Implement NFC filters for Ambisonic rendering

NFC filters currently only work when rendering to ambisonic buffers, which
includes HQ rendering and ambisonic output. There are two new config options:
'decoder/nfc' (default on) enables or disables use of NFC filters globally, and
'decoder/nfc-ref-delay' (default 0) specifies the reference delay parameter for
NFC-HOA rendering with ambisonic output (a value of 0 disables NFC).

Currently, NFC filters rely on having an appropriate value set for
AL_METERS_PER_UNIT to get the correct scaling. HQ rendering uses the averaged
speaker distances as a control/reference, and currently doesn't correct for
individual speaker distances (if the speakers are all equidistant, this is
fine, otherwise per-speaker correction should be done as well).

1 files changed, 12 insertions, 0 deletions

diff --git a/OpenAL32/alSource.c b/OpenAL32/alSource.c
index c4c0bfb1..55a4aae1 100644
--- a/OpenAL32/alSource.c
+++ b/OpenAL32/alSource.c
@@ -3084,6 +3084,7 @@ ALvoid SetSourceState(ALsource *Source, ALCcontext *Context, ALenum state)
         voice->Step = 0;
 
         voice->Moving = AL_FALSE;
+        voice->Flags = 0;
         for(i = 0;i < MAX_INPUT_CHANNELS;i++)
         {
             ALsizei j;
@@ -3095,6 +3096,17 @@ ALvoid SetSourceState(ALsource *Source, ALCcontext *Context, ALenum state)
                 voice->Direct.Params[i].Hrtf.State.Values[j][1] = 0.0f;
             }
         }
+        if(device->AvgSpeakerDist > 0.0f)
+        {
+            ALfloat w1 = SPEEDOFSOUNDMETRESPERSEC /
+                         (device->AvgSpeakerDist * device->Frequency);
+            for(i = 0;i < voice->NumChannels;i++)
+            {
+                NfcFilterCreate1(&voice->Direct.Params[i].NFCtrlFilter[0], 0.0f, w1);
+                NfcFilterCreate2(&voice->Direct.Params[i].NFCtrlFilter[1], 0.0f, w1);
+                NfcFilterCreate3(&voice->Direct.Params[i].NFCtrlFilter[2], 0.0f, w1);
+            }
+        }
 
         ATOMIC_STORE(&voice->Source, Source, almemory_order_relaxed);
         ATOMIC_STORE(&voice->Playing, true, almemory_order_release);