Codex
76 lines
3.8 KiB
JavaScript
76 lines
3.8 KiB
JavaScript
import { dbToLinear, TAU } from "./math.js";
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import { hashString, pinkNoiseAt, whiteNoiseAt } from "./noise.js";
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function sampleAsset(signal, assetBuffers, time) {
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const asset = assetBuffers.get(signal.assetId);
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if (!asset) throw new Error(`오디오 asset을 찾을 수 없습니다: ${signal.assetId}`);
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const channel = asset.channels[signal.channel ?? 0];
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if (!channel) throw new Error(`${signal.assetId}의 channel ${signal.channel ?? 0}을 찾을 수 없습니다.`);
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let sourceIndex = time * asset.sampleRate;
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if (signal.loop && channel.length > 0) sourceIndex %= channel.length;
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if (sourceIndex < 0 || sourceIndex >= channel.length) return 0;
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const left = Math.floor(sourceIndex);
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const fraction = sourceIndex - left;
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const rightValue = channel[Math.min(left + 1, channel.length - 1)];
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return channel[left] + (rightValue - channel[left]) * fraction;
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}
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/**
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* Render one signal entry into the scene-sized output buffer.
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*
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* `timeMapping` lets a short, rebased scene window retain the original signal
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* timeline. `sceneSampleOffset` maps output sample zero to an absolute sample
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* in the original scene, while `signalStartTime`/`signalStartSample` preserve
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* the entry's original tone/asset time origin and deterministic noise index.
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* Omitting it keeps the historical whole-scene behaviour exactly unchanged.
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*/
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export function renderSignal(entry, scene, assetBuffers = new Map(), seedSalt = 0, timeMapping = {}) {
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const sampleCount = Math.ceil(scene.duration * scene.sampleRate);
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const output = new Float32Array(sampleCount);
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const startTime = entry.startTime ?? 0;
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const duration = entry.duration ?? scene.duration;
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const gain = dbToLinear(entry.gainDb ?? 0);
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const startSample = Math.max(0, Math.ceil(startTime * scene.sampleRate));
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const endSample = Math.min(sampleCount, Math.ceil((startTime + duration) * scene.sampleRate));
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const sceneSampleOffset = timeMapping.sceneSampleOffset ?? 0;
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const signalStartTime = timeMapping.signalStartTime ?? startTime;
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const signalStartSample = timeMapping.signalStartSample ?? Math.ceil(startTime * scene.sampleRate);
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if (!Number.isSafeInteger(sceneSampleOffset) || sceneSampleOffset < 0) {
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throw new RangeError("sceneSampleOffset must be a non-negative safe integer.");
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}
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if (!Number.isFinite(signalStartTime)) {
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throw new TypeError("signalStartTime must be finite.");
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}
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if (!Number.isSafeInteger(signalStartSample) || signalStartSample < 0) {
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throw new RangeError("signalStartSample must be a non-negative safe integer.");
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}
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const signal = entry.signal;
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const seed = (scene.seed + (signal.seedOffset ?? 0) + hashString(entry.id ?? "signal") + seedSalt) >>> 0;
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for (let sampleIndex = startSample; sampleIndex < endSample; sampleIndex += 1) {
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const absoluteSampleIndex = sceneSampleOffset + sampleIndex;
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const localIndex = absoluteSampleIndex - signalStartSample;
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const localTime = absoluteSampleIndex / scene.sampleRate - signalStartTime;
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let value;
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if (signal.type === "tone") {
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value = Math.sin(TAU * signal.frequency * localTime + ((signal.phaseDeg ?? 0) * Math.PI) / 180);
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} else if (signal.type === "noise") {
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value = signal.color === "pink" ? pinkNoiseAt(seed, localIndex) : whiteNoiseAt(seed, localIndex);
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} else if (signal.type === "asset") {
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value = sampleAsset(signal, assetBuffers, localTime);
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} else {
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throw new Error(`지원하지 않는 signal type: ${signal.type}`);
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}
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output[sampleIndex] = value * gain;
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}
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return output;
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}
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export function sampleLinear(buffer, sampleIndex) {
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if (sampleIndex < 0 || sampleIndex >= buffer.length) return 0;
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const left = Math.floor(sampleIndex);
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const fraction = sampleIndex - left;
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const rightValue = buffer[Math.min(left + 1, buffer.length - 1)];
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return buffer[left] + (rightValue - buffer[left]) * fraction;
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}
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