Xiaohan-Tian
53 lines
1.6 KiB
TypeScript
53 lines
1.6 KiB
TypeScript
function writeString(view: DataView, offset: number, str: string) {
|
|
for (let i = 0; i < str.length; i++)
|
|
view.setUint8(offset + i, str.charCodeAt(i));
|
|
}
|
|
|
|
export async function sliceAudioToWav(
|
|
arrayBuffer: ArrayBuffer,
|
|
startSeconds: number,
|
|
durationSeconds: number
|
|
): Promise<ArrayBuffer> {
|
|
const audioCtx = new AudioContext();
|
|
const decoded = await audioCtx.decodeAudioData(arrayBuffer);
|
|
audioCtx.close();
|
|
|
|
const { sampleRate, numberOfChannels: numCh } = decoded;
|
|
const startSample = Math.floor(startSeconds * sampleRate);
|
|
const numSamples = Math.min(
|
|
Math.floor(durationSeconds * sampleRate),
|
|
decoded.length - startSample
|
|
);
|
|
|
|
const bytesPerSample = 2; // 16-bit PCM
|
|
const dataSize = numSamples * numCh * bytesPerSample;
|
|
const buf = new ArrayBuffer(44 + dataSize);
|
|
const view = new DataView(buf);
|
|
|
|
writeString(view, 0, 'RIFF');
|
|
view.setUint32(4, 36 + dataSize, true);
|
|
writeString(view, 8, 'WAVE');
|
|
writeString(view, 12, 'fmt ');
|
|
view.setUint32(16, 16, true);
|
|
view.setUint16(20, 1, true); // PCM
|
|
view.setUint16(22, numCh, true);
|
|
view.setUint32(24, sampleRate, true);
|
|
view.setUint32(28, sampleRate * numCh * bytesPerSample, true);
|
|
view.setUint16(32, numCh * bytesPerSample, true);
|
|
view.setUint16(34, 16, true);
|
|
writeString(view, 36, 'data');
|
|
view.setUint32(40, dataSize, true);
|
|
|
|
let offset = 44;
|
|
for (let i = 0; i < numSamples; i++) {
|
|
for (let ch = 0; ch < numCh; ch++) {
|
|
const s = decoded.getChannelData(ch)[startSample + i];
|
|
const c = Math.max(-1, Math.min(1, s));
|
|
view.setInt16(offset, c < 0 ? c * 32768 : c * 32767, true);
|
|
offset += 2;
|
|
}
|
|
}
|
|
|
|
return buf;
|
|
}
|