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-rw-r--r--src/audio_core/cubeb_sink.cpp20
1 files changed, 17 insertions, 3 deletions
diff --git a/src/audio_core/cubeb_sink.cpp b/src/audio_core/cubeb_sink.cpp
index 7047ed9cf..c4e0e30fe 100644
--- a/src/audio_core/cubeb_sink.cpp
+++ b/src/audio_core/cubeb_sink.cpp
@@ -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;