T13: NativeMixer mirror server pipeline (track gain/pan constant-power + brickwall limiter tanh, wired VST2/VST3 bridge, golden test 0.0001dB)

native_host/NativeMixer.h

@@ -0,0 +1,54 @@
+// NativeMixer.h — track gain/pan + master brickwall limiter (T13).
+//
+// MIRROR server render pipeline (`app/core/render_engine.py` track volume/pan
+// + `app/core/mastering_engine.py` _apply_limiter):
+// - track gain: 10^(dB/20)
+// - pan constant-power: theta = ((pan+1)/2)*pi/2, L *= cos(theta), R *= sin(theta)
+//   (pan == 0 -> unity, khong nhan — dung nhu render_engine.py)
+// - master: tong cac track (processInPlace ap dung gain/pan roi limiter)
+// - brickwall limiter: t_lin = 10^(thresholdDb/20) (clamp -24..0, default -1);
+//   k = 1/max(0.02, t_lin); tk = tanh(k); out = tanh(x*k)/tk; roi hard clip [-1,1]
+//   (clip giong render_project sau apply_mastering).
+//
+// Audio thread an toan: chi setTrack/setLimiter tu UI thread truoc khi
+// AudioStart; processInPlace doc state da set, khong lock, khong cap phat.
+#pragma once
+#include <cstdint>
+#include <cmath>
+
+namespace sonicforge {
+
+using int32 = int32_t;
+
+struct TrackGainPan
+{
+    float gainLin = 1.0f; // 10^(dB/20)
+    float panL = 1.0f;    // cos(theta)
+    float panR = 1.0f;    // sin(theta)
+
+    static TrackGainPan fromDbPan (float gainDb, float pan);
+};
+
+class NativeMixer
+{
+public:
+    // gainDb: -inf..+inf dB; pan: -1..+1 (clamp). Mirrors render_engine.py.
+    void setTrack (const TrackGainPan& t) { m_track = t; }
+
+    // thresholdDb clamp -24..0, NaN -> -1 (mirror _clamp trong mastering_engine).
+    void setLimiter (bool active, float thresholdDb);
+
+    // Ap track gain/pan vao buffer roi (neu active) limiter + hard clip [-1,1]
+    // ngay tai buffer (in-place). frames > 0.
+    void processInPlace (float* outL, float* outR, int32 frames) const;
+
+    bool limiterActive () const { return m_limActive; }
+
+private:
+    TrackGainPan m_track;
+    bool m_limActive = false;
+    float m_limK = 1.0f;   // 1/max(0.02, t_lin)
+    float m_limTk = 1.0f;  // tanh(k)
+};
+
+} // namespace sonicforge