Feature - Voice Synthesizer (TTS)

.gitmodules

@@ -2,3 +2,7 @@
 	path = dependencies/vosk_gd/godot-cpp
 	url = https://github.com/godotengine/godot-cpp
 	branch = 4.4
+[submodule "dependencies/piper_gd/godot-cpp"]
+	path = dependencies/piper_gd/godot-cpp
+	url = https://github.com/godotengine/godot-cpp
+	branch = 4.5

dependencies/piper_gd/README.md

@@ -0,0 +1,77 @@
+# piper_gd
+GDExtension that runs the Piper TTS CLI as a separate process for offline speech in Godot.
+
+## Methods
+```cpp
+void set_piper_path(String path);
+void set_voice(String model, String config);
+bool is_ready() const;
+bool synthesize_to_file(String text, String wav_path, Dictionary opts = {});
+Ref<AudioStreamWAV> synthesize_to_stream(String text, Dictionary opts = {});
+int64_t synthesize_to_stream_async(String text, Dictionary opts = {});
+void wait();
+signal synthesis_completed(int id, AudioStreamWAV stream);
+signal synthesis_failed(int id, String message);
+```
+*See `src/piper_gd.h` for full signatures and comments.*
+
+## Setup
+### Prerequisits
+- [SCons](https://scons.org/) 
+- [Python3](https://www.python.org/)
+
+### Build
+[Docs](https://docs.godotengine.org/en/4.4/tutorials/scripting/gdextension/gdextension_cpp_example.html#doc-gdextension-cpp-example)
+1. Initialize the submodule
+```bash
+cd godot-cpp
+git submodule update --init
+cd ..
+```
+
+2. Build the C++ bindings
+```bash
+godot --dump-extension-api
+```
+and compile them:
+```bash
+cd godot-cpp
+scons platform=<platform> custom_api_file=<PATH_TO_FILE>
+cd ..
+```
+
+3. Build the extension
+```bash
+scons platform=<platform> target=<editor, template_debug or template_release>
+```
+
+### Install
+Copy the built library (if not already in place) into:
+`src/addons/piper_gd/<platform-arch>/`
+
+Place the Piper CLI binary and voices here:
+```bash
+src/third_party/piper/
+  win64/piper.exe
+  voices/<quality-locale>/<your-voice>/*.onnx
+  voices/<quality-locale>/<your-voice>/*.onnx.json
+```
+*(Keep them as files, not packed into the PCK.)*
+
+## License adherence
+- The game never links to Piper code. We spawn an external process (Piper CLI), pass text in, receive audio out.
+- This is mere aggregation: the game keeps its own license (e.g., CC BY-NC-SA 4.0), while Piper remains GPL-3.0.
+- Compliance we follow in this repo:
+  - Include GPL text for the exact Piper build under `src/third_party/piper/`.
+  - Provide the corresponding source (link the exact commit/tag + build steps or include a source offer file).
+  - Keep all notices intact.
+- Voices carry their own licenses. We include those under `src/third_party/piper/voices/<quality-locale>/<voice>/`.
+
+### Attribution
+- Piper binary: built from `OHF-Voice/piper1-gpl` @ `387ca06`, method: `onefile`.
+- Voices: `ryan`, license `MIT`.
+
+## License
+- piper_gd code (this extension): follow the repo’s main license (`CC BY-NC-SA 4.0`).
+- Piper CLI binary: GPL-3.0.
+- Voices: per-voice licenses.

dependencies/piper_gd/SConstruct

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+#!/usr/bin/env python
+import os
+import sys
+
+env = SConscript("godot-cpp/SConstruct") # type: ignore
+
+# For reference:
+# - CCFLAGS are compilation flags shared between C and C++
+# - CFLAGS are for C-specific compilation flags
+# - CXXFLAGS are for C++-specific compilation flags
+# - CPPFLAGS are for pre-processor flags
+# - CPPDEFINES are for pre-processor defines
+# - LINKFLAGS are for linking flags
+
+# tweak this if you want to use different folders, or more folders, to store your source code in.
+env.Append(CPPPATH=["src/"])
+env.Append(LIBPATH=["bin/"])
+sources = Glob("src/*.cpp") # type: ignore
+
+# Copy over binaries
+binaries = []
+if (env["platform"] == "windows"):
+    binaries = Glob("bin/win64/*.exe") # type: ignore
+elif env["platform"] == "linux":
+    binaries = Glob("bin/linux/*") # type: ignore
+
+for binary in binaries:
+    Copy("../../src/addons/piper_gd/", binary) # type: ignore
+
+if env["platform"] == "macos":
+    library = env.SharedLibrary(
+        "../../src/addons/piper_gd/piper_gd.{}.{}.framework/piper_gd.{}.{}".format(
+            env["platform"], env["target"], env["platform"], env["target"]
+        ),
+        source=sources,
+    )
+else:
+    library = env.SharedLibrary(
+        "../../src/addons/piper_gd/piper_gd{}{}".format(env["suffix"], env["SHLIBSUFFIX"]),
+        source=sources,
+    )
+
+Default(library) # type: ignore