void HrtfPanner::pan(float* input, float *left_output, float *right_output) {
//Do we need to crossfade? We do if we've moved more than the threshold and crossfading is being allowed.
bool needsCrossfade = should_crossfade && fabs(azimuth-prev_azimuth)+fabs(elevation-prev_elevation) >= crossfade_threshold;
if(azimuth != prev_azimuth || elevation != prev_elevation) {
if(needsCrossfade) {
std::swap(left_convolver, prev_left_convolver);
std::swap(right_convolver, prev_right_convolver);
left_convolver->reset();
right_convolver->reset();
}
float* left_response_ptr = left_response_workspace.get(response_length);
float* right_response_ptr = right_response_workspace.get(response_length);
float leftDelay, rightDelay;
std::tie(leftDelay, rightDelay) = hrtf->computeCoefficientsStereo(elevation, azimuth, left_response_ptr, right_response_ptr);
left_convolver->setResponse(response_length, left_response_ptr);
right_convolver->setResponse(response_length, right_response_ptr);
left_delay->setDelay(leftDelay, needsCrossfade);
right_delay->setDelay(rightDelay, needsCrossfade);
}
//These two convolutions always happen.
left_convolver->convolve(input, left_output);
right_convolver->convolve(input, right_output);
if(needsCrossfade) {
double delta = 1.0/block_size;
float* crossfade_ptr = crossfade_workspace.get(block_size);
prev_left_convolver->convolve(input, crossfade_ptr);
for(int i = 0; i < block_size; i++) left_output[i] = (block_size-i)*delta*crossfade_ptr[i]+i*delta*left_output[i];
prev_right_convolver->convolve(input, crossfade_ptr);
for(int i = 0; i < block_size; i++) right_output[i] = (block_size-i)*delta*crossfade_ptr[i]+i*delta*right_output[i];
}
prev_azimuth = azimuth;
prev_elevation = elevation;
left_delay->process(block_size, left_output, left_output);
right_delay->process(block_size, right_output, right_output);
}
HrtfPanner::HrtfPanner(int _block_size, float _sr, std::shared_ptr<HrtfData> _hrtf): block_size(_block_size), sr(_sr), hrtf(_hrtf) {
response_length = hrtf->getLength();
float* left_response_ptr= left_response_workspace.get(response_length);
float* right_response_ptr = right_response_workspace.get(response_length);
hrtf->computeCoefficientsStereo(azimuth, elevation, left_response_ptr, right_response_ptr);
left_convolver = new BlockConvolver(block_size);
right_convolver = new BlockConvolver(block_size);
prev_left_convolver = new BlockConvolver(block_size);
prev_right_convolver = new BlockConvolver(block_size);
left_convolver->setResponse(response_length, left_response_ptr);
right_convolver->setResponse(response_length, right_response_ptr);
left_delay = new DoppleringDelayLine(hrtf->getMaxDelay(), _sr);
right_delay = new DoppleringDelayLine(hrtf->getMaxDelay(), _sr);
// Move delay over 1 MS.
left_delay->setInterpolationTime(0.003);
right_delay->setInterpolationTime(0.003);
}