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pcm/Dsd2Pcm: move formula to CalculateCtableValue()

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This commit is contained in:
Max Kellermann
2020-01-14 22:03:19 +01:00
parent 4d102c4770
commit 4d95402e4e
1 changed files with 13 additions and 7 deletions

20
src/pcm/Dsd2Pcm.cxx

@ -124,21 +124,27 @@ static constexpr double htaps[HTAPS] = {
static float ctables[CTABLES][256]; static float ctables[CTABLES][256];
static int precalculated = 0; static int precalculated = 0;
static constexpr float
CalculateCtableValue(int t, int k, int e) noexcept
{
double acc = 0;
for (int m = 0; m < k; ++m) {
acc += (((e >> (7 - m)) & 1) * 2 - 1) * htaps[t * 8 + m];
}
return acc;
}
static void static void
precalc() noexcept precalc() noexcept
{ {
int t, e, m, k; int t, e, k;
double acc;
if (precalculated) return; if (precalculated) return;
for (t=0; t<CTABLES; ++t) { for (t=0; t<CTABLES; ++t) {
k = HTAPS - t*8; k = HTAPS - t*8;
if (k>8) k=8; if (k>8) k=8;
for (e=0; e<256; ++e) { for (e=0; e<256; ++e) {
acc = 0.0; ctables[CTABLES-1-t][e] = CalculateCtableValue(t, k, e);
for (m=0; m<k; ++m) {
acc += (((e >> (7-m)) & 1)*2-1) * htaps[t*8+m];
}
ctables[CTABLES-1-t][e] = (float)acc;
} }
} }
precalculated = 1; precalculated = 1;