ref: 1e43b50e5d6817507fd8dc0849f052d4d7a6c0a8
dir: /src/pt2_paula.c/
/* Simple Paula emulator by 8bitbubsy (with BLEP synthesis by aciddose).
** The Amiga filters are handled in pt2_amigafilters.c
**
** Limitation: The audio output frequency can't be below 31389Hz ( ceil(PAULA_PAL_CLK / 113.0) )
*/
#include <stdint.h>
#include <stdbool.h>
#include "pt2_audio.h"
#include "pt2_paula.h"
#include "pt2_blep.h"
#include "pt2_sync.h"
#include "pt2_scopes.h"
#include "pt2_config.h"
paulaVoice_t paula[PAULA_VOICES]; // globalized
static blep_t blep[PAULA_VOICES];
static double dPeriodToDeltaDiv;
void paulaSetOutputFrequency(double dAudioFreq, bool oversampling2x)
{
dPeriodToDeltaDiv = PAULA_PAL_CLK / dAudioFreq;
if (oversampling2x)
dPeriodToDeltaDiv /= 2.0;
}
void paulaSetPeriod(int32_t ch, uint16_t period)
{
paulaVoice_t *v = &paula[ch];
int32_t realPeriod = period;
if (realPeriod == 0)
realPeriod = 65535; // On Amiga: period 0 = one full cycle with period 65536, then period 65535 for the rest
else if (realPeriod < 113)
realPeriod = 113; // close to what happens on real Amiga (and needed for BLEP synthesis)
// to be read on next sampling step (or on DMA trigger)
v->AUD_PER_delta = dPeriodToDeltaDiv / realPeriod;
v->AUD_PER_deltamul = 1.0 / v->AUD_PER_delta; // for BLEP synthesis (prevents division in inner mixing loop)
// handle BLEP synthesis edge-cases
if (v->dLastDelta == 0.0)
v->dLastDelta = v->AUD_PER_delta;
if (v->dLastDeltaMul == 0.0)
v->dLastDeltaMul = v->AUD_PER_deltamul;
// handle visualizers
if (editor.songPlaying)
{
v->syncPeriod = realPeriod;
v->syncFlags |= SET_SCOPE_PERIOD;
}
else
{
scopeSetPeriod(ch, realPeriod);
}
}
void paulaSetVolume(int32_t ch, uint16_t vol)
{
paulaVoice_t *v = &paula[ch];
int32_t realVol = vol & 127;
if (realVol > 64)
realVol = 64;
// multiplying sample point by this also scales the sample from -128..127 -> -1.0 .. ~0.99
v->AUD_VOL = realVol * (1.0 / (128.0 * 64.0));
// handle visualizers
if (editor.songPlaying)
{
v->syncVolume = (uint8_t)realVol;
v->syncFlags |= SET_SCOPE_VOLUME;
}
else
{
scope[ch].volume = (uint8_t)realVol;
}
}
void paulaSetLength(int32_t ch, uint16_t len)
{
paulaVoice_t *v = &paula[ch];
v->AUD_LEN = len;
// handle visualizers
if (editor.songPlaying)
v->syncFlags |= SET_SCOPE_LENGTH;
else
scope[ch].newLength = len * 2;
}
void paulaSetData(int32_t ch, const int8_t *src)
{
paulaVoice_t *v = &paula[ch];
// if pointer is NULL, use empty 128kB sample slot after sample 31 in the tracker
if (src == NULL)
src = &song->sampleData[config.reservedSampleOffset];
v->AUD_LC = src;
// handle visualizers
if (editor.songPlaying)
v->syncFlags |= SET_SCOPE_DATA;
else
scope[ch].newData = src;
}
static inline void refetchPeriod(paulaVoice_t *v) // Paula stage
{
// set BLEP stuff
v->dLastPhase = v->dPhase;
v->dLastDelta = v->dDelta;
v->dLastDeltaMul = v->dDeltaMul;
v->dBlepOffset = v->dLastPhase * v->dLastDeltaMul;
// Paula only updates period (delta) during period refetching (this stage)
v->dDelta = v->AUD_PER_delta;
v->dDeltaMul = v->AUD_PER_deltamul;
v->nextSampleStage = true;
}
static void startPaulaDMA(int32_t ch)
{
paulaVoice_t *v = &paula[ch];
// if pointer is NULL, use empty 128kB sample slot after sample 31 in the tracker
if (v->AUD_LC == NULL)
v->AUD_LC = &song->sampleData[config.reservedSampleOffset];
// immediately update AUD_LC/AUD_LEN
v->location = v->AUD_LC;
v->lengthCounter = v->AUD_LEN;
// make Paula fetch new samples immediately
v->sampleCounter = 0;
v->DMATriggerFlag = true;
refetchPeriod(v);
v->dPhase = 0.0; // kludge: must be cleared *after* refetchPeriod()
v->DMA_active = true;
// handle visualizers
if (editor.songPlaying)
{
v->syncTriggerData = v->AUD_LC;
v->syncTriggerLength = v->AUD_LEN * 2;
v->syncFlags |= TRIGGER_SCOPE;
}
else
{
scope_t *s = &scope[ch];
s->newData = v->AUD_LC;
s->newLength = v->AUD_LEN * 2;
scopeTrigger(ch);
}
}
static void stopPaulaDMA(int32_t ch)
{
paulaVoice_t *v = &paula[ch];
v->DMA_active = false;
// handle visualizers
if (editor.songPlaying)
v->syncFlags |= STOP_SCOPE;
else
scope[ch].active = false;
}
void paulaSetDMACON(uint16_t bits) // $DFF096 register write (only controls paula DMAs)
{
if (bits & 0x8000)
{
// set
if (bits & 1) startPaulaDMA(0);
if (bits & 2) startPaulaDMA(1);
if (bits & 4) startPaulaDMA(2);
if (bits & 8) startPaulaDMA(3);
}
else
{
// clear
if (bits & 1) stopPaulaDMA(0);
if (bits & 2) stopPaulaDMA(1);
if (bits & 4) stopPaulaDMA(2);
if (bits & 8) stopPaulaDMA(3);
}
}
static inline void nextSample(paulaVoice_t *v, blep_t *b)
{
if (v->sampleCounter == 0)
{
// it's time to read new samples from DMA
// don't update AUD_LEN/AUD_LC yet on DMA trigger
if (!v->DMATriggerFlag)
{
if (--v->lengthCounter == 0)
{
v->lengthCounter = v->AUD_LEN;
v->location = v->AUD_LC;
}
}
v->DMATriggerFlag = false;
// fill DMA data buffer
v->AUD_DAT[0] = *v->location++;
v->AUD_DAT[1] = *v->location++;
v->sampleCounter = 2;
}
/* Pre-compute current sample point.
** Output volume is only read from AUDxVOL at this stage,
** and we don't emulate volume PWM anyway, so we can
** pre-multiply by volume here.
*/
v->dSample = v->AUD_DAT[0] * v->AUD_VOL; // -128..127 * 0.0 .. 1.0
// fill BLEP buffer if the new sample differs from the old one
if (v->dSample != b->dLastValue)
{
if (v->dLastDelta > v->dLastPhase)
blepAdd(b, v->dBlepOffset, b->dLastValue - v->dSample);
b->dLastValue = v->dSample;
}
// progress AUD_DAT buffer
v->AUD_DAT[0] = v->AUD_DAT[1];
v->sampleCounter--;
}
void paulaGenerateSamples(double *dOutL, double *dOutR, int32_t numSamples)
{
double *dMixBufSelect[PAULA_VOICES] = { dOutL, dOutR, dOutR, dOutL };
memset(dOutL, 0, numSamples * sizeof (double));
memset(dOutR, 0, numSamples * sizeof (double));
paulaVoice_t *v = paula;
blep_t *b = blep;
for (int32_t i = 0; i < PAULA_VOICES; i++, v++, b++)
{
if (!v->DMA_active || v->location == NULL || v->AUD_LC == NULL)
continue;
double *dMixBuffer = dMixBufSelect[i]; // what output channel to mix into (L, R, R, L)
for (int32_t j = 0; j < numSamples; j++)
{
if (v->nextSampleStage)
{
v->nextSampleStage = false;
nextSample(v, b); // inlined
}
double dSample = v->dSample; // current Paula sample, pre-multiplied by volume, scaled to -1.0 .. 0.9921875
if (b->samplesLeft > 0)
dSample = blepRun(b, dSample);
dMixBuffer[j] += dSample;
v->dPhase += v->dDelta;
if (v->dPhase >= 1.0)
{
v->dPhase -= 1.0;
refetchPeriod(v); // inlined
}
}
}
}