DC-1 sample and sustain=1, while both are held:
// render sum == G_old + G_new.
//
// After noteOff (must release newest), the newer voice enters a short release.
// Render past releaseFrames: newer voice finishes; only the older voice remains.
// Sum then equals G_old, and activeVoiceCount drops to 1. If the WRONG voice
// were released, the older would finish and the remaining sum would equal G_new
// (1.0 vs ~0.504) — the velocities make the error distinguishable.
const int velOld = 64;
const int velNew = 127;
const double gainOld = velOld / 127.0; // ~0.504
const double gainNew = velNew / 127.0; // 1.0
Keymap km = Keymap::singleSampleChromatic(dcSample(100000, 60));
AdsrParams a = flatAdsr();
a.releaseFrames = 10; // short but non-zero so voice stays active through release
VoiceEngine eng(8, km, a);
std::size_t first = eng.noteOn(60, velOld); // older voice, lower gain
std::size_t second = eng.noteOn(60, velNew); // newer voice, higher gain
CHECK(first != second);
CHECK(eng.activeVoiceCount() == 2);
// While both are held, combined output equals gainOld + gainNew.
{
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(approx(out[0], gainOld + gainNew, 1e-4));
}
// Release once — must target the NEWEST voice (second).
eng.noteOff(60);
// Render past the release (releaseFrames == 10): newer voice goes Finished.
std::vector<AudioSample> out;
eng.render(out, 20);
// Newer voice must be done; only the older voice remains.
CHECK(eng.activeVoiceCount() == 1);
// Tail frames must equal gainOld (~0.504), NOT gainNew (1.0).
// If the older voice were released instead, the tail would be ~1.0 here.
for (std::size_t i = 15; i < out.size(); ++i) {
CHECK(approx(out[i], gainOld, 1e-4));
}
// A second note-off releases the remaining older voice.
eng.noteOff(60);
eng.render(out, 20);
CHECK(eng.activeVoiceCount() == 0);
}
static void testOutOfZoneNoteConsumesNoVoice() {
Keymap km;
km.samples.push_back(dcSample(100, 60));
km.zones.push_back(KeyZone{60, 72, 60, 0});
VoiceEngine eng(4, km, flatAdsr());
std::size_t v = eng.noteOn(30, 100); // below the only zone
CHECK(v == VoiceEngine::kNoVoice);
CHECK(eng.activeVoiceCount() == 0); // no voice consumed
}
// ---------------------------------------------------------------------------
// 2. Voice stealing at the bound.
// ---------------------------------------------------------------------------
static void testStealsReleasingVoiceFirst() {
Keymap km = Keymap::singleSampleChromatic(dcSample(100000, 60));
AdsrParams a = flatAdsr();
a.releaseFrames = 100000; // long release so a released voice stays "active".
VoiceEngine eng(2, km, a);
std::size_t vA = eng.noteOn(60, 100); // startOrder 1
std::size_t vB = eng.noteOn(62, 100); // startOrder 2
CHECK(eng.activeVoiceCount() == 2);
// Release the NEWER voice (62) — it becomes the only releasing voice.
eng.noteOff(62);
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(eng.activeVoiceCount() == 2); // both still ringing (long release)
// A new note with the pool full must steal the RELEASING voice (vB), not the
// older held voice (vA) — release-first policy.
std::size_t vC = eng.noteOn(64, 100);
CHECK(vC == vB);
CHECK(eng.activeVoiceCount() == 2);
}
static void testStealsOldestWhenNoneReleasing() {
Keymap km = Keymap::singleSampleChromatic(dcSample(100000, 60));
AdsrParams a = flatAdsr();
a.releaseFrames = 100000;
VoiceEngine eng(2, km, a);
std::size_t vA = eng.noteOn(60, 100); // startOrder 1 (oldest)
std::size_t vB = eng.noteOn(62, 100); // startOrder 2
CHECK(vA != vB);
// No voice released; both held. A new note steals the OLDEST (vA).
std::size_t vC = eng.noteOn(64, 100);
CHECK(vC == vA);
CHECK(eng.activeVoiceCount() == 2);
// The stolen voice now carries note 64; a note-off on 60 (the stolen-away note)
// finds nothing to release.
std::size_t before = eng.activeVoiceCount();
eng.noteOff(60);
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(eng.activeVoiceCount() == before); // 60 no longer exists; no-op
}
// ---------------------------------------------------------------------------
// 5. Loop-point-aware sustain.
// ---------------------------------------------------------------------------
static void testLoopSustainSeamless() {
// A sample whose [0,20) frames are a distinctive ramp and [20,40) is a flat loop
// region of value 0.5. Held far past the sample end, the voice must keep emitting
// the loop region (0.5) rather than going silent.
SampleData s;
s.frames.resize(40);
for (int i = 0; i < 20; ++i) s.frames[i] = static_cast<float>(i) / 20.0f; // attack
for (int i = 20; i < 40; ++i) s.frames[i] = 0.5f; // loop body
s.rootNote = 60;
s.loop.hasLoop = true;
s.loop.start = 20;
s.loop.end = 40;
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127); // unity ratio, full velocity
std::vector<AudioSample> out;
eng.render(out, 200); // 5x the sample length
// Voice is still active (looping), not exhausted.
CHECK(eng.activeVoiceCount() == 1);
// Frames well past the loop start must sit at the loop body value 0.5.
for (std::size_t i = 60; i < out.size(); ++i) {
CHECK(approx(out[i], 0.5, 1e-4));
}
}
static void testZeroLengthLoopGoesSilent() {
// A zero-length loop (start == end) is the "no sustain" marker: the note runs off
// the sample end and the voice goes idle, rather than spinning on an empty span.
SampleData s = dcSample(50, 60); // 50 frames of 1.0
s.loop.hasLoop = true;
s.loop.start = 25;
s.loop.end = 25; // zero length
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127);
std::vector<AudioSample> out;
eng.render(out, 100); // past the 50-frame end
// After frame ~50 the voice should have gone idle (no loop to sustain it).
CHECK(eng.activeVoiceCount() == 0);
// Tail frames are silent.
for (std::size_t i = 60; i < out.size(); ++i) CHECK(approx(out[i], 0.0, 1e-6));
}
static void testSingleFrameLoop() {
// A loop of exactly one frame [start, start+1) — the narrowest valid loop.
// The path is correct-by-luck (loopLen = 1.0 divides evenly into any integer
// readPos advance at unity ratio), but Tier-2 tight loops make it load-bearing.
SampleData s;
s.frames.resize(10);
for (int i = 0; i < 10; ++i) s.frames[i] = static_cast<float>(i) * 0.1f;
s.rootNote = 60;
s.loop.hasLoop = true;
s.loop.start = 5;
s.loop.end = 6; // single-frame loop: [5, 6)
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127); // unity ratio, full velocity
std::vector<AudioSample> out;
eng.render(out, 50); // well past the sample end
// Voice must still be active — the single-frame loop keeps it alive.
CHECK(eng.activeVoiceCount() == 1);
// Every frame from the loop-start onward must be the value of frame 5 (0.5).
for (std::size_t i = 10; i < out.size(); ++i) {
CHECK(approx(out[i], 0.5, 1e-4));
}
}
static void testAbsentLoopGoesSilent() {
// No loop at all: held note runs off the end and goes idle (same as zero-length).
SampleData s = dcSample(50, 60);
// s.loop.hasLoop stays false.
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127);
std::vector<AudioSample> out;
eng.render(out, 100);
CHECK(eng.activeVoiceCount() == 0);
for (std::size_t i = 60; i < out.size(); ++i) CHECK(approx(out[i], 0.0, 1e-6));
}
// ---------------------------------------------------------------------------
// start point (S11): the voice's initial read position is SampleData::startFrame.
// ---------------------------------------------------------------------------
static void testStartFrameOffsetsInitialRead() {
// A per-frame ramp (frame i holds i*0.01) so the first rendered value pinpoints the
// read position. startFrame = 30 -> the first output frame reads frame 30 (0.30).
SampleData s;
s.frames.resize(100);
for (int i = 0; i < 100; ++i) s.frames[i] = static_cast<float>(i) * 0.01f;
s.rootNote = 60;
s.startFrame = 30;
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127); // unity ratio, full velocity, flat gain
std::vector<AudioSample> out;
eng.render(out, 3);
CHECK(approx(out[0], 0.30, 1e-4)); // starts at frame 30, not 0
CHECK(approx(out[1], 0.31, 1e-4)); // advances by unity ratio
CHECK(approx(out[2], 0.32, 1e-4));
}
static void testStartFrameZeroIsUnchanged() {
// startFrame default 0 is exactly the pre-S11 behavior: read begins at frame 0.
SampleData s;
s.frames.resize(20);
for (int i = 0; i < 20; ++i) s.frames[i] = static_cast<float>(i) * 0.05f;
s.rootNote = 60; // startFrame stays 0
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127);
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(approx(out[0], 0.0, 1e-6)); // frame 0
}
static void testStartFrameOutOfRangeClampsToZero() {
// A start point at/past the sample end degrades to frame 0 (play from the top), never an
// out-of-bounds read that would start the voice already exhausted.
SampleData s = dcSample(10, 60); // 10 frames of 1.0
s.startFrame = 10; // == frameCount: out of range
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127);
std::vector<AudioSample> out;
eng.render(out, 5);
// Reads from frame 0: the DC sample plays its 1.0 body rather than an immediate idle.
CHECK(eng.activeVoiceCount() == 1);
CHECK(approx(out[0], 1.0, 1e-4));
}
static void testStartFrameWithLoop() {
// Start point and loop compose: begin reading mid-sample, then sustain the loop region.
SampleData s;
s.frames.resize(40);
for (int i = 0; i < 40; ++i) s.frames[i] = static_cast<float>(i) * 0.01f;
for (int i = 20; i < 40; ++i) s.frames[i] = 0.5f; // loop body
s.rootNote = 60;
s.startFrame = 10; // begin at frame 10
s.loop.hasLoop = true;
s.loop.start = 20;
s.loop.end = 40;
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127);
std::vector<AudioSample> out;
eng.render(out, 200);
CHECK(approx(out[0], 0.10, 1e-4)); // started at frame 10
CHECK(eng.activeVoiceCount() == 1); // loop sustains it
for (std::size_t i = 60; i < out.size(); ++i) CHECK(approx(out[i], 0.5, 1e-4));
}
static void testStartAfterLoopEndWrapsIntoLoop() {
// Regression (S11 reviewer finding): if startFrame > loop.end (but still < frameCount),
// the voice's initial read head is past the loop end. The wrap-while in renderFrame must
// pull it back into [loopStart, loopEnd) on the very first frame, so the note sounds from
// somewhere inside the loop rather than running off the sample end silently.
//
// Setup: 100-frame sample; loop is [20, 40); startFrame = 60 (past loop.end = 40).
// loop body is a constant 0.5 so every frame inside it reads 0.5.
// After wrap: readPos starts inside [20, 40), first output frame == 0.5.
// Voice must stay active (loop sustains it) and emit the loop value, NOT go silent.
SampleData s;
s.frames.resize(100, 0.0f);
for (int i = 20; i < 40; ++i) s.frames[i] = 0.5f; // loop body
s.rootNote = 60;
s.startFrame = 60; // > loop.end (40), < frameCount (100)
s.loop.hasLoop = true;
s.loop.start = 20;
s.loop.end = 40;
Keymap km = Keymap::singleSampleChromatic(std::move(s));
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127); // unity ratio, full velocity
std::vector<AudioSample> out;
eng.render(out, 50);
// Voice must still be active — the usable loop keeps it alive indefinitely.
CHECK(eng.activeVoiceCount() == 1);
// Every frame after the first wrap must read 0.5 (the loop body). We skip the very
// first frame because the fractional-position wrap lands somewhere in [20,40) and the
// exact offset depends on how many loop lengths fit into 60; what matters is that the
// voice is alive and emitting the loop value, not 0.0 (pre-loop region).
for (std::size_t i = 5; i < out.size(); ++i) {
CHECK(approx(out[i], 0.5, 1e-4));
}
}
// ---------------------------------------------------------------------------
// velocity -> volume.
// ---------------------------------------------------------------------------
static void testVelocityToVolume() {
Keymap km = Keymap::singleSampleChromatic(dcSample(100, 60)); // DC 1.0
// Full velocity -> full gain; half velocity -> ~half gain (flat envelope so the
// rendered value is exactly velocity/127 on a DC-1 sample).
{
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 127);
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(approx(out[0], 1.0, 1e-4));
}
{
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 64);
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(approx(out[0], 64.0 / 127.0, 1e-4));
}
{
VoiceEngine eng(1, km, flatAdsr());
eng.noteOn(60, 1);
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(approx(out[0], 1.0 / 127.0, 1e-4));
}
}
// Two voices summed: polyphony mixes additively.
static void testPolyphonyMixesAdditively() {
Keymap km = Keymap::singleSampleChromatic(dcSample(100, 60)); // DC 1.0
VoiceEngine eng(4, km, flatAdsr());
eng.noteOn(60, 127); // gain 1.0
eng.noteOn(60, 127); // gain 1.0 (second voice, same note)
std::vector<AudioSample> out;
eng.render(out, 1);
CHECK(approx(out[0], 2.0, 1e-4)); // both voices sum
}
int main() {
testChromaticSingleRoot();
testZonedRangesBoundaries();
testFirstMatchOnOverlap();
testPitchRatioMath();
testRepitchObservedPeriod();
testAdsrShape();
testAdsrReleaseBeforeSustain();
testAdsrZeroAttackDecay();
testPolyphonicAllocation();
testNoteOffReleasesNewestSameNote();
testOutOfZoneNoteConsumesNoVoice();
testStealsReleasingVoiceFirst();
testStealsOldestWhenNoneReleasing();
testLoopSustainSeamless();
testZeroLengthLoopGoesSilent();
testSingleFrameLoop();
testAbsentLoopGoesSilent();
testStartFrameOffsetsInitialRead();
testStartFrameZeroIsUnchanged();
testStartFrameOutOfRangeClampsToZero();
testStartFrameWithLoop();
testStartAfterLoopEndWrapsIntoLoop();
testVelocityToVolume();
testPolyphonyMixesAdditively();
if (g_fail == 0) {
std::printf("all sampler_core tests passed\n");
return 0;
}
std::printf("%d sampler_core check(s) failed\n", g_fail);
return 1;
}
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