{Documentation} Website - Add Timecode Bridge integration docs

Summary:
Explanation:
Adds a new "Timecode Bridge" page under `docs-ark/device/` describing the open-source LTC-to-SubGHz hardware companion (`github.com/facebookresearch/projectaria_timecode_bridge`), and adds concise cross-link callouts on the existing Time Domain Mapping surfaces so readers arrive at the new page from wherever they already are:

- `docs-ark/device/timecode-bridge.mdx` (new) — what Timecode Bridge is, when to use it, hardware summary, and a link out to the source repo for build/flash/CLI details.
- `docs-ark/client-sdk/multi-device.mdx` — `:::tip:::` in "Broadcaster and Receivers" noting the broadcaster does not have to be another Aria device.
- `docs-ark/companion-app/time-domain-mapping.mdx` — same `:::tip:::` after the Broadcaster/Receiver mode table.
- `docs-ark/device/manual.mdx` — expanded the SubGHz sensor bullet to mention LTC-timecoded external gear.
- `docs-technical-specs/device/hardware.mdx` — replaced the "may be made available in the future" placeholder sentence in the "Multi-device time alignment" section with a concrete pointer to Timecode Bridge.

All specific build, wiring, flashing, and CLI reference content lives in the source repo; website pages only cover the high-level concept and link out. From the glasses' perspective nothing new needs to be configured — the Bridge just replaces another Aria as a Broadcaster, and the glasses run as Receivers with the same protocol, channels, and regulatory rules.

Reproducibility:
- Docusaurus build (`yarn build` under `projectaria_tools/website/`) renders all five affected pages without errors.
- New page appears in the ARK → Aria Gen 2 sidebar (position 4, after Accessories and On-Device MP — adjust `sidebar_position` if a different order is preferred).
- All cross-links resolve: `/ark/device/timecode-bridge`, `/ark/client-sdk/multi-device`, `/ark/companion-app/time-domain-mapping`, `/research-tools/projectariatools/pythontutorials/time-sync`, `https://github.com/facebookresearch/projectaria_timecode_bridge`.

___

Differential Revision: D114919814

fbshipit-source-id: 80734f95d565a171a34c421f8f6a7a816fda4379

Author: kongchen1992

website/docs-ark/client-sdk/multi-device.mdx

@@ -37,6 +37,10 @@ Time-domain-mapping (TDM) requires one device to emit a periodic timing signal t
 aria_gen2 recording start --profile profile8 --all --broadcaster 1M0YDD5H7K0047
 ```
 
+:::tip External LTC gear as broadcaster
+The broadcaster does not have to be another Aria device. **[Timecode Bridge](/ark/device/timecode-bridge)** is an open-source hardware companion that re-broadcasts SMPTE LTC over the same sub-GHz protocol — set all your glasses as receivers on the Bridge's channel to align Aria captures with LTC-timecoded external gear (mocap systems, professional cameras, audio recorders).
+:::
+
 If you only need coordinated start and stop without timestamp alignment, disable TDM entirely:
 
 ```bash

website/docs-ark/companion-app/time-domain-mapping.mdx

@@ -30,6 +30,10 @@ Choose one of the following modes based on your device's role:
 | Broadcaster | This device transmits timing signals. This sets the glasses as the primary/reference device. A unique Broadcaster ID is auto-generated. |
 | Receiver | This device listens for timing signals from a Broadcaster (primary device). Use for secondary devices. |
 
+:::tip Sync with external LTC gear
+The Broadcaster does not have to be another Aria device. **[Timecode Bridge](/ark/device/timecode-bridge)** is an open-source hardware companion that broadcasts SMPTE LTC on the same sub-GHz protocol — configure all your glasses as **Receiver** and select the Bridge's channel to align Aria recordings with LTC-timecoded external gear.
+:::
+
 ## Configuring Channel and Broadcaster ID
 
 1. Select a **Channel** from the dropdown. All devices in your recording session must use the same channel.

website/docs-ark/device/manual.mdx

@@ -27,7 +27,7 @@ Aria Gen2 introduces a state-of-the-art sensor suite that expands the range of r
 - IMU, Barometer, Magnetometer, GNSS: Support accurate localization, motion tracking, and environmental sensing.
 - Ambient Light Sensor (ALS) with UV Channel: Distinguishes between indoor and outdoor lighting, opening new avenues for context-aware research.
 - PPG Sensor (Nosepad): Measures heart rate, supporting physiological and affective computing studies.
-- Multi-device time alignment using SubGHz radio based custom protocols allow for multiple Aria Gen 2 device to align their timebases to 10’s of microseconds accuracy.
+- Multi-device time alignment using SubGHz radio based custom protocols allow for multiple Aria Gen 2 devices — and, via [Timecode Bridge](/ark/device/timecode-bridge), LTC-timecoded external gear — to align their timebases to 10’s of microseconds accuracy.
 
 These new sensors, especially the ALS with UV channel, contact-mics and the physiological sensors in the nosepad, unlock research opportunities in context-aware computing, health monitoring, and robust multimodal perception.
 

website/docs-ark/device/timecode-bridge.mdx

@@ -0,0 +1,30 @@
+---
+sidebar_position: 4
+title: Timecode Bridge
+---
+
+# Timecode Bridge
+
+**Timecode Bridge** is an open-source hardware companion that lets Aria Gen 2 glasses time-align with external LTC-timecoded video and audio equipment — motion capture systems, professional cameras, audio recorders, and similar gear. It receives SMPTE **LTC (Linear Timecode)** on a BNC input and re-broadcasts the timing on the same **sub-1 GHz radio protocol** that Aria's built-in [Time Domain Mapping](/ark/companion-app/time-domain-mapping) already uses.
+
+From the glasses' perspective nothing new needs to be configured. Timecode Bridge simply acts as an additional **broadcaster** — same protocol, same channels, same regulatory rules. Set the glasses to **Receiver** mode ([Companion App guide](/ark/companion-app/time-domain-mapping) or [Client SDK guide](/ark/client-sdk/multi-device)) and choose the channel and broadcaster ID that the Bridge is transmitting on. Recorded VRS timestamps expose the Bridge's clock through the existing `SubGHz` [TimeDomain queries](/research-tools/projectariatools/pythontutorials/time-sync).
+
+## When to use it
+
+- Your recording rig is anchored to a master clock outside the Aria ecosystem — a mocap system generating LTC, a video switcher, an SMPTE / MTC generator box.
+- You want Aria captures to align with LTC-stamped footage or audio in post-production; tens of microseconds of offset is achievable.
+- You want to run multi-glass sessions where the timing master is external hardware rather than one of the glasses.
+
+## What it is
+
+- STM32-based, open-source firmware and hardware, built on the **STEVAL-FKI868V2** kit (NUCLEO-L053R8 host board + X-NUCLEO-S2915A1 sub-GHz daughterboard).
+- Regulatory channels match the Aria glasses' supported set: ETSI `0–2` (865.6–867.2 MHz) and FCC `10–40` (903.4–927.4 MHz).
+- Fully documented: 3D-printable enclosure, wiring diagram, hardware build guide, and CLI reference in the source repo.
+
+## Get started
+
+The complete hardware BOM, build guide, flashing instructions, and CLI reference live in the source repo:
+
+**[github.com/facebookresearch/projectaria_timecode_bridge](https://github.com/facebookresearch/projectaria_timecode_bridge)**
+
+Follow the repo's `README.md` and `hw/README.md` for step-by-step assembly and firmware flashing, then configure the glasses as a Receiver on the same channel and broadcaster ID.

website/docs-technical-specs/device/hardware.mdx

@@ -100,7 +100,7 @@ The VD6281 sensor provides correlated color temperature (CCT) and lux measuremen
 The device’s coprocessor supports on-device compression for image/video using H265 HEVC and audio data using OPUS encoders. It also features hardware-accelerated support for machine perception, including 3D articulated hand tracking, eye-tracking with gaze per eye output, and advanced signals such as pupil diameter and blink detection, as well as 6DoF localization.
 
 ## Multi-device time alignment
-A SubGHz radio facilitates the transmission of device timestamps between devices. One broadcaster device transmits its time, while other devices receive this broadcast and subsequently compute time alignment (difference) between the broadcaster and receiver. (Note that this does not synchronize the devices.) This approach circumvents the need for round-trip communication typically associated with TicSync. The system operates under the assumption of negligible time-of-flight within its 30m indoor and 100m outdoor operating ranges. The measured time offset error has been observed to be less than 10 μs. Methodologies for integrating Aria Gen2's time alignment capabilities with other systems may be made available in the future.
+A SubGHz radio facilitates the transmission of device timestamps between devices. One broadcaster device transmits its time, while other devices receive this broadcast and subsequently compute time alignment (difference) between the broadcaster and receiver. (Note that this does not synchronize the devices.) This approach circumvents the need for round-trip communication typically associated with TicSync. The system operates under the assumption of negligible time-of-flight within its 30m indoor and 100m outdoor operating ranges. The measured time offset error has been observed to be less than 10 μs. Aria Gen2's time alignment can also extend to LTC-timecoded external systems (motion capture, professional video and audio gear) via **[Timecode Bridge](https://github.com/facebookresearch/projectaria_timecode_bridge)** — an open-source hardware companion that decodes SMPTE LTC on a BNC input and re-broadcasts on the same sub-GHz protocol. The glasses receive the Bridge's transmissions using the built-in Time Domain Mapping receiver, with no additional glasses-side configuration.
 
 <ThemedImage
   alt="Ambient Light Sensor"