Video · Practical guide

DeckLink 8K Pro: Sync Outputs across cards and TouchDesigner output profiles

If Sync Outputs works within one DeckLink 8K Pro but fails when another card is added, first record the reference state recognized by each card. Then identify its subdevices and connectors.

DeckLink 8K Pro: profile, reference and format

Identify each card, subdevice and connector before adding outputs to a group. Record video format and reference separately: a signal on a cable does not establish the state reported by the driver.

DeckLink 8K Pro: profile, reference and format
Item	Proposed check
Model and profile of each card	Compare with available subdevices
Output format and reference	Record the selected format and lock state
Synchronization group	Test one card, then add another while preserving earlier readings

Common reference across cards: check each card separately

The March 2026 Blackmagic SDK, section 2.4.13.2, page 37 distinguishes a group across devices from the internal 8K Pro exception. It requires the same frame rate and checking reference lock where applicable.

Derivative Latest requires Pro for Sync Outputs and describes connected reference for Blackmagic. Sync Group Index groups nodes. Keep the SDK’s model-specific scope and record each card: a manufacturer-level description does not establish every feature of a particular model.

We suggest starting with one card, then the other, keeping format and content fixed. Save states and errors at each step. Only after both recognize the reference should you prepare an off-show comparison of the combined group.

Common reference across cards: check each card separately
Proposed comparison	What to preserve	Next step
Card A alone	Device, profile, format, reference and error.	Identify which outputs belong to that card.
Card B alone	The same data, without nodes from A.	If reference is not recognized, investigate that input before combining cards.
Group A+B	Sync Group Index, both cards’ states and received content.	Record the change that introduces the error; a longer test remains to be done.

Separate signal presence, lock state and timing adjustment

A signal measurement at the cable and the card’s reported state are different data. Record the generator, distributed format, cable, reference port and what Desktop Video shows on each card.

Under Reference Input, page 23 of the March 2026 Desktop Video manual, the setting shifts output timing relative to reference. That section does not present it as a repair for an unrecognized reference. Preserve the initial value; this guide does not add a default offset.

The output Info CHOP uses genlocked values 1, 0 and -1: known lock, no lock and unknown. Save the available state with dropped_frames, skipped_frames and readings before Reset Stats. An unknown value calls for another observation; it does not prove a failure.

Four-subdevice profile: identify the 8K Pro BNC connectors

The SDK, section 2.4.11, page 31 shows one shared profile for the four 8K Pro subdevices. Changing it affects the group and can alter modes, SDI links or activity. Save the profile before changing a port.

The following table summarizes only the four-subdevice half-duplex profile in the diagram. It does not describe other profiles or establish which names a TouchDesigner version will show. Map logical device, cable and receiver in your own worksheet.

Four-subdevice profile: identify the 8K Pro BNC connectors
Subdevice index	Connector in the 8K Pro diagram	Profile scope
0	SDI 1	Input or output; half-duplex.
1	SDI 3	Input or output; half-duplex.
2	SDI 2	Input or output; half-duplex.
3	SDI 4	Input or output; half-duplex.

Record the test before putting the group on air

Complete the blank DeckLink reference and profiles worksheet. Add duration, content, changes and return to the agreed configuration. Keep the manufacturer’s requirement separate from the result of a test on your setup.

Use the general GPU and video-card output guide and the capture guide as appropriate for the path. The GEN10 guide helps document the generator. For a conference with LED and recording, record each destination in the video processing path.

Before putting the group on air, complete the version, profile, generator model and accepted-format records. Test intended content at each destination and preserve the initial configuration so it can be restored.

What the SDK reports: detected reference, lock and output mode

To record reference before grouping outputs, request three separate data points: detected reference mode, lock state and enabled output mode. The March 2026 SDK, section 3.58, pages 296–297 assigns a status identifier to each. These are data for an SDK-based application or diagnostic tool, not new TouchDesigner controls.

bmdDeckLinkStatusReferenceSignalMode identifies the detected reference mode if the device supports that detection. bmdDeckLinkStatusReferenceSignalLocked reports reference lock. bmdDeckLinkStatusCurrentVideoOutputMode reports the enabled output mode. Record the exact rate and whether scan is progressive, interlaced or PsF; image dimensions alone do not describe timing.

GetReferenceStatus returns a BMDReferenceStatus mask: the section 2.5.3.28, page 59 describes the call, and section 3.39, page 290 distinguishes bmdReferenceLocked, bmdReferenceUnlocked and bmdReferenceNotSupportedByHardware. The last value means the hardware has no genlock connector.

Compare the exact rate and scan type of reference and output mode, and check the card’s supported formats. The SDK requires the same frame rate when grouping outputs. Matching image dimensions do not establish lock or path compatibility.

We suggest recording states with output enabled, per card and outside the live show. If a valid state reports no lock, inspect reference, timing and distribution before building the group again.

What the SDK reports: detected reference, lock and output mode
Recorded value	What it tells you	What still needs checking
Detected reference mode	Format reported by the device, if detection is supported.	Lock and compatibility with the chosen output.
Reference lock	Device’s valid reference state.	Continuity and content synchronization at the destinations.
Enabled output mode	Current output configuration.	Reference state and signal received at the destination.
API call result	Success, error or unsupported function.	If the call fails, preserve the error; do not interpret its value as a valid lock state.

Video input and reference: use the state for the failing path

A camera may deliver video while the output still lacks reference lock. For capture, the SDK, section 3.58, page 296 defines bmdDeckLinkStatusVideoInputSignalLocked. For reference it uses another identifier: bmdDeckLinkStatusReferenceSignalLocked. Record which one was queried, on which device and with which input selected.

IDeckLinkStatus lets an application query device states. Check that it uses the input or reference identifier for the path being diagnosed.

To plan a capture test with automatic detection, follow section 2.4.6, page 25: check BMDDeckLinkSupportsInputFormatDetection for the device and driver, configure the callback, enable input with an initial format and bmdVideoInputEnableFormatDetection, and start capture. Record detected and enabled modes separately. This manual sequence does not establish that every connector can be monitored simultaneously.

If investigating image loss, start with the input record and that signal’s receiver. If Sync Outputs fails between cards, inspect output-reference records. A frame-arrival callback or visible video does not replace reference state. To compare without disturbing an on-air capture, use a separate test interval and record one selected input per entry.

The DeckLink status worksheet has fields for queried function, result code, value and observation. Complete it alongside the capture guide and the earlier profile worksheet. Actual model and driver, supported functions and a test with event content remain open.

Frequently asked questions

Does Sync Outputs working within one 8K Pro prove that external reference is valid?

The SDK allows subdevices within a single 8K Pro to synchronize without a common external reference. That does not prove a group across two cards. Save each card’s recognized state and output format before adding the second.

Does an error when adding a fifth output confirm a TouchDesigner bug?

The error alone does not identify a bug. Test each card separately with the same content and format; then add the second to the group. Record the change that introduces the failure, the complete error and both cards’ reference states. If one card already fails alone, inspect that path before investigating the group.

When does testing a 720p50 reference make sense?

Only when the generator and every device in the path supports that format. Compare reference with the actual video outputs, then check lock and image before keeping the change.

Does subdevice 1 output correspond to SDI 2?

In the four-subdevice half-duplex profile in the 8K Pro diagram, index 1 corresponds to SDI 3 and index 2 to SDI 2. Check the installed profile before matching a node name to a cable.

Can I change the profile without affecting the card’s other outputs?

The four subdevices share a profile according to the SDK. A change may alter modes, links and group activity. Record initial settings and inspect every destination outside the live show before using another layout.

Can Reference Input fix any undetected reference?

The Desktop Video manual describes adjusting output timing relative to reference. It does not document that setting as a repair for an unrecognized signal. Save the state and initial value; first identify what reference reaches the card.

Does genlocked = -1 mean lock was lost?

Derivative defines it as an unknown state. One indicates known lock and zero means no lock. Record which card and operator report it, compare with Desktop Video and preserve available readings before Reset Stats.

Does enabling the group confirm content stays synchronized throughout an event?

Playback at the destinations still needs to be checked over an agreed interval. Record continuity, states, counters and clips for each output; this worksheet contains no measured results.

Does S_OK from GetReferenceStatus confirm that DeckLink is locked to reference?

Read the BMDReferenceStatus mask: bmdReferenceLocked means locked, bmdReferenceUnlocked means lock was not achieved, and bmdReferenceNotSupportedByHardware means the device has no genlock connector. Record the call result and value separately; a failed API call does not provide a valid lock state.

What should I compare between the reference and output formats?

Record resolution, exact rate and scan type for both. Check modes supported by the 8K Pro and verify lock with output enabled. The SDK requires the same frame rate across the group; resolution alone cannot approve a combination.

Does VideoInputSignalLocked confirm genlock on the SDI outputs?

That identifier reports video-input lock. For reference, the SDK defines ReferenceSignalLocked and GetReferenceStatus. Record the complete function, card and path queried: a camera delivering an image does not prove common reference for the outputs.

Does automatic detection monitor HDMI while Mini Recorder captures SDI?

Automatic detection does not establish simultaneous monitoring of both connectors. First identify the exact Mini Recorder model and driver, then check detection support for the selected input. The SDK describes the callback and enabled capture; test one input per record outside the live show and leave simultaneous operation open until checked against device documentation.