C

libmoq exposes MoQ to C, C++, and any language with a C FFI through a stable ABI: a generated moq.h, a static libmoq.a that links the whole Rust runtime in, and a pkg-config file for its native link dependencies. The OBS plugin is built on it.

Install

Each libmoq-v* release ships moq-<version>-<target>.tar.gz with include/moq.h, lib/, and a pkg-config file listing the system libraries the static archive needs. Targets: Linux x86_64 and aarch64, macOS arm64, Windows x64.

export PKG_CONFIG_PATH="moq-$ver-$target/lib/pkgconfig"
cc app.c $(pkg-config --cflags --libs --static moq) -o app

From source: cargo build --release -p libmoq writes the library and header under target/release/.

Shape of the API

• Handles and callbacks. Every object is an integer handle; every async result arrives on a callback with a void *user_data. A status > 0 is a live result, 0 a clean close, < 0 an error, and the last two are terminal: libmoq never touches user_data again, so free it there. *_close only requests shutdown; the terminal callback still fires.
• Errors. Negative return codes, with moq_error() giving the reason for the last failure on the calling thread. Auth rejections (401, 403) have their own codes so you don't retry them.
• Threading. Any function from any thread. Raw publish calls block until the codec takes the frame, which paces a publisher.
• Client config. moq_client_create() plus one setter per knob (moq_client_set_versions, _tls_fingerprints, _tls_roots, _tls_cert/_key, _backend, _connect_timeout, _websocket_enabled, _quic_congestion_control, reconnect backoff, and so on), with getters that report defaults. One setter per knob is what keeps the ABI stable when a knob is added.
• Everything the bindings can do (list): media publish and consume with the catalog managed for you, raw pixels and PCM with the codec inside (moq_publish_video_raw, moq_publish_audio_raw, and the _consume_*_raw mirrors), raw tracks with timestamps and datagrams, JSON snapshot and stream tracks, group fetch, dynamic tracks and broadcasts, catalog sections, shared video properties, and stalled hints.

int client = moq_client_create();
struct moq_string fp = { hex_sha256, strlen(hex_sha256) };
if (moq_client_set_tls_fingerprints(client, &fp, 1) < 0)
    return fail(moq_error());   // never dial without the pin you asked for
int session = moq_client_connect(url, url_len, client, origin, 0, on_status, user_data);
moq_client_close(client);   // the config was copied into the session

The header is the reference; each function carries a doc comment. Source and a worked example: rs/libmoq, API docs on docs.rs/libmoq.