Don't do direct channels with UHJ output

Directly mixing a non-UHJ stereo signal into a UHJ stereo signal results in a
non-UHJ stereo signal. Such a mix can't be properly decoded anymore.

An option can probably be added for users that intend to listen to UHJ output
undecoded and let a stereo sound come through as-is on their speakers, but it
probably shouldn't be the default for cases where the output may be decoded
back.

1 files changed, 14 insertions, 20 deletions

diff --git a/alc/alc.cpp b/alc/alc.cpp
index b63f0f82..bbcd6d01 100644
--- a/alc/alc.cpp
+++ b/alc/alc.cpp
@@ -1430,15 +1430,6 @@ ALCenum EnumFromDevAmbi(DevAmbiScaling scaling)
  * existing ones. Based on Wine's DSound downmix values, which are based on
  * PulseAudio's.
  */
-const std::array<InputRemixMap,7> MonoDownmix{{
-    { FrontLeft,   {{{FrontCenter, 0.5f},      {LFE, 0.0f}}} },
-    { FrontRight,  {{{FrontCenter, 0.5f},      {LFE, 0.0f}}} },
-    { SideLeft,    {{{FrontCenter, 0.5f/9.0f}, {LFE, 0.0f}}} },
-    { SideRight,   {{{FrontCenter, 0.5f/9.0f}, {LFE, 0.0f}}} },
-    { BackLeft,    {{{FrontCenter, 0.5f/9.0f}, {LFE, 0.0f}}} },
-    { BackRight,   {{{FrontCenter, 0.5f/9.0f}, {LFE, 0.0f}}} },
-    { BackCenter,  {{{FrontCenter, 1.0f/9.0f}, {LFE, 0.0f}}} },
-}};
 const std::array<InputRemixMap,6> StereoDownmix{{
     { FrontCenter, {{{FrontLeft, 0.5f},      {FrontRight, 0.5f}}} },
     { SideLeft,    {{{FrontLeft, 1.0f/9.0f}, {FrontRight, 0.0f}}} },
@@ -1855,17 +1846,6 @@ ALCenum UpdateDeviceParams(ALCdevice *device, const int *attrList)
         DevFmtChannelsString(device->FmtChans), DevFmtTypeString(device->FmtType),
         device->Frequency, device->UpdateSize, device->BufferSize);
 
-    switch(device->FmtChans)
-    {
-    case DevFmtMono: device->RealOut.RemixMap = MonoDownmix; break;
-    case DevFmtStereo: device->RealOut.RemixMap = StereoDownmix; break;
-    case DevFmtQuad: device->RealOut.RemixMap = QuadDownmix; break;
-    case DevFmtX51: device->RealOut.RemixMap = X51Downmix; break;
-    case DevFmtX61: device->RealOut.RemixMap = X61Downmix; break;
-    case DevFmtX71: device->RealOut.RemixMap = X71Downmix; break;
-    case DevFmtAmbi3D: break;
-    }
-
     if(device->Type != DeviceType::Loopback)
     {
         if(auto modeopt = device->configValue<std::string>(nullptr, "stereo-mode"))
@@ -1899,6 +1879,20 @@ ALCenum UpdateDeviceParams(ALCdevice *device, const int *attrList)
         device->SourcesMax, device->NumMonoSources, device->NumStereoSources,
         device->AuxiliaryEffectSlotMax, device->NumAuxSends);
 
+    switch(device->FmtChans)
+    {
+    case DevFmtMono: break;
+    case DevFmtStereo:
+        if(!device->mUhjEncoder)
+            device->RealOut.RemixMap = StereoDownmix;
+        break;
+    case DevFmtQuad: device->RealOut.RemixMap = QuadDownmix; break;
+    case DevFmtX51: device->RealOut.RemixMap = X51Downmix; break;
+    case DevFmtX61: device->RealOut.RemixMap = X61Downmix; break;
+    case DevFmtX71: device->RealOut.RemixMap = X71Downmix; break;
+    case DevFmtAmbi3D: break;
+    }
+
     nanoseconds::rep sample_delay{0};
     if(device->mUhjEncoder)
         sample_delay += UhjEncoder::sFilterDelay;