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Publishing Media

This guide covers publishing audio and video tracks to a LiveKit room.

Overview

To publish media, use RtcClient which provides full WebRTC integration. The SDK uses webrtc-java for native WebRTC support.

Setup

import io.livekit.sdk.Room;
import io.livekit.sdk.rtc.RtcClient;
import io.livekit.sdk.rtc.LocalAudioTrack;
import io.livekit.sdk.rtc.LocalVideoTrack;
import io.livekit.sdk.rtc.MediaDeviceInfo;

RtcClient client = new RtcClient();
client.connect(url, token).join();

Device Enumeration

List Available Devices

// Audio input devices (microphones)
List<MediaDeviceInfo> microphones = client.getAudioInputDevices();
for (MediaDeviceInfo device : microphones) {
    System.out.println("Mic: " + device.getLabel() + " (id: " + device.getDeviceId() + ")");
}

// Audio output devices (speakers)
List<MediaDeviceInfo> speakers = client.getAudioOutputDevices();
for (MediaDeviceInfo device : speakers) {
    System.out.println("Speaker: " + device.getLabel());
}

// Video input devices (cameras)
List<MediaDeviceInfo> cameras = client.getVideoInputDevices();
for (MediaDeviceInfo device : cameras) {
    System.out.println("Camera: " + device.getLabel());
}

MediaDeviceInfo

public class MediaDeviceInfo {
    String getDeviceId();   // Device identifier
    String getLabel();      // Human-readable name
    Kind getKind();         // AUDIO_INPUT, AUDIO_OUTPUT, or VIDEO_INPUT
}

Publishing Audio

Using Default Microphone

// Create audio track with default device
LocalAudioTrack audioTrack = client.createAudioTrack();
if (audioTrack != null) {
    client.publishAudioTrack(audioTrack);
}

Using Specific Microphone

// Get device list
List<MediaDeviceInfo> mics = client.getAudioInputDevices();
String deviceId = mics.get(0).getDeviceId();

// Create track with specific device
LocalAudioTrack audioTrack = client.createAudioTrack(deviceId, "my-mic");
client.publishAudioTrack(audioTrack);

Publishing Video

Using Default Camera

// Create video track with default device (1280x720 @ 30fps)
LocalVideoTrack videoTrack = client.createVideoTrack();
if (videoTrack != null) {
    client.publishVideoTrack(videoTrack);
}

Using Specific Camera and Resolution

// Get camera list
List<MediaDeviceInfo> cameras = client.getVideoInputDevices();
String deviceId = cameras.get(0).getDeviceId();

// Create track with specific parameters
LocalVideoTrack videoTrack = client.createVideoTrack(
    deviceId,   // Device ID
    "my-cam",   // Track name
    1920,       // Width
    1080,       // Height
    30          // Frame rate
);
client.publishVideoTrack(videoTrack);

Common Video Resolutions

Preset Resolution Frame Rate Use Case
360p 640x360 30 Low bandwidth
720p 1280x720 30 Standard HD
1080p 1920x1080 30 Full HD
4K 3840x2160 30 Ultra HD

Unpublishing Tracks

// Unpublish by track ID
client.unpublishTrack(audioTrack.getSid());
client.unpublishTrack(videoTrack.getSid());

LocalParticipant Controls

You can also control media through LocalParticipant:

LocalParticipant local = room.getLocalParticipant();

// Enable/disable microphone
local.setMicrophoneEnabled(true);
local.setMicrophoneEnabled(false);

// Enable/disable camera
local.setCameraEnabled(true);
local.setCameraEnabled(false);

Subscribing to Remote Tracks

Remote tracks are automatically subscribed when autoSubscribe is enabled (default). Handle them via RoomListener:

room.addListener(new RoomListener() {
    @Override
    public void onTrackSubscribed(Room room, Track track, 
            TrackPublication publication, RemoteParticipant participant) {
        
        switch (track.getType()) {
            case AUDIO:
                handleAudioTrack((AudioTrack) track, participant);
                break;
            case VIDEO:
                handleVideoTrack((VideoTrack) track, participant);
                break;
        }
    }
    
    @Override
    public void onTrackUnsubscribed(Room room, Track track,
            TrackPublication publication, RemoteParticipant participant) {
        System.out.println("Track unsubscribed: " + track.getSid());
    }
});

void handleAudioTrack(AudioTrack track, RemoteParticipant participant) {
    System.out.println("Audio from: " + participant.getIdentity());
    // Audio plays automatically through default output device
}

void handleVideoTrack(VideoTrack track, RemoteParticipant participant) {
    System.out.println("Video from: " + participant.getIdentity());
    // Access native WebRTC track for rendering
    // RemoteVideoTrack has getNativeTrack() for integration with video renderers
}

Track Types and Sources

TrackType

public enum TrackType {
    AUDIO,
    VIDEO,
    DATA
}

TrackSource

public enum TrackSource {
    UNKNOWN,
    CAMERA,
    MICROPHONE,
    SCREEN_SHARE,
    SCREEN_SHARE_AUDIO
}

Track Publications

Track publications contain metadata about published tracks:

TrackPublication pub = participant.getTrackPublicationBySource(TrackSource.CAMERA);
if (pub != null) {
    System.out.println("Track SID: " + pub.getSid());
    System.out.println("Track name: " + pub.getName());
    System.out.println("Track type: " + pub.getType());
    System.out.println("Is muted: " + pub.isMuted());
    System.out.println("Is subscribed: " + pub.isSubscribed());
    System.out.println("MIME type: " + pub.getMimeType());
}

Known Limitations

  • Screen sharing: webrtc-java supports ScreenCapturer/WindowCapturer but this is not yet exposed in the SDK
  • Simulcast/SVC: Layer selection for adaptive streaming is not yet implemented
  • Audio processing: Advanced audio options (noise suppression, echo cancellation) are not yet configurable

Next Steps