skcblitz/opl3.h

// Envelope generator

short OPL3_EnvelopeCalcExp(uint level)
{
    if (level > 0x1fff)
    {
        level = 0x1fff;
    }
    return (exprom[level & 0xff] << 1) >> (level >> 8);
}

short OPL3_EnvelopeCalcSin0(ushort phase, ushort envelope)
{
    ushort out = 0;
    ushort neg = 0;
    phase &= 0x3ff;
    if (phase & 0x200)
    {
        neg = 0xffff;
    }
    if (phase & 0x100)
    {
        out = logsinrom[(phase & 0xff) ^ 0xff];
    }
    else
    {
        out = logsinrom[phase & 0xff];
    }
    return OPL3_EnvelopeCalcExp(out + (envelope << 3)) ^ neg;
}

short OPL3_EnvelopeCalcSin1(ushort phase, ushort envelope)
{
    ushort out = 0;
    phase &= 0x3ff;
    if (phase & 0x200)
    {
        out = 0x1000;
    }
    else if (phase & 0x100)
    {
        out = logsinrom[(phase & 0xff) ^ 0xff];
    }
    else
    {
        out = logsinrom[phase & 0xff];
    }
    return OPL3_EnvelopeCalcExp(out + (envelope << 3));
}

short OPL3_EnvelopeCalcSin2(ushort phase, ushort envelope)
{
    ushort out = 0;
    phase &= 0x3ff;
    if (phase & 0x100)
    {
        out = logsinrom[(phase & 0xff) ^ 0xff];
    }
    else
    {
        out = logsinrom[phase & 0xff];
    }
    return OPL3_EnvelopeCalcExp(out + (envelope << 3));
}

short OPL3_EnvelopeCalcSin3(ushort phase, ushort envelope)
{
    ushort out = 0;
    phase &= 0x3ff;
    if (phase & 0x100)
    {
        out = 0x1000;
    }
    else
    {
        out = logsinrom[phase & 0xff];
    }
    return OPL3_EnvelopeCalcExp(out + (envelope << 3));
}

short OPL3_EnvelopeCalcSin4(ushort phase, ushort envelope)
{
    ushort out = 0;
    ushort neg = 0;
    phase &= 0x3ff;
    if ((phase & 0x300) == 0x100)
    {
        neg = 0xffff;
    }
    if (phase & 0x200)
    {
        out = 0x1000;
    }
    else if (phase & 0x80)
    {
        out = logsinrom[((phase ^ 0xff) << 1) & 0xff];
    }
    else
    {
        out = logsinrom[(phase << 1) & 0xff];
    }
    return OPL3_EnvelopeCalcExp(out + (envelope << 3)) ^ neg;
}

short OPL3_EnvelopeCalcSin5(ushort phase, ushort envelope)
{
    ushort out = 0;
    phase &= 0x3ff;
    if (phase & 0x200)
    {
        out = 0x1000;
    }
    else if (phase & 0x80)
    {
        out = logsinrom[((phase ^ 0xff) << 1) & 0xff];
    }
    else
    {
        out = logsinrom[(phase << 1) & 0xff];
    }
    return OPL3_EnvelopeCalcExp(out + (envelope << 3));
}

short OPL3_EnvelopeCalcSin6(ushort phase, ushort envelope)
{
    ushort neg = 0;
    phase &= 0x3ff;
    if (phase & 0x200)
    {
        neg = 0xffff;
    }
    return OPL3_EnvelopeCalcExp(envelope << 3) ^ neg;
}

short OPL3_EnvelopeCalcSin7(ushort phase, ushort envelope)
{
    ushort out = 0;
    ushort neg = 0;
    phase &= 0x3ff;
    if (phase & 0x200)
    {
        neg = 0xffff;
        phase = (phase & 0x1ff) ^ 0x1ff;
    }
    out = phase << 3;
    return OPL3_EnvelopeCalcExp(out + (envelope << 3)) ^ neg;
}

short OPL3_EnvelopeCalcTri(ushort phase, ushort envelope)
{
    ushort out = 0;
    ushort neg = 0;
    phase &= 0x3ff;
    if (phase & 0x200)
    {
        neg = 0xffff;
    }
    if (phase & 0x100)
    {
        out = (phase & 0xff) << 3;
    }
    else
    {
        out = ~(phase & 0xff) << 3;
    }
    return OPL3_EnvelopeCalcExp(out + (envelope << 3)) ^ neg;
}

short OPL3_EnvelopeCalcSqr25(ushort phase, ushort envelope)
{
    ushort neg = 0;
    phase &= 0x3ff;
    if (phase & 0x300)
    {
        neg = 0xffff;
    }
    return OPL3_EnvelopeCalcExp(envelope << 3) ^ neg;
}

short OPL3_EnvelopeCalcSqr12(ushort phase, ushort envelope)
{
    ushort neg = 0;
    phase &= 0x3ff;
    if (phase & 0x380)
    {
        neg = 0xffff;
    }
    return OPL3_EnvelopeCalcExp(envelope << 3) ^ neg;
}

short OPL3_EnvelopeCalcSaw(ushort phase, ushort envelope)
{
    ushort out = 0;
    ushort neg = 0;
    phase &= 0x3ff;
    if (phase & 0x200)
    {
        neg = 0xffff;
        out = ~(phase & 0x1ff) << 2;
    }
    else
    {
        out = (phase & 0x1ff) << 2;
    }
    return OPL3_EnvelopeCalcExp(out + (envelope << 3)) ^ neg;
}

short OPL3_EnvelopeCalcNoise(ushort phase, ushort envelope)
{
    ushort out = 0;
    ushort neg = 0;
    phase &= 0x3ff;
    if ((phase ^ rng_table[~phase & 0xff]) & 1)
    {
        neg = 0xffff;
    }
    out = rng_table[phase & 0xff] << 2;
    return OPL3_EnvelopeCalcExp(out + (envelope << 3)) ^ neg;
}

static const envelope_sinfunc envelope_sin[16] = {
	OPL3_EnvelopeCalcSin0,
	OPL3_EnvelopeCalcSin1,
	OPL3_EnvelopeCalcSin2,
	OPL3_EnvelopeCalcSin3,
	OPL3_EnvelopeCalcSin4,
	OPL3_EnvelopeCalcSin5,
	OPL3_EnvelopeCalcSin6,
	OPL3_EnvelopeCalcSin7,
	OPL3_EnvelopeCalcTri,
	OPL3_EnvelopeCalcSqr25,
	OPL3_EnvelopeCalcSqr12,
	OPL3_EnvelopeCalcSaw,
	OPL3_EnvelopeCalcNoise,
	OPL3_EnvelopeCalcNoise,
	OPL3_EnvelopeCalcNoise,
	OPL3_EnvelopeCalcNoise,
};

void OPL3_EnvelopeCalc(opl3_slot *slot)
{
    byte nonzero;
    byte rate;
    byte rate_hi;
    byte rate_lo;
    byte reg_rate = 0;
    byte ks;
    byte eg_shift, shift;
    ushort eg_rout;
    short eg_inc;
    byte eg_off;
    byte reset = 0;
    if(slot->retrigger) {
        slot->eg_rout = 0x1ff;
    }
    slot->eg_out = slot->eg_rout + (slot->reg_tl << 2)
                 + (slot->eg_ksl >> kslshift[slot->reg_ksl]) + *slot->trem;
    if (slot->key && slot->eg_gen == envelope_gen_num_release)
    {
        reset = 1;
        reg_rate = slot->reg_ar;
    }
    else
    {
        switch (slot->eg_gen)
        {
        case envelope_gen_num_attack:
            reg_rate = slot->reg_ar;
            break;
        case envelope_gen_num_decay:
            reg_rate = slot->reg_dr;
            break;
        case envelope_gen_num_sustain:
            if (!slot->reg_type)
            {
                reg_rate = slot->reg_rr;
            }
            break;
        case envelope_gen_num_release:
            reg_rate = slot->reg_rr;
            break;
        }
    }
    slot->pg_reset = reset;
    ks = slot->channel->ksv >> ((slot->reg_ksr ^ 1) << 1);
    nonzero = (reg_rate != 0);
    rate = ks + (reg_rate << 2);
    rate_hi = rate >> 2;
    rate_lo = rate & 0x03;
    if (rate_hi & 0x10)
    {
        rate_hi = 0x0f;
    }
    eg_shift = rate_hi + slot->chip->eg_add;
    shift = 0;
    if (nonzero)
    {
        if (rate_hi < 12)
        {
            if (slot->chip->eg_state)
            {
                switch (eg_shift)
                {
                case 12:
                    shift = 1;
                    break;
                case 13:
                    shift = (rate_lo >> 1) & 0x01;
                    break;
                case 14:
                    shift = rate_lo & 0x01;
                    break;
                default:
                    break;
                }
            }
        }
        else
        {
            shift = (rate_hi & 0x03) + eg_incstep[rate_lo][slot->chip->timer & 0x03];
            if (shift & 0x04)
            {
                shift = 0x03;
            }
            if (!shift)
            {
                shift = slot->chip->eg_state;
            }
        }
    }
    eg_rout = slot->eg_rout;
    eg_inc = 0;
    eg_off = 0;
    /* Instant attack */
    if (reset && rate_hi == 0x0f)
    {
        eg_rout = 0x00;
    }
    /* Envelope off */
    if ((slot->eg_rout & 0x1f8) == 0x1f8)
    {
        eg_off = 1;
    }
    if (slot->eg_gen != envelope_gen_num_attack && !reset && eg_off)
    {
        eg_rout = 0x1ff;
    }
    switch (slot->eg_gen)
    {
    case envelope_gen_num_attack:
        if (!(slot->eg_rout))
        {
            slot->eg_gen = envelope_gen_num_decay;
        }
        else if (slot->key && shift > 0 && rate_hi != 0x0f)
        {
            eg_inc = ~slot->eg_rout >> (4 - shift);
        }
        break;
    case envelope_gen_num_decay:
        if ((slot->eg_rout >> 4) == slot->reg_sl)
        {
            slot->eg_gen = envelope_gen_num_sustain;
        }
        else if (!eg_off && !reset && shift > 0)
        {
            eg_inc = 1 << (shift - 1);
        }
        break;
    case envelope_gen_num_sustain:
    case envelope_gen_num_release:
        if (!eg_off && !reset && shift > 0)
        {
            eg_inc = 1 << (shift - 1);
        }
        break;
    }
    slot->eg_rout = (eg_rout + eg_inc) & 0x1ff;
    /* Key off */
    if (reset)
    {
        slot->eg_gen = envelope_gen_num_attack;
    }
    if (!(slot->key))
    {
        slot->eg_gen = envelope_gen_num_release;
    }
    slot->detrigger = 0;
    slot->retrigger = 0;
}

void OPL3_EnvelopeUpdateKSL(opl3_slot *slot)
{
    short ksl = (kslrom[slot->channel->f_num >> 6] << 2)
               - ((0x08 - slot->channel->block) << 5);
    if (ksl < 0)
    {
        ksl = 0;
    }
    slot->eg_ksl = (byte)ksl;
}

void OPL3_EnvelopeKeyOn(opl3_slot *slot)
{
    slot->key = 0x01;
    if(slot->detrigger) {
        slot->eg_gen = envelope_gen_num_release;
        // slot->eg_rout = 0x1ff;
        // slot->eg_out = slot->eg_rout = 0x1ff;
        slot->detrigger = 0;
    }
    slot->retrigger = 1;
}

void OPL3_EnvelopeKeyOff(opl3_slot *slot)
{
    slot->key = 0x00;
    slot->detrigger = 1;
    slot->retrigger = 0;
}

void OPL3_PhaseGenerate(opl3_slot *slot)
{
    opl3_chip *chip;
    ushort f_num;
    uint basefreq;
    ushort phase;

    chip = slot->chip;
    f_num = slot->channel->f_num;
    if (slot->reg_vib)
    {
        char range;
        byte vibpos;

        range = (f_num >> 7) & 7;
        vibpos = slot->chip->vibpos;

        if (!(vibpos & 3))
        {
            range = 0;
        }
        else if (vibpos & 1)
        {
            range >>= 1;
        }
        range >>= slot->chip->vibshift;

        if (vibpos & 4)
        {
            range = -range;
        }
        f_num += range;
    }
    basefreq = (f_num << slot->channel->block) >> 1;
    phase = (ushort)(slot->pg_phase >> 9);
    if (slot->pg_reset)
    {
        slot->pg_phase = 0;
    }
    slot->pg_phase += (basefreq * op_mt[slot->reg_mult]) >> 1;
    slot->pg_phase_out = phase;
}

void OPL3_SlotGenerate(opl3_slot *slot)
{
    slot->out = envelope_sin[slot->reg_wf](slot->pg_phase_out + *slot->mod, slot->eg_out);
}

void OPL3_SlotCalcFB(opl3_slot *slot)
{
    if (slot->channel->fb != 0x00)
    {
        slot->fbmod = (slot->prout + slot->out) >> (0x09 - slot->channel->fb);
    }
    else
    {
        slot->fbmod = 0;
    }
    slot->prout = slot->out;
}

void OPL3_ProcessSlot(opl3_slot *slot)
{
    OPL3_SlotCalcFB(slot);
    OPL3_EnvelopeCalc(slot);
    OPL3_PhaseGenerate(slot);
    OPL3_SlotGenerate(slot);
}

short OPL3_ClipSampleOld(int sample)
{
    if (sample > 32767)
    {
        sample = 32767;
    }
    else if (sample < -32768)
    {
        sample = -32768;
    }
    return (short)sample;
}

short OPL3_ClipSample(int sample)
{
	int sign = (sample < 0) ? -1 : 1;
	sample = (sample < 0) ? -sample : sample;
	sample *= 5;
	sample /= 8; 
    sample = sample > 32767 ? 32767 : sample;
	sample *= sign;
    return (short)sample;
}

void OPL3_Generate(opl3_chip *chip, short *buf)
{
    opl3_channel *channel;
    short **out;
    int mix[2];
    byte ii;
    short accm;
    byte shift = 0;

    buf[0] = OPL3_ClipSample(chip->mixbuff[0]);
    buf[1] = OPL3_ClipSample(chip->mixbuff[1]);

    for (ii = 0; ii < (chip->n_voices * 2); ii++)
    {
        OPL3_ProcessSlot(&chip->slot[ii]);
    }

    mix[0] = mix[1] = 0;
    for (ii = 0; ii < chip->n_voices; ii++)
    {
        channel = &chip->channel[ii];
        out = channel->out;
        accm = *out[0] + *out[1] + *out[2] + *out[3];
        mix[0] += (short)((accm * channel->level[0]) >> 16);
        mix[1] += (short)((accm * channel->level[1]) >> 16);
    }
    chip->mixbuff[0] = mix[0];
    chip->mixbuff[1] = mix[1];

    if ((chip->timer & 0x3f) == 0x3f)
    {
        chip->tremolopos = (chip->tremolopos + 1) % 210;
    }
    if (chip->tremolopos < 105)
    {
        chip->tremolo = chip->tremolopos >> chip->tremoloshift;
    }
    else
    {
        chip->tremolo = (210 - chip->tremolopos) >> chip->tremoloshift;
    }

    if ((chip->timer & 0x3ff) == 0x3ff)
    {
        chip->vibpos = (chip->vibpos + 1) & 7;
    }

    chip->timer++;

    chip->eg_add = 0;
    if (chip->eg_timer)
    {
        while (shift < 36 && ((chip->eg_timer >> shift) & 1) == 0)
        {
            shift++;
        }
        if (shift > 12)
        {
            chip->eg_add = 0;
        }
        else
        {
            chip->eg_add = shift + 1;
        }
    }

    if (chip->eg_timerrem || chip->eg_state)
    {
        if (chip->eg_timer == 0xfffffffff)
        {
            chip->eg_timer = 0;
            chip->eg_timerrem = 1;
        }
        else
        {
            chip->eg_timer++;
            chip->eg_timerrem = 0;
        }
    }

    chip->eg_state ^= 1;
}

void OPL3_GenerateResampled(opl3_chip *chip, short *buf)
{
    while (chip->samplecnt >= chip->rateratio)
    {
        chip->oldsamples[0] = chip->samples[0];
        chip->oldsamples[1] = chip->samples[1];
        OPL3_Generate(chip, chip->samples);
        chip->samplecnt -= chip->rateratio;
    }
    buf[0] = (short)((chip->oldsamples[0] * (chip->rateratio - chip->samplecnt)
                        + chip->samples[0] * chip->samplecnt) / chip->rateratio);
    buf[1] = (short)((chip->oldsamples[1] * (chip->rateratio - chip->samplecnt)
                        + chip->samples[1] * chip->samplecnt) / chip->rateratio);
    chip->samplecnt += 1 << RSM_FRAC;
}

// Operator

void OPL3_SlotFlags(opl3_slot *slot, byte tremolo, byte vibrato, byte sustaining, byte ksr) {
	if (tremolo)
    {
        slot->trem = &slot->chip->tremolo;
    }
    else
    {
        slot->trem = (byte*)&slot->chip->zeromod;
    }
    slot->reg_vib = vibrato & 0x01;
    slot->reg_type = sustaining & 0x01;
    slot->reg_ksr = ksr & 0x01;
}

void OPL3_SlotMult(opl3_slot *slot, byte mult) {
	slot->reg_mult = mult & 0x0f;
}

void OPL3_SlotKSL(opl3_slot *slot, byte ksl) {
	slot->reg_ksl = ksl & 0x03;
    OPL3_EnvelopeUpdateKSL(slot);
}

void OPL3_SlotLevel(opl3_slot *slot, byte level) {
	slot->reg_tl = level & 0x3f;
}

void OPL3_SlotADSR(opl3_slot *slot, byte attack, byte decay, byte sustain, byte release) {
	slot->reg_ar = attack & 0x0f;
    slot->reg_dr = decay & 0x0f;
	slot->reg_sl = sustain & 0x0f;
    if (slot->reg_sl == 0x0f)
    {
        slot->reg_sl = 0x1f;
    }
    slot->reg_rr = release & 0x0f;
	if (slot->reg_rr == 0x00)
    {
        slot->reg_rr = 0x01;
    }
}

void OPL3_SlotWaveform(opl3_slot *slot, byte waveform) {
	slot->reg_wf = waveform & 0x07;
}

void OPL3_SlotWaveformNew(opl3_slot *slot, byte waveform) {
	slot->reg_wf = waveform & 0x0f;
}

// Channel

void OPL3_ChannelSetupAlg(opl3_channel *channel)
{
    if (channel->alg & 0x08)
    {
        return;
    }
    if (channel->alg & 0x04)
    {
        channel->pair->out[0] = &channel->chip->zeromod;
        channel->pair->out[1] = &channel->chip->zeromod;
        channel->pair->out[2] = &channel->chip->zeromod;
        channel->pair->out[3] = &channel->chip->zeromod;
        switch (channel->alg & 0x03)
        {
        case 0x00:
            channel->pair->slots[0]->mod = &channel->pair->slots[0]->fbmod;
            channel->pair->slots[1]->mod = &channel->pair->slots[0]->out;
            channel->slots[0]->mod = &channel->pair->slots[1]->out;
            channel->slots[1]->mod = &channel->slots[0]->out;
            channel->out[0] = &channel->slots[1]->out;
            channel->out[1] = &channel->chip->zeromod;
            channel->out[2] = &channel->chip->zeromod;
            channel->out[3] = &channel->chip->zeromod;
            break;
        case 0x01:
            channel->pair->slots[0]->mod = &channel->pair->slots[0]->fbmod;
            channel->pair->slots[1]->mod = &channel->pair->slots[0]->out;
            channel->slots[0]->mod = &channel->chip->zeromod;
            channel->slots[1]->mod = &channel->slots[0]->out;
            channel->out[0] = &channel->pair->slots[1]->out;
            channel->out[1] = &channel->slots[1]->out;
            channel->out[2] = &channel->chip->zeromod;
            channel->out[3] = &channel->chip->zeromod;
            break;
        case 0x02:
            channel->pair->slots[0]->mod = &channel->pair->slots[0]->fbmod;
            channel->pair->slots[1]->mod = &channel->chip->zeromod;
            channel->slots[0]->mod = &channel->pair->slots[1]->out;
            channel->slots[1]->mod = &channel->slots[0]->out;
            channel->out[0] = &channel->pair->slots[0]->out;
            channel->out[1] = &channel->slots[1]->out;
            channel->out[2] = &channel->chip->zeromod;
            channel->out[3] = &channel->chip->zeromod;
            break;
        case 0x03:
            channel->pair->slots[0]->mod = &channel->pair->slots[0]->fbmod;
            channel->pair->slots[1]->mod = &channel->chip->zeromod;
            channel->slots[0]->mod = &channel->pair->slots[1]->out;
            channel->slots[1]->mod = &channel->chip->zeromod;
            channel->out[0] = &channel->pair->slots[0]->out;
            channel->out[1] = &channel->slots[0]->out;
            channel->out[2] = &channel->slots[1]->out;
            channel->out[3] = &channel->chip->zeromod;
            break;
        }
    }
    else
    {
        switch (channel->alg & 0x01)
        {
        case 0x00:
            channel->slots[0]->mod = &channel->slots[0]->fbmod;
            channel->slots[1]->mod = &channel->slots[0]->out;
            channel->out[0] = &channel->slots[1]->out;
            channel->out[1] = &channel->chip->zeromod;
            channel->out[2] = &channel->chip->zeromod;
            channel->out[3] = &channel->chip->zeromod;
            break;
        case 0x01:
            channel->slots[0]->mod = &channel->slots[0]->fbmod;
            channel->slots[1]->mod = &channel->chip->zeromod;
            channel->out[0] = &channel->slots[0]->out;
            channel->out[1] = &channel->slots[1]->out;
            channel->out[2] = &channel->chip->zeromod;
            channel->out[3] = &channel->chip->zeromod;
            break;
        }
    }
}

void OPL3_ChannelUpdateAlg(opl3_channel *channel)
{
    channel->alg = channel->con;
    if (channel->chtype == ch_4op)
    {
        channel->pair->alg = 0x04 | (channel->con << 1) | (channel->pair->con);
        channel->alg = 0x08;
        OPL3_ChannelSetupAlg(channel->pair);
    }
    else if (channel->chtype == ch_4op2)
    {
        channel->alg = 0x04 | (channel->pair->con << 1) | (channel->con);
        channel->pair->alg = 0x08;
        OPL3_ChannelSetupAlg(channel);
    }
    else
    {
        OPL3_ChannelSetupAlg(channel);
    }
}

void OPL3_ChannelFreq(opl3_channel *channel, byte block, ushort f_num) {
	if (channel->chtype == ch_4op2)
    {
        return;
    }
    channel->f_num = f_num & 0x3ff;
    channel->block = block & 0x07;
    channel->ksv = (channel->block << 1)
                 | ((channel->f_num >> (0x09 - channel->chip->nts)) & 0x01);
    OPL3_EnvelopeUpdateKSL(channel->slots[0]);
    OPL3_EnvelopeUpdateKSL(channel->slots[1]);
    if (channel->chtype == ch_4op)
    {
        channel->pair->f_num = channel->f_num;
        channel->pair->block = channel->block;
        channel->pair->ksv = channel->ksv;
        OPL3_EnvelopeUpdateKSL(channel->pair->slots[0]);
        OPL3_EnvelopeUpdateKSL(channel->pair->slots[1]);
    }
}

void OPL3_ChannelOutput(opl3_channel *channel, byte output, uint level) {
	channel->level[output & 1] = level;
}

void OPL3_Channel4Op(opl3_channel *channel, byte op4) {
	if (op4)
    {
        channel->chtype = ch_4op;
        channel->pair->chtype = ch_4op2;
        OPL3_ChannelUpdateAlg(channel);
    }
    else
    {
        channel->chtype = ch_2op;
        channel->pair->chtype = ch_2op;
        OPL3_ChannelUpdateAlg(channel);
        OPL3_ChannelUpdateAlg(channel->pair);
    }
}

void OPL3_ChannelFeedback(opl3_channel *channel, byte feedback) {
	channel->fb = feedback & 0x07;
}

void OPL3_ChannelAM(opl3_channel *channel, byte am) {
	channel->con = am & 0x01;
    OPL3_ChannelUpdateAlg(channel);
}

void OPL3_ChannelKeyOn(opl3_channel *channel)
{
    if (channel->chtype == ch_4op)
    {
        OPL3_EnvelopeKeyOn(channel->slots[0]);
        OPL3_EnvelopeKeyOn(channel->slots[1]);
        OPL3_EnvelopeKeyOn(channel->pair->slots[0]);
        OPL3_EnvelopeKeyOn(channel->pair->slots[1]);
    }
    else if (channel->chtype == ch_2op)
    {
        OPL3_EnvelopeKeyOn(channel->slots[0]);
        OPL3_EnvelopeKeyOn(channel->slots[1]);
    }
}

void OPL3_ChannelKeyOff(opl3_channel *channel)
{
    if (channel->chtype == ch_4op)
    {
        OPL3_EnvelopeKeyOff(channel->slots[0]);
        OPL3_EnvelopeKeyOff(channel->slots[1]);
        OPL3_EnvelopeKeyOff(channel->pair->slots[0]);
        OPL3_EnvelopeKeyOff(channel->pair->slots[1]);
    }
    else if (channel->chtype == ch_2op)
    {
        OPL3_EnvelopeKeyOff(channel->slots[0]);
        OPL3_EnvelopeKeyOff(channel->slots[1]);
    }
}

void OPL3_Reset(opl3_chip *chip)
{
    byte slotnum;
    byte channum;
	
	int rateratio = chip->rateratio;
	byte n_voices = chip->n_voices;
    opl3_slot *slot = chip->slot;
    opl3_channel *channel = chip->channel;
	
    memset(chip, 0, sizeof(opl3_chip) + (n_voices * (sizeof(opl3_slot) * 2 + sizeof(opl3_channel))));
	
	chip->rateratio = rateratio;
	chip->n_voices = n_voices;
	chip->slot = slot;
	chip->channel = channel;
	
    for (slotnum = 0; slotnum < (chip->n_voices * 2); slotnum++)
    {
        slot = &chip->slot[slotnum];
        slot->chip = chip;
        slot->mod = &chip->zeromod;
        slot->eg_rout = 0x1ff;
        slot->eg_out = 0x1ff;
        slot->eg_gen = envelope_gen_num_release;
        slot->trem = (byte*)&chip->zeromod;
        slot->slot_num = slotnum;
    }
    for (channum = 0; channum < chip->n_voices; channum++)
    {
        channel = &chip->channel[channum];
        channel->slots[0] = &chip->slot[channum * 2];
        channel->slots[1] = &chip->slot[channum * 2 + 1];
        chip->slot[channum * 2].channel = channel;
        chip->slot[channum * 2 + 1].channel = channel;
        channel->pair = &chip->channel[(channum & 1) ? (channum - 1) : (channum + 1)];
        channel->chip = chip;
        channel->out[0] = &chip->zeromod;
        channel->out[1] = &chip->zeromod;
        channel->out[2] = &chip->zeromod;
        channel->out[3] = &chip->zeromod;
        channel->chtype = ch_2op;
        channel->level[0] = 0x10000;
        channel->level[1] = 0x10000;
        channel->ch_num = channum;
        OPL3_ChannelSetupAlg(channel);
    }
    chip->tremoloshift = 4;
    chip->vibshift = 1;
}

void OPL3_Rate(opl3_chip *chip, uint samplerate) {
	chip->rateratio = (samplerate << RSM_FRAC) / 49716;
}

void OPL3_ChipFlags(opl3_chip *chip, byte nts, byte vibrato, byte deeptremolo, byte deepvibrato) {
	chip->nts = nts;
	chip->tremoloshift = ((deeptremolo ^ 1) << 1) + 2;
	chip->vibshift = deepvibrato ^ 1;
}

opl3_chip *OPL3_Alloc(uint samplerate, byte voices) {
	opl3_chip *chip = malloc(sizeof(opl3_chip) + (voices * (sizeof(opl3_slot) * 2 + sizeof(opl3_channel))));
	chip->channel = (opl3_channel*)(((byte*)chip) + sizeof(opl3_chip));
	chip->slot = (opl3_slot*)(((byte*)chip->channel) + (voices * sizeof(opl3_channel)));
	chip->n_voices = voices;
	OPL3_Rate(chip, samplerate);
	OPL3_Reset(chip);
	return chip;
}

byte OPL3_Playing(opl3_chip *chip) {
    opl3_slot *slot;
	for(int z = 0; z < (chip->n_voices * 2); z++) {
		slot = &chip->slot[z];
		if(slot->eg_out <= 0x100) {
			return 1;
		}
	}
	return 0;
}