Use an interpolated FIR filter for cubic resampling

Similar to how the bsinc filters work, but optimized for 4-point filtering. At
least the SSE version is notably faster than calculating the coefficients in
real time.

1 files changed, 9 insertions, 0 deletions

diff --git a/core/mixer/defs.h b/core/mixer/defs.h
index 80d9fc7f..74a474fe 100644
--- a/core/mixer/defs.h
+++ b/core/mixer/defs.h
@@ -8,6 +8,7 @@
 #include "core/bufferline.h"
 #include "core/resampler_limits.h"
 
+struct CubicCoefficients;
 struct HrtfChannelState;
 struct HrtfFilter;
 struct MixHrtfFilter;
@@ -51,7 +52,15 @@ struct BsincState {
     const float *filter;
 };
 
+struct CubicState {
+    /* Filter coefficients, and coefficient deltas. Starting at phase index 0,
+     * each subsequent phase index follows contiguously.
+     */
+    const CubicCoefficients *filter;
+};
+
 union InterpState {
+    CubicState cubic;
     BsincState bsinc;
 };