melonDS/src/SPU.cpp

/*
    Copyright 2016-2024 melonDS team

    This file is part of melonDS.

    melonDS is free software: you can redistribute it and/or modify it under
    the terms of the GNU General Public License as published by the Free
    Software Foundation, either version 3 of the License, or (at your option)
    any later version.

    melonDS is distributed in the hope that it will be useful, but WITHOUT ANY
    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with melonDS. If not, see http://www.gnu.org/licenses/.
*/

#include <stdio.h>
#include <string.h>
#include <cmath>
#include "Platform.h"
#include "NDS.h"
#include "DSi.h"
#include "SPU.h"

namespace melonDS
{
using Platform::Log;
using Platform::LogLevel;


// SPU TODO
// * capture addition modes, overflow bugs
// * channel hold


const s8 SPUChannel::ADPCMIndexTable[8] = {-1, -1, -1, -1, 2, 4, 6, 8};

const u16 SPUChannel::ADPCMTable[89] =
{
    0x0007, 0x0008, 0x0009, 0x000A, 0x000B, 0x000C, 0x000D, 0x000E,
    0x0010, 0x0011, 0x0013, 0x0015, 0x0017, 0x0019, 0x001C, 0x001F,
    0x0022, 0x0025, 0x0029, 0x002D, 0x0032, 0x0037, 0x003C, 0x0042,
    0x0049, 0x0050, 0x0058, 0x0061, 0x006B, 0x0076, 0x0082, 0x008F,
    0x009D, 0x00AD, 0x00BE, 0x00D1, 0x00E6, 0x00FD, 0x0117, 0x0133,
    0x0151, 0x0173, 0x0198, 0x01C1, 0x01EE, 0x0220, 0x0256, 0x0292,
    0x02D4, 0x031C, 0x036C, 0x03C3, 0x0424, 0x048E, 0x0502, 0x0583,
    0x0610, 0x06AB, 0x0756, 0x0812, 0x08E0, 0x09C3, 0x0ABD, 0x0BD0,
    0x0CFF, 0x0E4C, 0x0FBA, 0x114C, 0x1307, 0x14EE, 0x1706, 0x1954,
    0x1BDC, 0x1EA5, 0x21B6, 0x2515, 0x28CA, 0x2CDF, 0x315B, 0x364B,
    0x3BB9, 0x41B2, 0x4844, 0x4F7E, 0x5771, 0x602F, 0x69CE, 0x7462,
    0x7FFF
};

const s16 SPUChannel::PSGTable[8][8] =
{
    {-0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF,  0x7FFF},
    {-0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF,  0x7FFF,  0x7FFF},
    {-0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF},
    {-0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF},
    {-0x7FFF, -0x7FFF, -0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF},
    {-0x7FFF, -0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF},
    {-0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF,  0x7FFF},
    {-0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF, -0x7FFF}
};

template <typename T>
constexpr T ipow(T num, unsigned int pow)
{
    T product = 1;
    for (int i = 0; i < pow; ++i)
    {
        product *= num;
    }

    return product;
}

template <typename T>
constexpr T factorial(T num)
{
    T product = 1;
    for (T i = 1; i <= num; ++i)
    {
        product *= i;
    }

    return product;
}

// We can't use std::cos in constexpr functions until C++26,
// so we need to compute the cosine ourselves with the Taylor series.
// Code adapted from https://prosepoetrycode.potterpcs.net/2015/07/a-simple-constexpr-power-function-c/
template <int Iterations = 10>
constexpr double cosine (double theta)
{
    return (ipow(-1, Iterations) * ipow(theta, 2 * Iterations)) /
            static_cast<double>(factorial(2ull * Iterations))
        + cosine<Iterations-1>(theta);
}

template <>
constexpr double cosine<0> (double theta)
{
    return 1.0;
}

// generate interpolation tables
// values are 1:1:14 fixed-point
constexpr std::array<s16, 0x100> InterpCos = []() constexpr {
    std::array<s16, 0x100> interp {};

    for (int i = 0; i < 0x100; i++)
    {
        float ratio = (i * M_PI) / 255.0f;
        ratio = 1.0f - cosine(ratio);

        interp[i] = (s16)(ratio * 0x2000);
    }

    return interp;
}();

constexpr array2d<s16, 0x100, 4> InterpCubic = []() constexpr {
    array2d<s16, 0x100, 4> interp {};

    for (int i = 0; i < 0x100; i++)
    {
        s32 i1 = i << 6;
        s32 i2 = (i * i) >> 2;
        s32 i3 = (i * i * i) >> 10;

        interp[i][0] = -i3 + 2*i2 - i1;
        interp[i][1] = i3 - 2*i2 + 0x4000;
        interp[i][2] = -i3 + i2 + i1;
        interp[i][3] = i3 - i2;
    }

    return interp;
}();

const std::array<s16, 0x200> InterpSNESGauss = {
    0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
    0x001, 0x001, 0x001, 0x001, 0x001, 0x001, 0x001, 0x001, 0x001, 0x001, 0x001, 0x002, 0x002, 0x002, 0x002, 0x002,
    0x002, 0x002, 0x003, 0x003, 0x003, 0x003, 0x003, 0x004, 0x004, 0x004, 0x004, 0x004, 0x005, 0x005, 0x005, 0x005,
    0x006, 0x006, 0x006, 0x006, 0x007, 0x007, 0x007, 0x008, 0x008, 0x008, 0x009, 0x009, 0x009, 0x00A, 0x00A, 0x00A,
    0x00B, 0x00B, 0x00B, 0x00C, 0x00C, 0x00D, 0x00D, 0x00E, 0x00E, 0x00F, 0x00F, 0x00F, 0x010, 0x010, 0x011, 0x011,
    0x012, 0x013, 0x013, 0x014, 0x014, 0x015, 0x015, 0x016, 0x017, 0x017, 0x018, 0x018, 0x019, 0x01A, 0x01B, 0x01B,
    0x01C, 0x01D, 0x01D, 0x01E, 0x01F, 0x020, 0x020, 0x021, 0x022, 0x023, 0x024, 0x024, 0x025, 0x026, 0x027, 0x028,
    0x029, 0x02A, 0x02B, 0x02C, 0x02D, 0x02E, 0x02F, 0x030, 0x031, 0x032, 0x033, 0x034, 0x035, 0x036, 0x037, 0x038,
    0x03A, 0x03B, 0x03C, 0x03D, 0x03E, 0x040, 0x041, 0x042, 0x043, 0x045, 0x046, 0x047, 0x049, 0x04A, 0x04C, 0x04D,
    0x04E, 0x050, 0x051, 0x053, 0x054, 0x056, 0x057, 0x059, 0x05A, 0x05C, 0x05E, 0x05F, 0x061, 0x063, 0x064, 0x066,
    0x068, 0x06A, 0x06B, 0x06D, 0x06F, 0x071, 0x073, 0x075, 0x076, 0x078, 0x07A, 0x07C, 0x07E, 0x080, 0x082, 0x084,
    0x086, 0x089, 0x08B, 0x08D, 0x08F, 0x091, 0x093, 0x096, 0x098, 0x09A, 0x09C, 0x09F, 0x0A1, 0x0A3, 0x0A6, 0x0A8,
    0x0AB, 0x0AD, 0x0AF, 0x0B2, 0x0B4, 0x0B7, 0x0BA, 0x0BC, 0x0BF, 0x0C1, 0x0C4, 0x0C7, 0x0C9, 0x0CC, 0x0CF, 0x0D2,
    0x0D4, 0x0D7, 0x0DA, 0x0DD, 0x0E0, 0x0E3, 0x0E6, 0x0E9, 0x0EC, 0x0EF, 0x0F2, 0x0F5, 0x0F8, 0x0FB, 0x0FE, 0x101,
    0x104, 0x107, 0x10B, 0x10E, 0x111, 0x114, 0x118, 0x11B, 0x11E, 0x122, 0x125, 0x129, 0x12C, 0x130, 0x133, 0x137,
    0x13A, 0x13E, 0x141, 0x145, 0x148, 0x14C, 0x150, 0x153, 0x157, 0x15B, 0x15F, 0x162, 0x166, 0x16A, 0x16E, 0x172,
    0x176, 0x17A, 0x17D, 0x181, 0x185, 0x189, 0x18D, 0x191, 0x195, 0x19A, 0x19E, 0x1A2, 0x1A6, 0x1AA, 0x1AE, 0x1B2,
    0x1B7, 0x1BB, 0x1BF, 0x1C3, 0x1C8, 0x1CC, 0x1D0, 0x1D5, 0x1D9, 0x1DD, 0x1E2, 0x1E6, 0x1EB, 0x1EF, 0x1F3, 0x1F8,
    0x1FC, 0x201, 0x205, 0x20A, 0x20F, 0x213, 0x218, 0x21C, 0x221, 0x226, 0x22A, 0x22F, 0x233, 0x238, 0x23D, 0x241,
    0x246, 0x24B, 0x250, 0x254, 0x259, 0x25E, 0x263, 0x267, 0x26C, 0x271, 0x276, 0x27B, 0x280, 0x284, 0x289, 0x28E,
    0x293, 0x298, 0x29D, 0x2A2, 0x2A6, 0x2AB, 0x2B0, 0x2B5, 0x2BA, 0x2BF, 0x2C4, 0x2C9, 0x2CE, 0x2D3, 0x2D8, 0x2DC,
    0x2E1, 0x2E6, 0x2EB, 0x2F0, 0x2F5, 0x2FA, 0x2FF, 0x304, 0x309, 0x30E, 0x313, 0x318, 0x31D, 0x322, 0x326, 0x32B,
    0x330, 0x335, 0x33A, 0x33F, 0x344, 0x349, 0x34E, 0x353, 0x357, 0x35C, 0x361, 0x366, 0x36B, 0x370, 0x374, 0x379,
    0x37E, 0x383, 0x388, 0x38C, 0x391, 0x396, 0x39B, 0x39F, 0x3A4, 0x3A9, 0x3AD, 0x3B2, 0x3B7, 0x3BB, 0x3C0, 0x3C5,
    0x3C9, 0x3CE, 0x3D2, 0x3D7, 0x3DC, 0x3E0, 0x3E5, 0x3E9, 0x3ED, 0x3F2, 0x3F6, 0x3FB, 0x3FF, 0x403, 0x408, 0x40C,
    0x410, 0x415, 0x419, 0x41D, 0x421, 0x425, 0x42A, 0x42E, 0x432, 0x436, 0x43A, 0x43E, 0x442, 0x446, 0x44A, 0x44E,
    0x452, 0x455, 0x459, 0x45D, 0x461, 0x465, 0x468, 0x46C, 0x470, 0x473, 0x477, 0x47A, 0x47E, 0x481, 0x485, 0x488,
    0x48C, 0x48F, 0x492, 0x496, 0x499, 0x49C, 0x49F, 0x4A2, 0x4A6, 0x4A9, 0x4AC, 0x4AF, 0x4B2, 0x4B5, 0x4B7, 0x4BA,
    0x4BD, 0x4C0, 0x4C3, 0x4C5, 0x4C8, 0x4CB, 0x4CD, 0x4D0, 0x4D2, 0x4D5, 0x4D7, 0x4D9, 0x4DC, 0x4DE, 0x4E0, 0x4E3,
    0x4E5, 0x4E7, 0x4E9, 0x4EB, 0x4ED, 0x4EF, 0x4F1, 0x4F3, 0x4F5, 0x4F6, 0x4F8, 0x4FA, 0x4FB, 0x4FD, 0x4FF, 0x500,
    0x502, 0x503, 0x504, 0x506, 0x507, 0x508, 0x50A, 0x50B, 0x50C, 0x50D, 0x50E, 0x50F, 0x510, 0x511, 0x511, 0x512,
    0x513, 0x514, 0x514, 0x515, 0x516, 0x516, 0x517, 0x517, 0x517, 0x518, 0x518, 0x518, 0x518, 0x518, 0x519, 0x519
};

SPU::SPU(melonDS::NDS& nds, AudioBitDepth bitdepth, AudioInterpolation interpolation) :
    NDS(nds),
    Channels {
        SPUChannel(0, nds, interpolation),
        SPUChannel(1, nds, interpolation),
        SPUChannel(2, nds, interpolation),
        SPUChannel(3, nds, interpolation),
        SPUChannel(4, nds, interpolation),
        SPUChannel(5, nds, interpolation),
        SPUChannel(6, nds, interpolation),
        SPUChannel(7, nds, interpolation),
        SPUChannel(8, nds, interpolation),
        SPUChannel(9, nds, interpolation),
        SPUChannel(10, nds, interpolation),
        SPUChannel(11, nds, interpolation),
        SPUChannel(12, nds, interpolation),
        SPUChannel(13, nds, interpolation),
        SPUChannel(14, nds, interpolation),
        SPUChannel(15, nds, interpolation),
    },
    Capture {
        SPUCaptureUnit(0, nds),
        SPUCaptureUnit(1, nds),
    },
    AudioLock(Platform::Mutex_Create()),
    Degrade10Bit(bitdepth == AudioBitDepth::_10Bit || (nds.ConsoleType == 1 && bitdepth == AudioBitDepth::Auto))
{
    NDS.RegisterEventFunc(Event_SPU, 0, MemberEventFunc(SPU, Mix));

    ApplyBias = true;
    Degrade10Bit = false;

    memset(OutputFrontBuffer, 0, 2*OutputBufferSize*2);

    OutputBackbufferWritePosition = 0;
    OutputFrontBufferReadPosition = 0;
    OutputFrontBufferWritePosition = 0;
}

SPU::~SPU()
{
    Platform::Mutex_Free(AudioLock);
    AudioLock = nullptr;

    NDS.UnregisterEventFunc(Event_SPU, 0);
}

void SPU::Reset()
{
    InitOutput();

    Cnt = 0;
    MasterVolume = 0;
    Bias = 0;

    for (int i = 0; i < 16; i++)
        Channels[i].Reset();

    Capture[0].Reset();
    Capture[1].Reset();

    NDS.ScheduleEvent(Event_SPU, false, 1024, 0, 0);
}

void SPU::Stop()
{
    Platform::Mutex_Lock(AudioLock);
    memset(OutputFrontBuffer, 0, 2*OutputBufferSize*2);

    OutputBackbufferWritePosition = 0;
    OutputFrontBufferReadPosition = 0;
    OutputFrontBufferWritePosition = 0;
    Platform::Mutex_Unlock(AudioLock);
}

void SPU::DoSavestate(Savestate* file)
{
    file->Section("SPU.");

    file->Var16(&Cnt);
    file->Var8(&MasterVolume);
    file->Var16(&Bias);

    for (SPUChannel& channel : Channels)
        channel.DoSavestate(file);

    for (SPUCaptureUnit& capture : Capture)
        capture.DoSavestate(file);
}


void SPU::SetPowerCnt(u32 val)
{
    // TODO
}


void SPU::SetInterpolation(AudioInterpolation type)
{
    for (SPUChannel& channel : Channels)
        channel.InterpType = type;
}

void SPU::SetBias(u16 bias)
{
    Bias = bias;
}

void SPU::SetApplyBias(bool enable)
{
    ApplyBias = enable;
}

void SPU::SetDegrade10Bit(bool enable)
{
    Degrade10Bit = enable;
}

void SPU::SetDegrade10Bit(AudioBitDepth depth)
{
    switch (depth)
    {
    case AudioBitDepth::Auto:
        Degrade10Bit = (NDS.ConsoleType == 0);
        break;
    case AudioBitDepth::_10Bit:
        Degrade10Bit = true;
        break;
    case AudioBitDepth::_16Bit:
        Degrade10Bit = false;
        break;
    }
}

SPUChannel::SPUChannel(u32 num, melonDS::NDS& nds, AudioInterpolation interpolation) :
    NDS(nds),
    Num(num),
    InterpType(interpolation)
{
}

void SPUChannel::Reset()
{
    KeyOn = false;

    SetCnt(0);
    SrcAddr = 0;
    TimerReload = 0;
    LoopPos = 0;
    Length = 0;

    Timer = 0;

    Pos = 0;
    FIFOReadPos = 0;
    FIFOWritePos = 0;
    FIFOReadOffset = 0;
    FIFOLevel = 0;
}

void SPUChannel::DoSavestate(Savestate* file)
{
    file->Var32(&Cnt);
    file->Var32(&SrcAddr);
    file->Var16(&TimerReload);
    file->Var32(&LoopPos);
    file->Var32(&Length);

    file->Var8(&Volume);
    file->Var8(&VolumeShift);
    file->Var8(&Pan);

    file->Var8((u8*)&KeyOn);
    file->Var32(&Timer);
    file->Var32((u32*)&Pos);
    file->VarArray(PrevSample, sizeof(PrevSample));
    file->Var16((u16*)&CurSample);
    file->Var16(&NoiseVal);

    file->Var32((u32*)&ADPCMVal);
    file->Var32((u32*)&ADPCMIndex);
    file->Var32((u32*)&ADPCMValLoop);
    file->Var32((u32*)&ADPCMIndexLoop);
    file->Var8(&ADPCMCurByte);

    file->Var32(&FIFOReadPos);
    file->Var32(&FIFOWritePos);
    file->Var32(&FIFOReadOffset);
    file->Var32(&FIFOLevel);
    file->VarArray(FIFO, sizeof(FIFO));
}

void SPUChannel::FIFO_BufferData()
{
    u32 totallen = LoopPos + Length;

    if (FIFOReadOffset >= totallen)
    {
        u32 repeatmode = (Cnt >> 27) & 0x3;
        if      (repeatmode & 1) FIFOReadOffset = LoopPos;
        else if (repeatmode & 2) return; // one-shot sound, we're done
    }

    u32 burstlen = 16;
    if ((FIFOReadOffset + 16) > totallen)
        burstlen = totallen - FIFOReadOffset;

    // sound DMA can't read from the ARM7 BIOS
    if ((SrcAddr + FIFOReadOffset) >= 0x00004000)
    {
        for (u32 i = 0; i < burstlen; i += 4)
        {
            FIFO[FIFOWritePos] = NDS.ARM7Read32(SrcAddr + FIFOReadOffset);
            FIFOReadOffset += 4;
            FIFOWritePos++;
            FIFOWritePos &= 0x7;
        }
    }
    else
    {
        for (u32 i = 0; i < burstlen; i += 4)
        {
            FIFO[FIFOWritePos] = 0;
            FIFOReadOffset += 4;
            FIFOWritePos++;
            FIFOWritePos &= 0x7;
        }
    }

    FIFOLevel += burstlen;
}

template<typename T>
T SPUChannel::FIFO_ReadData()
{
    T ret = *(T*)&((u8*)FIFO)[FIFOReadPos];

    FIFOReadPos += sizeof(T);
    FIFOReadPos &= 0x1F;
    FIFOLevel -= sizeof(T);

    if (FIFOLevel <= 16)
        FIFO_BufferData();

    return ret;
}

void SPUChannel::Start()
{
    Timer = TimerReload;

    if (((Cnt >> 29) & 0x3) == 3)
        Pos = -1;
    else
        Pos = -3;

    NoiseVal = 0x7FFF;
    PrevSample[0] = 0;
    PrevSample[1] = 0;
    PrevSample[2] = 0;
    CurSample = 0;

    FIFOReadPos = 0;
    FIFOWritePos = 0;
    FIFOReadOffset = 0;
    FIFOLevel = 0;

    // when starting a channel, buffer data
    if (((Cnt >> 29) & 0x3) != 3)
    {
        FIFO_BufferData();
        FIFO_BufferData();
    }
}

void SPUChannel::NextSample_PCM8()
{
    Pos++;
    if (Pos < 0) return;
    if (Pos >= (LoopPos + Length))
    {
        u32 repeat = (Cnt >> 27) & 0x3;
        if (repeat & 1)
        {
            Pos = LoopPos;
        }
        else if (repeat & 2)
        {
            CurSample = 0;
            Cnt &= ~(1<<31);
            return;
        }
    }

    s8 val = FIFO_ReadData<s8>();
    CurSample = val << 8;
}

void SPUChannel::NextSample_PCM16()
{
    Pos++;
    if (Pos < 0) return;
    if ((Pos<<1) >= (LoopPos + Length))
    {
        u32 repeat = (Cnt >> 27) & 0x3;
        if (repeat & 1)
        {
            Pos = LoopPos>>1;
        }
        else if (repeat & 2)
        {
            CurSample = 0;
            Cnt &= ~(1<<31);
            return;
        }
    }

    s16 val = FIFO_ReadData<s16>();
    CurSample = val;
}

void SPUChannel::NextSample_ADPCM()
{
    Pos++;
    if (Pos < 8)
    {
        if (Pos == 0)
        {
            // setup ADPCM
            u32 header = FIFO_ReadData<u32>();
            ADPCMVal = (s32)(s16)(header & 0xFFFF);
            ADPCMIndex = (header >> 16) & 0x7F;
            if (ADPCMIndex > 88) ADPCMIndex = 88;

            ADPCMValLoop = ADPCMVal;
            ADPCMIndexLoop = ADPCMIndex;
        }

        return;
    }

    if ((Pos>>1) >= (LoopPos + Length))
    {
        u32 repeat = (Cnt >> 27) & 0x3;
        if (repeat & 1)
        {
            Pos = LoopPos<<1;
            ADPCMVal = ADPCMValLoop;
            ADPCMIndex = ADPCMIndexLoop;
            ADPCMCurByte = FIFO_ReadData<u8>();
        }
        else if (repeat & 2)
        {
            CurSample = 0;
            Cnt &= ~(1<<31);
            return;
        }
    }
    else
    {
        if (!(Pos & 0x1))
            ADPCMCurByte = FIFO_ReadData<u8>();
        else
            ADPCMCurByte >>= 4;

        u16 val = ADPCMTable[ADPCMIndex];
        u16 diff = val >> 3;
        if (ADPCMCurByte & 0x1) diff += (val >> 2);
        if (ADPCMCurByte & 0x2) diff += (val >> 1);
        if (ADPCMCurByte & 0x4) diff += val;

        if (ADPCMCurByte & 0x8)
        {
            ADPCMVal -= diff;
            if (ADPCMVal < -0x7FFF) ADPCMVal = -0x7FFF;
        }
        else
        {
            ADPCMVal += diff;
            if (ADPCMVal > 0x7FFF) ADPCMVal = 0x7FFF;
        }

        ADPCMIndex += ADPCMIndexTable[ADPCMCurByte & 0x7];
        if      (ADPCMIndex < 0)  ADPCMIndex = 0;
        else if (ADPCMIndex > 88) ADPCMIndex = 88;

        if (Pos == (LoopPos<<1))
        {
            ADPCMValLoop = ADPCMVal;
            ADPCMIndexLoop = ADPCMIndex;
        }
    }

    CurSample = ADPCMVal;
}

void SPUChannel::NextSample_PSG()
{
    Pos++;
    CurSample = PSGTable[(Cnt >> 24) & 0x7][Pos & 0x7];
}

void SPUChannel::NextSample_Noise()
{
    if (NoiseVal & 0x1)
    {
        NoiseVal = (NoiseVal >> 1) ^ 0x6000;
        CurSample = -0x7FFF;
    }
    else
    {
        NoiseVal >>= 1;
        CurSample = 0x7FFF;
    }
}

template<u32 type>
s32 SPUChannel::Run()
{
    if (!(Cnt & (1<<31))) return 0;

    if ((type < 3) && ((Length+LoopPos) < 16)) return 0;

    if (KeyOn)
    {
        Start();
        KeyOn = false;
    }

    Timer += 512; // 1 sample = 512 cycles at 16MHz

    while (Timer >> 16)
    {
        Timer = TimerReload + (Timer - 0x10000);

        // for optional interpolation: save previous samples
        // the interpolated audio will be delayed by a couple samples,
        // but it's easier to deal with this way
        if ((type < 3) && (InterpType != AudioInterpolation::None))
        {
            PrevSample[2] = PrevSample[1];
            PrevSample[1] = PrevSample[0];
            PrevSample[0] = CurSample;
        }

        switch (type)
        {
        case 0: NextSample_PCM8(); break;
        case 1: NextSample_PCM16(); break;
        case 2: NextSample_ADPCM(); break;
        case 3: NextSample_PSG(); break;
        case 4: NextSample_Noise(); break;
        }
    }

    s32 val = (s32)CurSample;

    // interpolation (emulation improvement, not a hardware feature)
    if ((type < 3) && (InterpType != AudioInterpolation::None))
    {
        s32 samplepos = ((Timer - TimerReload) * 0x100) / (0x10000 - TimerReload);
        if (samplepos > 0xFF) samplepos = 0xFF;

        switch (InterpType)
        {
        case AudioInterpolation::Linear:
            val = ((val           * samplepos) +
                   (PrevSample[0] * (0xFF-samplepos))) >> 8;
            break;

        case AudioInterpolation::Cosine:
            val = ((val           * InterpCos[samplepos]) +
                   (PrevSample[0] * InterpCos[0xFF-samplepos])) >> 14;
            break;

        case AudioInterpolation::Cubic:
            val = ((PrevSample[2] * InterpCubic[samplepos][0]) +
                   (PrevSample[1] * InterpCubic[samplepos][1]) +
                   (PrevSample[0] * InterpCubic[samplepos][2]) +
                   (val           * InterpCubic[samplepos][3])) >> 14;
            break;

        case AudioInterpolation::SNESGaussian: {
                // Avoid clipping (from fullsnes)
#define CLAMP(s) (std::clamp((s) >> 1, -0x3FFA, 0x3FF8))
                s32 out =    (InterpSNESGauss[0x0FF - samplepos] * CLAMP(PrevSample[2]) >> 10);
                out = out + ((InterpSNESGauss[0x1FF - samplepos] * CLAMP(PrevSample[1])) >> 10);
                out = out + ((InterpSNESGauss[0x100 + samplepos] * CLAMP(PrevSample[0])) >> 10);
                out = out + ((InterpSNESGauss[0x000 + samplepos] * CLAMP(val)) >> 10);
                val = std::clamp(out, -0x8000, 0x7FFF);
#undef CLAMP
                break;
            }

        default:
            break;
        }
    }

    val <<= VolumeShift;
    val *= Volume;
    return val;
}

void SPUChannel::PanOutput(s32 in, s32& left, s32& right)
{
    left += ((s64)in * (128-Pan)) >> 10;
    right += ((s64)in * Pan) >> 10;
}


SPUCaptureUnit::SPUCaptureUnit(u32 num, melonDS::NDS& nds) : NDS(nds), Num(num)
{
}

void SPUCaptureUnit::Reset()
{
    SetCnt(0);
    DstAddr = 0;
    TimerReload = 0;
    Length = 0;

    Timer = 0;

    Pos = 0;
    FIFOReadPos = 0;
    FIFOWritePos = 0;
    FIFOWriteOffset = 0;
    FIFOLevel = 0;
}

void SPUCaptureUnit::DoSavestate(Savestate* file)
{
    file->Var8(&Cnt);
    file->Var32(&DstAddr);
    file->Var16(&TimerReload);
    file->Var32(&Length);

    file->Var32(&Timer);
    file->Var32((u32*)&Pos);

    file->Var32(&FIFOReadPos);
    file->Var32(&FIFOWritePos);
    file->Var32(&FIFOWriteOffset);
    file->Var32(&FIFOLevel);
    file->VarArray(FIFO, 4*4);
}

void SPUCaptureUnit::FIFO_FlushData()
{
    for (u32 i = 0; i < 4; i++)
    {
        NDS.ARM7Write32(DstAddr + FIFOWriteOffset, FIFO[FIFOReadPos]);
        // Calls the NDS or DSi version, depending on the class

        FIFOReadPos++;
        FIFOReadPos &= 0x3;
        FIFOLevel -= 4;

        FIFOWriteOffset += 4;
        if (FIFOWriteOffset >= Length)
        {
            FIFOWriteOffset = 0;
            break;
        }
    }
}

template<typename T>
void SPUCaptureUnit::FIFO_WriteData(T val)
{
    *(T*)&((u8*)FIFO)[FIFOWritePos] = val;

    FIFOWritePos += sizeof(T);
    FIFOWritePos &= 0xF;
    FIFOLevel += sizeof(T);

    if (FIFOLevel >= 16)
        FIFO_FlushData();
}

void SPUCaptureUnit::Run(s32 sample)
{
    Timer += 512;

    if (Cnt & 0x08)
    {
        while (Timer >> 16)
        {
            Timer = TimerReload + (Timer - 0x10000);

            FIFO_WriteData<s8>((s8)(sample >> 8));
            Pos++;
            if (Pos >= Length)
            {
                if (FIFOLevel >= 4)
                    FIFO_FlushData();

                if (Cnt & 0x04)
                {
                    Cnt &= 0x7F;
                    return;
                }
                else
                    Pos = 0;
            }
        }
    }
    else
    {
        while (Timer >> 16)
        {
            Timer = TimerReload + (Timer - 0x10000);

            FIFO_WriteData<s16>((s16)sample);
            Pos += 2;
            if (Pos >= Length)
            {
                if (FIFOLevel >= 4)
                    FIFO_FlushData();

                if (Cnt & 0x04)
                {
                    Cnt &= 0x7F;
                    return;
                }
                else
                    Pos = 0;
            }
        }
    }
}


void SPU::Mix(u32 dummy)
{
    s32 left = 0, right = 0;
    s32 leftoutput = 0, rightoutput = 0;

    if ((Cnt & (1<<15)) && (!dummy))
    {
        s32 ch0 = Channels[0].DoRun();
        s32 ch1 = Channels[1].DoRun();
        s32 ch2 = Channels[2].DoRun();
        s32 ch3 = Channels[3].DoRun();

        // TODO: addition from capture registers
        Channels[0].PanOutput(ch0, left, right);
        Channels[2].PanOutput(ch2, left, right);

        if (!(Cnt & (1<<12))) Channels[1].PanOutput(ch1, left, right);
        if (!(Cnt & (1<<13))) Channels[3].PanOutput(ch3, left, right);

        for (int i = 4; i < 16; i++)
        {
            SPUChannel* chan = &Channels[i];

            s32 channel = chan->DoRun();
            chan->PanOutput(channel, left, right);
        }

        // sound capture
        // TODO: other sound capture sources, along with their bugs

        if (Capture[0].Cnt & (1<<7))
        {
            s32 val = left;

            val >>= 8;
            if      (val < -0x8000) val = -0x8000;
            else if (val > 0x7FFF)  val = 0x7FFF;

            Capture[0].Run(val);
        }

        if (Capture[1].Cnt & (1<<7))
        {
            s32 val = right;

            val >>= 8;
            if      (val < -0x8000) val = -0x8000;
            else if (val > 0x7FFF)  val = 0x7FFF;

            Capture[1].Run(val);
        }

        // final output

        switch (Cnt & 0x0300)
        {
        case 0x0000: // left mixer
            leftoutput = left;
            break;
        case 0x0100: // channel 1
            {
                s32 pan = 128 - Channels[1].Pan;
                leftoutput = ((s64)ch1 * pan) >> 10;
            }
            break;
        case 0x0200: // channel 3
            {
                s32 pan = 128 - Channels[3].Pan;
                leftoutput = ((s64)ch3 * pan) >> 10;
            }
            break;
        case 0x0300: // channel 1+3
            {
                s32 pan1 = 128 - Channels[1].Pan;
                s32 pan3 = 128 - Channels[3].Pan;
                leftoutput = (((s64)ch1 * pan1) >> 10) + (((s64)ch3 * pan3) >> 10);
            }
            break;
        }

        switch (Cnt & 0x0C00)
        {
        case 0x0000: // right mixer
            rightoutput = right;
            break;
        case 0x0400: // channel 1
            {
                s32 pan = Channels[1].Pan;
                rightoutput = ((s64)ch1 * pan) >> 10;
            }
            break;
        case 0x0800: // channel 3
            {
                s32 pan = Channels[3].Pan;
                rightoutput = ((s64)ch3 * pan) >> 10;
            }
            break;
        case 0x0C00: // channel 1+3
            {
                s32 pan1 = Channels[1].Pan;
                s32 pan3 = Channels[3].Pan;
                rightoutput = (((s64)ch1 * pan1) >> 10) + (((s64)ch3 * pan3) >> 10);
            }
            break;
        }
    }

    leftoutput = ((s64)leftoutput * MasterVolume) >> 7;
    rightoutput = ((s64)rightoutput * MasterVolume) >> 7;

    leftoutput >>= 8;
    rightoutput >>= 8;

    // Add SOUNDBIAS value
    // The value used by all commercial games is 0x200, so we subtract that so it won't offset the final sound output.
    if (ApplyBias)
    {
        leftoutput += (Bias << 6) - 0x8000;
        rightoutput += (Bias << 6) - 0x8000;
    }

    if      (leftoutput < -0x8000) leftoutput = -0x8000;
    else if (leftoutput > 0x7FFF)  leftoutput = 0x7FFF;
    if      (rightoutput < -0x8000) rightoutput = -0x8000;
    else if (rightoutput > 0x7FFF)  rightoutput = 0x7FFF;

    // The original DS and DS lite degrade the output from 16 to 10 bit before output
    if (Degrade10Bit)
    {
        leftoutput &= 0xFFFFFFC0;
        rightoutput &= 0xFFFFFFC0;
    }

    // OutputBufferFrame can never get full because it's
    // transfered to OutputBuffer at the end of the frame
    // FIXME: apparently this does happen!!!
    if (OutputBackbufferWritePosition * 2 < OutputBufferSize - 1)
    {
        OutputBackbuffer[OutputBackbufferWritePosition    ] = leftoutput >> 1;
        OutputBackbuffer[OutputBackbufferWritePosition + 1] = rightoutput >> 1;
        OutputBackbufferWritePosition += 2;
    }

    NDS.ScheduleEvent(Event_SPU, true, 1024, 0, 0);
}

void SPU::TransferOutput()
{
    Platform::Mutex_Lock(AudioLock);
    for (u32 i = 0; i < OutputBackbufferWritePosition; i += 2)
    {
        OutputFrontBuffer[OutputFrontBufferWritePosition    ] = OutputBackbuffer[i   ];
        OutputFrontBuffer[OutputFrontBufferWritePosition + 1] = OutputBackbuffer[i + 1];

        OutputFrontBufferWritePosition += 2;
        OutputFrontBufferWritePosition &= OutputBufferSize*2-1;
        if (OutputFrontBufferWritePosition == OutputFrontBufferReadPosition)
        {
            // advance the read position too, to avoid losing the entire FIFO
            OutputFrontBufferReadPosition += 2;
            OutputFrontBufferReadPosition &= OutputBufferSize*2-1;
        }
    }
    OutputBackbufferWritePosition = 0;
    Platform::Mutex_Unlock(AudioLock);;
}

void SPU::TrimOutput()
{
    Platform::Mutex_Lock(AudioLock);
    const int halflimit = (OutputBufferSize / 2);

    int readpos = OutputFrontBufferWritePosition - (halflimit*2);
    if (readpos < 0) readpos += (OutputBufferSize*2);

    OutputFrontBufferReadPosition = readpos;
    Platform::Mutex_Unlock(AudioLock);
}

void SPU::DrainOutput()
{
    Platform::Mutex_Lock(AudioLock);
    OutputFrontBufferWritePosition = 0;
    OutputFrontBufferReadPosition = 0;
    Platform::Mutex_Unlock(AudioLock);
}

void SPU::InitOutput()
{
    Platform::Mutex_Lock(AudioLock);
    memset(OutputBackbuffer, 0, 2*OutputBufferSize*2);
    memset(OutputFrontBuffer, 0, 2*OutputBufferSize*2);
    OutputFrontBufferReadPosition = 0;
    OutputFrontBufferWritePosition = 0;
    Platform::Mutex_Unlock(AudioLock);
}

int SPU::GetOutputSize() const
{
    Platform::Mutex_Lock(AudioLock);

    int ret;
    if (OutputFrontBufferWritePosition >= OutputFrontBufferReadPosition)
        ret = OutputFrontBufferWritePosition - OutputFrontBufferReadPosition;
    else
        ret = (OutputBufferSize*2) - OutputFrontBufferReadPosition + OutputFrontBufferWritePosition;

    ret >>= 1;

    Platform::Mutex_Unlock(AudioLock);
    return ret;
}

void SPU::Sync(bool wait)
{
    // this function is currently not used anywhere
    // depending on the usage context the thread safety measures could be made
    // a lot faster

    // sync to audio output in case the core is running too fast
    // * wait=true: wait until enough audio data has been played
    // * wait=false: merely skip some audio data to avoid a FIFO overflow

    const int halflimit = (OutputBufferSize / 2);

    if (wait)
    {
        // TODO: less CPU-intensive wait?
        while (GetOutputSize() > halflimit);
    }
    else if (GetOutputSize() > halflimit)
    {
        Platform::Mutex_Lock(AudioLock);

        int readpos = OutputFrontBufferWritePosition - (halflimit*2);
        if (readpos < 0) readpos += (OutputBufferSize*2);

        OutputFrontBufferReadPosition = readpos;

        Platform::Mutex_Unlock(AudioLock);
    }
}

int SPU::ReadOutput(s16* data, int samples)
{
    Platform::Mutex_Lock(AudioLock);
    if (OutputFrontBufferReadPosition == OutputFrontBufferWritePosition)
    {
        Platform::Mutex_Unlock(AudioLock);
        return 0;
    }

    for (int i = 0; i < samples; i++)
    {
        *data++ = OutputFrontBuffer[OutputFrontBufferReadPosition];
        *data++ = OutputFrontBuffer[OutputFrontBufferReadPosition + 1];

        OutputFrontBufferReadPosition += 2;
        OutputFrontBufferReadPosition &= ((2*OutputBufferSize)-1);

        if (OutputFrontBufferWritePosition == OutputFrontBufferReadPosition)
        {
            Platform::Mutex_Unlock(AudioLock);
            return i+1;
        }
    }

    Platform::Mutex_Unlock(AudioLock);
    return samples;
}


u8 SPU::Read8(u32 addr)
{
    if (addr < 0x04000500)
    {
        SPUChannel* chan = &Channels[(addr >> 4) & 0xF];

        switch (addr & 0xF)
        {
        case 0x0: return chan->Cnt & 0xFF;
        case 0x1: return (chan->Cnt >> 8) & 0xFF;
        case 0x2: return (chan->Cnt >> 16) & 0xFF;
        case 0x3: return chan->Cnt >> 24;
        }
    }
    else
    {
        switch (addr)
        {
        case 0x04000500: return Cnt & 0x7F;
        case 0x04000501: return Cnt >> 8;

        case 0x04000508: return Capture[0].Cnt;
        case 0x04000509: return Capture[1].Cnt;
        }
    }

    Log(LogLevel::Warn, "unknown SPU read8 %08X\n", addr);
    return 0;
}

u16 SPU::Read16(u32 addr)
{
    if (addr < 0x04000500)
    {
        SPUChannel* chan = &Channels[(addr >> 4) & 0xF];

        switch (addr & 0xF)
        {
        case 0x0: return chan->Cnt & 0xFFFF;
        case 0x2: return chan->Cnt >> 16;
        }
    }
    else
    {
        switch (addr)
        {
        case 0x04000500: return Cnt;
        case 0x04000504: return Bias;

        case 0x04000508: return Capture[0].Cnt | (Capture[1].Cnt << 8);
        }
    }

    Log(LogLevel::Warn, "unknown SPU read16 %08X\n", addr);
    return 0;
}

u32 SPU::Read32(u32 addr)
{
    if (addr < 0x04000500)
    {
        SPUChannel* chan = &Channels[(addr >> 4) & 0xF];

        switch (addr & 0xF)
        {
        case 0x0: return chan->Cnt;
        }
    }
    else
    {
        switch (addr)
        {
        case 0x04000500: return Cnt;
        case 0x04000504: return Bias;

        case 0x04000508: return Capture[0].Cnt | (Capture[1].Cnt << 8);

        case 0x04000510: return Capture[0].DstAddr;
        case 0x04000518: return Capture[1].DstAddr;
        }
    }

    Log(LogLevel::Warn, "unknown SPU read32 %08X\n", addr);
    return 0;
}

void SPU::Write8(u32 addr, u8 val)
{
    if (addr < 0x04000500)
    {
        SPUChannel* chan = &Channels[(addr >> 4) & 0xF];

        switch (addr & 0xF)
        {
        case 0x0: chan->SetCnt((chan->Cnt & 0xFFFFFF00) | val); return;
        case 0x1: chan->SetCnt((chan->Cnt & 0xFFFF00FF) | (val << 8)); return;
        case 0x2: chan->SetCnt((chan->Cnt & 0xFF00FFFF) | (val << 16)); return;
        case 0x3: chan->SetCnt((chan->Cnt & 0x00FFFFFF) | (val << 24)); return;
        }
    }
    else
    {
        switch (addr)
        {
        case 0x04000500:
            Cnt = (Cnt & 0xBF00) | (val & 0x7F);
            MasterVolume = Cnt & 0x7F;
            if (MasterVolume == 127) MasterVolume++;
            return;
        case 0x04000501:
            Cnt = (Cnt & 0x007F) | ((val & 0xBF) << 8);
            return;

        case 0x04000508:
            Capture[0].SetCnt(val);
            if (val & 0x03) Log(LogLevel::Warn, "!! UNSUPPORTED SPU CAPTURE MODE %02X\n", val);
            return;
        case 0x04000509:
            Capture[1].SetCnt(val);
            if (val & 0x03) Log(LogLevel::Warn, "!! UNSUPPORTED SPU CAPTURE MODE %02X\n", val);
            return;
        }
    }

    Log(LogLevel::Warn, "unknown SPU write8 %08X %02X\n", addr, val);
}

void SPU::Write16(u32 addr, u16 val)
{
    if (addr < 0x04000500)
    {
        SPUChannel* chan = &Channels[(addr >> 4) & 0xF];

        switch (addr & 0xF)
        {
        case 0x0: chan->SetCnt((chan->Cnt & 0xFFFF0000) | val); return;
        case 0x2: chan->SetCnt((chan->Cnt & 0x0000FFFF) | (val << 16)); return;
        case 0x8:
            chan->SetTimerReload(val);
            if      ((addr & 0xF0) == 0x10) Capture[0].SetTimerReload(val);
            else if ((addr & 0xF0) == 0x30) Capture[1].SetTimerReload(val);
            return;
        case 0xA: chan->SetLoopPos(val); return;

        case 0xC: chan->SetLength(((chan->Length >> 2) & 0xFFFF0000) | val); return;
        case 0xE: chan->SetLength(((chan->Length >> 2) & 0x0000FFFF) | (val << 16)); return;
        }
    }
    else
    {
        switch (addr)
        {
        case 0x04000500:
            Cnt = val & 0xBF7F;
            MasterVolume = Cnt & 0x7F;
            if (MasterVolume == 127) MasterVolume++;
            return;

        case 0x04000504:
            Bias = val & 0x3FF;
            return;

        case 0x04000508:
            Capture[0].SetCnt(val & 0xFF);
            Capture[1].SetCnt(val >> 8);
            if (val & 0x0303) Log(LogLevel::Warn, "!! UNSUPPORTED SPU CAPTURE MODE %04X\n", val);
            return;

        case 0x04000514: Capture[0].SetLength(val); return;
        case 0x0400051C: Capture[1].SetLength(val); return;
        }
    }

    Log(LogLevel::Warn, "unknown SPU write16 %08X %04X\n", addr, val);
}

void SPU::Write32(u32 addr, u32 val)
{
    if (addr < 0x04000500)
    {
        SPUChannel* chan = &Channels[(addr >> 4) & 0xF];

        switch (addr & 0xF)
        {
        case 0x0: chan->SetCnt(val); return;
        case 0x4: chan->SetSrcAddr(val); return;
        case 0x8:
            chan->SetLoopPos(val >> 16);
            val &= 0xFFFF;
            chan->SetTimerReload(val);
            if      ((addr & 0xF0) == 0x10) Capture[0].SetTimerReload(val);
            else if ((addr & 0xF0) == 0x30) Capture[1].SetTimerReload(val);
            return;
        case 0xC: chan->SetLength(val); return;
        }
    }
    else
    {
        switch (addr)
        {
        case 0x04000500:
            Cnt = val & 0xBF7F;
            MasterVolume = Cnt & 0x7F;
            if (MasterVolume == 127) MasterVolume++;
            return;

        case 0x04000504:
            Bias = val & 0x3FF;
            return;

        case 0x04000508:
            Capture[0].SetCnt(val & 0xFF);
            Capture[1].SetCnt(val >> 8);
            if (val & 0x0303) Log(LogLevel::Warn, "!! UNSUPPORTED SPU CAPTURE MODE %04X\n", val);
            return;

        case 0x04000510: Capture[0].SetDstAddr(val); return;
        case 0x04000514: Capture[0].SetLength(val & 0xFFFF); return;
        case 0x04000518: Capture[1].SetDstAddr(val); return;
        case 0x0400051C: Capture[1].SetLength(val & 0xFFFF); return;
        }
    }
}

}