Handle 3D7.1 as a separate channel configuration

It's treated as 5.1 + 2 aux channels. This allows AL_DIRECT_CHANNELS_SOFT to
behave better, not forwarding rear left/right channel inputs to lower front and
upper rear, and allows reporting a more appropriate output mode to the app
instead of 7.1.

22 files changed, 219 insertions, 129 deletions

diff --git a/alc/alc.cpp b/alc/alc.cpp
index 3bbe43d0..686b794e 100644
--- a/alc/alc.cpp
+++ b/alc/alc.cpp
@@ -1441,6 +1441,8 @@ ALCenum EnumFromDevFmt(DevFmtChannels channels)
     case DevFmtX61: return ALC_6POINT1_SOFT;
     case DevFmtX71: return ALC_7POINT1_SOFT;
     case DevFmtAmbi3D: return ALC_BFORMAT3D_SOFT;
+    /* FIXME: Shouldn't happen. */
+    case DevFmtX3D71: break;
     }
     throw std::runtime_error{"Invalid DevFmtChannels: "+std::to_string(int(channels))};
 }
@@ -1911,6 +1913,7 @@ ALCenum UpdateDeviceParams(ALCdevice *device, const int *attrList)
                 { "surround51", DevFmtX51,    0 },
                 { "surround61", DevFmtX61,    0 },
                 { "surround71", DevFmtX71,    0 },
+                { "surround3d71", DevFmtX3D71, 0 },
                 { "surround51rear", DevFmtX51, 0 },
                 { "ambi1", DevFmtAmbi3D, 1 },
                 { "ambi2", DevFmtAmbi3D, 2 },
@@ -2090,6 +2093,7 @@ ALCenum UpdateDeviceParams(ALCdevice *device, const int *attrList)
     case DevFmtX51: device->RealOut.RemixMap = X51Downmix; break;
     case DevFmtX61: device->RealOut.RemixMap = X61Downmix; break;
     case DevFmtX71: device->RealOut.RemixMap = X71Downmix; break;
+    case DevFmtX3D71: device->RealOut.RemixMap = X51Downmix; break;
     case DevFmtAmbi3D: break;
     }
 
diff --git a/alc/backends/base.cpp b/alc/backends/base.cpp
index cd1b76ba..4abd7c03 100644
--- a/alc/backends/base.cpp
+++ b/alc/backends/base.cpp
@@ -98,6 +98,16 @@ void BackendBase::setDefaultWFXChannelOrder()
         mDevice->RealOut.ChannelIndex[SideLeft]    = 6;
         mDevice->RealOut.ChannelIndex[SideRight]   = 7;
         break;
+    case DevFmtX3D71:
+        mDevice->RealOut.ChannelIndex[FrontLeft]   = 0;
+        mDevice->RealOut.ChannelIndex[FrontRight]  = 1;
+        mDevice->RealOut.ChannelIndex[FrontCenter] = 2;
+        mDevice->RealOut.ChannelIndex[LFE]         = 3;
+        mDevice->RealOut.ChannelIndex[Aux0]        = 4;
+        mDevice->RealOut.ChannelIndex[Aux1]        = 5;
+        mDevice->RealOut.ChannelIndex[SideLeft]    = 6;
+        mDevice->RealOut.ChannelIndex[SideRight]   = 7;
+        break;
     case DevFmtAmbi3D:
         break;
     }
@@ -127,6 +137,16 @@ void BackendBase::setDefaultChannelOrder()
         mDevice->RealOut.ChannelIndex[SideLeft]    = 6;
         mDevice->RealOut.ChannelIndex[SideRight]   = 7;
         return;
+    case DevFmtX3D71:
+        mDevice->RealOut.ChannelIndex[FrontLeft]   = 0;
+        mDevice->RealOut.ChannelIndex[FrontRight]  = 1;
+        mDevice->RealOut.ChannelIndex[Aux0]        = 2;
+        mDevice->RealOut.ChannelIndex[Aux1]        = 3;
+        mDevice->RealOut.ChannelIndex[FrontCenter] = 4;
+        mDevice->RealOut.ChannelIndex[LFE]         = 5;
+        mDevice->RealOut.ChannelIndex[SideLeft]    = 6;
+        mDevice->RealOut.ChannelIndex[SideRight]   = 7;
+        return;
 
     /* Same as WFX order */
     case DevFmtMono:
@@ -138,57 +158,3 @@ void BackendBase::setDefaultChannelOrder()
         break;
     }
 }
-
-#ifdef _WIN32
-void BackendBase::setChannelOrderFromWFXMask(uint chanmask)
-{
-    static constexpr uint x51{SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT | SPEAKER_FRONT_CENTER
-        | SPEAKER_LOW_FREQUENCY | SPEAKER_SIDE_LEFT | SPEAKER_SIDE_RIGHT};
-    static constexpr uint x51rear{SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT | SPEAKER_FRONT_CENTER
-        | SPEAKER_LOW_FREQUENCY | SPEAKER_BACK_LEFT | SPEAKER_BACK_RIGHT};
-    /* Swap a 5.1 mask using the back channels for one with the sides. */
-    if(chanmask == x51rear) chanmask = x51;
-
-    auto get_channel = [](const DWORD chanbit) noexcept -> al::optional<Channel>
-    {
-        switch(chanbit)
-        {
-        case SPEAKER_FRONT_LEFT: return al::make_optional(FrontLeft);
-        case SPEAKER_FRONT_RIGHT: return al::make_optional(FrontRight);
-        case SPEAKER_FRONT_CENTER: return al::make_optional(FrontCenter);
-        case SPEAKER_LOW_FREQUENCY: return al::make_optional(LFE);
-        case SPEAKER_BACK_LEFT: return al::make_optional(BackLeft);
-        case SPEAKER_BACK_RIGHT: return al::make_optional(BackRight);
-        case SPEAKER_FRONT_LEFT_OF_CENTER: break;
-        case SPEAKER_FRONT_RIGHT_OF_CENTER: break;
-        case SPEAKER_BACK_CENTER: return al::make_optional(BackCenter);
-        case SPEAKER_SIDE_LEFT: return al::make_optional(SideLeft);
-        case SPEAKER_SIDE_RIGHT: return al::make_optional(SideRight);
-        case SPEAKER_TOP_CENTER: return al::make_optional(TopCenter);
-        case SPEAKER_TOP_FRONT_LEFT: return al::make_optional(TopFrontLeft);
-        case SPEAKER_TOP_FRONT_CENTER: return al::make_optional(TopFrontCenter);
-        case SPEAKER_TOP_FRONT_RIGHT: return al::make_optional(TopFrontRight);
-        case SPEAKER_TOP_BACK_LEFT: return al::make_optional(TopBackLeft);
-        case SPEAKER_TOP_BACK_CENTER: return al::make_optional(TopBackCenter);
-        case SPEAKER_TOP_BACK_RIGHT: return al::make_optional(TopBackRight);
-        }
-        WARN("Unhandled WFX channel bit 0x%lx\n", chanbit);
-        return al::nullopt;
-    };
-
-    const uint numchans{mDevice->channelsFromFmt()};
-    uint idx{0};
-    while(chanmask)
-    {
-        const int bit{al::countr_zero(chanmask)};
-        const uint mask{1u << bit};
-        chanmask &= ~mask;
-
-        if(auto label = get_channel(mask))
-        {
-            mDevice->RealOut.ChannelIndex[*label] = idx;
-            if(++idx == numchans) break;
-        }
-    }
-}
-#endif
diff --git a/alc/backends/base.h b/alc/backends/base.h
index a3562f54..65bc636b 100644
--- a/alc/backends/base.h
+++ b/alc/backends/base.h
@@ -41,11 +41,6 @@ protected:
     void setDefaultChannelOrder();
     /** Sets the default channel order used by WaveFormatEx. */
     void setDefaultWFXChannelOrder();
-
-#ifdef _WIN32
-    /** Sets the channel order given the WaveFormatEx mask. */
-    void setChannelOrderFromWFXMask(uint chanmask);
-#endif
 };
 using BackendPtr = std::unique_ptr<BackendBase>;
 
diff --git a/alc/backends/coreaudio.cpp b/alc/backends/coreaudio.cpp
index ed85e2a9..b81bd58a 100644
--- a/alc/backends/coreaudio.cpp
+++ b/alc/backends/coreaudio.cpp
@@ -764,6 +764,7 @@ void CoreAudioCapture::open(const char *name)
     case DevFmtX51:
     case DevFmtX61:
     case DevFmtX71:
+    case DevFmtX3D71:
     case DevFmtAmbi3D:
         throw al::backend_exception{al::backend_error::DeviceError, "%s not supported",
             DevFmtChannelsString(mDevice->FmtChans)};
diff --git a/alc/backends/dsound.cpp b/alc/backends/dsound.cpp
index 0edc286f..36c4cd78 100644
--- a/alc/backends/dsound.cpp
+++ b/alc/backends/dsound.cpp
@@ -421,6 +421,7 @@ bool DSoundPlayback::reset()
         case DevFmtX51: OutputType.dwChannelMask = X5DOT1; break;
         case DevFmtX61: OutputType.dwChannelMask = X6DOT1; break;
         case DevFmtX71: OutputType.dwChannelMask = X7DOT1; break;
+        case DevFmtX3D71: OutputType.dwChannelMask = X7DOT1; break;
         }
 
 retry_open:
@@ -514,7 +515,7 @@ retry_open:
     }
 
     ResetEvent(mNotifyEvent);
-    setChannelOrderFromWFXMask(OutputType.dwChannelMask);
+    setDefaultWFXChannelOrder();
 
     return true;
 }
@@ -635,6 +636,7 @@ void DSoundCapture::open(const char *name)
     case DevFmtX51: InputType.dwChannelMask = X5DOT1; break;
     case DevFmtX61: InputType.dwChannelMask = X6DOT1; break;
     case DevFmtX71: InputType.dwChannelMask = X7DOT1; break;
+    case DevFmtX3D71:
     case DevFmtAmbi3D:
         WARN("%s capture not supported\n", DevFmtChannelsString(mDevice->FmtChans));
         throw al::backend_exception{al::backend_error::DeviceError, "%s capture not supported",
@@ -689,7 +691,7 @@ void DSoundCapture::open(const char *name)
     }
 
     mBufferBytes = DSCBDescription.dwBufferBytes;
-    setChannelOrderFromWFXMask(InputType.dwChannelMask);
+    setDefaultWFXChannelOrder();
 
     mDevice->DeviceName = name;
 }
diff --git a/alc/backends/oboe.cpp b/alc/backends/oboe.cpp
index 38f048cb..03930ad8 100644
--- a/alc/backends/oboe.cpp
+++ b/alc/backends/oboe.cpp
@@ -234,6 +234,7 @@ void OboeCapture::open(const char *name)
     case DevFmtX51:
     case DevFmtX61:
     case DevFmtX71:
+    case DevFmtX3D71:
     case DevFmtAmbi3D:
         throw al::backend_exception{al::backend_error::DeviceError, "%s capture not supported",
             DevFmtChannelsString(mDevice->FmtChans)};
diff --git a/alc/backends/opensl.cpp b/alc/backends/opensl.cpp
index 85a5f483..76b2095e 100644
--- a/alc/backends/opensl.cpp
+++ b/alc/backends/opensl.cpp
@@ -71,7 +71,8 @@ constexpr SLuint32 GetChannelMask(DevFmtChannels chans) noexcept
     case DevFmtX61: return SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT |
         SL_SPEAKER_FRONT_CENTER | SL_SPEAKER_LOW_FREQUENCY | SL_SPEAKER_BACK_CENTER |
         SL_SPEAKER_SIDE_LEFT | SL_SPEAKER_SIDE_RIGHT;
-    case DevFmtX71: return SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT |
+    case DevFmtX71:
+    case DevFmtX3D71: return SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT |
         SL_SPEAKER_FRONT_CENTER | SL_SPEAKER_LOW_FREQUENCY | SL_SPEAKER_BACK_LEFT |
         SL_SPEAKER_BACK_RIGHT | SL_SPEAKER_SIDE_LEFT | SL_SPEAKER_SIDE_RIGHT;
     case DevFmtAmbi3D:
diff --git a/alc/backends/pipewire.cpp b/alc/backends/pipewire.cpp
index a19dcb61..95845158 100644
--- a/alc/backends/pipewire.cpp
+++ b/alc/backends/pipewire.cpp
@@ -1181,6 +1181,7 @@ spa_audio_info_raw make_spa_info(DeviceBase *device, bool is51rear, use_f32p_e u
         break;
     case DevFmtX61: map = X61Map; break;
     case DevFmtX71: map = X71Map; break;
+    case DevFmtX3D71: map = X71Map; break;
     case DevFmtAmbi3D:
         info.flags |= SPA_AUDIO_FLAG_UNPOSITIONED;
         info.channels = device->channelsFromFmt();
diff --git a/alc/backends/pulseaudio.cpp b/alc/backends/pulseaudio.cpp
index 67e00234..30f486c7 100644
--- a/alc/backends/pulseaudio.cpp
+++ b/alc/backends/pulseaudio.cpp
@@ -893,6 +893,7 @@ bool PulsePlayback::reset()
         chanmap = X61ChanMap;
         break;
     case DevFmtX71:
+    case DevFmtX3D71:
         chanmap = X71ChanMap;
         break;
     }
@@ -1173,6 +1174,7 @@ void PulseCapture::open(const char *name)
     case DevFmtX71:
         chanmap = X71ChanMap;
         break;
+    case DevFmtX3D71:
     case DevFmtAmbi3D:
         throw al::backend_exception{al::backend_error::DeviceError, "%s capture not supported",
             DevFmtChannelsString(mDevice->FmtChans)};
diff --git a/alc/backends/wasapi.cpp b/alc/backends/wasapi.cpp
index 063fca98..4e0f67a2 100644
--- a/alc/backends/wasapi.cpp
+++ b/alc/backends/wasapi.cpp
@@ -926,6 +926,7 @@ HRESULT WasapiPlayback::resetProxy()
         OutputType.dwChannelMask = X6DOT1;
         break;
     case DevFmtX71:
+    case DevFmtX3D71:
         OutputType.Format.nChannels = 8;
         OutputType.dwChannelMask = X7DOT1;
         break;
@@ -1021,6 +1022,7 @@ HRESULT WasapiPlayback::resetProxy()
                 chansok = (chancount >= 7 && (chanmask&X61Mask) == X6DOT1);
                 break;
             case DevFmtX71:
+            case DevFmtX3D71:
                 chansok = (chancount >= 8 && (chanmask&X71Mask) == X7DOT1);
                 break;
             case DevFmtAmbi3D:
@@ -1087,7 +1089,7 @@ HRESULT WasapiPlayback::resetProxy()
     const EndpointFormFactor formfactor{get_device_formfactor(mMMDev.get())};
     mDevice->Flags.set(DirectEar, (formfactor == Headphones || formfactor == Headset));
 
-    setChannelOrderFromWFXMask(OutputType.dwChannelMask);
+    setDefaultWFXChannelOrder();
 
     hr = mClient->Initialize(AUDCLNT_SHAREMODE_SHARED, AUDCLNT_STREAMFLAGS_EVENTCALLBACK,
         buf_time.count(), 0, &OutputType.Format, nullptr);
@@ -1476,6 +1478,7 @@ HRESULT WasapiCapture::resetProxy()
         InputType.dwChannelMask = X7DOT1;
         break;
 
+    case DevFmtX3D71:
     case DevFmtAmbi3D:
         return E_FAIL;
     }
@@ -1556,6 +1559,7 @@ HRESULT WasapiCapture::resetProxy()
             case DevFmtX61:
                 return (chancount == 7 && (chanmask == 0 || (chanmask&X61Mask) == X6DOT1));
             case DevFmtX71:
+            case DevFmtX3D71:
                 return (chancount == 8 && (chanmask == 0 || (chanmask&X71Mask) == X7DOT1));
             case DevFmtAmbi3D:
                 return (chanmask == 0 && chancount == device->channelsFromFmt());
diff --git a/alc/backends/wave.cpp b/alc/backends/wave.cpp
index 6360166c..80e93f69 100644
--- a/alc/backends/wave.cpp
+++ b/alc/backends/wave.cpp
@@ -265,6 +265,8 @@ bool WaveBackend::reset()
     case DevFmtX51: chanmask = 0x01 | 0x02 | 0x04 | 0x08 | 0x200 | 0x400; break;
     case DevFmtX61: chanmask = 0x01 | 0x02 | 0x04 | 0x08 | 0x100 | 0x200 | 0x400; break;
     case DevFmtX71: chanmask = 0x01 | 0x02 | 0x04 | 0x08 | 0x010 | 0x020 | 0x200 | 0x400; break;
+    /* NOTE: Same as 7.1. */
+    case DevFmtX3D71: chanmask = 0x01 | 0x02 | 0x04 | 0x08 | 0x010 | 0x020 | 0x200 | 0x400; break;
     case DevFmtAmbi3D:
         /* .amb output requires FuMa */
         mDevice->mAmbiOrder = minu(mDevice->mAmbiOrder, 3);
diff --git a/alc/backends/winmm.cpp b/alc/backends/winmm.cpp
index 0fdd8a02..14cc4f9e 100644
--- a/alc/backends/winmm.cpp
+++ b/alc/backends/winmm.cpp
@@ -301,23 +301,16 @@ bool WinMMPlayback::reset()
         return false;
     }
 
-    uint chanmask{};
     if(mFormat.nChannels >= 2)
-    {
         mDevice->FmtChans = DevFmtStereo;
-        chanmask = SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT;
-    }
     else if(mFormat.nChannels == 1)
-    {
         mDevice->FmtChans = DevFmtMono;
-        chanmask = SPEAKER_FRONT_CENTER;
-    }
     else
     {
         ERR("Unhandled channel count: %d\n", mFormat.nChannels);
         return false;
     }
-    setChannelOrderFromWFXMask(chanmask);
+    setDefaultWFXChannelOrder();
 
     uint BufferSize{mDevice->UpdateSize * mFormat.nChannels * mDevice->bytesFromFmt()};
 
@@ -476,6 +469,7 @@ void WinMMCapture::open(const char *name)
     case DevFmtX51:
     case DevFmtX61:
     case DevFmtX71:
+    case DevFmtX3D71:
     case DevFmtAmbi3D:
         throw al::backend_exception{al::backend_error::DeviceError, "%s capture not supported",
             DevFmtChannelsString(mDevice->FmtChans)};
diff --git a/alc/context.cpp b/alc/context.cpp
index 456c054e..34da3784 100644
--- a/alc/context.cpp
+++ b/alc/context.cpp
@@ -558,6 +558,10 @@ unsigned long ALCcontext::eax_detect_speaker_configuration() const
     case DevFmtX51: return SPEAKERS_5;
     case DevFmtX61: return SPEAKERS_6;
     case DevFmtX71: return SPEAKERS_7;
+    /* 3D7.1 is only compatible with 5.1. This could instead be HEADPHONES to
+     * suggest full-sphere surround sound (like HRTF).
+     */
+    case DevFmtX3D71: return SPEAKERS_5;
     /* This could also be HEADPHONES, since headphones-based HRTF and Ambi3D
      * provide full-sphere surround sound. Depends if apps are more likely to
      * consider headphones or 7.1 for surround sound support.
diff --git a/alc/device.cpp b/alc/device.cpp
index e06c0d74..6eeb907e 100644
--- a/alc/device.cpp
+++ b/alc/device.cpp
@@ -84,6 +84,7 @@ auto ALCdevice::getOutputMode1() const noexcept -> OutputMode1
     case DevFmtX51: return OutputMode1::X51;
     case DevFmtX61: return OutputMode1::X61;
     case DevFmtX71: return OutputMode1::X71;
+    case DevFmtX3D71:
     case DevFmtAmbi3D: break;
     }
     return OutputMode1::Any;
diff --git a/alc/panning.cpp b/alc/panning.cpp
index 00bf5662..d0afd577 100644
--- a/alc/panning.cpp
+++ b/alc/panning.cpp
@@ -89,6 +89,23 @@ inline const char *GetLabelFromChannel(Channel channel)
         case TopBackCenter: return "top-back-center";
         case TopBackRight: return "top-back-right";
 
+        case Aux0: return "Aux0";
+        case Aux1: return "Aux1";
+        case Aux2: return "Aux2";
+        case Aux3: return "Aux3";
+        case Aux4: return "Aux4";
+        case Aux5: return "Aux5";
+        case Aux6: return "Aux6";
+        case Aux7: return "Aux7";
+        case Aux8: return "Aux8";
+        case Aux9: return "Aux9";
+        case Aux10: return "Aux10";
+        case Aux11: return "Aux11";
+        case Aux12: return "Aux12";
+        case Aux13: return "Aux13";
+        case Aux14: return "Aux14";
+        case Aux15: return "Aux15";
+
         case MaxChannels: break;
     }
     return "(unknown)";
@@ -202,6 +219,8 @@ struct DecoderConfig<DualBand, 0> {
         mCoeffsLF = rhs.mCoeffsLF;
         return *this;
     }
+
+    explicit operator bool() const noexcept { return mOrder != 0; }
 };
 using DecoderView = DecoderConfig<DualBand, 0>;
 
@@ -412,8 +431,15 @@ DecoderView MakeDecoderView(ALCdevice *device, const AmbDecConf *conf,
             ch = BackCenter;
         else
         {
-            ERR("AmbDec speaker label \"%s\" not recognized\n", speaker.Name.c_str());
-            continue;
+            int idx{};
+            char c{};
+            if(sscanf(speaker.Name.c_str(), "AUX%d%c", &idx, &c) != 1 || idx < 0
+                || idx >= MaxChannels-Aux0)
+            {
+                ERR("AmbDec speaker label \"%s\" not recognized\n", speaker.Name.c_str());
+                continue;
+            }
+            ch = static_cast<Channel>(Aux0+idx);
         }
 
         decoder.mChannels[chan_count] = ch;
@@ -537,11 +563,33 @@ constexpr DecoderConfig<DualBand, 6> X71Config{
         {{1.66666667e-1f, -9.62250449e-2f, -1.66666667e-1f,  1.49071198e-1f,  8.60662966e-2f, -7.96819073e-2f, 0.00000000e+0f}},
     }}
 };
+constexpr DecoderConfig<DualBand, 6> X3D71Config{
+    1, true, {{Aux0, SideLeft, FrontLeft, FrontRight, SideRight, Aux1}},
+    DevAmbiScaling::N3D,
+    /*HF*/{{1.73205081e+0f, 1.00000000e+0f}},
+    {{
+        {{1.66669447e-1f,  0.00000000e+0f,  2.36070520e-1f, -1.66153012e-1f}},
+        {{1.66669447e-1f,  2.04127551e-1f, -1.17487922e-1f, -1.66927066e-1f}},
+        {{1.66669447e-1f,  2.04127551e-1f,  1.17487922e-1f,  1.66927066e-1f}},
+        {{1.66669447e-1f, -2.04127551e-1f,  1.17487922e-1f,  1.66927066e-1f}},
+        {{1.66669447e-1f, -2.04127551e-1f, -1.17487922e-1f, -1.66927066e-1f}},
+        {{1.66669447e-1f,  0.00000000e+0f, -2.36070520e-1f,  1.66153012e-1f}},
+    }},
+    /*LF*/{{1.00000000e+0f, 1.00000000e+0f}},
+    {{
+        {{1.66669447e-1f,  0.00000000e+0f,  2.36070520e-1f, -1.66153012e-1f}},
+        {{1.66669447e-1f,  2.04127551e-1f, -1.17487922e-1f, -1.66927066e-1f}},
+        {{1.66669447e-1f,  2.04127551e-1f,  1.17487922e-1f,  1.66927066e-1f}},
+        {{1.66669447e-1f, -2.04127551e-1f,  1.17487922e-1f,  1.66927066e-1f}},
+        {{1.66669447e-1f, -2.04127551e-1f, -1.17487922e-1f, -1.66927066e-1f}},
+        {{1.66669447e-1f,  0.00000000e+0f, -2.36070520e-1f,  1.66153012e-1f}},
+    }}
+};
 
 void InitPanning(ALCdevice *device, const bool hqdec=false, const bool stablize=false,
     DecoderView decoder={})
 {
-    if(!decoder.mOrder)
+    if(!decoder)
     {
         switch(device->FmtChans)
         {
@@ -551,6 +599,7 @@ void InitPanning(ALCdevice *device, const bool hqdec=false, const bool stablize=
         case DevFmtX51: decoder = X51Config; break;
         case DevFmtX61: decoder = X61Config; break;
         case DevFmtX71: decoder = X71Config; break;
+        case DevFmtX3D71: decoder = X3D71Config; break;
         case DevFmtAmbi3D:
             auto&& acnmap = GetAmbiLayout(device->mAmbiLayout);
             auto&& n3dscale = GetAmbiScales(device->mAmbiScale);
@@ -906,6 +955,7 @@ void aluInitRenderer(ALCdevice *device, int hrtf_id, al::optional<StereoEncoding
         case DevFmtX51: layout = "surround51"; break;
         case DevFmtX61: layout = "surround61"; break;
         case DevFmtX71: layout = "surround71"; break;
+        case DevFmtX3D71: layout = "surround3d71"; break;
         /* Mono, Stereo, and Ambisonics output don't use custom decoders. */
         case DevFmtMono:
         case DevFmtStereo:
@@ -915,7 +965,7 @@ void aluInitRenderer(ALCdevice *device, int hrtf_id, al::optional<StereoEncoding
 
         std::unique_ptr<DecoderConfig<DualBand,MAX_OUTPUT_CHANNELS>> decoder_store;
         DecoderView decoder{};
-        float speakerdists[MaxChannels]{};
+        float speakerdists[MAX_OUTPUT_CHANNELS]{};
         auto load_config = [device,&decoder_store,&decoder,&speakerdists](const char *config)
         {
             AmbDecConf conf{};
diff --git a/core/devformat.cpp b/core/devformat.cpp
index c841b634..cbe8eaf3 100644
--- a/core/devformat.cpp
+++ b/core/devformat.cpp
@@ -28,6 +28,7 @@ uint ChannelsFromDevFmt(DevFmtChannels chans, uint ambiorder) noexcept
     case DevFmtX51: return 6;
     case DevFmtX61: return 7;
     case DevFmtX71: return 8;
+    case DevFmtX3D71: return 8;
     case DevFmtAmbi3D: return (ambiorder+1) * (ambiorder+1);
     }
     return 0;
@@ -57,6 +58,7 @@ const char *DevFmtChannelsString(DevFmtChannels chans) noexcept
     case DevFmtX51: return "5.1 Surround";
     case DevFmtX61: return "6.1 Surround";
     case DevFmtX71: return "7.1 Surround";
+    case DevFmtX3D71: return "3D7.1 Surround";
     case DevFmtAmbi3D: return "Ambisonic 3D";
     }
     return "(unknown channels)";
diff --git a/core/devformat.h b/core/devformat.h
index e6d30924..f2a372c1 100644
--- a/core/devformat.h
+++ b/core/devformat.h
@@ -25,6 +25,23 @@ enum Channel : unsigned char {
     TopBackCenter,
     TopBackRight,
 
+    Aux0,
+    Aux1,
+    Aux2,
+    Aux3,
+    Aux4,
+    Aux5,
+    Aux6,
+    Aux7,
+    Aux8,
+    Aux9,
+    Aux10,
+    Aux11,
+    Aux12,
+    Aux13,
+    Aux14,
+    Aux15,
+
     MaxChannels
 };
 
@@ -48,6 +65,7 @@ enum DevFmtChannels : unsigned char {
     DevFmtX51,
     DevFmtX61,
     DevFmtX71,
+    DevFmtX3D71,
     DevFmtAmbi3D,
 
     DevFmtChannelsDefault = DevFmtStereo
diff --git a/docs/3D7.1.txt b/docs/3D7.1.txt
index 1d40bec6..b7249c22 100644
--- a/docs/3D7.1.txt
+++ b/docs/3D7.1.txt
@@ -58,17 +58,10 @@ Software Setup
 ==============
 
 To enable 3D7.1 on OpenAL Soft, first make sure the audio device is configured
-for 7.1 output. Then in the alsoft-config utility, under the Renderer tab,
-select the 3D7.1.ambdec preset for the 7.1 Surround decoder configuration. And
-that's it. Any applications using OpenAL Soft can take advantage of fully 3D
-audio, and multi-channel sounds will be properly remixed for the speaker
-layout.
-
-Playback can be improved by (copying and) modifying the 3D7.1.ambdec preset,
-changing the specified speaker distances to match the the real distance (in
-meters) from the center of the speaker array, then enable High Quality Mode in
-alsoft-config. That will improve the quality when the speakers are not all
-equidistant.
+for 7.1 output. Then in the alsoft-config utility, for the Channels setting
+choose "3D7.1 Surround" from the drop-down list. And that's it. Any application
+using OpenAL Soft can take advantage of fully 3D audio, and multi-channel
+sounds will be properly remixed for the speaker layout.
 
 Note that care must be taken that the audio device is not treated as a "true"
 7.1 device by non-3D7.1-capable applications. In particular, the audio server
diff --git a/presets/3D7.1.ambdec b/presets/3D7.1.ambdec
index 66e56501..8ab0b060 100644
--- a/presets/3D7.1.ambdec
+++ b/presets/3D7.1.ambdec
@@ -5,6 +5,10 @@
 
 /description     3D7-noCenter_1h1v_pinv_even_energy_rV_max_rE_2_band
 
+# In OpenAL Soft, 3D7.1 is a distinct configuration that uses the standard 5.1
+# channels (FL, FR, FC, SL, SR), plus two auxiliary channels (AUX0, AUX1) in
+# place of the rear speakers.
+
 # Similar to the the ITU-5.1-nocenter configuration, the front-center is
 # declared here so that an appropriate distance may be set (for proper delaying
 # or attenuating of dialog and such which feed it directly). It otherwise does
@@ -25,15 +29,15 @@
 /opt/xover_ratio  	0.000000
 
 /speakers/{
-#        	id	 dist     	 azim     	 elev    	conn
+#       	id  	 dist    	 azim      	 elev     	conn
 #-----------------------------------------------------------------------
-add_spkr 	FL	 1.828800	 51.000000	 24.000000
-add_spkr 	FR	 1.828800	-51.000000	 24.000000
-add_spkr 	FC	 1.828800	 0.000000	 0.000000
-add_spkr 	BL	 1.828800	 180.000000	 55.000000
-add_spkr 	BR	 1.828800	 0.000000	-55.000000
-add_spkr 	SL	 1.828800	 129.000000	-24.000000
-add_spkr 	SR	 1.828800	-129.000000	-24.000000
+add_spkr 	FL		 1.828800	  51.000000	 24.000000
+add_spkr 	FR		 1.828800	 -51.000000	 24.000000
+add_spkr 	FC		 1.828800	   0.000000	  0.000000
+add_spkr 	AUX0	 1.828800	 180.000000	 55.000000
+add_spkr 	AUX1	 1.828800	   0.000000	-55.000000
+add_spkr 	SL		 1.828800	 129.000000	-24.000000
+add_spkr 	SR		 1.828800	-129.000000	-24.000000
 /}
 
 /lfmatrix/{
diff --git a/utils/alsoft-config/mainwindow.cpp b/utils/alsoft-config/mainwindow.cpp
index 8a179ada..3565493e 100644
--- a/utils/alsoft-config/mainwindow.cpp
+++ b/utils/alsoft-config/mainwindow.cpp
@@ -86,6 +86,7 @@ static const struct NameValuePair {
     { "5.1 Surround", "surround51" },
     { "6.1 Surround", "surround61" },
     { "7.1 Surround", "surround71" },
+    { "3D7.1 Surround", "surround3d71" },
 
     { "Ambisonic, 1st Order", "ambi1" },
     { "Ambisonic, 2nd Order", "ambi2" },
@@ -412,6 +413,8 @@ MainWindow::MainWindow(QWidget *parent) :
     connect(ui->decoder61Button, &QPushButton::clicked, this, &MainWindow::select61DecoderFile);
     connect(ui->decoder71LineEdit, &QLineEdit::textChanged, this, &MainWindow::enableApplyButton);
     connect(ui->decoder71Button, &QPushButton::clicked, this, &MainWindow::select71DecoderFile);
+    connect(ui->decoder3D71LineEdit, &QLineEdit::textChanged, this, &MainWindow::enableApplyButton);
+    connect(ui->decoder3D71Button, &QPushButton::clicked, this, &MainWindow::select3D71DecoderFile);
 
     connect(ui->preferredHrtfComboBox, qcb_cicint, this, &MainWindow::enableApplyButton);
     connect(ui->hrtfStateComboBox, qcb_cicint, this, &MainWindow::enableApplyButton);
@@ -1252,6 +1255,8 @@ void MainWindow::select61DecoderFile()
 { selectDecoderFile(ui->decoder61LineEdit, "Select 6.1 Surround Decoder");}
 void MainWindow::select71DecoderFile()
 { selectDecoderFile(ui->decoder71LineEdit, "Select 7.1 Surround Decoder");}
+void MainWindow::select3D71DecoderFile()
+{ selectDecoderFile(ui->decoder3D71LineEdit, "Select 3D7.1 Surround Decoder");}
 void MainWindow::selectDecoderFile(QLineEdit *line, const char *caption)
 {
     QString dir{line->text()};
diff --git a/utils/alsoft-config/mainwindow.h b/utils/alsoft-config/mainwindow.h
index ca53582b..f7af8eac 100644
--- a/utils/alsoft-config/mainwindow.h
+++ b/utils/alsoft-config/mainwindow.h
@@ -39,6 +39,7 @@ private slots:
     void select51DecoderFile();
     void select61DecoderFile();
     void select71DecoderFile();
+    void select3D71DecoderFile();
 
     void updateJackBufferSizeEdit(int size);
     void updateJackBufferSizeSlider();
diff --git a/utils/alsoft-config/mainwindow.ui b/utils/alsoft-config/mainwindow.ui
index 84a99385..8d057679 100644
--- a/utils/alsoft-config/mainwindow.ui
+++ b/utils/alsoft-config/mainwindow.ui
@@ -668,9 +668,9 @@ configuration file.</string>
       <property name="geometry">
        <rect>
         <x>-10</x>
-        <y>160</y>
+        <y>140</y>
         <width>551</width>
-        <height>161</height>
+        <height>231</height>
        </rect>
       </property>
       <property name="title">
@@ -682,10 +682,10 @@ configuration file.</string>
       <widget class="QLineEdit" name="decoderQuadLineEdit">
        <property name="geometry">
         <rect>
-         <x>120</x>
+         <x>130</x>
          <y>30</y>
-         <width>311</width>
-         <height>21</height>
+         <width>301</width>
+         <height>25</height>
         </rect>
        </property>
       </widget>
@@ -694,8 +694,8 @@ configuration file.</string>
         <rect>
          <x>20</x>
          <y>30</y>
-         <width>91</width>
-         <height>21</height>
+         <width>101</width>
+         <height>25</height>
         </rect>
        </property>
        <property name="text">
@@ -711,7 +711,7 @@ configuration file.</string>
          <x>440</x>
          <y>30</y>
          <width>91</width>
-         <height>21</height>
+         <height>25</height>
         </rect>
        </property>
        <property name="text">
@@ -721,10 +721,10 @@ configuration file.</string>
       <widget class="QLineEdit" name="decoder51LineEdit">
        <property name="geometry">
         <rect>
-         <x>120</x>
-         <y>60</y>
-         <width>311</width>
-         <height>21</height>
+         <x>130</x>
+         <y>70</y>
+         <width>301</width>
+         <height>25</height>
         </rect>
        </property>
       </widget>
@@ -732,9 +732,9 @@ configuration file.</string>
        <property name="geometry">
         <rect>
          <x>440</x>
-         <y>60</y>
+         <y>70</y>
          <width>91</width>
-         <height>21</height>
+         <height>25</height>
         </rect>
        </property>
        <property name="text">
@@ -745,9 +745,9 @@ configuration file.</string>
        <property name="geometry">
         <rect>
          <x>20</x>
-         <y>60</y>
-         <width>91</width>
-         <height>21</height>
+         <y>70</y>
+         <width>101</width>
+         <height>25</height>
         </rect>
        </property>
        <property name="text">
@@ -761,9 +761,9 @@ configuration file.</string>
        <property name="geometry">
         <rect>
          <x>20</x>
-         <y>90</y>
-         <width>91</width>
-         <height>21</height>
+         <y>110</y>
+         <width>101</width>
+         <height>25</height>
         </rect>
        </property>
        <property name="text">
@@ -776,10 +776,10 @@ configuration file.</string>
       <widget class="QLineEdit" name="decoder61LineEdit">
        <property name="geometry">
         <rect>
-         <x>120</x>
-         <y>90</y>
-         <width>311</width>
-         <height>21</height>
+         <x>130</x>
+         <y>110</y>
+         <width>301</width>
+         <height>25</height>
         </rect>
        </property>
       </widget>
@@ -787,9 +787,9 @@ configuration file.</string>
        <property name="geometry">
         <rect>
          <x>440</x>
-         <y>90</y>
+         <y>110</y>
          <width>91</width>
-         <height>21</height>
+         <height>25</height>
         </rect>
        </property>
        <property name="text">
@@ -800,9 +800,9 @@ configuration file.</string>
        <property name="geometry">
         <rect>
          <x>440</x>
-         <y>120</y>
+         <y>150</y>
          <width>91</width>
-         <height>21</height>
+         <height>25</height>
         </rect>
        </property>
        <property name="text">
@@ -812,10 +812,10 @@ configuration file.</string>
       <widget class="QLineEdit" name="decoder71LineEdit">
        <property name="geometry">
         <rect>
-         <x>120</x>
-         <y>120</y>
-         <width>311</width>
-         <height>21</height>
+         <x>130</x>
+         <y>150</y>
+         <width>301</width>
+         <height>25</height>
         </rect>
        </property>
       </widget>
@@ -823,9 +823,9 @@ configuration file.</string>
        <property name="geometry">
         <rect>
          <x>20</x>
-         <y>120</y>
-         <width>91</width>
-         <height>21</height>
+         <y>150</y>
+         <width>101</width>
+         <height>25</height>
         </rect>
        </property>
        <property name="text">
@@ -835,6 +835,45 @@ configuration file.</string>
         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
        </property>
       </widget>
+      <widget class="QLabel" name="label_33">
+       <property name="geometry">
+        <rect>
+         <x>20</x>
+         <y>190</y>
+         <width>101</width>
+         <height>25</height>
+        </rect>
+       </property>
+       <property name="text">
+        <string>3D7.1 Surround:</string>
+       </property>
+       <property name="alignment">
+        <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+       </property>
+      </widget>
+      <widget class="QLineEdit" name="decoder3D71LineEdit">
+       <property name="geometry">
+        <rect>
+         <x>130</x>
+         <y>190</y>
+         <width>301</width>
+         <height>25</height>
+        </rect>
+       </property>
+      </widget>
+      <widget class="QPushButton" name="decoder3D71Button">
+       <property name="geometry">
+        <rect>
+         <x>440</x>
+         <y>190</y>
+         <width>91</width>
+         <height>25</height>
+        </rect>
+       </property>
+       <property name="text">
+        <string>Browse...</string>
+       </property>
+      </widget>
      </widget>
      <widget class="QCheckBox" name="decoderNFEffectsCheckBox">
       <property name="geometry">