Codex
44 lines
1.9 KiB
JavaScript
44 lines
1.9 KiB
JavaScript
function writeAscii(view, offset, value) {
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for (let index = 0; index < value.length; index += 1) view.setUint8(offset + index, value.charCodeAt(index));
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}
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export const MAX_PCM_WAV_BYTES = 384 * 1024 * 1024;
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export function encodeMonoPcm16Wav(samples, sampleRate) {
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if (!Number.isInteger(sampleRate) || sampleRate < 1 || sampleRate > 0xffffffff) {
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throw new Error(`WAV sample rate가 올바르지 않습니다: ${sampleRate}`);
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}
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if (!samples || !Number.isSafeInteger(samples.length)) {
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throw new Error("WAV samples는 길이가 있는 배열이어야 합니다.");
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}
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const bytesPerSample = 2;
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const dataByteLength = samples.length * bytesPerSample;
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if (!Number.isSafeInteger(dataByteLength) || dataByteLength > 0xffffffff - 36) {
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throw new Error("PCM16 WAV가 RIFF 4 GiB 한도를 넘습니다.");
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}
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if (44 + dataByteLength > MAX_PCM_WAV_BYTES) {
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throw new Error(`PCM16 WAV가 ${(MAX_PCM_WAV_BYTES / 1024 ** 2).toFixed(0)} MiB 메모리 한도를 넘습니다.`);
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}
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const buffer = new ArrayBuffer(44 + dataByteLength);
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const view = new DataView(buffer);
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writeAscii(view, 0, "RIFF");
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view.setUint32(4, 36 + dataByteLength, true);
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writeAscii(view, 8, "WAVE");
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writeAscii(view, 12, "fmt ");
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view.setUint32(16, 16, true);
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view.setUint16(20, 1, true);
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view.setUint16(22, 1, true);
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view.setUint32(24, sampleRate, true);
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view.setUint32(28, sampleRate * bytesPerSample, true);
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view.setUint16(32, bytesPerSample, true);
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view.setUint16(34, 16, true);
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writeAscii(view, 36, "data");
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view.setUint32(40, dataByteLength, true);
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for (let index = 0; index < samples.length; index += 1) {
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if (!Number.isFinite(samples[index])) throw new Error(`WAV sample ${index}가 유한한 숫자가 아닙니다.`);
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const value = Math.max(-1, Math.min(1, samples[index]));
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view.setInt16(44 + index * 2, value < 0 ? value * 0x8000 : value * 0x7fff, true);
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}
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return new Blob([buffer], { type: "audio/wav" });
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}
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