camera-streaming

Camera Streaming (iOS)

Guide for implementing camera streaming and photo capture with the DAT SDK.

Key concepts

• Stream: Main interface for camera streaming
• VideoFrame: Individual video frames — call .makeUIImage() to render
• StreamConfiguration: Configure resolution, frame rate, and codec
• PhotoData: Still image captured from glasses

Creating a DeviceSession

import MWDATCamera
import MWDATCore

let wearables = Wearables.shared
let deviceSelector = AutoDeviceSelector(wearables: wearables)
// Or for a specific device: SpecificDeviceSelector(device: deviceId)
let deviceSession = try wearables.createSession(deviceSelector: deviceSelector)
try deviceSession.start()

// Wait for the device session to reach the started state
for await state in deviceSession.stateStream() {
    if state == .started { break }
}

Adding a Stream

Once the DeviceSession is started, add a Stream capability:

let config = StreamConfiguration(
    videoCodec: .raw,
    resolution: .medium,  // 504x896
    frameRate: 24
)

guard let stream = try deviceSession.addStream(config: config) else {
    // DeviceSession must be in the started state before adding a stream
    return
}

Resolution options

Resolution	Size
.high	720 x 1280
.medium	504 x 896
.low	360 x 640

Frame rate options

Valid values: 2, 7, 15, 24, 30 FPS.

Lower resolution and frame rate yield higher visual quality due to less Bluetooth compression.

Observing stream state

StreamState transitions: stopping → stopped → waitingForDevice → starting → streaming → paused

let stateToken = stream.statePublisher.listen { state in
    Task { @MainActor in
        switch state {
        case .streaming:
            // Stream is active, frames are flowing
        case .waitingForDevice:
            // Waiting for glasses to connect
        case .stopped:
            // Stream ended — release resources
        case .paused:
            // Temporarily suspended — keep connection, wait
        default:
            break
        }
    }
}

Receiving video frames

let frameToken = stream.videoFramePublisher.listen { frame in
    guard let image = frame.makeUIImage() else { return }
    Task { @MainActor in
        self.previewImage = image
    }
}

Starting and stopping

// Start the stream capability
Task { await stream.start() }

// Stop streaming
Task { await stream.stop() }

// Stop the parent device session when you're done with all capabilities
deviceSession.stop()

Photo capture

Capture a still photo while streaming:

// Listen for photo data
let photoToken = stream.photoDataPublisher.listen { photoData in
    let imageData = photoData.data
    // Convert to UIImage or save
}

// Trigger capture
stream.capturePhoto(format: .jpeg)

Bandwidth and quality

Resolution and frame rate are constrained by Bluetooth Classic bandwidth. The SDK automatically reduces quality when bandwidth is limited:

1. First lowers resolution (e.g., High → Medium)
2. Then reduces frame rate (e.g., 30 → 24), never below 15 FPS

Request lower settings for higher visual quality per frame.

Links

• Stream API reference
• StreamConfiguration API reference
• Integration guide