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/*############################################################################*/
/*# #*/
/*# Ambisonic C++ Library #*/
/*# CAmbisonicZoomer - Ambisonic Zoomer #*/
/*# Copyright © 2007 Aristotel Digenis #*/
/*# Copyright © 2017 Videolabs #*/
/*# #*/
/*# Filename: AmbisonicZoomer.cpp #*/
/*# Version: 0.2 #*/
/*# Date: 19/05/2007 #*/
/*# Author(s): Aristotel Digenis, Peter Stitt #*/
/*# Licence: LGPL (+ Proprietary) #*/
/*# #*/
/*############################################################################*/
#include "AmbisonicZoomer.h"
#include <iostream>
#include <algorithm>
CAmbisonicZoomer::CAmbisonicZoomer()
{
m_fZoom = 0;
}
bool CAmbisonicZoomer::Configure(unsigned nOrder, bool b3D, unsigned nMisc)
{
bool success = CAmbisonicBase::Configure(nOrder, b3D, nMisc);
if(!success)
return false;
m_AmbDecoderFront.Configure(m_nOrder, 1, kAmblib_Mono, 1);
//Calculate all the speaker coefficients
m_AmbDecoderFront.Refresh();
m_fZoomRed = 0.f;
m_AmbEncoderFront.reset(new float[m_nChannelCount]);
m_AmbEncoderFront_weighted.reset(new float[m_nChannelCount]);
a_m.reset(new float[m_nOrder + 1]);
// These weights a_m are applied to the channels of a corresponding order within the Ambisonics signals.
// When applied to the encoded channels and decoded to a particular loudspeaker direction they will create a
// virtual microphone pattern with no rear lobes.
// When used for decoding this is known as in-phase decoding.
for(unsigned iOrder = 0; iOrder < m_nOrder + 1; iOrder++)
a_m[iOrder] = (2*iOrder+1)*factorial(m_nOrder)*factorial(m_nOrder+1) / (factorial(m_nOrder+iOrder+1)*factorial(m_nOrder-iOrder));
unsigned iDegree=0;
for(unsigned iChannel = 0; iChannel<m_nChannelCount; iChannel++)
{
m_AmbEncoderFront[iChannel] = m_AmbDecoderFront.GetCoefficient(0, iChannel);
iDegree = (int)floor(sqrt(iChannel));
m_AmbEncoderFront_weighted[iChannel] = m_AmbEncoderFront[iChannel] * a_m[iDegree];
// Normalisation factor
m_AmbFrontMic += m_AmbEncoderFront[iChannel] * m_AmbEncoderFront_weighted[iChannel];
}
return true;
}
void CAmbisonicZoomer::Reset()
{
}
void CAmbisonicZoomer::Refresh()
{
m_fZoomRed = sqrtf(1.f - m_fZoom * m_fZoom);
m_fZoomBlend = 1.f - m_fZoom;
}
void CAmbisonicZoomer::SetZoom(float fZoom)
{
// Limit the zoom value to always preserve the spacial effect.
m_fZoom = std::min(fZoom, 0.99f);
}
float CAmbisonicZoomer::GetZoom()
{
return m_fZoom;
}
void CAmbisonicZoomer::Process(CBFormat* pBFSrcDst, unsigned nSamples)
{
for(unsigned niSample = 0; niSample < nSamples; niSample++)
{
float fMic = 0.f;
for(unsigned iChannel=0; iChannel<m_nChannelCount; iChannel++)
{
// virtual microphone with polar pattern narrowing as Ambisonic order increases
fMic += m_AmbEncoderFront_weighted[iChannel] * pBFSrcDst->m_ppfChannels[iChannel][niSample];
}
for(unsigned iChannel=0; iChannel<m_nChannelCount; iChannel++)
{
if(abs(m_AmbEncoderFront[iChannel])>1e-6)
{
// Blend original channel with the virtual microphone pointed directly to the front
// Only do this for Ambisonics components that aren't zero for an encoded frontal source
pBFSrcDst->m_ppfChannels[iChannel][niSample] = (m_fZoomBlend * pBFSrcDst->m_ppfChannels[iChannel][niSample]
+ m_AmbEncoderFront[iChannel]*m_fZoom*fMic) / (m_fZoomBlend + fabs(m_fZoom)*m_AmbFrontMic);
}
else{
// reduce the level of the Ambisonic components that are zero for a frontal source
pBFSrcDst->m_ppfChannels[iChannel][niSample] = pBFSrcDst->m_ppfChannels[iChannel][niSample] * m_fZoomRed;
}
}
}
}
float CAmbisonicZoomer::factorial(unsigned M)
{
unsigned ret = 1;
for(unsigned int i = 1; i <= M; ++i)
ret *= i;
return ret;
}
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