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Low-latency Windows remote desktop streaming with AV1 hardware encoding (NVENC) and WebRTC. Features secure authentication, multi-monitor support, system audio, and full input control. Browser-based client, no plugins required.

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SlipStream

Ultra-low-latency remote desktop streaming with AV1 hardware encoding and WebRTC data channels.

Overview

SlipStream captures the host display using the Windows Graphics Capture API and encodes frames with NVIDIA NVENC AV1 (with libsvtav1 software fallback). Video streams to any modern browser via WebRTC unreliable data channels for minimal latency. System audio is captured via WASAPI loopback and encoded with Opus. Full mouse and keyboard input is relayed back to the host with rate limiting and security filtering.

Features

  • AV1 Hardware Encoding — NVIDIA NVENC with automatic libsvtav1 software fallback
  • WebRTC Data Channels — DTLS-encrypted unreliable transport for lowest latency
  • System Audio — Opus-encoded WASAPI loopback capture at 48kHz stereo
  • Multi-Monitor — Live monitor switching with tabbed browser UI
  • Full Input Control — Mouse, scroll wheel, and keyboard with modifier support
  • Secure Authentication — PBKDF2-SHA256 (600k iterations) with rate limiting and session tokens
  • GPU Synchronization — D3D11 fence-based sync with query fallback
  • Adaptive Frame Pacing — Queue-based sending with overflow protection

Requirements

Server (Host Machine)

Component Requirement
OS Windows 10/11 64-bit (build 1903+)
IDE Visual Studio 2022 with C++20 Desktop workload
GPU NVIDIA GPU with NVENC support (optional, enables hardware encoding)
Package Manager vcpkg

Client (Browser)

Component Requirement
Browser Chrome 94+, Edge 94+, Firefox 98+ (with AV1 decoding)
APIs WebRTC, VideoDecoder, AudioDecoder, WebGL2

Quick Start

1. Install vcpkg

git clone https://github.com/microsoft/vcpkg.git C:\vcpkg
cd C:\vcpkg
.\bootstrap-vcpkg.bat
.\vcpkg integrate install

2. Build

build.bat

Output: build\bin\Release\SlipStream.exe

3. Run

run.bat

First run prompts for credentials:

  • Username — 3-32 alphanumeric characters (plus _ and -)
  • Password — 8+ characters with at least one letter and one digit

Credentials are hashed with PBKDF2-SHA256 and saved to auth.json.

4. Connect

  1. Open browser to http://<HOST_IP>:6060
  2. Enter username and password
  3. Stream begins automatically after authentication

Network Configuration

Port Protocol Purpose
6060 TCP HTTP server (web client, REST API, WebRTC signaling)
50000-50020 UDP WebRTC media transport (DTLS/SCTP data channels)

Firewall Rules

# Allow HTTP server
netsh advfirewall firewall add rule name="SlipStream HTTP" dir=in action=allow protocol=tcp localport=6060

# Allow WebRTC UDP
netsh advfirewall firewall add rule name="SlipStream WebRTC" dir=in action=allow protocol=udp localport=50000-50020

Authentication

Password Security

Passwords are hashed using PBKDF2-SHA256 with:

  • 600,000 iterations — Resistant to brute-force attacks
  • 16-byte random salt — Prevents rainbow table attacks
  • 32-byte derived key — Stored as 64-character hex string

The plaintext password is never stored or logged.

Rate Limiting

Threshold Action
5 failed attempts in 15 minutes 30-minute IP lockout
Successful login Clears attempt counter
Lockout expiry Automatic after 30 minutes

Session Management

Property Value
Token length 64 characters (cryptographic random)
Absolute timeout 24 hours
Inactivity timeout 4 hours
Storage Browser localStorage

auth.json Format

{
  "username": "admin",
  "passwordHash": "<64-char hex SHA-256 derived key>",
  "salt": "<32-char hex random salt>"
}

API Reference

Endpoint Method Auth Request Response
/ GET No — Web client HTML
/styles.css GET No — Stylesheet
/js/*.js GET No — JavaScript modules
/api/auth POST No {username, password} {token, expiresIn}
/api/session GET Bearer — {valid, username}
/api/logout POST Bearer — {success}
/api/offer POST Bearer {sdp, type} {sdp, type}

Error Responses

{"error": "Invalid credentials", "remainingAttempts": 3}
{"error": "Too many attempts", "lockoutSeconds": 1800}
{"error": "Session expired"}
{"error": "Authentication required"}

Video Pipeline

Capture Stage

Windows Graphics Capture API
         │
         ▼
┌─────────────────────┐
│   Frame Pool (4)    │  WinRT Direct3D11CaptureFramePool
└─────────────────────┘
         │
         ▼
┌─────────────────────┐
│  Texture Pool (6)   │  D3D11 staging textures with fence sync
└─────────────────────┘
         │
         ▼
┌─────────────────────┐
│   Frame Slot (4)    │  Lock-free ring buffer for encoder handoff
└─────────────────────┘

Encoding Stage

Setting NVENC (Hardware) libsvtav1 (Software)
Preset P1 (fastest) 12 (fastest)
Tune Ultra-low latency —
Rate Control CBR CRF 28
Target Bitrate 20 Mbps —
Max Bitrate 40 Mbps —
B-Frames Disabled Disabled
Lookahead Disabled Disabled
Keyframe Interval 2 seconds 2 seconds
Thread Count 1 CPU cores / 2 (max 4)

Transport Stage

┌─────────────────────┐
│  Encoded Frame      │
│  (up to 2MB)        │
└─────────────────────┘
         │
         ▼  Split into 1400-byte chunks
┌─────────────────────┐
│   Packet Header     │  21 bytes: timestamp, encodeTime, frameId,
│   + Chunk Data      │           chunkIndex, totalChunks, frameType
└─────────────────────┘
         │
         ▼  Queue with overflow protection
┌─────────────────────┐
│   Send Queue        │  Max 3 frames, paced drain on buffer low
└─────────────────────┘
         │
         ▼
┌─────────────────────┐
│  WebRTC DataChannel │  Unreliable, unordered (maxRetransmits: 0)
└─────────────────────┘

Audio Pipeline

Capture

Property Value
API WASAPI Loopback
Sample Rate 48,000 Hz (resampled from system)
Channels Stereo (max 2, downmixed if needed)
Frame Duration 20 ms (960 samples)

Encoding

Property Value
Codec Opus
Application Restricted Low Delay
Bitrate 128 kbps
Complexity 5

Transport

┌─────────────────────┐
│  Audio Packet       │  16-byte header + Opus payload
│  Header:            │  magic (4) + timestamp (8) +
│                     │  samples (2) + dataLength (2)
└─────────────────────┘

Input Handling

Mouse Events

Event Protocol Bytes Description
Move 12 magic (4) + x (4, float) + y (4, float)
Button 6 magic (4) + button (1) + action (1)
Wheel 8 magic (4) + deltaX (2) + deltaY (2)

Keyboard Events

Field Size Description
magic 4 0x4B455920 ("KEY ")
keyCode 2 JavaScript keyCode
scanCode 2 Hardware scan code (reserved)
action 1 1 = down, 0 = up
modifiers 1 Ctrl (1) + Alt (2) + Shift (4) + Meta (8)

Rate Limiting

Input Type Max per Second
Mouse moves 500
Mouse clicks 50
Keystrokes 100

Blocked Combinations

  • Windows key (left/right)
  • Ctrl+Alt+Delete

Client Architecture

Module Structure

File Purpose
network.js HTTP auth, WebRTC signaling, message routing
renderer.js WebGL2 video rendering with letterboxing
media.js VideoDecoder/AudioDecoder with keyframe retry
input.js Mouse/keyboard capture and transmission
state.js Shared state, constants, clock synchronization
ui.js Settings panel, tabbed mode, fullscreen

Clock Synchronization

The client maintains synchronized time with the server for latency measurement:

Client Send Time ─────────────────────▶ Server Time
       │                                    │
       │◀────────── RTT / 2 ───────────────│
       │                                    │
       ▼                                    ▼
    Offset = ServerTime - (ClientSend + RTT/2)
  • 8 samples maintained for median filtering
  • Drift tracking for long sessions
  • Used for end-to-end latency calculation

Jitter Buffer

Setting Value
Target frames 1
Max frames 2
Max age 50 ms

Frames exceeding limits are dropped with keyframe request.

Server Metrics

The server logs detailed metrics every second when streaming:

━━━ [42s] [LIVE] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
[THROUGHPUT] FPS: 60/60 (100.0%) | Bitrate: 18.45 Mbps | V:60 A:50 | Res: 2560x1440
[PIPELINE] Total: 8.23ms | Cap:1.12 + Hand:0.45 + Enc:4.56 + GPU:1.23 + Net:0.87ms
[CAPTURE] Captured: 60/60 arrived | Interval: 16.45/16.67/16.89ms | Miss:0 Skip:0
[ENCODER] Handoff: 0.32/0.45/0.67ms | Encode: 3.45/4.56/5.67ms
[NETWORK] Queue: avg:2 max:4 depth:1 | Burst: 12/18 avg/max | Drains:60
[INPUT] Mouse: 245 moves, 3 clicks | Keys: 12
[SESSION] Uptime: 42s | Frames: 2520 (60.0 avg) | Data: 95.23MB (18.12 Mbps avg)

UI Features

Settings Panel

Access by clicking the right edge of the screen:

  • Logout — Disconnect and clear session
  • Fullscreen — Enter fullscreen with keyboard lock (Escape captured)
  • Audio — Toggle system audio streaming
  • Monitor — Switch between host displays
  • Frame Rate — Select 15/30/60/host native/client native FPS
  • Tabbed Mode — Show monitor tabs at top of screen

Tabbed Mode

When enabled, displays a Chrome-style tab bar showing all available monitors:

  • Click tabs to switch monitors
  • Shows resolution and primary indicator
  • Preference saved to localStorage

Troubleshooting

Build Issues

Problem Solution
vcpkg not found Set VCPKG_ROOT environment variable or install to C:\vcpkg
CMake configuration failed Ensure Visual Studio 2022 with C++ Desktop workload is installed
NVENC not available Update NVIDIA drivers; software encoding will be used as fallback

Connection Issues

Problem Solution
Connection refused Check firewall allows TCP 6060 and UDP 50000-50020
WebRTC timeout Ensure UDP is not blocked by NAT/firewall
Session expired Re-authenticate; sessions expire after 24h or 4h inactivity
Rate limited Wait 30 minutes or use different IP

Streaming Issues

Problem Solution
Black screen Wait for keyframe or refresh page
Choppy video Lower frame rate; check network bandwidth
No audio Click "Enable" in audio section; browser requires user gesture
High latency Use wired connection; reduce frame rate; check server CPU usage

Client Issues

Problem Solution
"No AV1 decoder" Use Chrome 94+, Edge 94+, or Firefox 98+
Input not working Click on video canvas to capture input
Keyboard locked Press Escape twice or exit fullscreen

Building Installer

build_installer.bat

Creates:

  • SlipStream-1.0.0-win64.exe (NSIS installer, if available)
  • SlipStream-1.0.0-win64.zip (fallback)

Dependencies

Managed via vcpkg:

Package Purpose
libdatachannel WebRTC implementation
cpp-httplib[openssl] HTTP server with TLS support
nlohmann-json JSON parsing
opus Audio encoding
openssl Cryptography
ffmpeg[nvcodec,avcodec] Video encoding (NVENC + libsvtav1)

System Architecture

┌─────────────────────────────────────────────────────────────────────┐
│                         SERVER (Windows)                            │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│  ┌────────────────┐    ┌────────────────┐    ┌──────────────────┐  │
│  │  Screen        │───▶│    AV1         │───▶│    WebRTC        │  │
│  │  Capture       │    │    Encoder     │    │    Server        │  │
│  │  (WGC API)     │    │  (NVENC/SVT)   │    │  (DataChannel)   │  │
│  └────────────────┘    └────────────────┘    └────────┬─────────┘  │
│         │                      │                      │            │
│  ┌──────┴──────┐        ┌──────┴──────┐               │            │
│  │  Texture    │        │  GPU Fence  │               │            │
│  │  Pool (6)   │        │  Sync       │               │            │
│  └─────────────┘        └─────────────┘               │            │
│                                                       │            │
│  ┌────────────────┐    ┌────────────────┐             │            │
│  │  Audio         │───▶│    Opus        │─────────────┤            │
│  │  Capture       │    │    Encoder     │             │            │
│  │  (WASAPI)      │    │  (128kbps)     │             │            │
│  └────────────────┘    └────────────────┘             │            │
│                                                       │            │
│  ┌────────────────┐    ┌────────────────┐             │            │
│  │  Input         │◀───│  HTTP Server   │◀────────────┘            │
│  │  Handler       │    │  + Auth API    │                          │
│  │  (SendInput)   │    │  (Port 6060)   │                          │
│  └────────────────┘    └────────────────┘                          │
│                                                                     │
└─────────────────────────────────────────────────────────────────────┘
                               │
                               │ DTLS + Unreliable DataChannel
                               │ (UDP 50000-50020)
                               ▼
┌─────────────────────────────────────────────────────────────────────┐
│                         CLIENT (Browser)                            │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│  ┌────────────────┐    ┌────────────────┐    ┌──────────────────┐  │
│  │  WebRTC        │───▶│    AV1         │───▶│    WebGL2        │  │
│  │  Receiver      │    │    Decoder     │    │    Renderer      │  │
│  │  (DataChannel) │    │  (VideoDecoder)│    │                  │  │
│  └────────────────┘    └────────────────┘    └──────────────────┘  │
│         │                                                          │
│         │              ┌────────────────┐    ┌──────────────────┐  │
│         └─────────────▶│    Opus        │───▶│    Audio         │  │
│                        │    Decoder     │    │    Playback      │  │
│                        │ (AudioDecoder) │    │  (AudioContext)  │  │
│                        └────────────────┘    └──────────────────┘  │
│                                                                    │
│  ┌────────────────┐    ┌────────────────┐                          │
│  │  Mouse +       │───▶│   Clock Sync   │                          │
│  │  Keyboard      │    │   + Metrics    │                          │
│  │  (Normalized)  │    │                │                          │
│  └────────────────┘    └────────────────┘                          │
│                                                                     │
└─────────────────────────────────────────────────────────────────────┘

Performance Tuning

Server Optimizations

Setting Location Effect
Process priority main.cpp ABOVE_NORMAL_PRIORITY_CLASS
Encoder thread main.cpp THREAD_PRIORITY_TIME_CRITICAL
Audio thread main.cpp THREAD_PRIORITY_HIGHEST
D3D11 multithread capture.hpp Thread-safe context access

Recommended Settings

Scenario Frame Rate Expected Bitrate
LAN (1Gbps) 60 FPS 15-25 Mbps
LAN (100Mbps) 60 FPS 15-25 Mbps
WAN (50Mbps) 30 FPS 8-15 Mbps
WAN (10Mbps) 15 FPS 3-8 Mbps

Security Considerations

Server Hardening

  • Credentials hashed with PBKDF2 (600k iterations)
  • Rate limiting prevents brute-force attacks
  • Session tokens are cryptographically random
  • CORS restricted to same-origin
  • CSP headers prevent XSS
  • Input validation on all API endpoints
  • SDP size limited to 64KB

Input Filtering

  • Windows key blocked (prevents accidental OS shortcuts)
  • Ctrl+Alt+Delete blocked (security boundary)
  • Rate limiting prevents input flooding
  • Coordinate clamping to monitor bounds

Network Security

  • WebRTC uses DTLS encryption
  • Session tokens required for all streaming operations
  • Automatic session expiry on inactivity

Known Limitations

  • Windows only (server requires WGC API and WASAPI)
  • Single client at a time (multi-client not implemented)
  • No clipboard sync
  • No file transfer
  • Hardware cursor only (no cursor rendering fallback)

License

Business Source License (Personal-Online / No-Company) v1.1

Personal use permitted. Commercial and company use requires a separate license.

See LICENSE.txt for full terms.

Copyright

© 2025-2026 Daniel Chrobak. All rights reserved.

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Low-latency Windows remote desktop streaming with AV1 hardware encoding (NVENC) and WebRTC. Features secure authentication, multi-monitor support, system audio, and full input control. Browser-based client, no plugins required.

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