Avoid (expensive) audio interpolation when sample rates already match

2 files changed, 8 insertions, 4 deletions

diff --git a/src/audio_core/algorithm/interpolate.cpp b/src/audio_core/algorithm/interpolate.cpp
index 3aea9b0f2..5005ba519 100644
--- a/src/audio_core/algorithm/interpolate.cpp
+++ b/src/audio_core/algorithm/interpolate.cpp
@@ -54,8 +54,9 @@ std::vector<s16> Interpolate(InterpolationState& state, std::vector<s16> input,
             double l = 0.0;
             double r = 0.0;
             for (std::size_t j = 0; j < h.size(); j++) {
-                l += Lanczos(taps, pos + j - taps + 1) * h[j][0];
-                r += Lanczos(taps, pos + j - taps + 1) * h[j][1];
+                const double lanczos_calc = Lanczos(taps, pos + j - taps + 1);
+                l += lanczos_calc * h[j][0];
+                r += lanczos_calc * h[j][1];
             }
             output.emplace_back(static_cast<s16>(std::clamp(l, -32768.0, 32767.0)));
             output.emplace_back(static_cast<s16>(std::clamp(r, -32768.0, 32767.0)));
diff --git a/src/audio_core/audio_renderer.cpp b/src/audio_core/audio_renderer.cpp
index 2e59894ab..2683f3a5f 100644
--- a/src/audio_core/audio_renderer.cpp
+++ b/src/audio_core/audio_renderer.cpp
@@ -285,8 +285,11 @@ void AudioRenderer::VoiceState::RefreshBuffer() {
         break;
     }
 
-    samples =
-        Interpolate(interp_state, std::move(samples), GetInfo().sample_rate, STREAM_SAMPLE_RATE);
+    // Only interpolate when necessary, expensive.
+    if (GetInfo().sample_rate != STREAM_SAMPLE_RATE) {
+        samples = Interpolate(interp_state, std::move(samples), GetInfo().sample_rate,
+                              STREAM_SAMPLE_RATE);
+    }
 
     is_refresh_pending = false;
 }