mini-mdr

中文

mini-mdr is a tray-only, cross-platform UPnP/DLNA Digital Media Renderer (DMR). It receives playback commands from a phone or desktop control point and plays audio or video through a replaceable player backend.

The default player backend is an external mpv process controlled through mpv's JSON IPC interface.

Features

• Windows, macOS, and Linux target design
• Audio and video playback URLs
• UPnP/DLNA MediaRenderer device description
• SSDP discovery (M-SEARCH responses, periodic ssdp:alive, ssdp:byebye on stop)
• ConnectionManager with protocol info and connection queries
• AVTransport with SetAVTransportURI, Play, Pause, Stop, Seek (REL_TIME), GetTransportInfo, GetPositionInfo, GetMediaInfo
• RenderingControl with master-channel volume and mute
• GENA event subscriptions with renewal, expiry, and LastChange notifications
• Pluggable PlayerBackend abstraction
• Default mpv backend over JSON IPC (named pipe on Windows, Unix socket elsewhere); the mpv process starts lazily on first media load
• Optional VLC backend over HTTP interface
• System-tray-only application control with a dynamic Start/Stop Cast label
• Local settings server with an editable form that persists configuration
• Media history tracking with configurable max entries (persisted to disk)
• Signal handling for clean shutdown (SIGINT, SIGHUP, SIGTERM on Unix)
• Auto-start cast on launch
• Embedded 32x32 RGBA8 tray icon with no runtime image decoding
• i18n support: English and Chinese, auto-detected from system locale

The tray menu has the following structure:

1. Start Cast / Stop Cast (checkbox reflecting current Cast state)
2. More > (submenu)
   • Open Settings
   • Open Directory (opens the config/log directory in the file manager)
3. Quit

Architecture

DMC: phone / desktop controller
    │ SSDP, SOAP, GENA
    ▼
mini-mdr
    ├── SSDP discovery
    ├── UPnP HTTP and SOAP services
    ├── renderer state
    ├── player backend abstraction
    └── system tray
            │
            ▼
        mpv JSON IPC
            │
            ├── video output
            └── audio output

The DMC sends control commands to mini-mdr. The DMR then gives the media URL to the player backend. The player, not the DMC, retrieves the actual media from the DMS over HTTP.

DMC ── SOAP control ──> mini-mdr ── IPC ──> mpv
DMS ── HTTP media ───────────────────────> mpv

Requirements

• Rust stable toolchain
• A desktop environment with a system tray
• mpv installed and available in PATH, unless a custom path is configured
• A UPnP/DLNA control point on the same local network

On Windows, use the MSVC Rust toolchain. On Linux, the desktop environment must provide a tray-compatible notification area or StatusNotifier host. Headless environments may run the non-tray protocol components, but tray creation is expected to fail gracefully.

Running

Install mpv, then run:

cargo run

The application starts with Cast services and the settings HTTP server enabled. The settings server binds to 127.0.0.1:7878 (or an ephemeral fallback port if busy) and opens the page with the system default browser when Open Settings is selected.

Runtime Behavior

Start / Stop Cast

Start Cast starts the UPnP HTTP server and SSDP discovery service. It also creates the configured player backend. Once running, compatible DMC clients can discover and control the renderer.

Stop Cast stops the current player, releases the player backend, and stops the Cast services. It does not stop the settings server if that server was already started.

Open Settings

The settings server starts automatically on launch:

Application startup       -> bind 127.0.0.1:7878
Port conflict             -> select an ephemeral fallback port
Open Settings click       -> open the page in the default browser

The server listens only on loopback and opens the page with the system default browser. Current settings include the device name, player backend, mpv path, and vlc path.

Quit

Quit stops Cast services, stops the player process, closes the settings server when present, and terminates the application.

Configuration

The default configuration is:

[device]
name = "mini-mdr(<hostname>)"   # hostname from $HOSTNAME or $HOST

[player]
backend = "mpv"
mpv_path = "mpv"
vlc_path = "vlc"

[settings]
port = 7878
max_history = 200

Device name includes the system hostname by default (e.g., mini-mdr(laptop)). History entries are persisted to history.json in the same config directory.

The configuration is loaded from the platform-specific user configuration directory provided by the directories crate. If no file exists, these defaults are used.

Player Backends

The protocol layer depends on the PlayerBackend trait rather than directly on mpv:

PlayerBackend
    ├── MpvBackend (default)
    └── VlcBackend

The interface currently covers loading, play, pause, stop, seek, volume, mute, status queries, and protocol info reporting. Future backends such as GStreamer or FFmpeg should implement this trait and be registered in player::create_backend.

The current plugin model is compile-time extensibility through Rust implementations selected by configuration. Runtime loading of third-party DLLs or shared libraries is not implemented.

Device and service descriptions are maintained as standalone files under resources/ and embedded into the executable at compile time with include_str!. Deployment therefore does not require separate XML files.

The editable tray artwork is resources/icon.png. Before committing an icon change, convert it offline to resources/icon.rgba: 32x32, row-major, non-premultiplied RGBA8 (4096 bytes). The executable embeds the raw bytes with include_bytes! and passes them directly to ldtray; no image decoder or startup transformation is involved.

UPnP Scope

The current implementation provides a deliberately small protocol surface:

• device.xml plus one SCPD file per service, embedded at compile time
• SSDP discovery with standard search targets and lifecycle announcements
• SOAP control for transport, position/media queries, seek, volume, and mute
• Standard UPnP error responses with error codes
• GENA SUBSCRIBE/UNSUBSCRIBE with SID renewal, timeout clamping, expiry cleanup, and LastChange notifications to subscriber callbacks

The implementation is not yet a complete DLNA certification implementation. In particular, requests are served sequentially, track metadata is minimal (no DIDLLite), and only instance 0 exists.

Development

Format and verify the project with:

cargo fmt --all -- --check
cargo clippy --all-targets --all-features -- -D warnings
cargo test

Before testing playback, verify that mpv is available:

mpv --version

Useful manual checks:

1. Start the application and confirm the settings port is listening on 127.0.0.1.
2. Click Open Settings and confirm a browser opens on 127.0.0.1.
3. Click Start Cast and send an SSDP M-SEARCH request.
4. Fetch the returned device.xml URL.
5. Use a compatible DMC to send SetAVTransportURI and Play.
6. Stop Cast and confirm the UPnP and SSDP services are released.

Project Status

This is an early MVP under active development. Current status:

• Core UPnP/DLNA protocol implemented (AVTransport, ConnectionManager, RenderingControl)
• SSDP discovery and lifecycle management working
• mpv backend with JSON IPC control
• System tray integration with start/stop cast, settings, and quit
• Settings page with configuration editing and media history
• History persistence to disk with configurable max entries
• Signal handling for clean shutdown on Unix
• AUR packaging for Arch Linux

Priority follow-up work: concurrent request handling, persistent per-install UPnP UDN, DIDLLite metadata, and integration tests.