1 files changed, 59 insertions, 0 deletions
diff --git a/gateway/src/opus.js b/gateway/src/opus.js
new file mode 100644
index 0000000..b1805d6
--- /dev/null
+++ b/gateway/src/opus.js
@@ -0,0 +1,59 @@
+// Opus codec wrapper. Uses the native @discordjs/opus addon when it happens to
+// be installed (faster), otherwise opusscript (WASM): no compiler needed, so it
+// installs cleanly on arm64 SBCs.
+import { createRequire } from "node:module";
+
+const require = createRequire(import.meta.url);
+
+export const SAMPLE_RATE = 48_000;
+export const FRAME_SAMPLES = 960; // 20 ms @ 48 kHz
+export const FRAME_BYTES = FRAME_SAMPLES * 2; // mono Int16
+
+let backend = null;
+
+function loadBackend() {
+  if (backend) return backend;
+  try {
+    const { OpusEncoder } = require("@discordjs/opus");
+    backend = {
+      name: "@discordjs/opus (native)",
+      create(channels) {
+        const codec = new OpusEncoder(SAMPLE_RATE, channels);
+        return {
+          encode: (pcm) => codec.encode(pcm),
+          decode: (data) => codec.decode(data),
+          setBitrate: (bps) => codec.setBitrate(bps),
+          dispose() {},
+        };
+      },
+    };
+  } catch {
+    const OpusScript = require("opusscript");
+    backend = {
+      name: "opusscript (wasm)",
+      create(channels) {
+        const codec = new OpusScript(SAMPLE_RATE, channels, OpusScript.Application.VOIP);
+        return {
+          encode: (pcm) => Buffer.from(codec.encode(pcm, pcm.length / (2 * channels))),
+          decode: (data) => Buffer.from(codec.decode(data)),
+          setBitrate: (bps) => codec.setBitrate(bps),
+          dispose: () => codec.delete(),
+        };
+      },
+    };
+  }
+  return backend;
+}
+
+export function opusBackendName() {
+  return loadBackend().name;
+}
+
+/** Mono 48 kHz Opus codec (encoder + decoder state). */
+export function createOpusCodec({ bitrate } = {}) {
+  const codec = loadBackend().create(1);
+  if (bitrate) {
+    try { codec.setBitrate(bitrate); } catch { /* keep the library default */ }
+  }
+  return codec;
+}