Open-source drop-in replacement for the Miles Sound System (MSS) DLL
OpenMiles is a clean-room reimplementation of the Miles Sound System (MSS) in Zig, designed as a drop-in mss32.dll replacement for legacy Windows games running on modern systems and under Wine.
One -Dmss-version flag selects which historical MSS release the export table mimics. Every selectable version (v3 through v9) reproduces its reference mss32.dll's decorated stdcall export table with zero missing exports — verified by diffing against the real DLLs with winedump.
It replaces the proprietary MSS audio stack with miniaudio for audio output, TinySoundFont for MIDI synthesis, and native decoders for MP3, OGG, and WAV (replacing MSS's proprietary ASI plugins), plus FLAC as a bonus format not in the original MSS.
- Drop-in binary compatible -- exports the same stdcall ABI as
mss32.dll - Digital audio -- sample playback, streaming, volume/pan/pitch/loop control
- MIDI/XMIDI -- real-time synthesis via SF2 soundfonts, tempo control, beat callbacks, XMIDI loop/branch support
- 3D positional audio -- full spatial audio with distance attenuation, Doppler, cones, obstruction/occlusion
- ASI codec system -- built-in MP3/OGG/WAV/FLAC decoding; also loads external
.asiplugins as fallback - RIB provider system -- full provider enumeration and interface registration
- Filter API -- real-time low-pass filtering via miniaudio DSP nodes
- Reverb -- per-sample delay-based reverb
- Timer API -- background timer threads with configurable frequency
- Quick API -- high-level one-call playback
- Event system (v8/v9) -- byte-faithful event-text codec (
AIL_create_event/AIL_next_event_step, all step types) plus the v9Miles*API: variables, event enqueue, and a sound-instance lifecycle (durations, label filtering, per-label caps, state reporting) - SoundBank (v8/v9) -- loads the
BANK-format soundbank into a global container, enumerates event/sound/preset/environment assets, resolves event bytecode + sound info/duration by name - Perceptual volume curve -- cubic attenuation matching the original MSS ~60dB dynamic range
- Full export-ABI parity -- v3–v9 export tables diff to zero against the reference DLLs; every exported function is fuzzed and unit-tested
Requires Zig 0.16.0.
# Native build (Linux/Windows -- for tests)
zig build
zig build test# Cross-compile for Windows (game deployment)
zig build -Dtarget=x86-windows -Doptimize=ReleaseFast
# Target a specific MSS version's API surface (ABI-shape the export table)
zig build -Dtarget=x86-windows -Doptimize=ReleaseFast -Dmss-version=5-Dmss-version=<3|4|5|6|6.0|6.1|6.5|6.6|7|8|9> (default 9) selects which Miles
release the export table mimics. Each value reproduces that version's reference
mss32.dll export table with zero missing decorated exports — including the
per-version ABI quirks (functions whose stdcall arity changed across releases,
e.g. init_sample@4→@12→@8, the v4/v5 5-arg 3D-distance variants, the v7-only
DSP-stage API, and the v8 vs v9 Miles* event-API arities).
| Version | Adds | Exports | Parity vs ref |
|---|---|---|---|
| 3 | Core, Digital, Sample, Streaming, MIDI, Redbook, Timer | 251 | 0 missing (vs 3.6f) |
| 4 | RIB/ASI plugin system + ASI compression, Quick, Input, Memory | 347 | 0 missing (vs 4.0h) |
| 5 | 3D audio, filters | 375 | 0 missing (vs 5.0r) |
| 6 | Filter API maturity | 375 | 0 missing (vs 6.0i) |
| 7 | Unified 2D/3D sample API, master/speaker reverb, DSP stages | 447 | 0 missing (vs 7.0b) |
| 8 | Event system, soundbanks, channel levels, in-memory I/O | 542 | 0 missing (vs 8.0b) |
| 9 | Miles* event/variable API, environment presets, 64-bit counters | 641 | 0 missing (vs 9.3f) |
Each build is a superset of its reference: it exports every name the real DLL does (0 missing) plus a small set of harmless cross-era extras. The export count exceeds the reference count for that reason; the faithfulness metric is the zero-missing diff.
The v7 unified audio API runs on the engine (3D on the normal HSAMPLE,
master/sample reverb, low-pass). The v8/v9 event system is byte-faithful
(text constructor + decoder for every step type), the soundbank loader reads
real BANK files into a global container, and the event execution VM parses
enqueued events into tracked sound instances with a full PENDING→PLAYING→COMPLETE
lifecycle (durations resolved from the bank, label-query filtering, per-label
concurrent caps, event-length, cache/persist accounting). The remaining gap is
routing those instances through the miniaudio mixer for actual audio output
(blocked on the bank's embedded-audio data format) — until then event-driven
sounds are tracked and queryable but silent.
The .asi plugin ABI (RIB_INTERFACE_ENTRY layout + ASI/RIB callback
signatures) is stable across MSS v4–v9, so a plugin built for any v4+ release
loads into any v4+ build; the loader is absent only from a v3 build.
Note: Native builds on macOS aarch64 (Apple Silicon) are not supported because Zig's stage2 backend does not implement the
aarch64_aapcs_wincalling convention used by the stdcall exports. Use Linux or Windows for native builds, or cross-compile tox86-windows.
The output DLL is at zig-out/bin/mss32.dll.
- Build the Windows DLL with
zig build -Dtarget=x86-windows -Doptimize=ReleaseFast - Back up the original
mss32.dll/MSS32.DLLin your game directory - Copy
zig-out/bin/mss32.dllto the game directory (as bothmss32.dllandMSS32.DLLon case-sensitive filesystems) - Run the game (natively on Windows, or via Wine on Linux/macOS)
Set OPENMILES_DEBUG=1 in your environment to enable verbose logging to openmiles.log in the game directory.
OPENMILES_DEBUG=1 wine YourGame.exeDebug builds enable logging by default; set OPENMILES_DEBUG=0 to turn it off. Release builds log only when OPENMILES_DEBUG is set to 1 or true. The on-disk log is capped at 64 MiB per process to prevent unbounded growth.
graph TD
Game["Game (.exe)"] --> DLL["mss32.dll (OpenMiles)"]
subgraph OpenMiles
DLL --> API["src/api/<br/>C ABI exports (stdcall)"]
DLL --> Engine["src/engine/<br/>Zig engine layer<br/>Sample, Sequence, DigitalDriver, Filter"]
DLL --> RIB["src/rib/<br/>RIB provider system"]
DLL --> Utils["src/utils/<br/>Logging, filesystem compat"]
DLL --> Bindings["src/bindings/<br/>C implementations<br/>(AIL_debug_printf, AIL_sprintf)"]
end
Engine --> MA["miniaudio.h<br/>Audio output, decoding, mixing, 3D"]
Engine --> TSF["tsf.h<br/>SoundFont (SF2) synthesis"]
Engine --> TML["tml.h<br/>MIDI file parsing"]
MA --> Backend["WASAPI / PulseAudio / CoreAudio"]
The default (v9) DLL exports 641 functions spanning the v3–v9 API surface
(legacy waveOut/midiOut compatibility included; DIG_/MDI_ prefix aliases
not yet exported). Every one of the ~686 distinct exported functions is covered
by the fuzz harness and by unit or C-integration tests. See
docs/API_STATUS.md for the per-function implementation matrix.
Beyond export-table parity, behaviour is cross-checked against the MSS SDK
source: getter round-trips, null/error return sentinels, init defaults, and the
sample/stream lifecycle state machines are verified function-by-function against
wavefile.cpp/m3d.cpp/mssstrm.cpp (see the Behavioural fidelity audit
section of docs/API_STATUS.md).
| Category | Status |
|---|---|
| Core System | Mostly implemented (some Windows/hardware-specific APIs are no-ops) |
| Digital Audio (Samples & Streams) | Fully implemented |
| MIDI / XMIDI | Core playback fully implemented; DLS/SF2 loaded via TinySoundFont |
| 3D Positional Audio | Fully implemented |
| RIB / ASI Plugin System | Fully implemented |
| Filter API | Low-pass filter implemented |
| Timer API | Fully implemented |
| Quick API | Fully implemented |
| Event System (v8/v9) | Byte-faithful text codec; execution VM tracks sound instances (lifecycle, durations, label filtering/caps, state counts) — audio output not yet wired |
| SoundBank (v8/v9) | BANK loader + global container: asset enumeration, event-bytecode + sound-info/duration lookup |
| Redbook (CD) API | Emulated (no audio -- games proceed gracefully) |
| Game | Status |
|---|---|
| Europa 1400: The Guild (Gold Edition) | Working -- MP3 streaming, WAV SFX, multiple drivers |
- API Implementation Status -- per-function status matrix
- API Support Matrix -- version compatibility overview
- Plugin & Codec Coverage -- ASI/M3D/FLT replacement status
- MSS Version History -- historical MSS releases
All dependencies are vendored single-header C libraries in deps/:
| Library | Version | License | Purpose |
|---|---|---|---|
| miniaudio | v0.11.25 | MIT-0 / Public Domain | Audio output, decoding, mixing, 3D |
| TinySoundFont | v0.9 | MIT | SF2 synthesis |
| TinyMidiLoader | v0.7 | Zlib | MIDI parsing |
This project is licensed under the GNU General Public License v3.0.
OpenMiles is a clean-room reimplementation. It does not contain any code from the original Miles Sound System by RAD Game Tools.