CoopAllTheThings/tests/rate_estimator_test.cpp

// Unit test for the robust sample-rate estimator (hook/src/rate_estimator.hpp).
//
// Feeds the estimator synthetic, adversarial render cadences -- the exact failure modes
// that made the old 200 ms single-window measurement publish a bogus rate (e.g. 44100
// read as ~46205) -- and asserts the new estimator: converges to the right standard rate,
// rejects burst windows and never commits to a wrong neighbour, flags a genuinely
// non-standard rate low-confidence instead of forever spinning, and ignores idle windows.
#include <cstdint>
#include <cstdio>
#include <initializer_list>

#include "rate_estimator.hpp"

using namespace coop::hook;

namespace
{
int g_failures = 0;
void check(bool ok, const char* what)
{
	if (!ok)
	{
		std::printf("FAIL: %s\n", what);
		++g_failures;
	}
	else
	{
		std::printf("  ok: %s\n", what);
	}
}

// Drives an estimator with a controllable QPC clock. One feed per "window" (we use a
// 0.5 s step that matches the estimator's window, so each feed after the first completes
// exactly one window -- making each window's frame count individually controllable).
struct Sim
{
	RateEstimator est;
	static constexpr std::int64_t kFreq = 1'000'000; // 1 MHz (microseconds)
	std::int64_t qpc = 0;
	double frames = 0.0;

	// Advance one window (0.5 s) accumulating `rate` Hz plus `extra` burst frames, feed it.
	RateEstimate window(double rate, double extra = 0.0)
	{
		qpc += static_cast<std::int64_t>(0.5 * kFreq);
		frames += rate * 0.5 + extra;
		return est.feed(static_cast<std::uint64_t>(frames), qpc, kFreq);
	}
};

// Feed steady `rate` until done (or give up after `max` windows). Returns the result.
RateEstimate run_steady(double rate, int max = 40)
{
	Sim s;
	RateEstimate r;
	for (int i = 0; i < max; ++i)
	{
		r = s.window(rate);
		if (r.done)
		{
			return r;
		}
	}
	return r; // not done
}
} // namespace

int main()
{
	// --- snap_standard_rate: the core "reject non-standard" rule -----------------
	check(snap_standard_rate(44100.0) == 44100, "snap exact 44100");
	check(snap_standard_rate(48000.0) == 48000, "snap exact 48000");
	check(snap_standard_rate(44100.0 * 1.015) == 44100, "snap 44100 within +1.5%");
	check(snap_standard_rate(96000.0 * 0.99) == 96000, "snap 96000 within -1%");
	// 46205 is the real-world bogus reading: it sits between 44100 and 48000 and must NOT
	// snap to either (this is why the new estimator rejects it instead of publishing it).
	check(snap_standard_rate(46205.0) == 0, "46205 snaps to nothing (the old bug value)");
	check(snap_standard_rate(45000.0) == 0, "45000 (non-standard) snaps to nothing");

	// --- steady standard rates converge, confidently -----------------------------
	for (double rate : {44100.0, 48000.0, 96000.0, 22050.0})
	{
		const RateEstimate r = run_steady(rate);
		check(r.done && r.confident && r.rate == static_cast<std::uint32_t>(rate),
		      "steady rate converges confidently");
		if (!(r.done && r.rate == static_cast<std::uint32_t>(rate)))
		{
			std::printf("    (rate=%.0f -> done=%d confident=%d got=%u)\n", rate, r.done, r.confident, r.rate);
		}
	}

	// --- realistic jitter: 44100 with a small per-window wobble still snaps -------
	{
		Sim s;
		RateEstimate r;
		const double wobble[] = {+150.0, -120.0, +90.0, -150.0, +60.0, -90.0, +130.0, -40.0};
		for (int i = 0; i < 30 && !r.done; ++i)
		{
			r = s.window(44100.0, wobble[i % 8]); // ~0.3% jitter, within the snap band
		}
		check(r.done && r.confident && r.rate == 44100, "44100 with small jitter -> 44100 confident");
	}

	// --- a burst window can't decide the rate (consensus rejects it) -------------
	// Inflate a single window enough to read as 48000 (true is 44100); the surrounding
	// clean windows must still win, proving one burst never commits to the wrong rate.
	{
		Sim s;
		(void)s.window(44100.0); // window 1: discarded (warm-up)
		// window 2: burst -- 0.5 s of 48000 instead of 44100 (extra ~1950 frames) -> reads 48000.
		const RateEstimate burst = s.window(44100.0, (48000.0 - 44100.0) * 0.5);
		check(!burst.done, "single burst window does not commit");
		// windows 3..N: clean 44100 -> consensus on 44100.
		RateEstimate r = burst;
		for (int i = 0; i < 10 && !r.done; ++i)
		{
			r = s.window(44100.0);
		}
		check(r.done && r.confident && r.rate == 44100, "burst rejected; converges to 44100, not 48000");
	}

	// --- a genuinely non-standard rate ends as low-confidence, not a spin ---------
	{
		const RateEstimate r = run_steady(45000.0, 40);
		check(r.done && !r.confident, "non-standard 45000 -> done but LOW-confidence");
		check(r.rate >= 44600 && r.rate <= 45400, "low-confidence estimate is ~45000");
		if (r.done)
		{
			std::printf("    (45000 -> confident=%d rate=%u)\n", r.confident, r.rate);
		}
	}

	// --- idle windows never yield a bogus rate, then real audio converges --------
	{
		Sim s;
		RateEstimate r;
		for (int i = 0; i < 6; ++i)
		{
			r = s.window(0.0); // silent: no frames advance
			check(!r.done, "idle window never commits");
		}
		for (int i = 0; i < 12 && !r.done; ++i)
		{
			r = s.window(48000.0); // audio resumes
		}
		check(r.done && r.confident && r.rate == 48000, "after idle, real audio converges to 48000");
	}

	if (g_failures == 0)
	{
		std::printf("PASS rate_estimator_test\n");
		return 0;
	}
	std::printf("FAILED rate_estimator_test (%d)\n", g_failures);
	return 1;
}