Stride.Audio: enable Celt decode on macOS by stubbing variadic opus_custom_decoder_ctl GET_LOOKAHEAD

deps/Celt/buildApple.sh

@@ -17,6 +17,8 @@ fi
 cd "$EXTERNALS_DIR"
 
 CELT_SOURCES="celt/bands.c celt/celt.c celt/celt_decoder.c celt/celt_encoder.c celt/celt_lpc.c celt/cwrs.c celt/entcode.c celt/entdec.c celt/entenc.c celt/kiss_fft.c celt/laplace.c celt/mathops.c celt/mdct.c celt/modes.c celt/pitch.c celt/quant_bands.c celt/rate.c celt/vq.c"
+# Stride-specific helpers compiled in alongside the upstream sources (see celt_extras.c).
+CELT_EXTRAS="$CELT_DIR/celt_extras.c"
 CFLAGS="-O2 -fPIC -DUSE_ALLOCA -DHAVE_LRINTF -DCUSTOM_MODES -DOPUS_BUILD -Iinclude -Icelt"
 
 # Compile + archive Celt for one RID. Each (target, sdk) pair encodes the
@@ -36,6 +38,11 @@ build_rid() {
         bn=$(basename "$src" .c)
         clang -target "$target" -isysroot "$sdk_path" $CFLAGS -c -o "build/$rid/${bn}.o" "$src"
     done
+    for src in $CELT_EXTRAS; do
+        local bn
+        bn=$(basename "$src" .c)
+        clang -target "$target" -isysroot "$sdk_path" $CFLAGS -c -o "build/$rid/${bn}.o" "$src"
+    done
     ar rcs "build/$rid/libCelt.a" build/$rid/*.o
 
     local out_dir="$STRIDE_ROOT/deps/NativePath/dotnet/$rid"

deps/Celt/celt_extras.c

@@ -0,0 +1,18 @@
+// Copyright (c) .NET Foundation and Contributors (https://dotnetfoundation.org/ & https://stride3d.net)
+// Distributed under the MIT license. See the LICENSE.md file in the project root for more information.
+//
+// Stride-specific helpers compiled into libCelt.a alongside the upstream Opus/Celt sources.
+// Each function here is a non-variadic wrapper around a variadic opus_custom_decoder_ctl call,
+// so .NET DllImport can invoke them from C# (Mono on Apple does not support __arglist for
+// DllImport, and the Apple ARM64 variadic ABI passes overflow args on the stack — a plain
+// non-variadic DllImport would route them through registers and corrupt memory).
+
+#include <stdint.h>
+#include "opus_custom.h"
+
+// Returns the decoder's lookahead (encoder-delay) sample count via *out_delay.
+// OPUS_GET_LOOKAHEAD's macro arg is itself the int* (it pipes through opus_check_int_ptr).
+int stride_celt_get_lookahead(OpusCustomDecoder *decoder, int32_t *out_delay)
+{
+    return opus_custom_decoder_ctl(decoder, OPUS_GET_LOOKAHEAD(out_delay));
+}

deps/NativePath/dotnet/ios-arm64/libCelt.a

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:fe1a8f66a373c2a0571325000ed8727ddc45ab1f94848c07257a88f7c422613c
-size 165768
+oid sha256:80ead625c1ea1b3b6aef6b2117153963347f0c6c00e4211215724f08aa71f238
+size 166496

deps/NativePath/dotnet/iossimulator-arm64/libCelt.a

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:a462411e356672170267356d80cd236879062a3436c25fbab81bd3d9bd2a72a6
-size 169664
+oid sha256:31084e4ca9220a8617ed72dfe09e1dfd8048661bf816f8a1c879d0bd96c26405
+size 170392

deps/NativePath/dotnet/osx-arm64/libCelt.a

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:c538d24021f2ea5c098b0aac44f2dcb78a197e277903f17bc2bf0acba02a9b8d
-size 182776
+oid sha256:2809135fdd870d3c42c66847cbec9f52356a4fddf6bbd464223fdb69aff8118c
+size 173176

sources/engine/Stride.Audio/Native/Celt.AVFoundation.cs

@@ -38,12 +38,6 @@ namespace Stride.Audio
 
         public Celt(int sampleRate, int bufferSize, int channels, bool decoderOnly)
         {
-#if STRIDE_PLATFORM_MACOS
-            // Decode crashes inside libCelt.a's decode_pulses on osx-arm64 after a handful of
-            // packets — investigation pending. Bail cleanly so Sound loading raises a managed
-            // exception instead of taking down the whole process.
-            throw new NotSupportedException("Celt decoder not yet supported on macOS (osx-arm64 libCelt.a needs investigation).");
-#else
             SampleRate = sampleRate;
             BufferSize = bufferSize;
             Channels = channels;
@@ -62,7 +56,6 @@ namespace Stride.Audio
                 if (encoder == IntPtr.Zero)
                     throw new Exception("Failed to create Celt encoder.");
             }
-#endif
         }
 
         public void Dispose()
@@ -125,8 +118,13 @@ namespace Stride.Audio
 
         public unsafe int GetDecoderSampleDelay()
         {
+            // opus_custom_decoder_ctl is C-variadic and Mono on Apple rejects __arglist in
+            // DllImport ("Vararg calling convention not supported"). stride_celt_get_lookahead
+            // is a tiny non-variadic shim in libCelt.a (built from deps/Celt/celt_extras.c).
+            // Re-evaluate this shim once Apple platforms move to CoreCLR — at that point a
+            // pure-managed __arglist call should work and the shim can be retired.
             int delay = 0;
-            int err = opus_custom_decoder_ctl_get_int(decoder, OPUS_GET_LOOKAHEAD_REQUEST, &delay);
+            int err = stride_celt_get_lookahead(decoder, &delay);
             return err == 0 ? delay : 0;
         }
 
@@ -149,11 +147,14 @@ namespace Stride.Audio
         [SuppressUnmanagedCodeSecurity, DllImport(LibCelt, CallingConvention = CallingConvention.Cdecl)]
         private static extern unsafe int opus_custom_decode_float(IntPtr decoder, byte* data, int len, float* pcm, int frameSize);
 
+        // opus_custom_decoder_ctl is variadic. Calling it with no variadic args (RESET_STATE) is
+        // safe under any ABI — nothing for va_arg to read. For requests that need an out-pointer
+        // we go through stride_celt_get_lookahead (see celt_extras.c).
         [SuppressUnmanagedCodeSecurity, DllImport(LibCelt, EntryPoint = "opus_custom_decoder_ctl", CallingConvention = CallingConvention.Cdecl)]
         private static extern int opus_custom_decoder_ctl_reset(IntPtr decoder, int request);
 
-        [SuppressUnmanagedCodeSecurity, DllImport(LibCelt, EntryPoint = "opus_custom_decoder_ctl", CallingConvention = CallingConvention.Cdecl)]
-        private static extern unsafe int opus_custom_decoder_ctl_get_int(IntPtr decoder, int request, int* value);
+        [SuppressUnmanagedCodeSecurity, DllImport(LibCelt, CallingConvention = CallingConvention.Cdecl)]
+        private static extern unsafe int stride_celt_get_lookahead(IntPtr decoder, int* outDelay);
 
         [SuppressUnmanagedCodeSecurity, DllImport(LibCelt, CallingConvention = CallingConvention.Cdecl)]
         private static extern IntPtr opus_custom_encoder_create(IntPtr mode, int channels, IntPtr error);