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Slightly blend left and right audio channels #2038

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Slightly blend left and right audio channels #2038

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10 changes: 10 additions & 0 deletions libraries/audio/src/AudioSRC.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -963,6 +963,8 @@ void AudioSRC::convertOutput(float** inputs, int16_t* output, int numFrames) {

} else if (_numChannels == 2) {

__m128 d8 = _mm_set1_ps(8.0f);
__m128 m7 = _mm_set1_ps(7.0f / 8.0f);
int i = 0;
for (; i < numFrames - 3; i += 4) {
__m128 f0 = _mm_mul_ps(_mm_loadu_ps(&inputs[0][i]), scale);
Expand All @@ -972,6 +974,10 @@ void AudioSRC::convertOutput(float** inputs, int16_t* output, int numFrames) {
f0 = _mm_add_ps(f0, d0);
f1 = _mm_add_ps(f1, d0);

// blend left and right slightly to make headphones less painful to use
f0 = _mm_add_ps(_mm_mul_ps(f0, m7), _mm_div_ps(f1, d8));
f1 = _mm_add_ps(_mm_mul_ps(f1, m7), _mm_div_ps(f0, d8));

// round and saturate
__m128i a0 = _mm_cvtps_epi32(f0);
__m128i a1 = _mm_cvtps_epi32(f1);
Expand Down Expand Up @@ -1243,6 +1249,10 @@ void AudioSRC::convertOutput(float** inputs, int16_t* output, int numFrames) {
f0 += d;
f1 += d;

// blend left and right slightly to make headphones less painful to use
f0 = f0 * (7.0f / 8.0f) + f1 / 8.0f;
f1 = f1 * (7.0f / 8.0f) + f0 / 8.0f;

// round and saturate
f0 += (f0 < 0.0f ? -0.5f : +0.5f);
f1 += (f1 < 0.0f ? -0.5f : +0.5f);
Expand Down