x-law
A-Law, μ-Law and common audio utilites for JavaScript/TypeScript
This package started as a rewrite of the [alawmulaw](https://github.com/rochars/alawmulaw) library in TypeScript for a modernized build process and updated dependencies. It adds additional utilities and features for processing audio data, such as loudness calculation, more flexible encoding/decoding, and more.
Primarily intended for use in a backend environment.
## Install
```
npm install x-law
```
## Usage
CommonJS:
```javascript
const { alaw, mulaw, utils } = require("x-law");
```
ESM:
```javascript
import { alaw, mulaw, utils } from "x-law";
```
## Examples
### Basic Usage
```typescript
import { alaw, mulaw } from "x-law";
// Convert between PCM and μ-Law/A-Law
const pcmSamples = new Int16Array([
/* 16-bit PCM samples */
]);
// Encode to μ-Law
const mulawSamples = mulaw.encode(pcmSamples); // Returns Uint8Array
// Decode back to PCM
const decodedPcm = mulaw.decode(mulawSamples); // Returns Int16Array
// Encode to A-Law
const alawSamples = alaw.encode(pcmSamples); // Returns Uint8Array
// Decode back to PCM
const decodedAlawPcm = alaw.decode(alawSamples); // Returns Int16Array
// Working with Buffer objects
const pcmBuffer = Buffer.from(pcmSamples.buffer);
const encodedMulaw = mulaw.encodeBuffer(pcmBuffer);
const decodedBuffer = mulaw.decodeBuffer(encodedMulaw);
```
### Single Sample Processing
```typescript
import { alaw, mulaw } from "x-law";
// Single sample conversion
const pcmSample = 16384; // 16-bit PCM sample
const mulawSample = mulaw.encodeSample(pcmSample);
const decodedSample = mulaw.decodeSample(mulawSample);
const alawSample = alaw.encodeSample(pcmSample);
const decodedAlawSample = alaw.decodeSample(alawSample);
```
### Audio Processing Utilities
```typescript
import { utils } from "x-law";
// Calculate RMS loudness in decibels
const buffer = Buffer.from(/* PCM audio data */);
const loudness = utils.calculateLoudness(buffer, 16); // For 16-bit PCM
console.log(`RMS Loudness: ${loudness} dB`);
// Resample audio (e.g., from 48kHz to 16kHz)
const samples = [
/* PCM samples */
];
const resampled = utils.resample(samples, 48000, 16000, 16); // 16-bit depth
// Create a WAV header for audio data
const dataSize = pcmSamples.byteLength;
const wavHeader = utils.createWavHeader(
dataSize, // Size of audio data in bytes
44100, // Sample rate (Hz)
1, // Channels (1 = mono, 2 = stereo)
16 // Bit depth (8, 16, 24, or 32)
);
// Write WAV file
const wavFile = Buffer.concat([wavHeader, Buffer.from(pcmSamples.buffer)]);
fs.writeFileSync("output.wav", wavFile);
```
You can find the full documentation [here](https://nitodeco.github.io/xlaw/).
## Contributing
Contributions are welcome! See [CONTRIBUTING.md](CONTRIBUTING.md) for more details.
### LICENSE
This project is licensed under the MIT license. See [LICENSE](LICENSE) for more details.