Video chain & projectors

Part of Dome troubleshooting — start there for quick triage. These are the symptoms where no image (or one channel's image) is missing, or an image that is present looks wrong, worked from the projector back up the signal chain.

TODO verify with senior technician

The causes and step sequences on this page are informed reconstructions pending review — see the note on the main troubleshooting page.

Power-cycling a projector

A projector must always go down to standby before it is power-cycled — never cut power on a running unit. Put it in standby first (Dome Control panel, Showmaster WebPanel or the projector's web interface), let the cooldown complete, and only then cycle the power. A projector caught mid-cooldown may refuse to restart.

Where faults sit in the chain

The full chain for one eye of one channel, split into its encoder side and decoder side, with every part that can fail on its own — the other eye is an identical parallel chain, see How video reaches the dome.

Encoder side — from GPU to switch:

Decoder side — from switch to projector:

Each encoder and decoder connects to the switch with two 10 G links — a 4K signal needs ~18 Gbit/s, so one link is not enough. That means two SFP+ modules (and two fibre cables) on each side of the switch per chain, and any single one of them can fail while the rest of the chain stays healthy:

Part that fails	Typical symptom	Where to start
One SFP+ module / fibre link at the encoder	Wrong resolution on the channel (encoder blue or p60 on the status page)	Wrong resolution
One SFP+ module / fibre link at the decoder	Image black on that eye's input	One projector channel is black
Any SFP+ module / fibre link, or the DP cable decoder → projector	Image present but with artifacts (noise, corruption, flicker)	Image artifacts

The two DisplayPort cables (GPU → encoder and decoder → projector) are physical parts too — but always confirm what the Barco status page says before reseating or swapping anything.

One projector channel is black

Likely causes: decoder lost its stream; projector shuttered, on the wrong input, or in standby; PDU outlet off; render node output failed.

1. Open the Barco status page. Are the two decoders for that channel — left eye and right eye, see How video reaches the dome — present and linked?
   • Missing → go to Encoder/decoder link lost.
   • Present → the signal is arriving; the fault is at the projector.

2. Open the projector's web interface — addresses on Projectors, http://172.19.7.3x:9999/. Check power state, shutter/dowser, selected input and any active alarms.

3. If the projector is unreachable, check its PDU outlet on PDUs. Confirm the outlet name matches the projector before doing anything.
4. Switch cluster — Atlas 3D/2D / Draco 3D/2D on the Projectors tab of the Dome Control panel — and see whether an image appears.
   • Image appears after the switch → a computer in the previous cluster is likely faulty; restart that render node. If it does not respond, power-cycle it from the Showmaster tech interface — showmaster1.c.itn.liu.se, Systems tab, its purple button in the Power Cycle Section. Power drops for one minute and comes back; the node starts up again.
   • Still black, and the decoder shows yellow on the Barco status page → the signal is not genlocked; this is usually a resolution mismatch between the encoder and the decoder for that channel — see Reading the colours on the Barco status page.
5. If the projector is reachable and healthy but shows nothing, suspect the DisplayPort links between the decoders and the projector — there are two per projector (left eye and right eye), so check both chains on the Barco status page before touching cables.

Do not power-cycle the projector if a session is imminent — a projector caught mid-cooldown may refuse to restart.

All channels are black, but the projectors are on

This is almost never a projector problem. Work upwards from the content.

1. Is the playback application still running on the render cluster? Has it crashed or dropped to the desktop?
2. Is the correct source selected on the Showmaster tech panel?
3. Are the render nodes still powered and logged in? See ATLAS / DRACO.
4. Do the projectors show their own on-screen menu? If yes, everything from the projector down is fine and the fault is upstream.

RGB colour not complete on one channel

The image is present but only one or two of the three colour channels show — for example the dome renders red-only, with green and blue missing. This usually points at the projector rather than the content.

1. Switch cluster — Atlas 3D/2D / Draco 3D/2D on the Projectors tab of the Dome Control panel — and see whether the issue persists with the other cluster driving the same projector. If it does not persist, a computer in the previous cluster is likely faulty; restart that render node (if unresponsive, power-cycle it from the Showmaster tech interface — Systems tab → its purple button in the Power Cycle Section).
2. If the missing colour follows the projector across clusters, power-cycle it from Showmaster's WebPanel (http://172.19.6.6/, see Projectors): put the projector in standby first, then go to Projectors and press Power Cycle for the affected projector — a projector must always be in standby before a power cycle.

A projector caught mid-cooldown may refuse to restart — see the warning in One projector channel is black.

Wrong resolution on one channel

One projector shows an image at the wrong resolution — stretched, letterboxed or at a lower pixel count than its neighbours. The Barco status page shows the connected resolution per decoder; compare the affected channel against the healthy baseline (4096x2160p59 — correctly synced signals end in p59, see below).

• Encoder marked blue on the status page → its resolution is wrong compared to what it should be. Fix the source: check the render node's display settings, or restart that computer (step 1 below).
• Resolution ends in p60 instead of p59 → the pixel count may look right but the signal is not genlocked — see Cluster nodes are out of sync and Reading the colours on the Barco status page.

1. Restart the computer that is driving the channel showing the wrong resolution.
2. If the problem persists after two reboots, suspect a faulty SFP+ module in the encoder for that channel — record its unit number and escalate, since encoders are swappable within the fleet (see Encoder/decoder link lost).

Image artifacts on one channel

The image is present but shows noise, corruption or flicker that does not follow the content. Unlike a black channel, this usually points at the transport between encoder and projector — see Where faults sit in the chain.

1. Check the Barco status page for both decoders of the channel first, and note any encoder or decoder that is blue or yellow before touching hardware.
2. Suspect a broken SFP+ module in one of the two fibre links — either at the encoder or at the decoder. Record the unit number and escalate: encoders and decoders are swappable within the fleet, see Encoder/decoder link lost.
3. If both sides of the switch look healthy on the status page, suspect the DisplayPort cable between the decoder and the projector — reseat it, or swap it with a known-good one, only after steps 1–2.

Reading the colours on the Barco status page

The Barco status page colour-codes each encoder and decoder. Two colours matter when chasing a fault:

• Encoder marked blue — the encoder's resolution is wrong compared to what it should be. The problem is at the source: check (or restart) the render node driving that channel, and compare its output against the expected resolution for the channel.

  

• Decoder marked yellow — the signal arriving at the decoder has no genlock. The fault is usually a resolution mismatch between the encoder and the decoder for that channel; compare both sides before suspecting hardware such as an SFP+ module.

  

p60 versus p59: is the signal actually locked?

The refresh-rate suffix on an encoder's reported resolution tells you whether it is synced:

• ends in p59 — correctly synced (genlocked signals run at 59.94 Hz).
• ends in p60 — not synced properly; the node is free-running instead of locking to the sync master. See Cluster nodes are out of sync.

So a healthy, locked channel reports for example 4096x2160p59. If an encoder shows the right pixel count but ends in p60, the resolution is right and the lock is what's missing.

An encoder or decoder has lost its link

The dome's video distribution is a Barco ENA-340 virtual KVM over 10 G fibre — see Barco ENA-340.

1. Open the status page and note the Unit number of the missing device. Its IP is 172.19.7.<unit>, and the unit number links to the device web GUI.
2. If the unit is completely absent, check its PDU outlet — dome decoders such as dome-ena-dec01 and dome-ena-dec02 are named on PDUs.
3. If the unit is present but not passing video, check that it is bound to the correct stream — routing is done from the control computer.
4. Check the fibre pair physically only after the above; SFP+ pairs do occasionally seat badly after rack work.

Encoders and decoders are interchangeable within the fleet. Record the unit number before swapping so the routing can be reapplied.