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Avoid returning an array for initialization

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This commit is contained in:
Chris Robinson
2020-12-05 07:27:54 -08:00
parent 1679ab937e
commit 2fc10a2bc0
1 changed files with 38 additions and 37 deletions
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core/uhjfilter.cpp
+38 -37
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@@ -19,8 +19,9 @@ namespace {
using complex_d = std::complex<double>;
std::array<float,Uhj2Encoder::sFilterSize> GenerateFilter()
{
struct PhaseShifterT {
alignas(16) std::array<float,Uhj2Encoder::sFilterSize> Coeffs;
/* Some notes on this filter construction.
*
* A wide-band phase-shift filter needs a delay to maintain linearity. A
@@ -39,37 +40,37 @@ std::array<float,Uhj2Encoder::sFilterSize> GenerateFilter()
* The same filter can be applied regardless of the device's sample rate
* and achieve the same effect.
*/
constexpr size_t fft_size{Uhj2Encoder::sFilterSize * 2};
constexpr size_t half_size{fft_size / 2};
/* Generate a frequency domain impulse with a +90 degree phase offset.
* Reconstruct the mirrored frequencies to convert to the time domain.
*/
auto fftBuffer = std::make_unique<complex_d[]>(fft_size);
std::fill_n(fftBuffer.get(), fft_size, complex_d{});
fftBuffer[half_size] = 1.0;
forward_fft({fftBuffer.get(), fft_size});
for(size_t i{0};i < half_size+1;++i)
fftBuffer[i] = complex_d{-fftBuffer[i].imag(), fftBuffer[i].real()};
for(size_t i{half_size+1};i < fft_size;++i)
fftBuffer[i] = std::conj(fftBuffer[fft_size - i]);
inverse_fft({fftBuffer.get(), fft_size});
/* Reverse the filter for simpler processing, and store only the non-0
* coefficients.
*/
auto ret = std::make_unique<std::array<float,Uhj2Encoder::sFilterSize>>();
auto fftiter = fftBuffer.get() + half_size + (Uhj2Encoder::sFilterSize-1);
for(float &coeff : *ret)
PhaseShifterT()
{
coeff = static_cast<float>(fftiter->real() / double{fft_size});
fftiter -= 2;
}
return *ret;
}
alignas(16) const auto PShiftCoeffs = GenerateFilter();
constexpr size_t fft_size{Uhj2Encoder::sFilterSize * 2};
constexpr size_t half_size{fft_size / 2};
/* Generate a frequency domain impulse with a +90 degree phase offset.
* Reconstruct the mirrored frequencies to convert to the time domain.
*/
auto fftBuffer = std::make_unique<complex_d[]>(fft_size);
std::fill_n(fftBuffer.get(), fft_size, complex_d{});
fftBuffer[half_size] = 1.0;
forward_fft({fftBuffer.get(), fft_size});
for(size_t i{0};i < half_size+1;++i)
fftBuffer[i] = complex_d{-fftBuffer[i].imag(), fftBuffer[i].real()};
for(size_t i{half_size+1};i < fft_size;++i)
fftBuffer[i] = std::conj(fftBuffer[fft_size - i]);
inverse_fft({fftBuffer.get(), fft_size});
/* Reverse the filter for simpler processing, and store only the non-0
* coefficients.
*/
auto fftiter = fftBuffer.get() + half_size + (Uhj2Encoder::sFilterSize-1);
for(float &coeff : Coeffs)
{
coeff = static_cast<float>(fftiter->real() / double{fft_size});
fftiter -= 2;
}
}
};
const PhaseShifterT PShift{};
void allpass_process(al::span<float> dst, const float *RESTRICT src)
{
@@ -80,9 +81,9 @@ void allpass_process(al::span<float> dst, const float *RESTRICT src)
do {
__m128 r04{_mm_setzero_ps()};
__m128 r14{_mm_setzero_ps()};
for(size_t j{0};j < PShiftCoeffs.size();j+=4)
for(size_t j{0};j < PShift.Coeffs.size();j+=4)
{
const __m128 coeffs{_mm_load_ps(&PShiftCoeffs[j])};
const __m128 coeffs{_mm_load_ps(&PShift.Coeffs[j])};
const __m128 s0{_mm_loadu_ps(&src[j*2])};
const __m128 s1{_mm_loadu_ps(&src[j*2 + 4])};
@@ -106,9 +107,9 @@ void allpass_process(al::span<float> dst, const float *RESTRICT src)
if((dst.size()&1))
{
__m128 r4{_mm_setzero_ps()};
for(size_t j{0};j < PShiftCoeffs.size();j+=4)
for(size_t j{0};j < PShift.Coeffs.size();j+=4)
{
const __m128 coeffs{_mm_load_ps(&PShiftCoeffs[j])};
const __m128 coeffs{_mm_load_ps(&PShift.Coeffs[j])};
/* NOTE: This could alternatively be done with two unaligned loads
* and a shuffle. Which would be better?
*/
@@ -126,8 +127,8 @@ void allpass_process(al::span<float> dst, const float *RESTRICT src)
for(float &output : dst)
{
float ret{0.0f};
for(size_t j{0};j < PShiftCoeffs.size();++j)
ret += src[j*2] * PShiftCoeffs[j];
for(size_t j{0};j < PShift.Coeffs.size();++j)
ret += src[j*2] * PShift.Coeffs[j];
output += ret;
++src;