Glossary

This page defines the terms the wiki uses. Each term has one meaning on every page.

Devices and radios

Term	Meaning
the glasses	One pair of Meta smart glasses. Models and product ids are on Glasses-hardware.
the phone	The companion phone that speaks the protocol.
the Meta AI app	Meta's own companion app, package com.facebook.stella.
product id	Meta's number for a glasses model, sent in the advertisement. 266 is Ray-Ban Meta Gen 2.
codename	The firmware's name for a model, such as greathammerhead.
link	One radio connection: LE L2CAP, Classic RFCOMM or TCP over Wi-Fi Direct. See Radios-and-links.
PSM	The L2CAP channel number. The glasses publish it in a GATT characteristic.
SDP	The Bluetooth Classic service lookup. It maps the Meta service UUID to an RFCOMM channel.
identity address	The Bluetooth address a bond ends under. It can differ from the address in the advertisement.
Wi-Fi Direct group	A Wi-Fi network the phone creates and owns. The glasses join it. See Wi-Fi-Direct.
one-session rule	The glasses hold one AirShield session across all links. A new session ends the old one.

The link

Term	Meaning
SDU	One whole message from the transport. On a byte stream the phone cuts SDUs by length. See Transport-and-framing.
session	One AirShield session over one link, from the handshake to the close.
link setup	The handshake on service 5: RequestEncryption, EnableEncryption, then EndLinkSetup. See Link-setup-and-AirShield.
AirShield	The encryption layer. It seals each DataX payload in a DATA frame.
DATA frame	An encrypted frame: header byte, 8-byte tag, block count, ciphertext. See AirShield-frames-and-ciphers.
COMMAND frame	A two-byte cleartext control frame, such as stream 0 LOST.
block count	Byte 9 of a DATA frame: the number of 16-byte ciphertext blocks, minus one.
pad	The modified PKCS#7 tail on AirShield plaintext. Each pad byte is the pad length plus 0xC0.
channel binding	A 32-byte digest of the handshake values. The trust signature covers it.
EndLinkSetup UUIDs	The scope and lease UUIDs in EndLinkSetup. They must be RFC 4122 version 4.
DataX	The message layer inside AirShield: a 4-byte header, extension tags and a payload. See DataX-channels.
channel	A numbered DataX conversation that carries one service.
originator bit	Bit 15 of a channel id. It is set on frames from the side that opened the channel.
mirror channel	The same channel id with bit 15 cleared. Replies and status frames go there.
service, svcN	A DataX service id, written svc28. See Service-catalogue.
message type	A number that names a message within a service, written "type 2005".
continuation	A DataX message with no service or type tag. It belongs to the last type on its channel.
fragment	The head of a DataX message that runs past the end of an AirShield frame. The rest starts the next frame.
status frame	A DataX message with an error tag and no payload. 0x1000 is success.

Identity

Term	Meaning
owner key	The EC P-256 key that makes a phone the glasses' owner. The glasses know it by the SHA-256 of its public key. See Identity-and-trust.
trust	The exchange on svc36 that proves the phone holds the owner key, on every connect.
change owner	The svc36 flow that installs a new owner key with Meta's receipts. See Meta-login-and-ownership.
ownership receipt	Meta's signed JSON that names the new owner key. The flow uses a pending, a device pending and a final receipt.
FRLA, ARAe	The two Meta tokens setup uses: the first comes from the login, the second from the AR login.

Media

Term	Meaning
capture	One shutter press or one recording, as svc18 lists it. See Capture-list.
capture handle	The id of a capture in svc18 requests.
asset, asset id	One file of a capture. Its id equals the uuid of the airship offer that brings it.
capture kind	The kind number of a capture: absent for a live photo, 3073 photo, 3074 video, 3076 unknown.
asset kind	The low byte of an asset's type code: 1 video, 2 still, 3 IMU log, 4 frame log.
delivered flag	Bit 0x100000 of an asset's type code. The glasses set it once a phone has the asset.
airship	The file transfer on svc20. See Airship-file-transfer.
offer, cursor, chunk, drop	The airship steps: the sender offers a file, the receiver answers with a cursor, data comes in chunks, and a drop on type 7 ends the file.
link level	An airship link requirement: ALWAYS, LOW, MEDIUM or HIGH. HIGH is 7.
live photo	A still with a short clip, an IMU log and a frame log. See Live-photos-and-capture-formats.
IMU log, frame log	The SI and SF sensor files of a capture.
live stream	The glasses' camera streamed on svc51350. See Live-stream.
Annex-B	The HEVC byte format with start codes.

Settings

Term	Meaning
RLDrive	The replicated key-value store on svc33 that holds the settings. See Settings-and-RLDrive.
namespace	One RLDrive store, such as <device-uuid>@individual_device_settings.
kv object	An RLDrive object of type kv. Its uri is the setting key and its data is the value as text.
sync round	One of the four steps of an RLDrive sync, rounds 0 to 3.
writer id	The id of one replica that writes into a namespace.
parsed key	A setting key that svc31 applies. Other keys are acknowledged and dropped. See Settings-catalogue.
MobileConfig	Meta's feature flags and parameters on the glasses. See MobileConfig.
mctable	One MobileConfig table file, an FBMobileConfigTable flatbuffer in a small container.
params map	The glasses' map from each MobileConfig param to its type and slot.

Assistant

Term	Meaning
Oxide, svc15	The assistant service. The phone plays the role of Meta's server on it. See Assistant-protocol.
m0, s0	The two svc15 channels: m0 for messages and events, s0 for the audio stream.
envelope	The glasses' wrapper for what they send on m0, type 9000, acked with type 9001.
NetEvent, evN	An svc15 event with an id, written ev57. See Assistant-events.
ev57	The question from the glasses: transcript, intent, slots and visual context.
VARM	VoiceActionResponseMessage, ev53, the answer struct.
ev60	The event that carries the text when the glasses speak the answer in their own voice. See Assistant-voice-and-languages.
use case	Field 5 of START_INTERACTION: 3 is Live AI, 7 is a session turn.
session path	The path set by the flag session_centric_air_infra, where the glasses do not speak text from the phone.
attention state	The glasses' assistant state in svc28 field 31: IDLE, WAKE, LISTENING, PROCESSING, RESPONDING.
follow-up	A question after an answer that the glasses send as s0 audio, with no ev57. See Assistant-follow-ups-and-photos.
sub-interaction	A new interaction id the phone opens for a follow-up or a Live AI utterance.
Live AI	A continuous assistant session with the camera on.
language pack	A zip from Meta with the recognition and voices of one language, sent on airship language_resource.

Open questions

• None recorded.