romdev-audio-resampler

romdev-audio-resampler

A tiny WASM + SIMD linear audio resampler for interleaved S16LE stereo PCM.

Emulator cores report their audio at a native sample rate — usually 31–48 kHz, but sometimes a fractional rate derived from real hardware (e.g. the GameTank ACP at 315000000 / (88·256) ≈ 13983 Hz). A frontend that opens a fixed-rate audio device (SDL wants an integer frequency) must resample the core's stream to the device rate — exactly what a libretro frontend does. This package is that resampler, as a standalone native-speed WASM module (linear interpolation, 4 output frames per SIMD iteration).

Zero dependencies (only node:path / node:url). ~8 KB of wasm.

Usage

import { initResampler, resampleS16Stereo } from "romdev-audio-resampler";

await initResampler();               // lazily instantiate the wasm (returns false on failure)

// interleaved S16LE stereo Buffer from the core, at its native rate → device rate:
const out = resampleS16Stereo(coreBuffer, coreRate /* e.g. 13983 */, 48000);
device.enqueue(out);                 // out is a fresh S16LE stereo Buffer at 48000 Hz

• initResampler(): Promise<boolean> — instantiate once. If it returns false (wasm failed to load), resampleS16Stereo passes the input through unchanged, so callers degrade gracefully to the native rate rather than crashing.
• resampleS16Stereo(buf, srcRate, dstRate): Buffer — synchronous. Returns buf unchanged when srcRate === dstRate or the module isn't loaded.

Scope

Linear interpolation — cheap, small, and inaudible for upsampling low-rate cores (the target use). Not a sinc resampler; if you need studio-grade downsampling, resample with a higher-order kernel upstream. Good enough for real-time console audio, which is the job.

Build

./build.sh (needs an activated Emscripten SDK on PATH) → resampler.mjs + resampler.wasm.

License

MIT.