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cubeb_sink: Don't discard other channels when performing downmixing

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Previously, when performing downmixing, we would discard all channels except the left and right one.
This implementation respects them when mixing down to Stereo.
It is taken from this document: http://www.atsc.org/wp-content/uploads/2015/03/A52-201212-17.pdf.

Fixes Luigis Mansion 3 cutscene and Bayonetta audio.
This commit is contained in:
FearlessTobi 2020-02-24 18:34:00 +01:00 committed by bunnei
parent 84e9f9f395
commit 59d0d34dce
1 changed files with 17 additions and 3 deletions
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20
src/audio_core/cubeb_sink.cpp
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@ -8,6 +8,7 @@
#include "audio_core/cubeb_sink.h"
#include "audio_core/stream.h"
#include "audio_core/time_stretch.h"
#include "common/assert.h"
#include "common/logging/log.h"
#include "common/ring_buffer.h"
#include "core/settings.h"
@ -65,12 +66,25 @@ public:
void EnqueueSamples(u32 source_num_channels, const std::vector<s16>& samples) override {
if (source_num_channels > num_channels) {
// Downsample 6 channels to 2
ASSERT_MSG(source_num_channels == 6, "Channel count must be 6");
std::vector<s16> buf;
buf.reserve(samples.size() * num_channels / source_num_channels);
for (std::size_t i = 0; i < samples.size(); i += source_num_channels) {
for (std::size_t ch = 0; ch < num_channels; ch++) {
buf.push_back(samples[i + ch]);
}
// Downmixing implementation taken from the ATSC standard
const s16 left{samples[i + 0]};
const s16 right{samples[i + 1]};
const s16 center{samples[i + 2]};
const s16 surround_left{samples[i + 4]};
const s16 surround_right{samples[i + 5]};
// Not used in the ATSC reference implementation
[[maybe_unused]] const s16 low_frequency_effects { samples[i + 3] };
constexpr s32 clev{707}; // center mixing level coefficient
constexpr s32 slev{707}; // surround mixing level coefficient
buf.push_back(left + (clev * center / 1000) + (slev * surround_left / 1000));
buf.push_back(right + (clev * center / 1000) + (slev * surround_right / 1000));
}
queue.Push(buf);
return;