Add browser-local Piper WebAssembly speech

piper-worker.js

@@ -0,0 +1,41 @@
+import {TtsSession} from '@mintplex-labs/piper-tts-web';
+
+const VOICE_ID = 'sv_SE-nst-medium';
+const ASSET_ROOT = '/tts/piper-wasm-v1';
+let sessionPromise;
+let inferenceQueue = Promise.resolve();
+
+async function getSession(onProgress) {
+  if (!sessionPromise) {
+    sessionPromise = TtsSession.create({
+      voiceId: VOICE_ID,
+      progress: onProgress,
+      wasmPaths: {
+        onnxWasm: `${ASSET_ROOT}/onnx/`,
+        piperData: `${ASSET_ROOT}/piper/piper_phonemize.data`,
+        piperWasm: `${ASSET_ROOT}/piper/piper_phonemize.wasm`,
+      },
+    }).catch(error => {
+      sessionPromise = null;
+      throw error;
+    });
+  }
+  return sessionPromise;
+}
+
+async function synthesizeMessage(event) {
+  const {id, text} = event.data || {};
+  if (!Number.isSafeInteger(id) || typeof text !== 'string') return;
+  try {
+    const session = await getSession(progress => self.postMessage({id, type: 'progress', progress}));
+    const blob = await session.predict(text);
+    const audio = await blob.arrayBuffer();
+    self.postMessage({id, type: 'audio', audio}, [audio]);
+  } catch (error) {
+    self.postMessage({id, type: 'error', error: String(error?.message || error)});
+  }
+}
+
+self.addEventListener('message', event => {
+  inferenceQueue = inferenceQueue.then(() => synthesizeMessage(event));
+});