camera-streaming | mwdat-android

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camera-streaming | mwdat-android

Camera Streaming (Android)

Use a Session and attached Stream to receive frames and capture photos.

Key concepts

Session: Device connection lifecycle created through Wearables.createSession(...)
Stream: Camera capability attached to a session with session.addStream(...)
StreamConfiguration: Resolution and frame rate configuration for the stream
PhotoData: Still image captured from glasses while streaming

Create a session and attach a stream

import com.meta.wearable.dat.camera.Stream
import com.meta.wearable.dat.camera.addStream
import com.meta.wearable.dat.camera.types.StreamConfiguration
import com.meta.wearable.dat.camera.types.VideoQuality
import com.meta.wearable.dat.core.Wearables
import com.meta.wearable.dat.core.selectors.AutoDeviceSelector

val session = Wearables.createSession(AutoDeviceSelector()).getOrElse { error ->
    throw IllegalStateException(error.description)
}
session.start()

val stream: Stream = session.addStream(
    StreamConfiguration(
        videoQuality = VideoQuality.MEDIUM,
        frameRate = 24,
    ),
).getOrElse { error ->
    throw IllegalStateException(error.description)
}

stream.start().getOrElse { error ->
    throw IllegalStateException(error.description)
}

Resolution options

Quality	Size
`VideoQuality.HIGH`	720 x 1280
`VideoQuality.MEDIUM`	504 x 896
`VideoQuality.LOW`	360 x 640

Frame rate options

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

Lower resolution and frame rate usually produce better visual quality per frame over Bluetooth.

Observe stream state

StreamState transitions: STOPPED -> STARTING -> STARTED -> STREAMING -> STOPPING -> STOPPED -> CLOSED

lifecycleScope.launch {
    stream.state.collect { state ->
        when (state) {
            StreamState.STREAMING -> {
                // Frames are flowing
            }
            StreamState.STOPPED -> {
                // Streaming ended
            }
            StreamState.CLOSED -> {
                // Stream fully closed
            }
            else -> Unit
        }
    }
}

Receive frames

lifecycleScope.launch {
    stream.videoStream.collect { frame ->
        updatePreview(frame)
    }
}

Capture a photo

lifecycleScope.launch {
    stream.capturePhoto()
        .onSuccess { photoData ->
            val imageBytes = photoData.data
            savePhoto(imageBytes)
        }
        .onFailure { error, _ ->
            showCaptureError(error.description)
        }
}

Clean up

Stop the stream when you no longer need camera data, then stop the parent session if the device interaction is finished.

stream.stop()
session.stop()

If you want to remove the capability entirely before re-adding it, call session.removeStream().

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