Add a mixing function to blend HRIRs

This is a bit more efficient than calling the normal HRTF mixing function
twice, and helps solve the problem of the values generated from convolution not
being consistent with the new HRIR.

1 files changed, 52 insertions, 7 deletions

diff --git a/Alc/mixer_inc.c b/Alc/mixer_inc.c
index 16c3a61e..3c9d4dc5 100644
--- a/Alc/mixer_inc.c
+++ b/Alc/mixer_inc.c
@@ -32,21 +32,66 @@ void MixHrtf(ALfloat *restrict LeftOut, ALfloat *restrict RightOut,
     for(i = 0;i < BufferSize;i++)
     {
         hrtfstate->History[Offset&HRTF_HISTORY_MASK] = *(data++);
-        left = hrtfstate->History[(Offset-Delay[0])&HRTF_HISTORY_MASK];
-        right = hrtfstate->History[(Offset-Delay[1])&HRTF_HISTORY_MASK];
+        left = hrtfstate->History[(Offset-Delay[0])&HRTF_HISTORY_MASK]*gain;
+        right = hrtfstate->History[(Offset-Delay[1])&HRTF_HISTORY_MASK]*gain;
 
-        hrtfstate->Values[(Offset+IrSize)&HRIR_MASK][0] = 0.0f;
-        hrtfstate->Values[(Offset+IrSize)&HRIR_MASK][1] = 0.0f;
-        Offset++;
+        hrtfstate->Values[(Offset+IrSize-1)&HRIR_MASK][0] = 0.0f;
+        hrtfstate->Values[(Offset+IrSize-1)&HRIR_MASK][1] = 0.0f;
 
         ApplyCoeffs(Offset, hrtfstate->Values, IrSize, Coeffs, left, right);
-        *(LeftOut++)  += hrtfstate->Values[Offset&HRIR_MASK][0]*gain;
-        *(RightOut++) += hrtfstate->Values[Offset&HRIR_MASK][1]*gain;
+        *(LeftOut++)  += hrtfstate->Values[Offset&HRIR_MASK][0];
+        *(RightOut++) += hrtfstate->Values[Offset&HRIR_MASK][1];
+
         gain += gainstep;
+        Offset++;
     }
     hrtfparams->Gain = gain;
 }
 
+void MixHrtfBlend(ALfloat *restrict LeftOut, ALfloat *restrict RightOut,
+                  const ALfloat *data, ALsizei Offset, ALsizei OutPos,
+                  const ALsizei IrSize, const HrtfParams *oldparams,
+                  MixHrtfParams *newparams, HrtfState *hrtfstate,
+                  ALsizei BufferSize)
+{
+    const ALfloat (*OldCoeffs)[2] = ASSUME_ALIGNED(oldparams->Coeffs, 16);
+    const ALsizei OldDelay[2] = { oldparams->Delay[0], oldparams->Delay[1] };
+    ALfloat oldGain = oldparams->Gain;
+    ALfloat oldGainStep = -oldGain / (ALfloat)BufferSize;
+    const ALfloat (*NewCoeffs)[2] = ASSUME_ALIGNED(newparams->Coeffs, 16);
+    const ALsizei NewDelay[2] = { newparams->Delay[0], newparams->Delay[1] };
+    ALfloat newGain = newparams->Gain;
+    ALfloat newGainStep = newparams->GainStep;
+    ALfloat left, right;
+    ALsizei i;
+
+    LeftOut  += OutPos;
+    RightOut += OutPos;
+    for(i = 0;i < BufferSize;i++)
+    {
+        hrtfstate->Values[(Offset+IrSize-1)&HRIR_MASK][0] = 0.0f;
+        hrtfstate->Values[(Offset+IrSize-1)&HRIR_MASK][1] = 0.0f;
+
+        hrtfstate->History[Offset&HRTF_HISTORY_MASK] = *(data++);
+
+        left = hrtfstate->History[(Offset-OldDelay[0])&HRTF_HISTORY_MASK]*oldGain;
+        right = hrtfstate->History[(Offset-OldDelay[1])&HRTF_HISTORY_MASK]*oldGain;
+        ApplyCoeffs(Offset, hrtfstate->Values, IrSize, OldCoeffs, left, right);
+
+        left = hrtfstate->History[(Offset-NewDelay[0])&HRTF_HISTORY_MASK]*newGain;
+        right = hrtfstate->History[(Offset-NewDelay[1])&HRTF_HISTORY_MASK]*newGain;
+        ApplyCoeffs(Offset, hrtfstate->Values, IrSize, NewCoeffs, left, right);
+
+        *(LeftOut++)  += hrtfstate->Values[Offset&HRIR_MASK][0];
+        *(RightOut++) += hrtfstate->Values[Offset&HRIR_MASK][1];
+
+        oldGain += oldGainStep;
+        newGain += newGainStep;
+        Offset++;
+    }
+    newparams->Gain = newGain;
+}
+
 void MixDirectHrtf(ALfloat *restrict LeftOut, ALfloat *restrict RightOut,
                    const ALfloat *data, ALsizei Offset, const ALsizei IrSize,
                    const ALfloat (*restrict Coeffs)[2], ALfloat (*restrict Values)[2],