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DAC: add interpolation settings

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This commit is contained in:
tildearrow 2022-12-18 03:54:30 -05:00
parent 51ea3cec2a
commit e0723c7485
5 changed files with 101 additions and 2 deletions
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47
src/engine/platform/pcmdac.cpp
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@ -20,6 +20,7 @@
#define _USE_MATH_DEFINES
#include "pcmdac.h"
#include "../engine.h"
#include "../filter.h"
#include <math.h>
// to ease the driver, freqency register is a 8.16 counter relative to output sample rate
@ -103,7 +104,50 @@ void DivPlatformPCMDAC::acquire(short* bufL, short* bufR, size_t start, size_t l
}
}
if (chan[0].audPos>=0 && chan[0].audPos<(int)s->samples) {
output=s->data16[chan[0].audPos];
int s_4=((chan[0].audPos-4)>=0)?s->data16[chan[0].audPos-4]:0;
int s_3=((chan[0].audPos-3)>=0)?s->data16[chan[0].audPos-3]:0;
int s_2=((chan[0].audPos-2)>=0)?s->data16[chan[0].audPos-2]:0;
int s_1=((chan[0].audPos-1)>=0)?s->data16[chan[0].audPos-1]:0;
int s0=s->data16[chan[0].audPos];
int s1=((chan[0].audPos+1)<(int)s->samples)?s->data16[chan[0].audPos+1]:0;
int s2=((chan[0].audPos+2)<(int)s->samples)?s->data16[chan[0].audPos+2]:0;
int s3=((chan[0].audPos+3)<(int)s->samples)?s->data16[chan[0].audPos+3]:0;
switch (interp) {
case 1: // linear
output=s0+((s1-s0)*(chan[0].audSub&0xffff)>>16);
break;
case 2: { // cubic
float* cubicTable=DivFilterTables::getCubicTable();
float* t=&cubicTable[((chan[0].audSub&0xffff)>>6)<<2];
float result=(float)s_1*t[0]+(float)s0*t[1]+(float)s1*t[2]+(float)s2*t[3];
if (result<-32768) result=-32768;
if (result>32767) result=32767;
output=result;
break;
}
case 3: { // sinc
float* sincTable=DivFilterTables::getSincTable8();
float* t1=&sincTable[(8191-((chan[0].audSub&0xffff)>>3))<<2];
float* t2=&sincTable[((chan[0].audSub&0xffff)>>3)<<2];
float result=(
s_4*t2[3]+
s_3*t2[2]+
s_2*t2[1]+
s_1*t2[0]+
s0*t1[0]+
s1*t1[1]+
s2*t1[2]+
s3*t1[3]
);
if (result<-32768) result=-32768;
if (result>32767) result=32767;
output=result;
break;
}
default: // none
output=s0;
break;
}
}
} else {
chan[0].sample=-1;
@ -398,6 +442,7 @@ void DivPlatformPCMDAC::setFlags(const DivConfig& flags) {
chipClock=rate;
outDepth=(flags.getInt("outDepth",15))&15;
outStereo=flags.getBool("stereo",true);
interp=flags.getInt("interpolation",0);
}
int DivPlatformPCMDAC::init(DivEngine* p, int channels, int sugRate, const DivConfig& flags) {