Apply the ambisonic HF scaling in real-time with HRTF

Rather than applying the HF scale to the IRs necessitating them to be truncated
along with increasing the IR size, it can be applied to the input signal for
the same results. Consequently, the IR size can be notably shortened while
avoiding the extra truncation. In its place, the delayed reversed all-pass
technique can still be used on the input for maintaining phase when applying
the bandsplit/hfscalar filter to the input signal.

1 files changed, 17 insertions, 3 deletions

diff --git a/alc/hrtf.h b/alc/hrtf.h
index 5b709e30..7876265b 100644
--- a/alc/hrtf.h
+++ b/alc/hrtf.h
@@ -12,6 +12,8 @@
 #include "alspan.h"
 #include "ambidefs.h"
 #include "atomic.h"
+#include "bufferline.h"
+#include "filters/splitter.h"
 #include "intrusive_ptr.h"
 #include "vector.h"
 
@@ -77,12 +79,24 @@ struct AngularPoint {
     AzRadians Azim;
 };
 
+#define HRTF_DIRECT_DELAY 128
 struct DirectHrtfState {
+    struct ChannelData {
+        std::array<float,HRTF_DIRECT_DELAY> mDelay{};
+        BandSplitter mSplitter;
+        float mHfScale{};
+        alignas(16) HrirArray mCoeffs{};
+    };
+
+    std::array<float,HRTF_DIRECT_DELAY> mLeftDelay{};
+    std::array<float,HRTF_DIRECT_DELAY> mRightDelay{};
+    std::array<float,HRTF_DIRECT_DELAY+BUFFERSIZE> mTemp;
+
     /* HRTF filter state for dry buffer content */
     ALuint mIrSize{0};
-    al::FlexArray<HrirArray,16> mCoeffs;
+    al::FlexArray<ChannelData> mChannels;
 
-    DirectHrtfState(size_t numchans) : mCoeffs{numchans} { }
+    DirectHrtfState(size_t numchans) : mChannels{numchans} { }
     /**
      * Produces HRTF filter coefficients for decoding B-Format, given a set of
      * virtual speaker positions, a matching decoding matrix, and per-order
@@ -95,7 +109,7 @@ struct DirectHrtfState {
 
     static std::unique_ptr<DirectHrtfState> Create(size_t num_chans);
 
-    DEF_FAM_NEWDEL(DirectHrtfState, mCoeffs)
+    DEF_FAM_NEWDEL(DirectHrtfState, mChannels)
 };