@purinton/resampler

@purinton/resampler

A pure JavaScript, high-quality PCM audio resampler for Node.js. Converts s16le PCM between arbitrary sample rates and channel layouts (mono/stereo) with windowed-sinc filtering. Includes built-in volume control.

Table of Contents

• Features
• Installation
• Usage
  • ESM Example
  • CommonJS Example
• API
• TypeScript
• License

Features

• Pure JavaScript, no native dependencies
• High-quality windowed-sinc resampling
• Arbitrary input/output sample rates (e.g. 48kHz ↔ 24kHz)
• Channel mixing: stereo→mono (average), mono→stereo (duplicate)
• Streams API: drop-in replacement for ffmpeg pipes in Node.js
• Supports s16le PCM (signed 16-bit little-endian)
• Built-in output volume control
• TypeScript type definitions included

Installation

npm install @purinton/resampler

Usage

ESM Example

import { Resampler } from '@purinton/resampler';
import fs from 'fs';

// Downsample 48kHz stereo to 24kHz mono
const resampler = new Resampler({ inRate: 48000, outRate: 24000, inChannels: 2, outChannels: 1 });
fs.createReadStream('input-48k-stereo.s16le')
  .pipe(resampler)
  .pipe(fs.createWriteStream('output-24k-mono.s16le'));

// Downsample with half volume
const resamplerQuiet = new Resampler({ inRate: 48000, outRate: 24000, inChannels: 2, outChannels: 1, volume: 0.5 });
fs.createReadStream('input-48k-stereo.s16le')
  .pipe(resamplerQuiet)
  .pipe(fs.createWriteStream('output-24k-mono-quiet.s16le'));

CommonJS Example

const { Resampler } = require('@purinton/resampler');
const fs = require('fs');

// Upsample 24kHz mono to 48kHz stereo
const resampler = new Resampler({ inRate: 24000, outRate: 48000, inChannels: 1, outChannels: 2 });
fs.createReadStream('input-24k-mono.s16le')
  .pipe(resampler)
  .pipe(fs.createWriteStream('output-48k-stereo.s16le'));

// Upsample with lower volume
const resamplerQuiet = new Resampler({ inRate: 24000, outRate: 48000, inChannels: 1, outChannels: 2, volume: 0.2 });
fs.createReadStream('input-24k-mono.s16le')
  .pipe(resamplerQuiet)
  .pipe(fs.createWriteStream('output-48k-stereo-quiet.s16le'));

API

Resampler(options)

Creates a Transform stream that resamples s16le PCM audio.

Options

• inRate (number): Input sample rate (e.g. 48000)
• outRate (number): Output sample rate (e.g. 24000)
• inChannels (number, default 1): Number of input channels (1=mono, 2=stereo)
• outChannels (number, default 1): Number of output channels (1=mono, 2=stereo)
• filterWindow (number, default 8): Sinc filter window size (higher = better quality, more CPU)
• volume (number, default 1.0): Output volume multiplier (0.0 = silence, 1.0 = unchanged, >1.0 = amplify)

Example

const resampler = new Resampler({ inRate: 48000, outRate: 24000, inChannels: 2, outChannels: 1, volume: 0.5 });

Pipe PCM data through the resampler:

inputStream.pipe(resampler).pipe(outputStream);

TypeScript

Type definitions are included:

import { Resampler, ResamplerOptions } from '@purinton/resampler';

const resampler: Resampler = new Resampler({
  inRate: 48000,
  outRate: 24000,
  inChannels: 2,
  outChannels: 1,
  volume: 0.5,
});

Support

For help, questions, or to chat with the author and community, visit:

Purinton Dev on Discord

License

MIT © 2025 Russell Purinton

Links

• GitHub
• npm
• Discord