Introduction

Leviathan is the server component of Aethersea. Written in Go, it runs on the host machine, captures the desktop, encodes it with hardware acceleration, and streams it securely to Shen clients.

Supported Platforms

Key Features

• Hardware-accelerated encoding — H.265 (HEVC) and AV1 via NVENC (NVIDIA), QSV (Intel), AMF (AMD, untested), VideoToolbox (Apple); SVT-AV1 software fallback on both platforms.
• Low-latency capture — DXGI Desktop Duplication on Windows; ScreenCaptureKit on macOS; shared CaptureHub distributes one capture instance to all subscribed sessions.
• Multi-session — multiple clients can stream simultaneously from a single capture; on Windows the second session's encoder is automatically promoted to a separate D3D11 device to avoid Video Processor contention.
• Audio streaming — system audio captured via platform loopback and encoded with libopus. The host's default render endpoint is optionally muted for the duration of a session (refcounted across concurrent sessions) and restored on disconnect.
• Input injection — keyboard, mouse, and touch events from Shen are injected through SendInput (Windows) / CGEvent (macOS). Virtual gamepad injection via ViGEm on Windows is implemented; the end-to-end gamepad path is under active development.
• Telemetry — real-time RTT from RTCP Receiver Reports surfaced to the client over a dedicated DataChannel.
• Adaptive FEC — Reed-Solomon Forward Error Correction with overhead tuned to measured loss and the GCC delay-gradient signal, to avoid congestion-driven FEC death-spirals.
• Secure pairing — Argon2id password pairing with per-IP rate limiting; subsequent sessions authenticate by pinned DTLS fingerprint.
• Clipboard sync — bidirectional text, images, and files. On macOS a bundled clipboard-helper process owns NSPasteboard so lazy/delayed rendering works correctly.

Architecture

┌──────────────────────────────────────────┐
│               Leviathan                  │
│                                          │
│  ┌───────────┐    ┌────────────────────┐ │
│  │  Capture  │───>│  Hardware Encoder  │ │
│  │  (DXGI /  │    │  (NVENC/AMF/VT)   │ │
│  │  SCK)     │    └────────┬───────────┘ │
│  └───────────┘             │             │
│                            ▼             │
│  ┌───────────┐    ┌────────────────────┐ │
│  │  Audio    │───>│   RTP / Transport  │◄──── Shen (client)
│  │  Capture  │    └────────────────────┘ │
│  └───────────┘                           │
│                                          │
│  ┌────────────────────────────────────┐  │
│  │         Input Injection            │◄──── Input events from Shen
│  │   (keyboard / mouse / gamepad)     │  │
│  └────────────────────────────────────┘  │
└──────────────────────────────────────────┘

Next Steps

• Getting Started — install and run Leviathan
• Configuration — tune capture, encoding, and networking settings