FMOD.rs

Bindings to the FMOD adaptive audio engine. What is Adaptive Audio? (video)

Licensing

This is up top because it's important: FMOD is not free software! In order to use FMOD, you must acquire a license. However, if you make less than $200k revenue/year on a small (<$500k) development budget, FMOD provides a Free Indie License.

The examples in the examples folder are direct ports from the distributed FMOD examples, and are thus under the FMOD license. The media files used for the examples are not redistributable, and thus need to be acquired by you alongside the binaries to run the FMOD Engine.

The Rust code in this repository is licensed under MIT OR Apache-2.0, but this does not remove the requirement to comply with the FMOD license.

Providing the FMOD Engine

In order to comply with the FMOD license, we do not redistribute the FMOD Engine. You must download the engine yourself.

The currently vendored headers are for FMOD Engine 2.02.19 (build 137979). To pin the headers to a specific build, pin fmod-core-sys and fmod-studio-sys. The sys libraries are versioned based on the FMOD version for convenient version pins; for example, FMOD version 2.02.19 is served by sys crates version 2.19.X.

By default, this crate links to fmodL for development builds and fmod for release builds. This can be overridden using the [target.*.fmod] and [target.*.fmodstudio] config.toml keys.

The link-search optional feature will instruct FMOD.rs to add the host's conventional install location for the FMOD Studio API to the link search path. If this is not known for the current host, the buildscript will panic, requiring the use of config.toml to override the build script link config.

Windows Note

The Windows .lib files use a _vc decoration. The crate expects this to be there and appropriately links to fmod_vc/fmodL_vc on Windows.

Functionality

Complete

• Raw bindings to the FMOD C API linking and running on Windows.
• Some examples ported to the wrapped API.
• Thread-safe API.

Planned (Soon™)

• All FMOD Core examples ported using Rust idiomatic APIs.
• Occasional manual tests that linking/running works on macOS/Linux.

Stretch Goals

• bevy plugin.
• 99% API coverage.
• Thread-unsafe use[^1].
• Static linking support.
• Safety audit against misuse.
• Support multiple FMOD versions.

[^1]: FMOD is thread safe by default. For specifics on FMOD thread safety, see Threads and Thread Safety. For our purposes, FMOD is threadsafe, unless FMOD_INIT_THREAD_UNSAFE or FMOD_STUDIO_INIT_SYNCHRONOUS_UPDATE are used. FMOD_INIT_THREAD_UNSAFE can be used safely if and only if: 1) only FMOD Studio is used, and the Core API is never used; 2) FMOD Studio is not used, and Core API calls all happen on a single thread; or 3) FMOD Studio is initialized with FMOD_STUDIO_INIT_SYNCHRONOUS_UPDATE and all FMOD API calls are done in a single thread. FMOD_STUDIO_INIT_SYNCHRONOUS_UPDATE can be safely if and only if all Studio API calls happen on a single thread.

Thus, there are two ways to make the FMOD.rs wrapper thread-safe: forbid the use of the thread-unsafe flags, or encode thread safety into the type system. The former is trivial, but the latter is potentially desirable for users who are using FMOD Studio with their own asynchronous command queue. See the Studio API Threads for more on FMOD Studio threading. Synchronous Update is very much a power-user feature and needs to be encapsulated in a thread-safe worker queue to be used properly, though, so it is acceptable if the thread-unsafe API notably less ergonomic to use than the thread-safe API.

You might be tempted to thus just make System construction unsafe and call that enough; let the user deal with it. However, a) that goes against the Rust philosophy for typed correctness, as any "leakage" of FMOD.rs types to code not aware of the giant caveat would then be unsound; and b) would potentially still be unsound anyway if FMOD.rs API calls are still made from safe code without knowledge that the library has been initialized in the thread-unsafe mode.

Thus, exposing the thread-unsafe usage of FMOD is a high-effort endeavor with minimal payoff; FMOD permits thread-unsafe usage but recommends using the inbuilt thread-safe command batching.