SlipStream

Low-latency remote desktop streaming over WebRTC with hardware-accelerated encoding.

Overview

SlipStream captures the Windows desktop using the Windows Graphics Capture API and encodes frames in real-time using hardware encoders (NVIDIA NVENC, Intel QSV, or AMD AMF). Video and audio are streamed to web browsers via WebRTC data channels with DTLS encryption. The browser client renders frames using WebGL2 and decodes video/audio using the WebCodecs API. Bidirectional microphone support enables voice communication from the client to the server via VB-Cable.

Architecture

+------------------------------------------------------------------------------+
|                              SERVER (Windows)                                |
+------------------------------------------------------------------------------+
|  Screen Capture         Encoder             WebRTC              Audio        |
|  +--------------+    +--------------+    +--------------+    +----------+    |
|  | WGC API      |--->| NVENC/QSV/   |--->| Data Channel |<-->| WASAPI   |    |
|  | D3D11 Fence  |    | AMF          |    | libdatachan  |    | Opus     |    |
|  | 6-tex pool   |    | AV1/H265/264 |    | 5 channels   |    | 96 kbps  |    |
|  +--------------+    +--------------+    +--------------+    +----------+    |
|                                                 |                  |         |
|                                                 |            +----------+    |
|                                                 |            | VB-Cable |    |
|                                                 |            | Playback |    |
|                                                 |            +----------+    |
|                          +----------------------+----------------------+     |
|                          |       HTTPS Server (port 443)               |     |
|                          |    cpp-httplib + OpenSSL                    |     |
|                          |    JWT Auth + Rate Limiting                 |     |
|                          +----------------------+----------------------+     |
+---------------------------------------------+--------------------------------+
                                              |
                          WebRTC (UDP 50000-50020)
                                              |
+---------------------------------------------+--------------------------------+
|                              CLIENT (Browser)                                |
+------------------------------------------------------------------------------+
|  +--------------+    +--------------+    +--------------+    +----------+    |
|  | VideoDecoder |--->| WebGL2       |    | AudioDecoder |--->| Worklet  |    |
|  | HW or SW     |    | Letterbox    |    | Opus         |    | RingBuf  |    |
|  +--------------+    +--------------+    +--------------+    +----------+    |
|                                                                    |         |
|  +--------------+                                            +----------+    |
|  | AudioEncoder |<-------------------------------------------|  Mic     |    |
|  | Opus 32kbps  |                                            | Capture  |    |
|  +--------------+                                            +----------+    |
|                                                                              |
|  Input Handler -----> Mouse/Keyboard -----> Data Channel -----> Server       |
+------------------------------------------------------------------------------+

Requirements

Server

Component	Requirement
OS	Windows 10/11 64-bit (build 1903+)
GPU	NVIDIA (NVENC), Intel (QSV), or AMD (AMF) GPU
IDE	Visual Studio 2022 with C++20 Desktop workload
Package Manager	vcpkg
Microphone Output	VB-Cable (optional, for client mic playback)

Client

Component	Requirement
Browser	Chrome 94+, Edge 94+, Firefox 98+
APIs	WebRTC, WebCodecs (VideoDecoder, AudioDecoder, AudioEncoder), WebGL2, AudioWorklet

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

cmake -S . -B build -A x64 -DCMAKE_TOOLCHAIN_FILE="C:/vcpkg/scripts/buildsystems/vcpkg.cmake"
cmake --build build --config Release --target SlipStream

Output: build\bin\Release\SlipStream.exe

3. Run

build\bin\Release\SlipStream.exe

On first run:

Prompts for username (3-32 alphanumeric characters, underscores, hyphens)
Prompts for password (8+ characters with at least one letter and one digit)
Generates self-signed SSL certificate (server.crt, server.key) in %APPDATA%\\SlipStream
Saves hashed credentials to %APPDATA%\\SlipStream\\auth.json

4. Connect

Open browser to https://<HOST_IP>:443 and log in with your credentials.

At startup, SlipStream prints:

Local URL (https://localhost:443)
All detected non-loopback LAN IPv4 Network URLs

Note: Self-signed certificate will trigger a browser warning. Click through to proceed.

Network Configuration

Port	Protocol	Purpose
443	TCP	HTTPS server and WebRTC signaling
50000-50020	UDP	WebRTC media transport

Firewall

netsh advfirewall firewall add rule name="SlipStream HTTPS" dir=in action=allow protocol=tcp localport=443
netsh advfirewall firewall add rule name="SlipStream WebRTC" dir=in action=allow protocol=udp localport=50000-50020

Security

Password Storage

Parameter	Value
Algorithm	PBKDF2-HMAC-SHA256
Iterations	600,000
Salt	16 bytes (random)
Key Length	32 bytes

Passwords are never stored in plain text. Only the salt and derived hash are saved in %APPDATA%\\SlipStream\\auth.json.

Rate Limiting

Threshold	Action
5 failed attempts in 15 min	30-minute IP lockout
Successful login	Clears attempt counter

JWT Sessions

Parameter	Value
Algorithm	HS256
Issuer	slipstream
Expiry	24 hours
Storage	HttpOnly, Secure, SameSite=Strict cookie

SSL Certificates

Auto-generated on first run:

2048-bit RSA key
10-year validity
Subject Alt Names include localhost, host DNS name, and detected LAN IPv4 addresses

If you previously generated certificates, delete %APPDATA%\\SlipStream\\server.crt and %APPDATA%\\SlipStream\\server.key to regenerate with updated SANs.

To use custom certificates, replace %APPDATA%\\SlipStream\\server.crt and %APPDATA%\\SlipStream\\server.key before starting.

API Endpoints

Endpoint	Method	Auth	Description
`/`	GET	No	Web client HTML
`/styles.css`	GET	No	Stylesheet
`/js/*.js`	GET	No	JavaScript modules
`/api/auth`	POST	No	Login with `{username, password}`
`/api/session`	GET	Cookie	Validate current session
`/api/logout`	POST	No	Clear session cookie
`/api/offer`	POST	Cookie	WebRTC SDP offer exchange

Video Pipeline

Capture

Component	Detail
API	Windows Graphics Capture (WGC)
Texture Pool	6 textures with D3D11 fence sync
Frame Buffer	4-frame ring buffer with generation tracking
Cursor	Optional capture in stream
Border	Disabled (if OS supports)

GPU Vendor Detection

The encoder automatically detects the GPU vendor and selects the appropriate encoder:

Vendor ID	Vendor	Encoder
0x10DE	NVIDIA	NVENC
0x8086	Intel	QSV
0x1002	AMD	AMF

If the primary GPU's encoder fails, the system falls back to other available encoders.

Encoding

Setting	H.264	H.265	AV1
NVIDIA	h264_nvenc	hevc_nvenc	av1_nvenc
Intel	h264_qsv	hevc_qsv	av1_qsv
AMD	h264_amf	hevc_amf	av1_amf

NVIDIA NVENC Configuration

Setting	Value
Preset	P1 (fastest)
Tune	Ultra-low latency
Rate Control	VBR
CQ Level	23 (H.264), 25 (H.265), 28 (AV1)
Zero Latency	Enabled
B-Frames	0

Intel QSV Configuration

Setting	Value
Preset	veryfast
Look Ahead	Disabled
Async Depth	1
Low Power	Enabled
Global Quality	23 (H.264), 25 (H.265), 28 (AV1)

AMD AMF Configuration

Setting	Value
Usage	Ultra-low latency
Quality	Speed
Rate Control	VBR latency
Header Insertion	GOP
QP	23 (H.264), 25 (H.265), 28 (AV1)

Bitrate Formula: 0.18085 × width × height × fps bps

Example: 1920×1080 @ 60fps ≈ 22.5 Mbps

Transport

Parameter	Value
Chunk Size	1400 bytes max (1379 payload + 21 header)
Header Size	21 bytes
Video Buffer	256 KB threshold
Max Queue	3 frames worth of chunks
Delivery	Ordered, limited retransmits

Video Packet Header (21 bytes)

Offset	Size	Field	Description
0	8	timestamp	Capture timestamp (microseconds)
8	4	encodeTimeUs	Encode duration (microseconds)
12	4	frameId	Frame sequence number
16	2	chunkIndex	Current chunk index
18	2	totalChunks	Total chunks in frame
20	1	frameType	1=keyframe, 0=delta

Audio Pipeline (Server to Client)

Capture

Parameter	Value
API	WASAPI Loopback
Mode	Shared
Sample Rate	48,000 Hz (resampled if system differs)
Channels	Stereo (max 2)
Frame Duration	10 ms (480 samples)

Encoding

Parameter	Value
Codec	Opus
Application	Restricted Low Delay
Bitrate	96 kbps
Complexity	3
Signal Type	Music
FEC	Disabled
DTX	Disabled

Transport

Parameter	Value
Audio Buffer	128 KB threshold
Max Queue	8 packets
Delivery	Ordered, 1 retransmit

Audio Packet Header (16 bytes)

Offset	Size	Field	Description
0	4	magic	0x41554449 ("AUDI")
4	8	timestamp	Capture timestamp
12	2	samples	Sample count (480)
14	2	dataLength	Opus payload size

Client Playback

Component	Detail
Decoder	AudioDecoder (WebCodecs)
Processor	AudioWorklet with ring buffer
Buffer Capacity	9600 samples (200ms)
Prebuffer Threshold	1440 samples (30ms)
Target Buffer	2400 samples (50ms)
Max Buffer	4800 samples (100ms)

Microphone Pipeline (Client to Server)

Client Capture

Parameter	Value
API	MediaDevices.getUserMedia
Sample Rate	48,000 Hz
Channels	Mono
Frame Duration	10 ms (480 samples)
Processing	Echo cancellation, noise suppression, auto gain

Client Encoding

Parameter	Value
Codec	Opus (via WebCodecs AudioEncoder)
Application	VoIP
Bitrate	32 kbps
Complexity	5
Signal Type	Voice
Frame Duration	10 ms

Transport

Parameter	Value
Delivery	Ordered, 1 retransmit
Max Queue	20 packets

Microphone Packet Header (16 bytes)

Offset	Size	Field	Description
0	4	magic	0x4D494344 ("MICD")
4	8	timestamp	Capture timestamp
12	2	samples	Sample count (480)
14	2	dataLength	Opus payload size

Server Playback

Component	Detail
Output Device	VB-Cable Input (auto-detected)
Decoder	Opus (libopus)
Resampling	Linear interpolation if device rate differs
Fallback	Default audio endpoint if VB-Cable unavailable

Input Protocol

Mouse Move Absolute (12 bytes)

Offset	Size	Field
0	4	magic (0x4D4F5645)
4	4	x (float 0.0-1.0)
8	4	y (float 0.0-1.0)

Mouse Move Relative (8 bytes)

Offset	Size	Field
0	4	magic (0x4D4F5652)
4	2	dx (int16)
6	2	dy (int16)

Mouse Button (6 bytes)

Offset	Size	Field
0	4	magic (0x4D42544E)
4	1	button (0-4)
5	1	action (1=down, 0=up)

Button mapping: 0=left, 1=right, 2=middle, 3=X1, 4=X2

Mouse Wheel (8 bytes)

Offset	Size	Field
0	4	magic (0x4D57484C)
4	2	deltaX (int16)
6	2	deltaY (int16)

Keyboard (10 bytes)

Offset	Size	Field
0	4	magic (0x4B455920)
4	2	keyCode (JS keyCode)
6	2	scanCode
8	1	action (1=down, 0=up)
9	1	modifiers

Modifiers: Ctrl=1, Alt=2, Shift=4, Meta=8

Clipboard Data (8 + N bytes)

Offset	Size	Field
0	4	magic (0x434C4950)
4	4	length
8	N	UTF-8 text (max 1MB)

Cursor Shape (5 bytes)

Offset	Size	Field
0	4	magic (0x43555253)
4	1	cursorType (0-13, 255)

Cursor types: 0=default, 1=text, 2=pointer, 3=wait, 4=progress, 5=crosshair, 6=move, 7=ew-resize, 8=ns-resize, 9=nwse-resize, 10=nesw-resize, 11=not-allowed, 12=help, 13=none, 255=custom

Rate Limits (Server-Enforced)

Type	Max per Second
Mouse moves	500
Clicks	50
Keystrokes	100

Blocked Inputs

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

Control Messages

Message	Magic	Size	Description
PING	0x504E4750	16/24	Clock synchronization
HOST_INFO	0x484F5354	6	Host display refresh rate
FPS_SET	0x46505343	7	Set target frame rate
FPS_ACK	0x46505341	7	Frame rate acknowledgment
CODEC_SET	0x434F4443	5	Set video codec
CODEC_ACK	0x434F4441	5	Codec acknowledgment
CODEC_CAPS	0x434F4350	5	Server codec capabilities bitmask
REQUEST_KEY	0x4B455952	4	Request keyframe
MONITOR_LIST	0x4D4F4E4C	Variable	Monitor enumeration
MONITOR_SET	0x4D4F4E53	5	Switch monitor
AUDIO_ENABLE	0x41554445	5	Enable/disable audio streaming
MIC_ENABLE	0x4D494345	5	Enable/disable mic streaming
CURSOR_CAPTURE	0x43555243	5	Toggle cursor capture in video
CLIPBOARD_GET	0x434C4754	4	Request clipboard contents
CLIPBOARD_DATA	0x434C4950	8+N	Clipboard text transfer
KICKED	0x4B49434B	4	Client disconnected by server

Codec Capabilities (CODEC_CAPS)

The server sends a bitmask indicating supported codecs:

Bit 0 (0x01): AV1 supported
Bit 1 (0x02): H.265 supported
Bit 2 (0x04): H.264 supported

The client uses this to enable/disable codec options in the UI.

WebRTC Data Channels

Channel	Ordered	MaxRetransmits	Purpose
control	Yes	3	Commands, ping/pong, monitor list
video	Yes	1	Video frame chunks
audio	Yes	1	Audio packets
input	Yes	3	Mouse/keyboard events
mic	Yes	1	Microphone audio packets

Client Modules

File	Purpose
`state.js`	Shared state, constants, codec detection, metrics, clock sync
`network.js`	HTTP auth, WebRTC signaling, data channel handlers
`renderer.js`	WebGL2 rendering with aspect ratio letterboxing
`media.js`	VideoDecoder, AudioDecoder, AudioWorklet processor
`input.js`	Mouse/keyboard capture, RAF batching, pointer lock
`ui.js`	Settings panel, fullscreen, tabbed mode, stats overlay
`mic.js`	Microphone capture, AudioEncoder, packet transmission

Clock Synchronization

Parameter	Value
Ping interval	200 ms
Sample count	8
Offset calculation	Median filter
RTT estimation	Median of samples

Frame Handling

Parameter	Value
Max buffered frames	8
Frame timeout	200 ms
Max frame age (jitter)	50 ms
Decode queue limit	6 frames

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 playback
Mic - Toggle microphone transmission to server
Monitor - Switch between displays
Frame Rate - 15/30/60/120/144 or custom (1-240)
Codec - AV1, H.265, or H.264 (shows HW/SW status and host availability)
Tabbed Mode - Monitor tabs at top of screen
Debug Stats - Real-time performance overlay
Relative Mouse - Pointer lock mode for gaming
Clipboard Sync - Enable Ctrl+C/V synchronization

Tabbed Mode

When enabled, displays a tab strip showing all monitors with:

Monitor name (EDID friendly name)
Resolution and refresh rate
Primary indicator (star icon)
Click to switch monitors

Debug Stats Overlay

Real-time metrics display organized into sections:

Section	Metrics
Throughput	FPS (actual/target with efficiency %), bitrate, resolution, codec (with HW/SW indicator)
Latency	RTT, frame age
Jitter	Frame interval mean and standard deviation
Decode	Average decode time, queue size, HW acceleration status
Render	Average render time, frame count
Network	Packet count (total, video, audio), average packet size
Drops	Dropped frames, timeouts, late frames, decode errors
Audio	Packets received/decoded, buffer level (ms)
Audio Drops	Dropped, underruns, overflows
Input	Mouse moves/clicks, keystrokes
Session	Uptime, total frames, total data transferred

Server Components

Thread Architecture

Thread	Priority	Purpose
Main	Above Normal	HTTPS server, process priority
Encoder	Time Critical	Frame encoding and sending
Audio	Highest	Audio capture and encoding
Cursor	Below Normal	Cursor shape polling
Wiggle	Normal	Mouse cursor initialization after monitor switch

Server Header Files

File	Purpose
`common.hpp`	Types, auth utilities, monitor enumeration, SSL generation
`capture.hpp`	Screen capture with WGC, texture pool, frame slot
`encoder.hpp`	Hardware video encoding via FFmpeg (NVENC/QSV/AMF)
`webrtc.hpp`	WebRTC server, data channels
`audio.hpp`	WASAPI audio capture + Opus encoding
`input.hpp`	Input handling, keyboard/mouse injection, clipboard
`mic.hpp`	VB-Cable microphone playback

Dependencies

Managed via vcpkg (vcpkg.json):

Package	Purpose
libdatachannel	WebRTC implementation
cpp-httplib[openssl]	HTTPS server
nlohmann-json	JSON parsing
opus	Audio encoding/decoding
openssl	Cryptography, SSL/TLS
ffmpeg[nvcodec,avcodec]	Video encoding
jwt-cpp	JWT token handling
picojson	Required by jwt-cpp

Building

Standard Build

cmake -S . -B build -A x64 -DCMAKE_TOOLCHAIN_FILE="C:/vcpkg/scripts/buildsystems/vcpkg.cmake"
cmake --build build --config Release --target SlipStream

Standard Run

build\bin\Release\SlipStream.exe

Installer Build

build_installer.bat

Creates build\SlipStream-1.0.0-Setup.exe (Inno Setup).

File Structure

SlipStream/
├── include/
│   ├── common.hpp      # Common includes, types, auth utilities
│   ├── capture.hpp     # Screen capture with WGC
│   ├── encoder.hpp     # Hardware video encoding (NVENC/QSV/AMF)
│   ├── webrtc.hpp      # WebRTC server declarations
│   ├── audio.hpp       # WASAPI audio capture + Opus encoding
│   ├── input.hpp       # Input handling + clipboard
│   └── mic.hpp         # VB-Cable microphone playback
├── src/
│   ├── main.cpp        # Application entry point
│   ├── common.cpp      # Auth/SSL/shared runtime implementations
│   ├── app_support.cpp # App setup/auth/helpers
│   ├── webrtc.cpp      # WebRTC server implementation
│   ├── tray.cpp        # System tray integration
│   ├── capture.cpp     # Screen capture pipeline
│   ├── encoder.cpp     # Video encoder pipeline
│   ├── audio.cpp       # System audio capture
│   ├── mic.cpp         # Mic playback pipeline
│   └── input.cpp       # Input injection/clipboard
├── client/
│   ├── index.html      # Web client HTML
│   ├── styles.css      # Stylesheet
│   └── js/
│       ├── state.js    # Shared state and metrics
│       ├── network.js  # WebRTC and HTTP
│       ├── renderer.js # WebGL2 rendering
│       ├── media.js    # Video/audio decoding
│       ├── input.js    # Input capture
│       ├── ui.js       # UI controls
│       └── mic.js      # Microphone capture and encoding
├── vcpkg.json          # Dependencies
├── CMakeLists.txt      # Build configuration
├── build_installer.bat # Installer build script
├── LICENSE.md          # Styled license text
└── Installer-LICENSE.txt # Installer license text

Microphone Setup (VB-Cable)

To enable client microphone audio on the server:

Install VB-Cable Virtual Audio Device
The server automatically detects "CABLE Input" as the output device
Configure your application to use "CABLE Output" as its microphone input

If VB-Cable is not installed, microphone playback is unavailable until a matching render device is present.

Troubleshooting

Problem	Solution
vcpkg not found	Set `VCPKG_ROOT` environment variable or install to `C:\vcpkg`
No hardware encoder	Requires NVIDIA (GTX 600+), Intel (6th gen+), or AMD (RX 400+) GPU
Connection refused	Check firewall for TCP 443 and UDP 50000-50020
Black screen	Wait for keyframe or click canvas to focus
No audio	Click "Enable" in settings panel after first audio playback
Mic not working	Ensure browser has microphone permission, check VB-Cable installation
Input not working	Click the video canvas to capture input focus
Certificate warning	Expected with self-signed certificate, click proceed
Kicked message	Another client connected (single client only)
Monitor switch issues	Frames from previous monitor are automatically discarded
Codec grayed out	Either client browser or server GPU doesn't support that codec

Known Limitations

Windows server only
Single client connection (new client kicks existing)
Hardware GPU required for encoding (NVIDIA, Intel, or AMD)
No custom cursor image sync (standard cursors only)
Microphone requires VB-Cable for full functionality
WebCodecs AudioEncoder required for client microphone

Codec Support Detection

Server-Side

The server probes for encoder support on startup:

Detects primary GPU vendor (NVIDIA/Intel/AMD)
Tests each codec (AV1, H.265, H.264) with the vendor's encoder
Falls back to other vendors if primary fails
Sends codec capabilities bitmask to client

Client-Side

The client automatically detects codec support on connection:

Tests hardware acceleration for each codec (AV1, H.265, H.264)
Falls back to software decoding if hardware unavailable
Intersects with server capabilities to determine available options
Displays HW/SW status and availability in codec dropdown

License

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

Personal use permitted. Commercial use requires separate license.

Styled/readable version: LICENSE.md
Installer-rendered copy: Installer-LICENSE.txt

Name		Name	Last commit message	Last commit date
Latest commit History 11 Commits
client		client
include		include
src		src
.gitignore		.gitignore
CMakeLists.txt		CMakeLists.txt
Installer-LICENSE.txt		Installer-LICENSE.txt
LICENSE.md		LICENSE.md
README.MD		README.MD
SlipStream.iss		SlipStream.iss
build_installer.bat		build_installer.bat
vcpkg.json		vcpkg.json

License

DanielChrobak/SlipStream

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SlipStream

Overview

Architecture

Requirements

Server

Client

Quick Start

1. Install vcpkg

2. Build

3. Run

4. Connect

Network Configuration

Firewall

Security

Password Storage

Rate Limiting

JWT Sessions

SSL Certificates

API Endpoints

Video Pipeline

Capture

GPU Vendor Detection

Encoding

NVIDIA NVENC Configuration

Intel QSV Configuration

AMD AMF Configuration

Transport

Video Packet Header (21 bytes)

Audio Pipeline (Server to Client)

Capture

Encoding

Transport

Audio Packet Header (16 bytes)

Client Playback

Microphone Pipeline (Client to Server)

Client Capture

Client Encoding

Transport

Microphone Packet Header (16 bytes)

Server Playback

Input Protocol

Mouse Move Absolute (12 bytes)

Mouse Move Relative (8 bytes)

Mouse Button (6 bytes)

Mouse Wheel (8 bytes)

Keyboard (10 bytes)

Clipboard Data (8 + N bytes)

Cursor Shape (5 bytes)

Rate Limits (Server-Enforced)

Blocked Inputs

Control Messages

Codec Capabilities (CODEC_CAPS)

WebRTC Data Channels

Client Modules

Clock Synchronization

Frame Handling

UI Features

Settings Panel

Tabbed Mode

Debug Stats Overlay

Server Components

Thread Architecture

Server Header Files

Dependencies

Building

Standard Build

Standard Run

Installer Build

File Structure

Microphone Setup (VB-Cable)

Troubleshooting

Known Limitations

Codec Support Detection

Server-Side

Packages