Function testStereoLinked

tests/client_comp_test.cpp:277–326

Stereo linking: max(|L|,|R|) drives envelope, and the same gain is applied to both. Feed L-only signal and check R remains silent (no cross-channel leakage) but the L channel is still compressed.

// applied to both. Feed L-only signal and check R remains silent (no
// cross-channel leakage) but the L channel is still compressed.
void testStereoLinked()
{
    ClientComp comp;
    comp.prepare(kSampleRate);
    comp.setEnabled(true);
    comp.setThresholdDb(-20.0f);
    comp.setRatio(4.0f);
    comp.setKneeDb(0.0f);
    comp.setMakeupDb(0.0f);
    comp.setLimiterEnabled(false);

    const int frames = static_cast<int>(kSampleRate);
    std::vector<float> buf(frames * 2, 0.0f);
    const float amp = 0.5f;
    const double twoPi = 6.283185307179586476;
    for (int i = 0; i < frames; ++i) {
        buf[i * 2]     = amp * static_cast<float>(
            std::sin(twoPi * 1000.0 * i / kSampleRate));
        buf[i * 2 + 1] = 0.0f;  // R silent
    }

    // Warmup
    std::vector<float> warm(frames * 2, 0.0f);
    for (int i = 0; i < frames; ++i) {
        warm[i * 2] = amp * static_cast<float>(
            std::sin(twoPi * 1000.0 * i / kSampleRate));
    }
    processBlocks(comp, warm.data(), frames);

    processBlocks(comp, buf.data(), frames);

    // R channel should stay exactly zero (no cross-talk).
    float rPeak = 0.0f;
    for (int i = 0; i < frames; ++i) {
        rPeak = std::max(rPeak, std::fabs(buf[i * 2 + 1]));
    }
    // L channel should show compression (< input amplitude).
    float lPeak = 0.0f;
    for (int i = 0; i < frames; ++i) {
        lPeak = std::max(lPeak, std::fabs(buf[i * 2]));
    }

    report("stereo-linked: R stays silent when only L is active",
           rPeak < 1e-6f,
           "R peak=" + std::to_string(rPeak));
    report("stereo-linked: L channel still compressed",
           lPeak < amp * 0.95f,
           "L peak=" + std::to_string(lPeak)
               + " (input=" + std::to_string(amp) + ")");
}

// Attack timing: envelope should reach ~63 % of step in τ ms.
// Drive silence → 0.5 amp step, sample GR shortly after the step.