From dd24e1832ea951622ee6fda604a8c62244325790 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-Micha=C3=ABl=20Celerier?=
 <jeanmichael.celerier@gmail.com>
Date: Tue, 21 Apr 2026 10:16:24 +0200
Subject: [PATCH] wip: wasm: use miniaudio instead of sdl in emscripten

---
 src/ossia/audio/audio_engine.cpp       | 23 +++++++++++++++++++++
 src/ossia/audio/miniaudio_protocol.hpp | 28 +++++++++++++++++++++++---
 src/ossia_features.cmake               |  7 +++++++
 3 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/src/ossia/audio/audio_engine.cpp b/src/ossia/audio/audio_engine.cpp
index df5022b801e..cc67e022527 100644
--- a/src/ossia/audio/audio_engine.cpp
+++ b/src/ossia/audio/audio_engine.cpp
@@ -2,6 +2,7 @@
 #include <ossia/audio/audio_engine.hpp>
 #include <ossia/audio/dummy_protocol.hpp>
 #include <ossia/audio/jack_protocol.hpp>
+//#include <ossia/audio/miniaudio_protocol.hpp>
 #include <ossia/audio/pipewire_protocol.hpp>
 #include <ossia/audio/portaudio_protocol.hpp>
 #include <ossia/audio/pulseaudio_protocol.hpp>
@@ -56,6 +57,13 @@ void audio_engine::sync()
   req++;
   request.store(req);
 
+#if defined(__EMSCRIPTEN__)
+  // On WASM, the audio runs in a worklet thread. We cannot spin-wait
+  // on the main thread as it blocks the browser event loop entirely.
+  // The tick will pick up the new request on its next callback.
+  return;
+#endif
+
   // The engine has started running, we wait for a couple iterations
   // to leave some time for the ticks to be updated
   int k = 0;
@@ -120,7 +128,22 @@ ossia::audio_engine* make_audio_engine(
   bs = 1024;
   inputs = 0;
   outputs = 2;
+#if OSSIA_ENABLE_MINIAUDIO
+  {
+    static auto ctx = std::make_shared<ossia::miniaudio_context>();
+    static bool ctx_init = false;
+    if(!ctx_init)
+    {
+      auto cfg = ma_context_config_init();
+      ma_context_init(nullptr, 0, &cfg, &ctx->context);
+      ctx_init = true;
+    }
+    ma_device_id in_id{}, out_id{};
+    return new ossia::miniaudio_engine{ctx, name, in_id, out_id, inputs, outputs, rate, bs};
+  }
+#else
   return new ossia::sdl_protocol{rate, bs};
+#endif
 #endif
 
   if(0)
diff --git a/src/ossia/audio/miniaudio_protocol.hpp b/src/ossia/audio/miniaudio_protocol.hpp
index 83e492493ac..dcb19e12e83 100644
--- a/src/ossia/audio/miniaudio_protocol.hpp
+++ b/src/ossia/audio/miniaudio_protocol.hpp
@@ -8,8 +8,13 @@
 #define MA_NO_RUNTIME_LINKING 1
 #endif
 #define MA_ENABLE_ONLY_SPECIFIC_BACKENDS 1
+#if defined(__EMSCRIPTEN__)
+#define MA_ENABLE_WEBAUDIO 1
+#define MA_ENABLE_AUDIO_WORKLETS 1
+#else
 #define MA_ENABLE_COREAUDIO 1
 #define MA_ENABLE_ALSA 1
+#endif
 #define MA_NO_WAV 1
 #define MA_NO_FLAC 1
 #define MA_NO_MP3 1
@@ -22,7 +27,7 @@
 #include <ossia/audio/audio_engine.hpp>
 #include <ossia/detail/thread.hpp>
 
-#include <kfr/base/conversion.hpp>
+//#include <kfr/base/conversion.hpp>
 
 #include <miniaudio.h>
 
@@ -144,6 +149,7 @@ class miniaudio_engine final : public audio_engine
   static void
   callback(ma_device* pDevice, void* output, const void* input, ma_uint32 nframes)
   {
+#if !defined(__EMSCRIPTEN__)
     [[maybe_unused]]
     static const thread_local auto _
         = [] {
@@ -151,11 +157,10 @@ class miniaudio_engine final : public audio_engine
       ossia::set_thread_pinned(thread_type::Audio, 0);
       return 0;
     }();
+#endif
 
     auto& self = *static_cast<miniaudio_engine*>(pDevice->pUserData);
     self.tick_start();
-    if(!self.m_start)
-      self.m_start = std::chrono::steady_clock::now();
 
     if(self.stop_processing)
     {
@@ -167,7 +172,9 @@ class miniaudio_engine final : public audio_engine
     auto ins_data = self.ins_data.data();
     for(int i = 0; i < self.effective_inputs; i++)
       ins[i] = ins_data + i * nframes;
+#if !defined(__EMSCRIPTEN__)
     kfr::deinterleave(ins, (float*)input, self.effective_inputs, nframes);
+#endif
 
     auto outs = self.outs.data();
     auto outs_data = self.outs_data.data();
@@ -175,11 +182,20 @@ class miniaudio_engine final : public audio_engine
     for(int i = 0; i < self.effective_outputs; i++)
       outs[i] = outs_data + i * nframes;
 
+#if defined(__EMSCRIPTEN__)
+    // On WASM audio worklets, std::chrono::steady_clock is unavailable.
+    // Use the sample count to derive time instead.
+    self.m_frames_elapsed += nframes;
+    double nsecs = (double)self.m_frames_elapsed / self.effective_sample_rate;
+#else
+    if(!self.m_start)
+      self.m_start = std::chrono::steady_clock::now();
     auto now = std::chrono::steady_clock::now();
     auto nsecs
         = std::chrono::duration_cast<std::chrono::nanoseconds>(now - *self.m_start)
               .count()
           / 1e9;
+#endif
 
     ossia::audio_tick_state ts{(float* const*)ins,     outs,    self.effective_inputs,
                                self.effective_outputs, nframes, nsecs};
@@ -187,13 +203,19 @@ class miniaudio_engine final : public audio_engine
 
     self.tick_end();
 
+#if !defined(__EMSCRIPTEN__)
     kfr::interleave(
         (float*)output, (const float**)outs, self.effective_outputs, nframes);
+#endif
   }
 
   std::shared_ptr<miniaudio_context> m_ctx;
   ma_device m_stream;
+#if defined(__EMSCRIPTEN__)
+  uint64_t m_frames_elapsed{};
+#else
   std::optional<std::chrono::steady_clock::time_point> m_start;
+#endif
 
   boost::container::vector<float> ins_data;
   boost::container::vector<float*> ins;
diff --git a/src/ossia_features.cmake b/src/ossia_features.cmake
index a7c3e7dde30..9cc8b58456d 100644
--- a/src/ossia_features.cmake
+++ b/src/ossia_features.cmake
@@ -277,6 +277,13 @@ if(OSSIA_DATAFLOW)
     target_link_libraries(ossia PRIVATE $<BUILD_INTERFACE:ossia::sdl2>)
   endif()
 
+  # MiniAudio / Web Audio support
+  if(CMAKE_SYSTEM_NAME MATCHES Emscripten)
+    target_include_directories(ossia PRIVATE $<BUILD_INTERFACE:${OSSIA_3RDPARTY_FOLDER}/miniaudio>)
+    target_compile_definitions(ossia PRIVATE MA_ENABLE_AUDIO_WORKLETS MA_ENABLE_WEBAUDIO)
+    target_link_options(ossia PUBLIC -sAUDIO_WORKLET=1 -sWASM_WORKERS=1)
+  endif()
+
   if(OSSIA_ENABLE_LIBSAMPLERATE)
     target_link_libraries(ossia PRIVATE $<BUILD_INTERFACE:SampleRate::samplerate>)
   endif()