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Γ-W1-T7: make Preserve's splices pitch-synchronous — the jump is a whole number of the source's own period, detected once at load

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30 Hz out-of-band energy 15.45% -> 0.00%; the 29 Hz rate-2.0 detune -133 -> +0 cents.
An unknown period keeps the fixed-window geometry bit for bit. The detector cannot
reach process(): sampler_core does not link it.
This commit is contained in:
Daniel Harvey
2026-08-01 23:19:16 -04:00
parent 163ab11e05
commit 93230208ff
17 changed files with 1085 additions and 137 deletions
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tests/test_period_detect.cpp
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// Standalone tests for reasampler::instrument::engine::detectPeriod — the offline source-period
// estimate behind Preserve's pitch-synchronous splices. No VST3, no REAPER, no test framework.
//
// Covers:
// 1. accuracy on pure tones across the searched band, at 44.1k and 48k, including the
// non-integer periods every real capture actually has — the splice jump is n periods, so
// a fractional-frame error lands multiplied by n.
// 2. the fundamental, not a harmonic: a sawtooth and a missing-fundamental stack must both
// report the repeat period, which is what a splice has to align on.
// 3. graceful degradation — noise, silence, and a source whose period changes mid-sample all
// return NONE. That is the contract the shifter's fixed-window fallback rests on: an
// estimate that is merely wrong would misalign every splice, which is worse than none.
// 4. the band edges and the short-sample path.
// 5. what the load pays, and that it does not grow with the sample length.
#include "../src/core/instrument/engine/period_detect.h"
#include <chrono>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <vector>
using namespace reasampler;
using namespace reasampler::instrument::engine;
static int g_fail = 0;
#define CHECK(cond) do { if(!(cond)) { \
std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
constexpr double kPi = 3.14159265358979323846;
static std::vector<AudioSample> sineOfPeriod(std::size_t frames, double period,
double phase = 0.0) {
std::vector<AudioSample> s(frames);
for (std::size_t i = 0; i < frames; ++i) {
s[i] = static_cast<AudioSample>(
std::sin(2.0 * kPi * static_cast<double>(i) / period + phase));
}
return s;
}
// --- 1. Accuracy on pure tones -------------------------------------------------------------
static void testPureTonePeriodIsFoundToBetterThanATenthOfAFrame() {
// Deliberately non-integer periods: an integer-only estimator passes an integer-period
// sweep and still misaligns every real capture.
const double periods[] = {23.7, 50.0, 100.25, 200.45, 441.0, 999.9, 1470.0, 2000.3, 2756.0};
for (double p : periods) {
const std::vector<AudioSample> src = sineOfPeriod(120000, p);
const PeriodEstimate est = detectPeriod(src, 44100);
CHECK(est.valid());
if (!est.valid()) {
std::printf(" period %.2f: NOT DETECTED\n", p);
continue;
}
const double errFrames = std::fabs(est.frames - p);
std::printf(" period %8.2f -> %8.4f (err %.4f fr, conf %.3f)\n", p, est.frames,
errFrames, est.confidence);
CHECK(errFrames < 0.1);
CHECK(est.confidence > 0.8);
}
}
static void testTheEstimateIsInSourceFramesSoTheRateOnlyMovesTheBand() {
// The same 30 Hz tone at two rates: the answer is frames, so it must track the rate. This
// is what lets the shifter compare it against a window that is also in frames.
for (int rate : {44100, 48000}) {
const double p = static_cast<double>(rate) / 30.0;
const std::vector<AudioSample> src = sineOfPeriod(160000, p);
const PeriodEstimate est = detectPeriod(src, rate);
CHECK(est.valid());
if (est.valid()) {
std::printf(" 30 Hz @ %d: %.3f fr (want %.3f)\n", rate, est.frames, p);
CHECK(std::fabs(est.frames - p) < 0.5);
}
}
}
// --- 2. The fundamental, not a harmonic ----------------------------------------------------
static void testHarmonicRichSourceReportsTheRepeatPeriodNotAPartial() {
// A sawtooth's strongest correlation dips at EVERY multiple of its period; a global-minimum
// estimator picks 2P or 3P about as often as P. YIN's first-dip rule is what makes this
// pass, and a jump quantized to 2P would splice a whole cycle out of phase half the time.
const double p = 512.0;
std::vector<AudioSample> src(120000);
for (std::size_t i = 0; i < src.size(); ++i) {
double v = 0.0;
for (int h = 1; h <= 12; ++h) {
v += std::sin(2.0 * kPi * h * static_cast<double>(i) / p) / h;
}
src[i] = static_cast<AudioSample>(0.5 * v);
}
const PeriodEstimate est = detectPeriod(src, 44100);
CHECK(est.valid());
if (est.valid()) {
std::printf(" sawtooth P=512 -> %.3f\n", est.frames);
CHECK(std::fabs(est.frames - p) < 1.0);
}
}
static void testMissingFundamentalStillReportsTheRepeatPeriod() {
// Partials 2..6 of a 700-frame period: there is no energy AT the fundamental, but the
// waveform still repeats every 700 frames — and repetition, not spectral content, is what
// a splice has to land on.
const double p = 700.0;
std::vector<AudioSample> src(120000);
for (std::size_t i = 0; i < src.size(); ++i) {
double v = 0.0;
for (int h = 2; h <= 6; ++h) {
v += std::sin(2.0 * kPi * h * static_cast<double>(i) / p);
}
src[i] = static_cast<AudioSample>(0.2 * v);
}
const PeriodEstimate est = detectPeriod(src, 44100);
CHECK(est.valid());
if (est.valid()) {
std::printf(" missing fundamental P=700 -> %.3f\n", est.frames);
CHECK(std::fabs(est.frames - p) < 2.0);
}
}
// --- 3. Graceful degradation ---------------------------------------------------------------
static void testNoiseSilenceAndAPeriodChangeAllReportNone() {
// White noise: no dip below the absolute threshold anywhere.
{
std::vector<AudioSample> src(120000);
std::uint32_t rng = 22222u;
for (auto& x : src) {
rng = rng * 1664525u + 1013904223u;
x = static_cast<AudioSample>((static_cast<double>(rng >> 8) / 8388608.0) - 1.0);
}
const PeriodEstimate est = detectPeriod(src, 44100);
std::printf(" white noise -> %s (%.3f)\n", est.valid() ? "DETECTED" : "none",
est.frames);
CHECK(!est.valid());
}
// Digital silence: the difference function is degenerate, not merely inconclusive.
{
const std::vector<AudioSample> src(120000, 0.0f);
CHECK(!detectPeriod(src, 44100).valid());
}
// Two halves at genuinely different periods: the probes disagree, so there is no ONE
// period, and reporting either half's would misalign every splice in the other half.
{
std::vector<AudioSample> src(160000);
double phase = 0.0;
for (std::size_t i = 0; i < src.size(); ++i) {
phase += 2.0 * kPi / (i < 80000 ? 300.0 : 700.0);
src[i] = static_cast<AudioSample>(std::sin(phase));
}
const PeriodEstimate est = detectPeriod(src, 44100);
std::printf(" period change 300->700 -> %s (%.3f)\n", est.valid() ? "DETECTED" : "none",
est.frames);
CHECK(!est.valid());
}
// Degenerate inputs.
CHECK(!detectPeriod({}, 44100).valid());
CHECK(!detectPeriod(sineOfPeriod(120000, 441.0), 0).valid());
}
static void testAPercussiveDecayIsNotForcedIntoAPeriod() {
// Filtered noise with a fast decay — the shape of a one-shot drum hit. Nothing repeats, so
// the answer must be none rather than whatever the envelope's own length looks like.
std::vector<AudioSample> src(120000);
std::uint32_t rng = 909090u;
double lp = 0.0;
for (std::size_t i = 0; i < src.size(); ++i) {
rng = rng * 1664525u + 1013904223u;
const double n = (static_cast<double>(rng >> 8) / 8388608.0) - 1.0;
lp += 0.25 * (n - lp);
const double env = std::exp(-static_cast<double>(i % 22050) / 2000.0);
src[i] = static_cast<AudioSample>(lp * env);
}
const PeriodEstimate est = detectPeriod(src, 44100);
std::printf(" percussive decay -> %s (%.3f)\n", est.valid() ? "DETECTED" : "none",
est.frames);
CHECK(!est.valid());
}
// --- 4. Band edges and short sources -------------------------------------------------------
static void testBelowTheBandReportsNoneAndAboveItReportsAWholeMultiple() {
// Below kPeriodDetectMinHz: none. This is the load-bearing edge — such a period cannot fit
// the splice jump anyway, so an answer here would only be one the shifter must reject.
const std::vector<AudioSample> low = sineOfPeriod(200000, 44100.0 / 8.0); // 8 Hz
CHECK(!detectPeriod(low, 44100).valid());
// Above kPeriodDetectMaxHz the search floor sits well above the true period, so what comes
// back is a WHOLE MULTIPLE of it — which is still an exactly aligned splice target, since
// every multiple of a period is a period. That is why the high edge needs no special
// handling: being outside the band costs nothing, because alignment was never in question
// for a tone this short-period.
const double p = 44100.0 / 6000.0; // 7.35 frames
const PeriodEstimate high = detectPeriod(sineOfPeriod(120000, p), 44100);
std::printf(" 6 kHz (P=%.3f) -> %s (%.3f, = %.3f periods)\n", p,
high.valid() ? "detected" : "none", high.frames, high.frames / p);
if (high.valid()) {
const double n = high.frames / p;
CHECK(std::fabs(n - std::floor(n + 0.5)) < 0.02);
}
}
static void testAShortSourceShortensTheSearchRatherThanRefusing() {
// A 12000-frame one-shot cannot host a full-band probe; the search band shortens to fit and
// a 200-frame period is still found. Below that the answer is none, not a guess.
const std::vector<AudioSample> shortSrc = sineOfPeriod(12000, 200.0);
const PeriodEstimate est = detectPeriod(shortSrc, 44100);
std::printf(" 12000-frame source, P=200 -> %s (%.3f)\n", est.valid() ? "detected" : "none",
est.frames);
CHECK(est.valid());
if (est.valid()) CHECK(std::fabs(est.frames - 200.0) < 0.5);
// Too short for even the minimum lag: none.
CHECK(!detectPeriod(sineOfPeriod(40, 20.0), 44100).valid());
}
// --- 5. What the load pays ------------------------------------------------------------------
// The whole reason a detector is affordable in a sampler is that it runs ONCE, off the audio
// thread, on a source that is already fully known. This prints what that once costs, and
// asserts the property that makes it safe: the cost does NOT grow with the sample length —
// a fixed number of fixed-size probes is analysed however long the capture is. Meaningful
// only in a Release build; asserted as a RATIO so it holds at either optimization level.
static void testDetectionCostIsBoundedRegardlessOfSampleLength() {
double shortMs = 0.0, longMs = 0.0;
for (std::size_t frames : {std::size_t{220500}, std::size_t{4410000}}) { // 5 s and 100 s
const std::vector<AudioSample> src = sineOfPeriod(frames, 441.0);
const int reps = 5;
const auto t0 = std::chrono::steady_clock::now();
double guard = 0.0;
for (int r = 0; r < reps; ++r) guard += detectPeriod(src, 44100).frames;
const double ms =
1000.0 * std::chrono::duration<double>(std::chrono::steady_clock::now() - t0).count()
/ reps;
CHECK(guard > 0.0);
std::printf(" [measure] detectPeriod over %7.1f s of source: %.3f ms\n",
static_cast<double>(frames) / 44100.0, ms);
(frames == 220500 ? shortMs : longMs) = ms;
}
// 20x the source for well under 2x the cost — the probes are fixed-size and fixed in
// number, so the only length dependence left is the cache behaviour of reaching further
// into the buffer.
CHECK(longMs < shortMs * 2.0 + 0.5);
}
int main() {
testPureTonePeriodIsFoundToBetterThanATenthOfAFrame();
testTheEstimateIsInSourceFramesSoTheRateOnlyMovesTheBand();
testHarmonicRichSourceReportsTheRepeatPeriodNotAPartial();
testMissingFundamentalStillReportsTheRepeatPeriod();
testNoiseSilenceAndAPeriodChangeAllReportNone();
testAPercussiveDecayIsNotForcedIntoAPeriod();
testBelowTheBandReportsNoneAndAboveItReportsAWholeMultiple();
testAShortSourceShortensTheSearchRatherThanRefusing();
testDetectionCostIsBoundedRegardlessOfSampleLength();
if (g_fail == 0) {
std::printf("all period_detect tests passed\n");
return 0;
}
std::printf("%d period_detect check(s) failed\n", g_fail);
return 1;
}