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tighter bounds on interpolation accuracy

This commit is contained in:
Aikku93 2022-06-13 15:14:54 +10:00
parent 589084ec74
commit aa25e1dd54
1 changed files with 17 additions and 16 deletions
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33
desmume/src/SPU.cpp
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@ -105,8 +105,8 @@ static const u16 adpcmtbl[89] =
static s32 precalcdifftbl[89][16]; static s32 precalcdifftbl[89][16];
static u8 precalcindextbl[89][8]; static u8 precalcindextbl[89][8];
static s16 catmullrom_lut[CATMULLROM_INTERPOLATION_RESOLUTION][4]; static u16 catmullrom_lut[CATMULLROM_INTERPOLATION_RESOLUTION][4];
static s16 cos_lut[COSINE_INTERPOLATION_RESOLUTION]; static u16 cos_lut[COSINE_INTERPOLATION_RESOLUTION];
static const double ARM7_CLOCK = 33513982; static const double ARM7_CLOCK = 33513982;
@ -215,13 +215,13 @@ int SPU_Init(int coreid, int newBufferSizeBytes)
double b = x*x*(3*x - 5) + 2; double b = x*x*(3*x - 5) + 2;
double c = x*(x*(-3*x + 4) + 1); double c = x*(x*(-3*x + 4) + 1);
double d = x*x*(x - 1); double d = x*x*(x - 1);
catmullrom_lut[i][0] = (s16)(32767 * 0.5*a); catmullrom_lut[i][0] = (u16)(65535 * -0.5*a);
catmullrom_lut[i][1] = (s16)(32767 * 0.5*b); catmullrom_lut[i][1] = (u16)(65535 * 0.5*b);
catmullrom_lut[i][2] = (s16)(32767 * 0.5*c); catmullrom_lut[i][2] = (u16)(65535 * 0.5*c);
catmullrom_lut[i][3] = (s16)(32767 * 0.5*d); catmullrom_lut[i][3] = (u16)(65535 * -0.5*d);
} }
for (size_t i = 0; i < COSINE_INTERPOLATION_RESOLUTION; i++) for (size_t i = 0; i < COSINE_INTERPOLATION_RESOLUTION; i++)
cos_lut[i] = (s16)(32767 * ((1.0 - cos(((double)i/(double)COSINE_INTERPOLATION_RESOLUTION) * M_PI)) * 0.5)); cos_lut[i] = (u16)((1u<<16) * ((1.0 - cos(((double)i/(double)COSINE_INTERPOLATION_RESOLUTION) * M_PI)) * 0.5));
SPU_core = new SPU_struct((int)ceil(samples_per_hline)); SPU_core = new SPU_struct((int)ceil(samples_per_hline));
SPU_Reset(); SPU_Reset();
@ -1050,13 +1050,13 @@ template<SPUInterpolationMode INTERPOLATE_MODE> static FORCEINLINE s32 Interpola
case SPUInterpolation_CatmullRom: case SPUInterpolation_CatmullRom:
{ {
// Catmull-Rom spline // Catmull-Rom spline
// Delay: 2 samples // Delay: 2 samples, Maximum gain: 1.25
s32 a = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 3)]; s32 a = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 3)];
s32 b = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 2)]; s32 b = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 2)];
s32 c = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 1)]; s32 c = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 1)];
s32 d = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 0)]; s32 d = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 0)];
const s16 *w = catmullrom_lut[subPos >> (32 - CATMULLROM_INTERPOLATION_RESOLUTION_BITS)]; const u16 *w = catmullrom_lut[subPos >> (32 - CATMULLROM_INTERPOLATION_RESOLUTION_BITS)];
return (a*w[0] + b*w[1] + c*w[2] + d*w[3]) >> 15; return (-a*(s32)w[0] + b*(s32)w[1] + c*(s32)w[2] - d*(s32)w[3]) >> 16;
} }
case SPUInterpolation_Cosine: case SPUInterpolation_Cosine:
@ -1064,25 +1064,26 @@ template<SPUInterpolationMode INTERPOLATE_MODE> static FORCEINLINE s32 Interpola
// Cosine Interpolation Formula: // Cosine Interpolation Formula:
// ratio2 = (1 - cos(ratio * M_PI)) / 2 // ratio2 = (1 - cos(ratio * M_PI)) / 2
// sampleI = sampleA * (1 - ratio2) + sampleB * ratio2 // sampleI = sampleA * (1 - ratio2) + sampleB * ratio2
// Delay: 1 sample // Delay: 1 sample, Maximum gain: 1.0
s32 a = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 1)]; s32 a = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 1)];
s32 b = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 0)]; s32 b = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 0)];
return a + ((b - a)*cos_lut[subPos >> (32 - COSINE_INTERPOLATION_RESOLUTION_BITS)] >> 15); s32 subPos16 = (s32)cos_lut[subPos >> (32 - COSINE_INTERPOLATION_RESOLUTION_BITS)];
return a + ((b - a)*subPos16 >> 16);
} }
case SPUInterpolation_Linear: case SPUInterpolation_Linear:
{ {
// Linear Interpolation Formula: // Linear Interpolation Formula:
// sampleI = sampleA * (1 - ratio) + sampleB * ratio // sampleI = sampleA * (1 - ratio) + sampleB * ratio
// Delay: 1 sample // Delay: 1 sample, Maximum gain: 1.0
s32 a = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 1)]; s32 a = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 1)];
s32 b = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 0)]; s32 b = pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs - 0)];
s32 subPos15 = subPos >> (32 - 15); s32 subPos16 = subPos >> (32 - 16);
return a + ((b - a)*subPos15 >> 15); return a + ((b - a)*subPos16 >> 16);
} }
default: default:
// Delay: 0 samples // Delay: 0 samples, Maximum gain: 1.0
return pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs)]; return pcm16b[SPUCHAN_PCM16B_AT(pcm16bOffs)];
} }
} }