efp – Rust Bindings & GStreamer Plugin for Elastic Frame Protocol

Rust workspace providing safe bindings and a GStreamer plugin for the Elastic Frame Protocol (EFP), a modern framing layer for media transport over IP networks.

EFP abstracts media payloads from the underlying transport (UDP, TCP, SRT, RIST, etc.) with ~0.5% overhead, 64-bit timestamps, and robust error detection — designed for lossy and out-of-order IP delivery.

Workspace Structure

efp/
├── efp-sys/          – Raw FFI bindings (bindgen + cmake)
├── efp/              – Safe, idiomatic Rust wrapper
├── gst-plugin-efp/   – GStreamer elements (efpmux & efpdemux)
└── vendor/efp/       – Vendored C++17 library (git submodule)

efp-sys

Low-level FFI bindings generated with bindgen from the EFP C API. The build script compiles the vendored C++ library via CMake and links it statically.

efp

Safe Rust wrapper exposing:

• Sender – Fragments data into MTU-sized pieces, delivering them via callback.
• Receiver – Reassembles fragments with configurable bucket and head-of-line timeouts. Supports threaded and run-to-completion modes.
• SuperFrame – Reassembled frame carrying payload, timestamps (PTS/DTS), content type, stream ID, and flags.
• Embedded data – Optional metadata channel alongside frame data, carrying the data type and the stream ID of the frame it rode in on.
• Built-in content type constants for H.264, H.265, Opus, and private data.

gst-plugin-efp

GStreamer plugin registering two elements:

• efpmux – Muxes media streams into EFP format.
• efpdemux – Demultiplexes EFP streams back into media.

Embedded data

Embedded data is addressed to a media stream: it is buffered until the next frame on that stream and travels with it.

On efpmux, request an embed_%u sink pad and send caps carrying both fields. Both are required — caps without them are rejected rather than defaulting to stream 0, which no media stream is ever assigned:

application/x-efp-embedded, data-type=(int)7, stream-id=(int)1

Media stream IDs are allocated from 1 in sink-pad request order, so the first media pad requested is stream 1. Data addressed to a stream that carries no media is dropped with a warning, since there is no frame for it to ride out on.

On efpdemux, each stream that carries embedded data gets its own embedded_<stream-id> src pad, whose caps carry stream-id and the current data-type. A stream that later sends a different data type renegotiates.

Building

Prerequisites: Rust toolchain, CMake, a C++17 compiler, and GStreamer development libraries (for the plugin).

# Clone with submodules
git clone --recurse-submodules https://github.com/Eyevinn/efp.git
cd efp

# Build all crates
cargo build

# Run tests
cargo test

License

MIT