MidSide.h

// DSPark - Professional Audio DSP Framework
// Copyright (c) 2026 Cristian Moresi - MIT License
 
#pragma once
 
#include "../Core/AudioBuffer.h"
 
#include <cassert>
 
// DSPARK_RESTRICT is normally provided by SimdOps.h (via AudioBuffer.h).
// Guard against redefinition so this header stays self-contained if included alone.
#ifndef DSPARK_RESTRICT
  #if defined(__clang__) || defined(__GNUC__)
    #define DSPARK_RESTRICT __restrict__
  #elif defined(_MSC_VER)
    #define DSPARK_RESTRICT __restrict
  #else
    #define DSPARK_RESTRICT
  #endif
#endif
 
namespace dspark {
 
template <typename T>
struct MidSide
{
    static constexpr void encodeSample(T& left_mid, T& right_side) noexcept
    {
        const T l = left_mid;
        const T r = right_side;
        left_mid   = (l + r) * T(0.5);
        right_side = (l - r) * T(0.5);
    }
 
    static constexpr void decodeSample(T& mid_left, T& side_right) noexcept
    {
        const T m = mid_left;
        const T s = side_right;
        mid_left   = m + s;
        side_right = m - s;
    }
 
    static void encode(AudioBufferView<T> buffer) noexcept
    {
        assert(buffer.getNumChannels() >= 2);
 
        const int n = buffer.getNumSamples();
        if (buffer.getNumChannels() < 2 || n <= 0) return; // Release-safe
 
        T* DSPARK_RESTRICT left  = buffer.getChannel(0);
        T* DSPARK_RESTRICT right = buffer.getChannel(1);
 
        for (int i = 0; i < n; ++i)
        {
            const T l = left[i];
            const T r = right[i];
            left[i]  = (l + r) * T(0.5); // Mid
            right[i] = (l - r) * T(0.5); // Side
        }
    }
 
    static void decode(AudioBufferView<T> buffer) noexcept
    {
        assert(buffer.getNumChannels() >= 2);
 
        const int n = buffer.getNumSamples();
        if (buffer.getNumChannels() < 2 || n <= 0) return; // Release-safe
 
        T* DSPARK_RESTRICT mid  = buffer.getChannel(0);
        T* DSPARK_RESTRICT side = buffer.getChannel(1);
 
        for (int i = 0; i < n; ++i)
        {
            const T m = mid[i];
            const T s = side[i];
            mid[i]  = m + s; // Left
            side[i] = m - s; // Right
        }
    }
};
 
} // namespace dspark