41 lines
1.2 KiB
TypeScript
41 lines
1.2 KiB
TypeScript
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/**
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* Encode PCM Int16 samples into a WAV file blob.
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* Assumes mono channel at the given sample rate.
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*/
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export function encodeWav(samples: Int16Array, sampleRate: number): Blob {
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const byteLength = samples.length * 2;
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const buffer = new ArrayBuffer(44 + byteLength);
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const view = new DataView(buffer);
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// RIFF header
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writeString(view, 0, "RIFF");
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view.setUint32(4, 36 + byteLength, true);
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writeString(view, 8, "WAVE");
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// fmt chunk
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writeString(view, 12, "fmt ");
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view.setUint32(16, 16, true); // chunk size
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view.setUint16(20, 1, true); // PCM format
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view.setUint16(22, 1, true); // mono
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view.setUint32(24, sampleRate, true);
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view.setUint32(28, sampleRate * 2, true); // byte rate
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view.setUint16(32, 2, true); // block align
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view.setUint16(34, 16, true); // bits per sample
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// data chunk
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writeString(view, 36, "data");
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view.setUint32(40, byteLength, true);
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// PCM samples
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const output = new Int16Array(buffer, 44);
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output.set(samples);
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return new Blob([buffer], { type: "audio/wav" });
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}
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function writeString(view: DataView, offset: number, str: string) {
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for (let i = 0; i < str.length; i++) {
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view.setUint8(offset + i, str.charCodeAt(i));
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}
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}
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