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#include "config.h"
#include "mixer.h"
#include <cmath>
#include "alnumbers.h"
#include "devformat.h"
#include "device.h"
#include "mixer/defs.h"
struct CTag;
MixerFunc MixSamples{Mix_<CTag>};
std::array<float,MaxAmbiChannels> CalcAmbiCoeffs(const float y, const float z, const float x,
const float spread)
{
std::array<float,MaxAmbiChannels> coeffs{CalcAmbiCoeffs(y, z, x)};
if(spread > 0.0f)
{
/* Implement the spread by using a spherical source that subtends the
* angle spread. See:
* http://www.ppsloan.org/publications/StupidSH36.pdf - Appendix A3
*
* When adjusted for N3D normalization instead of SN3D, these
* calculations are:
*
* ZH0 = -sqrt(pi) * (-1+ca);
* ZH1 = 0.5*sqrt(pi) * sa*sa;
* ZH2 = -0.5*sqrt(pi) * ca*(-1+ca)*(ca+1);
* ZH3 = -0.125*sqrt(pi) * (-1+ca)*(ca+1)*(5*ca*ca - 1);
* ZH4 = -0.125*sqrt(pi) * ca*(-1+ca)*(ca+1)*(7*ca*ca - 3);
* ZH5 = -0.0625*sqrt(pi) * (-1+ca)*(ca+1)*(21*ca*ca*ca*ca - 14*ca*ca + 1);
*
* The gain of the source is compensated for size, so that the
* loudness doesn't depend on the spread. Thus:
*
* ZH0 = 1.0f;
* ZH1 = 0.5f * (ca+1.0f);
* ZH2 = 0.5f * (ca+1.0f)*ca;
* ZH3 = 0.125f * (ca+1.0f)*(5.0f*ca*ca - 1.0f);
* ZH4 = 0.125f * (ca+1.0f)*(7.0f*ca*ca - 3.0f)*ca;
* ZH5 = 0.0625f * (ca+1.0f)*(21.0f*ca*ca*ca*ca - 14.0f*ca*ca + 1.0f);
*/
const float ca{std::cos(spread * 0.5f)};
/* Increase the source volume by up to +3dB for a full spread. */
const float scale{std::sqrt(1.0f + al::numbers::inv_pi_v<float>/2.0f*spread)};
const float ZH0_norm{scale};
const float ZH1_norm{scale * 0.5f * (ca+1.f)};
const float ZH2_norm{scale * 0.5f * (ca+1.f)*ca};
const float ZH3_norm{scale * 0.125f * (ca+1.f)*(5.f*ca*ca-1.f)};
/* Zeroth-order */
coeffs[0] *= ZH0_norm;
/* First-order */
coeffs[1] *= ZH1_norm;
coeffs[2] *= ZH1_norm;
coeffs[3] *= ZH1_norm;
/* Second-order */
coeffs[4] *= ZH2_norm;
coeffs[5] *= ZH2_norm;
coeffs[6] *= ZH2_norm;
coeffs[7] *= ZH2_norm;
coeffs[8] *= ZH2_norm;
/* Third-order */
coeffs[9] *= ZH3_norm;
coeffs[10] *= ZH3_norm;
coeffs[11] *= ZH3_norm;
coeffs[12] *= ZH3_norm;
coeffs[13] *= ZH3_norm;
coeffs[14] *= ZH3_norm;
coeffs[15] *= ZH3_norm;
}
return coeffs;
}
void ComputePanGains(const MixParams *mix, const float*RESTRICT coeffs, const float ingain,
const al::span<float,MaxAmbiChannels> gains)
{
auto ambimap = mix->AmbiMap.cbegin();
auto iter = std::transform(ambimap, ambimap+mix->Buffer.size(), gains.begin(),
[coeffs,ingain](const BFChannelConfig &chanmap) noexcept -> float
{ return chanmap.Scale * coeffs[chanmap.Index] * ingain; }
);
std::fill(iter, gains.end(), 0.0f);
}
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