screentinker/brightsign/README.md

ScreenTinker on BrightSign

The player is the ordinary web player (server/player/index.html) running in an roHtmlWidget. It already runs unmodified on real hardware — a Series 5 (HD1026, BOS 9.1, Chromium 120) played 4,723 items over 12.4h averaging 9.4s against a 10s slot. So the port is not "can it run". It is the four things a page cannot do for itself.

  autorun.brs      the host: owns the widget, identity, outputs, recovery
      | @brightsign/messageport  (bidirectional)
  st-bridge.js     the page's half of the same contract
      |
  server/player/index.html        the unmodified player

Files

file	role
autorun.brs	BrightScript host. Builds the widget, supervises it, persists identity, drives a second output, executes what the page cannot.
st-bridge.js	Loaded by the player on this platform. Registry identity, restart-instead-of-reload, heartbeat, sync-backend reporting. Degrades to no-ops everywhere else, so it is safe to load unconditionally.
st-sync.js	Native SyncManager adapter. Inert without the platform module, so the player falls back to its own group sync.
probe.html	The original capability probe. Still useful on a new model/OS build.
offline.html	Local fallback page — names the server, keeps probing it, and asks the host to restart the player the moment it answers.

The four things the host exists for

1. It owns the widget lifecycle. A page-initiated location.reload() does not reliably bring an roHtmlWidget back. On 2026-07-28 a ScreenTinker deploy reloaded every connected player; the BrightSign was the only one that never returned, and a browser on the same deploy reloaded and was heartbeating minutes later. So the page never reloads itself here — it posts {type:"restart"} and the host tears the widget down and builds a new one. Without this, every deploy silently darkens every BrightSign panel until someone power-cycles it.

2. It recovers. load-error retries with backoff (5s → 15s → 30s → 60s) and after three failures falls back to a local page, so a dead server shows something truthful instead of white. On top of that, a watchdog: the page beats every 30s and three missed beats rebuild the widget. That covers the case load-error never reports — a page that loaded fine and then wedged on a dead socket, a JS exception, or a stalled decoder.

3. Identity lives in the registry. localStorage is tied to the page's origin and quota; the registry survives reboots, content updates and origin changes. The hardware serial is the stable id, so two panels imaged from the same card never collide — which is exactly how the web player's hardware-only fingerprint once merged two identical panels into a single device row.

4. It reaches BrightScript-only capabilities — video mode, a second output, and native BrightWall sync — on the page's behalf, over @brightsign/messageport.

Where the files go — card OR internal flash

autorun.brs          the host
offline.html         local fallback, used after three failed loads
screentinker.json    optional — server URL, sync backend, output mode

A player will boot autorun.brs from internal flash, not just from a card. Confirmed on real hardware (XT245, BOS 9.0.189) whose microSD interface is physically dead:

Loading 'FLASH:/autorun.brs'
BSPLAY: https://screentinker.com/player?platform=brightsign&serial=…&model=XT245

That matters far beyond one broken unit — it means a player with no card, or a failed card slot, is still fully deployable. Push the files over SFTP to /storage/flash (user brightsign, blank password, once SSH is enabled) and reboot.

StorageRoot() in autorun.brs therefore refuses to assume: it probes for FLASH:/autorun.brs and falls back to SD:. Hard-coding SD: is exactly the bug that made the first flash boot fail — the script loaded and then could not find its own index.html.

st-bridge.js and st-sync.js do NOT go on the card. The player pulls them from the server (/player/st-bridge.js, /player/st-sync.js) so they can never skew from the player that uses them. A stale copy on a card is precisely the version skew that would leave a panel unable to restart itself.

autorun.zip — one file instead of four

scripts/build-autorun-zip.sh packages the host, the fallback page and the config into a single autorun.zip, attached to every GitHub release:

scripts/build-autorun-zip.sh --server https://your-server

Drop it on the root of a player's storage and power-cycle. autozip.brs unpacks it in place, renames it autorun.zip.done so it never re-extracts, and reboots into the player.

Two rules the format imposes, both of which fail silently if broken:

• The archive must expand to files at its ROOT, with no wrapper directory — a player extracts to the storage root, so a nested folder puts autorun.brs somewhere the player never looks and the card appears to do nothing. The build script zips from inside the staging directory and then asserts the layout rather than trusting it.
• autorun.brs must NOT sit next to autorun.zip on the storage root; its presence stops the zip being processed at all. It belongs inside the archive.

The rename is what makes it idempotent. Without it the player extracts, reboots, extracts, reboots — a loop that looks exactly like a hardware fault. An extraction failure deliberately does not rename, so a truncated copy is retried after someone replaces it rather than skipped forever.

Requires BrightSignOS 7.0.60+ (roUnzip).

Provisioning

Config resolves screentinker.json on the card > registry > built-in default. The JSON file is how a batch gets imaged without touching each box:

{ "server_url": "https://screentinker.com", "sync_backend": "auto", "output_mode": "single" }

Dual output

output_mode is single | dual | clone.

• dual — a second widget loads the same player with &screen=2, so the server can hand it its own playlist. Two independent displays from one player.
• clone — the second widget loads &screen=1: the same content on both outputs.

Confirmed multi-output: XC2055 (dual HDMI) and XC4055 (quad).

⚠️ Do not trust the series-level spec blurb. It credits the whole XT5 family — XT245, XT1145, XT2145 — with "dual HDMI outputs", but an XT245 in hand is single-output; that phrase appears to cover HDMI in plus out. Verify the individual model before enabling dual.

Every other model is single-output, so the second widget is only ever created when the config asks for it — an unsupported model keeps working as a normal single-screen player rather than failing to start.

Synchronisation — ours or theirs

Both, chosen per group. server/lib/sync-backend.js decides and resolveSyncBackend() is pure, so the decision is tested without a fleet (server/test/sync-backend.test.js).

backend	reach	accuracy
screentinker	Android, web, Tizen, BrightSign — any mix	to the second; clock-derived, no leader, survives a server outage
brightsign	BrightSign only	frame-accurate (BrightWall)

auto picks native sync when every member is a BrightSign and ours otherwise. Explicit settings are honoured, with one refusal: native sync selected for a group containing a non-BrightSign display downgrades and reports why. A group that half-syncs is worse than one that syncs to the second everywhere — and the failure would be invisible from the dashboard, because the BrightSigns would look perfectly synchronised while the odd panel drifted alone.

A player paired before this port is still recognised, by its BrightSign user agent.

How the choice reaches a screen

device_groups.sync_backend (auto | screentinker | brightsign) is the operator's request. The server resolves it per push through resolveSyncBackend() and sends the answer — plus the reason and a downgraded flag — in the group_sync payload, so the players, the dashboard and the stored setting can never disagree about which protocol is running.

Three things force a fallback to our protocol, and each is reported rather than applied silently:

condition	why native sync cannot run
any non-BrightSign member	BrightWall cannot include a foreign screen
members on different subnets	it is multicast; it does not cross networks
the elected leader is offline	it is leader/follower — nobody would broadcast

That last one has no equivalent in our protocol, which is leaderless and carries on regardless. Leadership uses the existing election (resolveGroupLeader): the pinned leader if it is an online member on the shared playlist, else the first online member, else the first member by id.

Item selection stays clock-derived under both backends. Native sync only replaces the seek/nudge drift correction, because setSyncParams has the video element hold its own alignment — and correcting it ourselves would fight the platform. That also keeps images and widgets, which have no setSyncParams, advancing with the videos instead of drifting off on their own.

Command parity

The web player handles four of the ~20 fleet commands — launch, refresh, screen_on, screen_off — because a browser tab genuinely cannot do more. A BrightSign can, through the host and the platform APIs:

command	web player	BrightSign
screen_on / screen_off	black overlay; panel stays lit	CEC Image View On / Standby — the display actually sleeps
reboot	ignored	real reboot via RebootSystem in the host
set_volume	—	applied to current and future media
refresh	location.reload()	widget rebuilt by the host (reload is unreliable here)

⚠️ Nothing in the DOM can cover video

With hwz_default: "on" the widget decodes video onto a hardware plane, and the graphics plane — everything in the DOM — sits behind it. Blanking the screen took three attempts on real hardware, and each failure taught the same lesson from a different angle:

1. Black overlay → the video played straight through it. A z-index: 9999 div cannot cover a hardware plane.
2. Pause + hide the element → playback stopped, but the last decoded frame stayed on screen. Hiding a DOM element does nothing to the plane; the plane is not part of the DOM.
3. Pause + removeAttribute('src') + load() → releases the plane. Black at last.

Coming back out re-mounts through nextItem(), because a torn-down element cannot be resurrected. The playlist keeps advancing while the screen is off, so each newly started item is torn down too, caught on the play event in the capture phase — otherwise the next video lights the panel back up.

Any feature that assumes an overlay can hide video needs rethinking here: screen blanking, masking, fades over video.

displayPower() (CEC) is best effort and deliberately not load-bearing — it returns false when CEC is unavailable and the media teardown does the real work. Our XT245 reports failed to get cec clock in the kernel log and does not respond to CEC at all, which is exactly why blanking must not depend on it. Plenty of displays ignore broadcast CEC or need direct addressing. Volume is re-applied on every play event in the capture phase, because media elements are created per item across several code paths and setting it once would otherwise last only until the playlist advanced.

Still Android-only, and correctly inert here: the Tier-2 device-owner commands (kiosk_lock, install_apk, shell, block_uninstall, …) and set_brightness / set_screen_timeout, which have no BrightSign equivalent — a signage player has no per-window brightness or screen timeout.

Offline playback

Content bytes are cached by the service worker (server/player/sw.js) into a dedicated rd-content-v1 cache, so a player that loses its server keeps playing its playlist.

This used to be left to the browser's HTTP cache — the server sends Cache-Control: public, max-age=2592000, immutable. That is fine on a desktop and is not a documented-persistent store here: BrightSign guarantees survival across reloads, app restarts and reboots for IndexedDB, localStorage and SQLite, and their own answer for offline video is to cache the bytes explicitly. A panel could come back from a power cut with its playlist intact (that lives in localStorage) and no media to play.

The reason content was skipped originally is real, and server/lib/player-cache-policy.js is what makes intercepting it safe. Video elements issue range requests when they seek, and naive caching breaks playback in two ways that are worse than not caching at all:

• storing a 206 as if it were the whole file — every later full request gets a fragment, and it stays broken until eviction
• answering a range request with a 200 — some media stacks treat the mismatch as fatal and the video never starts

So only complete 200s are ever stored, and a range request is served by slicing the stored body into a correct 206. The content cache is deliberately not dropped when the shell is re-versioned, or every deploy would re-download the whole playlist over a link that may be exactly what is broken.

Self-update

The player can replace its own host package. This is the most dangerous thing it does: a truncated or half-applied autorun.brs is a dark panel and a site visit, because there is no app underneath.

The safety is the ordering, and every step earns its place:

1. Download to autorun.zip.part — never straight to autorun.zip. A file still downloading must never be a candidate for extraction.
2. Verify sha256 and size before promoting. A captive portal answering with a login page produces a perfectly well-formed small file; the size floor catches that, the hash catches the rest. sha256 specifically, because that is what BrightScript's roMessageDigest can compute — a checksum the player cannot verify is an unverifiable package.
3. Promote: delete the .done marker first, then rename .part → autorun.zip, then reboot. Marker first is not stylistic — leaving it makes the next boot skip the new archive and the update silently never happens.
4. A failed extract renames the archive to .bad rather than retrying. A zip that cannot be unpacked will not unpack on the tenth attempt, and retrying every boot is a loop that looks exactly like a hardware fault.

The decision is the server's, in server/lib/brightsign-update.js — unit-tested, and the same place the prerelease rule lives. The host only executes what it is told; re-implementing the version comparison in BrightScript would put the prerelease trap somewhere it cannot be tested.

The version is baked into autorun.brs, stamped at build time by both scripts/build-autorun-zip.sh and server/lib/brightsign-package.js, anchored on the ST_PACKAGE_VERSION marker. A version record that can disagree with the code actually running is the OTA-loop condition by the back door: apply, still report the old version, get offered the same package forever.

The manifest and the download come from one buffer, hashed once. Advertising a version whose checksum does not match the bytes served is the same loop from the front door.

Config: self_update (default on — a fleet that cannot be updated remotely needs a van) and allow_prerelease (default off, mirroring the Android beta channel; an opted-in player also holds a prerelease of its own core rather than being pulled back to the release).

Rotation

Rotate the OUTPUT, never the DOM. The web player rotates with a CSS transform — correct in a browser, wrong here: with hwz enabled the video decodes onto a hardware plane the DOM cannot transform, so a CSS rotation turns the images and widgets and leaves the video sideways on a portrait panel.

roVideoMode takes a transform (normal / 90 / 180 / 270) and rotating the screen rotates every layer, video included, because it happens below the compositor. The player asks the host first; when the host succeeds it clears its own CSS transform, or the graphics would rotate twice. If the host cannot, the CSS path stands — rotating most of the content beats rotating none.

Tizen reached the same conclusion independently and routes portrait video through AVPlay, with the comment that a CSS-rotated <video> "blacks out". Any platform that composites video below the DOM needs its rotation done at the output, and this is the second one we have found.

What is NOT done yet

Stated plainly so nobody reads this as finished:

• Nothing consumes the bs_model / bs_serial / bs_screen fields the player reports. Device telemetry (temperature, storage) also has no schema to land in yet.

• Native sync is wired but UNPROVEN on hardware. The player drives it end to end — the leader announces on each advance, every member (leader included) binds via attachVideo() on a new id, and the resolved backend is chosen per group and pushed down. It cannot be verified with one player: a single unit is trivially "in sync with itself". Two BrightSigns on one subnet are needed to confirm frame alignment, that the leader does not run ahead, and that the 1Hz repeat causes no visible reload.

  const SyncManager = require('@brightsign/syncmanager');          // BrightSignOS 8.2.10+
  const sync = new SyncManager('', 'ScreenTinkerSync', '224.0.126.10', 1539);
  sync.leader = true;                                              // followers just omit this
  sync.addEventListener('syncevent', (e) => {                      // BOTH roles listen
    if (e.id === lastId) return;                                   // 1Hz rebroadcast — dedupe!
    lastId = e.id;
    video.setSyncParams(e.domain, e.id, e.iso_timestamp);          // extension on <video>
    video.load(); video.play();
  });
  sync.synchronize('item_' + Date.now(), 1000);                    // leader only; msDelay to prep
  

  Three properties that shaped the design: it is leader/follower where ours is leaderless (and the leader starts from its OWN broadcast, or it runs ahead of the group); it synchronises video only, so images and widgets get item-boundary alignment at best; and it is multicast, so the whole group must share one L2 network — the resolver now treats differing subnets as evidence against it.

  Also: MP4/MOV are fine, MPEG-TS needs its presentation timestamp starting at 0, MPEG-PS is unsupported. synchronize() rebroadcasts at 1Hz so late-powered players still join, which is why the dedupe above is mandatory rather than an optimisation — without it every player reloads its video once a second, forever.

• Addressing a specific HDMI connector from JS is unverified. @brightsign/videooutput documents setMode({width,height,refreshRate}) with no output index. Dual output above assumes a second widget maps to the second connector; that needs hardware confirmation.

• Registry from a remote origin is still unproven — the original probe question. If injection turns out to be origin-dependent, identity moves to a local shim page that owns the registry and passes it to the hosted player in an iframe via postMessage.

• Nothing here has run on hardware. It is written against the BrightDeveloper docs and checked line-by-line against the brightsign/dev-cookbook examples, which corrected four config keys, the registry API and a hard SyncManager requirement (see below).

Verified against the dev-cookbook

autorun.brs and st-bridge.js were reviewed against the real examples rather than the prose:

• brightsign_js_objects_enabled: true is required alongside nodejs_enabled for require("@brightsign/*") (syncmanager-js/autorun.brs). Without it the bridge degrades to no-ops and the player silently loses identity and restart delegation — the failure would look like "BrightSign just doesn't work" rather than a missing flag.
• storage_path is a directory name ("/cache"), not a volume, and storage_quota is a string (indexeddb-caching/autorun.brs).
• security_params: { websecurity: true } and hwz_default: "on" are the shapes the examples use; local URLs carry the volume (file:/SD:/index.html).
• The registry API is asynchronous and section-oriented: read(section, key) returns a Promise and writes take an object — write(section, {k: v}). The bridge prefetches into a cache and exposes onReady(); the player waits for it before its first connect, because registering early would pair the panel as a new display and strand its real row.
• SyncManager needs networking/ptp_domain = "0", applied by a reboot (syncmanager-js/autorun.brs). Done only when this player is configured for native sync, and read-before-write so it reboots at most once rather than every boot.
• Confirmed correct as written: @brightsign/messageport (new, addEventListener('bsmessage'), PostBSMessage), the roHtmlWidgetEvent loop, and RebootSystem().
• The notes state a widget URL may be "an externally hosted page" with the same access to the BrightSign JS APIs, which is the answer the original probe was built to get — still worth confirming on hardware, but the documented answer is the favourable one.

Model notes

Target Series 5 (Chromium 120) or newer. Series 4 is pinned to Chromium 87, and Series 4 and older have fixed graphics/JS memory splits (XTx43/44: 512MB/512MB; HDx23: 256MB/128MB) where Series 5 allocates dynamically. Image size defaults to 2048x1280x32bpp (3840x2160 on XT/4K models) and is raised with roVideoMode.SetImageSizeThreshold().