Audio System - LCK Documentation

Module: LCKAudio | Version: 1.0 | Platforms: All

Overview

The LCK SDK features a modular audio capture system that supports multiple audio sources including game audio, microphone input, and voice chat. Audio sources implement a common interface and register via Unreal’s modular features system for automatic discovery.

Audio Source Plugins

LCKUnrealAudio

Unreal Engine native audio capture for game audio and microphone

LCKOboe

High-performance Android microphone capture via Google Oboe

LCKVivox

Vivox voice chat audio capture for multiplayer games

LCKFMOD

FMOD Studio game audio integration

LCKWwise

Audiokinetic Wwise game audio integration

Architecture

┌─────────────────────────────────────────────────────────────┐
│                    LCK Recording System                      │
├─────────────────────────────────────────────────────────────┤
│                     FLCKAudioMix                            │
│                    (Audio Mixer)                             │
├─────────────────────────────────────────────────────────────┤
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐      │
│  │ ILCKAudio    │  │ ILCKAudio    │  │ ILCKAudio    │      │
│  │   Source     │  │   Source     │  │   Source     │      │
│  └──────┬───────┘  └──────┬───────┘  └──────┬───────┘      │
│         │                 │                 │               │
└─────────┼─────────────────┼─────────────────┼───────────────┘
          │                 │                 │
┌─────────▼─────┐  ┌───────▼───────┐  ┌─────▼────────┐
│  LCKUnreal    │  │   LCKFMOD     │  │   LCKVivox   │
│    Audio      │  │   Source      │  │    Source     │
└───────────────┘  └───────────────┘  └──────────────┘

Plugin Capabilities

Source	Game	Microphone	VoiceChat	Module	Platform
LCKUnrealAudio	Yes	Yes	No	LCKUnrealAudio	All
LCKFMOD	Yes	No	No	LCKFMOD	All
LCKWwise	Yes	No	No	LCKWwise	Win64, Android
LCKOboe	No	Yes	No	LCKOboe	Android
LCKVivox	Yes	Yes	No	LCKVivox	All

Audio Configuration Validation

Before recording starts, the audio system validates the configuration to ensure audio sources are properly set up. Use FLCKAudioConfigValidation to inspect the current state:

FLCKAudioConfigValidation Validation = AudioSystem->ValidateConfig();

if (!Validation.bIsValid)
{
    for (const FString& Warning : Validation.Warnings)
    {
        UE_LOG(LogLCKAudio, Warning, TEXT("%s"), *Warning);
    }
}

// Check microphone configuration
if (Validation.bHasMicrophoneSource)
{
    UE_LOG(LogLCKAudio, Log, TEXT("Mic sources: %d enabled, %d total"),
        Validation.EnabledMicrophoneSources.Num(),
        Validation.MicrophoneSourceCount);
}

See FLCKAudioConfigValidation in the types reference.

Audio Plugin Discovery

Use FLCKAudioPluginInfo to query registered audio plugins at runtime:

TArray<FLCKAudioPluginInfo> Plugins = AudioSystem->GetPluginInfo();

for (const FLCKAudioPluginInfo& Plugin : Plugins)
{
    UE_LOG(LogLCKAudio, Log, TEXT("Plugin: %s (%s) - Loaded: %s, Game: %s, Mic: %s"),
        *Plugin.DisplayName,
        *Plugin.ModuleName,
        Plugin.bIsLoaded ? TEXT("Yes") : TEXT("No"),
        Plugin.bGameAudioEnabled ? TEXT("Yes") : TEXT("No"),
        Plugin.bMicrophoneEnabled ? TEXT("Yes") : TEXT("No"));
}

See FLCKAudioPluginInfo in the types reference.

Audio Channel System

Channel Types

enum ELCKAudioChannel : uint64
{
    None       = 0,           // No audio channel
    Game       = 1,           // Game audio output
    Microphone = 1 << 1,      // Microphone input
    VoiceChat  = 1 << 2,      // Voice chat audio (reserved)
    Max        = 1 << 3       // Maximum value marker
};

Channel	Sources
`Game`	UnrealAudio, FMOD, Wwise, Vivox (incoming)
`Microphone`	UnrealAudio, Oboe, Vivox (outgoing)
`VoiceChat`	Reserved for future use

LCKVivox maps incoming voice chat to Game channel and outgoing microphone to Microphone channel for unified handling.

Channel Masks

// Create a channel mask for multiple channels
TLCKAudioChannelsMask Channels = ELCKAudioChannel::Game | ELCKAudioChannel::Microphone;

// Start capture with specific channels
AudioSource->StartCapture(Channels);

// Check if mask contains a channel
bool HasMicrophone = (Channels & ELCKAudioChannel::Microphone) != 0;

Channel Source Configuration Types

The SDK provides helper structs for common channel configurations:

Struct	Channels	Use Case
`FLCKAudioSourceChannels`	Game + Microphone	Full audio capture
`FLCKAudioSourceGameOnly`	Game only	Game audio without mic
`FLCKAudioSourceMicOnly`	Microphone only	Mic-only capture
`FLCKAudioSourceVoiceChat`	Microphone + VoiceChat	Voice chat recording

See Audio Source Channel Types in the types reference.

ILCKAudioSource Interface

All audio sources implement this interface:

class ILCKAudioSource : public IModularFeature, public TSharedFromThis<ILCKAudioSource>
{
public:
    static FName GetModularFeatureName() noexcept;

    // Audio data delegate (single delegate, NOT multicast)
    DECLARE_MULTICAST_DELEGATE_FourParams(FDelegateRenderAudio,
        TArrayView<const float>/*PCM-interleaved*/, int32/*Channels*/, int32/*SampleRate*/, ELCKAudioChannel/*SourceChannel*/);
    typedef FDelegateRenderAudio::FDelegate FOnRenderAudioDelegate;
    FOnRenderAudioDelegate OnAudioDataDelegate;

    // Control methods
    virtual bool StartCapture() noexcept = 0;
    virtual bool StartCapture(TLCKAudioChannelsMask Channels) noexcept = 0;
    virtual void StopCapture() noexcept = 0;

    // Query methods
    virtual float GetVolume() const noexcept = 0;
    virtual const FString& GetSourceName() const noexcept = 0;
    TLCKAudioChannelsMask GetSupportedChannels() const noexcept;

protected:
    TLCKAudioChannelsMask SupportedChannels;
};

OnAudioDataDelegate is a single delegate, not multicast. Only one listener can be bound at a time using BindLambda(). The FLCKAudioMix class internally manages binding to multiple sources.

Discovering Audio Sources

#include "Features/IModularFeatures.h"

// Find all registered audio sources
TArray<ILCKAudioSource*> AudioSources;
IModularFeatures::Get().GetModularFeatureImplementations<ILCKAudioSource>(
    ILCKAudioSource::GetModularFeatureName(),
    AudioSources
);

for (ILCKAudioSource* Source : AudioSources)
{
    UE_LOG(LogTemp, Log, TEXT("Found audio source: %s"), *Source->GetSourceName());

    // Check supported channels
    if (Source->GetSupportedChannels() & ELCKAudioChannel::Game)
    {
        UE_LOG(LogTemp, Log, TEXT("  - Supports game audio"));
    }
    if (Source->GetSupportedChannels() & ELCKAudioChannel::Microphone)
    {
        UE_LOG(LogTemp, Log, TEXT("  - Supports microphone"));
    }
}

Listening to Audio Data

ILCKAudioSource* Source = /* obtained via modular features */;

// Use BindLambda for single delegate (replaces any existing binding)
Source->OnAudioDataDelegate.BindLambda([](
    TArrayView<const float> PCM,
    int32 Channels,
    int32 SampleRate,
    ELCKAudioChannel SourceChannel)
{
    // PCM: Interleaved float audio samples
    // Channels: Number of channels (typically 2 for stereo)
    // SampleRate: Audio sample rate in Hz (typically 48000)
    // SourceChannel: Which audio channel this data represents
});

Audio Format

All audio sources provide audio in this format:

Property	Value
Sample Format	32-bit float
Channels	Stereo (2 channels)
Layout	Interleaved (L,R,L,R,…)
Sample Rate	Match encoder (typically 48000 Hz)

Thread Safety

OnAudioDataDelegate may be called from any thread
Implementers should use thread-safe data structures
The encoder handles cross-thread data marshaling

Log Category

DECLARE_LOG_CATEGORY_EXTERN(LogLCKAudio, Log, All);

​Overview

​Audio Source Plugins

LCKUnrealAudio

LCKOboe

LCKVivox

LCKFMOD

LCKWwise

​Architecture

​Plugin Capabilities

​Audio Configuration Validation

​Audio Plugin Discovery

​Audio Channel System

​Channel Types

​Channel Masks

​Channel Source Configuration Types

​ILCKAudioSource Interface

​Discovering Audio Sources

​Listening to Audio Data

​Audio Format

​Thread Safety

​Log Category

Overview

Audio Source Plugins

Architecture

Plugin Capabilities

Audio Configuration Validation

Audio Plugin Discovery

Audio Channel System

Channel Types

Channel Masks

Channel Source Configuration Types

ILCKAudioSource Interface

Discovering Audio Sources

Listening to Audio Data

Audio Format

Thread Safety

Log Category