feat: implement free-field CPU beamforming

packages/acoustics-core/signal.js

@@ -0,0 +1,53 @@
+import { dbToLinear, TAU } from "./math.js";
+import { hashString, pinkNoiseAt, whiteNoiseAt } from "./noise.js";
+
+function sampleAsset(signal, assetBuffers, time) {
+  const asset = assetBuffers.get(signal.assetId);
+  if (!asset) throw new Error(`오디오 asset을 찾을 수 없습니다: ${signal.assetId}`);
+  const channel = asset.channels[signal.channel ?? 0];
+  if (!channel) throw new Error(`${signal.assetId}의 channel ${signal.channel ?? 0}을 찾을 수 없습니다.`);
+  let sourceIndex = time * asset.sampleRate;
+  if (signal.loop && channel.length > 0) sourceIndex %= channel.length;
+  if (sourceIndex < 0 || sourceIndex >= channel.length) return 0;
+  const left = Math.floor(sourceIndex);
+  const fraction = sourceIndex - left;
+  const rightValue = channel[Math.min(left + 1, channel.length - 1)];
+  return channel[left] + (rightValue - channel[left]) * fraction;
+}
+
+export function renderSignal(entry, scene, assetBuffers = new Map(), seedSalt = 0) {
+  const sampleCount = Math.ceil(scene.duration * scene.sampleRate);
+  const output = new Float32Array(sampleCount);
+  const startTime = entry.startTime ?? 0;
+  const duration = entry.duration ?? scene.duration;
+  const gain = dbToLinear(entry.gainDb ?? 0);
+  const startSample = Math.max(0, Math.ceil(startTime * scene.sampleRate));
+  const endSample = Math.min(sampleCount, Math.ceil((startTime + duration) * scene.sampleRate));
+  const signal = entry.signal;
+  const seed = (scene.seed + (signal.seedOffset ?? 0) + hashString(entry.id ?? "signal") + seedSalt) >>> 0;
+
+  for (let sampleIndex = startSample; sampleIndex < endSample; sampleIndex += 1) {
+    const localIndex = sampleIndex - startSample;
+    const localTime = sampleIndex / scene.sampleRate - startTime;
+    let value;
+    if (signal.type === "tone") {
+      value = Math.sin(TAU * signal.frequency * localTime + ((signal.phaseDeg ?? 0) * Math.PI) / 180);
+    } else if (signal.type === "noise") {
+      value = signal.color === "pink" ? pinkNoiseAt(seed, localIndex) : whiteNoiseAt(seed, localIndex);
+    } else if (signal.type === "asset") {
+      value = sampleAsset(signal, assetBuffers, localTime);
+    } else {
+      throw new Error(`지원하지 않는 signal type: ${signal.type}`);
+    }
+    output[sampleIndex] = value * gain;
+  }
+  return output;
+}
+
+export function sampleLinear(buffer, sampleIndex) {
+  if (sampleIndex < 0 || sampleIndex >= buffer.length) return 0;
+  const left = Math.floor(sampleIndex);
+  const fraction = sampleIndex - left;
+  const rightValue = buffer[Math.min(left + 1, buffer.length - 1)];
+  return buffer[left] + (rightValue - buffer[left]) * fraction;
+}