@bun-win32/mf

Zero-dependency, zero-overhead Win32 MF bindings for Bun on Windows.

Overview

@bun-win32/mf exposes the mf.dll exports using Bun's FFI. It provides a single class, Mf, which lazily binds native symbols on first use. You can optionally preload a subset or all symbols up-front via Preload().

mf.dll is the Media Foundation pipeline layer that sits on top of the already-shipped @bun-win32/mfplat (platform) and @bun-win32/mfreadwrite (source reader / sink writer): source resolution, the ASF authoring object graph, every container media sink (MP3/AAC-ADTS/AC-3/MPEG-4/fragmented-MP4/3GP), streaming sinks, the video renderer, network credential/proxy plumbing, and the protected-environment / signed-library surface.

The bindings are strongly typed for a smooth DX in TypeScript.

Features

• Bun-first ergonomics on Windows 10/11.
• Direct FFI to mf.dll (source resolver, ASF profile/multiplexer/indexer/splitter, MP3/AC-3/ADTS/MPEG-4/3GP media sinks, video renderer, network credential/proxy, and more).
• In-source docs in structs/Mf.ts with links to Microsoft Docs.
• Lazy binding on first call; optional eager preload (Mf.Preload()).
• No wrapper overhead; calls map 1:1 to native APIs.
• Strongly-typed Win32 aliases (see types/Mf.ts).

Requirements

• Bun runtime
• Windows 10 or later

Installation

bun add @bun-win32/mf

Quick Start

import Mf from '@bun-win32/mf';
import Mfplat from '@bun-win32/mfplat';

// Media Foundation must be started before mf.dll factories are used.
Mfplat.MFStartup(0x0002_0070 /* MF_VERSION */, 0x1 /* MFSTARTUP_LITE */);

// Create a source resolver — the entry point that turns a URL or byte stream
// into an IMFMediaSource for the playback / transcode pipeline.
const ppResolver = Buffer.alloc(8); // IMFSourceResolver**
const hr = Mf.MFCreateSourceResolver(ppResolver.ptr);
if (hr === 0) {
  const pResolver = ppResolver.readBigUInt64LE(0); // live COM interface pointer
  // …walk the IMFSourceResolver vtable, then Release() it…
  void pResolver;
}

Mfplat.MFShutdown();

[!NOTE] AI agents: see AI.md for the package binding contract and source-navigation guidance. It explains how to use the package without scanning the entire implementation.

Examples

Run the included examples:

bun run example:asf-pipeline-forge
bun run example:media-format-atlas

Notes

• Either rely on lazy binding or call Mf.Preload().
• mf.dll factories require Media Foundation to be initialized first — call MFStartup from @bun-win32/mfplat (and typically CoInitializeEx) before use.
• Windows only. Bun runtime required.