Streaming Overview

Module: LCKStreaming | Version: 1.0 | Platforms: Win64, Android (Quest)

What is LCKStreaming?

LCKStreaming adds live streaming to your Unreal Engine project. It connects to the LIV backend to authenticate users, resolve streaming targets, and push video/audio over RTMP to YouTube, Twitch, or any manual RTMP endpoint. The module handles the full lifecycle: device-based authentication, streaming configuration, RTMP connection management, encoder health monitoring, and automatic bitrate selection per platform.

Architecture

┌──────────────────────────────────────────────────────┐
│                   Your Game                          │
│                                                      │
│   ULCKStreamingSubsystem (GameInstanceSubsystem)     │
│       ├── StartLogin / Authenticate                  │
│       ├── StartStreaming / StopStreaming              │
│       └── Delegates (events)                         │
└──────────────────┬───────────────────────────────────┘
                   │
          ┌────────▼────────┐
          │  LIV API Client │  REST (dashboard.liv.tv)
          │  - Auth polling  │
          │  - Profile fetch │
          │  - RTMP resolve  │
          └────────┬────────┘
                   │
          ┌────────▼────────┐
          │  Native RTMP    │  librtmp (Win64)
          │  Bridge         │  librtmp.so (Android)
          │  - Mux & send   │
          │  - Health check │
          └─────────────────┘

The subsystem coordinates two layers: a REST API client that handles authentication, streaming config, and RTMP URL resolution, and a native RTMP bridge that muxes encoded video/audio and pushes it to the ingest server.

Module Structure

Module	Description
`LCKStreaming`	Core streaming subsystem, API client, RTMP logic
`LCKStreamingAndroid`	Android-specific RTMP bridge and LIV Hub interop

Prerequisites

All four prerequisites must be met before streaming will function. Missing any one of them causes StartStreaming() to return false silently.

Enable streaming — Set bEnableStreaming = true in Project Settings → Plugins → LCK SDK → Features. Defaults to false.
Valid Tracking ID — Your project must have a Tracking ID configured in LCK Developer Settings.
RTMP libraries loaded — librtmp DLLs (Win64) or librtmp.so (Android) must be present and loadable at runtime. Check FLCKStreamingModule::IsRtmpAvailable().
LIV account with subscription — The end user needs a LIV account with an active streaming subscription.

Platform Support

Platform	Status	Notes
Win64	Supported	Uses bundled librtmp
Android (Quest)	Supported	Uses librtmp.so, LIV Hub app
Other	—	Not supported at this time

Streaming Targets

Target	Description
YouTube	Automatic broadcast creation via LIV backend
Twitch	Direct RTMP ingest via LIV backend
Manual	User-provided RTMP URL for custom destinations

Platform Bitrates

Bitrates are selected automatically based on the target platform and resolution.

YouTube

Quality	Video Bitrate	Audio Bitrate
SD	4 Mbps	128 Kbps
HD @30	8 Mbps	128 Kbps
HD @60	12 Mbps	128 Kbps
2K	24 Mbps	128 Kbps
4K	35 Mbps	128 Kbps

Twitch

Quality	Video Bitrate	Audio Bitrate
SD	3 Mbps	96 Kbps
HD @30	4.5 Mbps	96 Kbps
HD @60	6 Mbps	96 Kbps
2K	9 Mbps	96 Kbps
4K	10 Mbps	96 Kbps

Keyframe interval is fixed at 2 seconds for all targets, as required by YouTube and Twitch ingest servers.

Relationship to Recording

Streaming and recording share the same encoder pipeline. When both are active simultaneously, the streaming module piggybacks on the active recording encoder rather than creating a second one. This means you can stream and record at the same time with no additional encoding overhead.

If a recording is already in progress when StartStreaming() is called, the stream reuses the existing encoder. If no recording is active, streaming acquires its own encoder instance.

Streaming State Machine

State	Description
`Idle`	No streaming activity
`Pairing`	Device login in progress
`Paired`	Authenticated, ready to stream
`Streaming`	RTMP connection active, pushing frames
`Error`	An error occurred (see `OnStreamError`)

Key Timing Constants

Constant	Value	Description
Auth poll interval	2.5s	How often the subsystem polls for pairing confirmation
Stream start timeout	15s	Maximum wait time for a stream to begin
Health check interval	5s	Frequency of encoder health monitoring
Health check tolerance	2	Consecutive failures before stopping stream

Delegates

The subsystem exposes seven delegates for responding to streaming lifecycle events:

Delegate	Parameters	Fired When
`OnPairingCodeReceived`	`FString Code`	A new pairing code is generated
`OnAuthenticated`	—	User successfully authenticates
`OnStreamingConfigReceived`	`ELCKStreamingTargetType, FLCKUserSubscription`	Stream configuration loaded from server
`OnStreamStarted`	—	Live stream begins
`OnStreamStopped`	—	Live stream ends
`OnStreamError`	`FString ErrorMessage`	A streaming error occurs
`OnLoggedOut`	—	User logs out

Log Category

DECLARE_LOG_CATEGORY_EXTERN(LogLCKStreaming, Log, All);

Quick Start

Get streaming in 5 minutes

Authentication

Device pairing and login flow

Streaming Subsystem API

Full API reference

Core SDK

Tablet Interface

Tablet Customization

Audio

Streaming

API Reference

What is LCKStreaming?

Architecture

Module Structure

Prerequisites

Platform Support

Streaming Targets

Platform Bitrates

YouTube

Twitch

Relationship to Recording

Streaming State Machine

Key Timing Constants

Delegates

Log Category

See Also

Quick Start

Authentication

Streaming Subsystem API

​What is LCKStreaming?

​Architecture

​Module Structure

​Prerequisites

​Platform Support

​Streaming Targets

​Platform Bitrates

​YouTube

​Twitch

​Relationship to Recording

​Streaming State Machine

​Key Timing Constants

​Delegates

​Log Category

​See Also

Quick Start

Authentication

Streaming Subsystem API

What is LCKStreaming?

Architecture

Module Structure

Prerequisites

Platform Support

Streaming Targets

Platform Bitrates

YouTube

Twitch

Relationship to Recording

Streaming State Machine

Key Timing Constants

Delegates

Log Category

See Also