Simplify handling effect output for spatial effects

Effects are given a 3D ambisonic buffer of the same order as the device, for
processing surround sound. Effects that pass input channels to matching output
channels as it processes them don't need to mix each input channel to all
output channels.

At most, an input channel may mix to a different output channel, if the target
buffer uses a different channel layout, and need a gain adjustment, if it uses
a different scaling. With a 2D output buffer, a number of channels can be
skipped altogether.

1 files changed, 28 insertions, 18 deletions

diff --git a/alc/effects/modulator.cpp b/alc/effects/modulator.cpp
index c854f1e9..29009247 100644
--- a/alc/effects/modulator.cpp
+++ b/alc/effects/modulator.cpp
@@ -84,10 +84,12 @@ struct ModulatorState final : public EffectState {
     uint mStep{1};
 
     struct {
-        BiquadFilter Filter;
+        uint mTargetChannel{INVALID_CHANNEL_INDEX};
 
-        float CurrentGains[MaxAmbiChannels]{};
-        float TargetGains[MaxAmbiChannels]{};
+        BiquadFilter mFilter;
+
+        float mCurrentGain{};
+        float mTargetGain{};
     } mChans[MaxAmbiChannels];
 
 
@@ -104,8 +106,9 @@ void ModulatorState::deviceUpdate(const DeviceBase*, const Buffer&)
 {
     for(auto &e : mChans)
     {
-        e.Filter.clear();
-        std::fill(std::begin(e.CurrentGains), std::end(e.CurrentGains), 0.0f);
+        e.mTargetChannel = INVALID_CHANNEL_INDEX;
+        e.mFilter.clear();
+        e.mCurrentGain = 0.0f;
     }
 }
 
@@ -129,14 +132,17 @@ void ModulatorState::update(const ContextBase *context, const EffectSlot *slot,
     float f0norm{props->Modulator.HighPassCutoff / static_cast<float>(device->Frequency)};
     f0norm = clampf(f0norm, 1.0f/512.0f, 0.49f);
     /* Bandwidth value is constant in octaves. */
-    mChans[0].Filter.setParamsFromBandwidth(BiquadType::HighPass, f0norm, 1.0f, 0.75f);
+    mChans[0].mFilter.setParamsFromBandwidth(BiquadType::HighPass, f0norm, 1.0f, 0.75f);
     for(size_t i{1u};i < slot->Wet.Buffer.size();++i)
-        mChans[i].Filter.copyParamsFrom(mChans[0].Filter);
+        mChans[i].mFilter.copyParamsFrom(mChans[0].mFilter);
 
     mOutTarget = target.Main->Buffer;
-    auto set_gains = [slot,target](auto &chan, al::span<const float,MaxAmbiChannels> coeffs)
-    { ComputePanGains(target.Main, coeffs.data(), slot->Gain, chan.TargetGains); };
-    SetAmbiPanIdentity(std::begin(mChans), slot->Wet.Buffer.size(), set_gains);
+    auto set_channel = [this](size_t idx, uint target, float gain)
+    {
+        mChans[idx].mTargetChannel = target;
+        mChans[idx].mTargetGain = gain;
+    };
+    target.Main->setAmbiMixParams(slot->Wet, slot->Gain, set_channel);
 }
 
 void ModulatorState::process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
@@ -153,14 +159,18 @@ void ModulatorState::process(const size_t samplesToDo, const al::span<const Floa
         auto chandata = std::begin(mChans);
         for(const auto &input : samplesIn)
         {
-            alignas(16) float temps[MAX_UPDATE_SAMPLES];
-
-            chandata->Filter.process({&input[base], td}, temps);
-            for(size_t i{0u};i < td;i++)
-                temps[i] *= modsamples[i];
-
-            MixSamples({temps, td}, samplesOut, chandata->CurrentGains, chandata->TargetGains,
-                samplesToDo-base, base);
+            const size_t outidx{chandata->mTargetChannel};
+            if(outidx != INVALID_CHANNEL_INDEX)
+            {
+                alignas(16) float temps[MAX_UPDATE_SAMPLES];
+
+                chandata->mFilter.process({&input[base], td}, temps);
+                for(size_t i{0u};i < td;i++)
+                    temps[i] *= modsamples[i];
+
+                MixSamples({temps, td}, {&samplesOut[outidx], 1}, &chandata->mCurrentGain,
+                    &chandata->mTargetGain, samplesToDo-base, base);
+            }
             ++chandata;
         }