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Add direct mix (non-spatialized) audio renderers with gain crossfade

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This commit is contained in:
Ken Cooke 2019-03-30 16:39:35 -07:00
parent ebc73bebc5
commit 423da7d737
2 changed files with 71 additions and 0 deletions
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65
libraries/audio/src/AudioHRTF.cpp
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@ -750,6 +750,43 @@ static void interpolate(const float* src0, const float* src1, float* dst, float
#endif
// apply gain crossfade with accumulation (interleaved)
static void gainfade_1x2(int16_t* src, float* dst, const float* win, float gain0, float gain1, int numFrames) {
gain0 *= (1/32768.0f); // int16_t to float
gain1 *= (1/32768.0f);
for (int i = 0; i < numFrames; i++) {
float frac = win[i];
float gain = gain1 + frac * (gain0 - gain1);
float x0 = (float)src[i] * gain;
dst[2*i+0] += x0;
dst[2*i+1] += x0;
}
}
// apply gain crossfade with accumulation (interleaved)
static void gainfade_2x2(int16_t* src, float* dst, const float* win, float gain0, float gain1, int numFrames) {
gain0 *= (1/32768.0f); // int16_t to float
gain1 *= (1/32768.0f);
for (int i = 0; i < numFrames; i++) {
float frac = win[i];
float gain = gain1 + frac * (gain0 - gain1);
float x0 = (float)src[2*i+0] * gain;
float x1 = (float)src[2*i+1] * gain;
dst[2*i+0] += x0;
dst[2*i+1] += x1;
}
}
// design a 2nd order Thiran allpass
static void ThiranBiquad(float f, float& b0, float& b1, float& b2, float& a1, float& a2) {
@ -1175,3 +1212,31 @@ void AudioHRTF::render(int16_t* input, float* output, int index, float azimuth,
_resetState = false;
}
void AudioHRTF::mixMono(int16_t* input, float* output, float gain, int numFrames) {
assert(numFrames == HRTF_BLOCK);
// apply global and local gain adjustment
gain *= _gainAdjust;
// crossfade gain and accumulate
gainfade_1x2(input, output, crossfadeTable, _gainState, gain, HRTF_BLOCK);
// new parameters become old
_gainState = gain;
}
void AudioHRTF::mixStereo(int16_t* input, float* output, float gain, int numFrames) {
assert(numFrames == HRTF_BLOCK);
// apply global and local gain adjustment
gain *= _gainAdjust;
// crossfade gain and accumulate
gainfade_2x2(input, output, crossfadeTable, _gainState, gain, HRTF_BLOCK);
// new parameters become old
_gainState = gain;
}

6
libraries/audio/src/AudioHRTF.h
View file

@ -50,6 +50,12 @@ public:
//
void render(int16_t* input, float* output, int index, float azimuth, float distance, float gain, int numFrames);
//
// Non-spatialized direct mix (accumulates into existing output)
//
void mixMono(int16_t* input, float* output, float gain, int numFrames);
void mixStereo(int16_t* input, float* output, float gain, int numFrames);
//
// Fast path when input is known to be silent and state as been flushed
//