BlackMagic DeckLink Capture v3

Introduction

The BlackMagic DeckLink Capture v3 input pulls live video and audio from a Blackmagic DeckLink card connected over SDI or HDMI — cameras, switchers, hardware players, encoders, anything the card can receive. It sits at the head of Composer's pipeline as a standard input, mixable with file inputs, NDI sources, network streams, and software generators on the same scene.

The v3 generation supersedes the original Capture and Capture v2 components (both still ship for backwards compatibility but are hidden from the docs); new projects should always use v3.

Embedded audio: stereo or 8-channel

The input captures the SDI / HDMI signal's embedded audio alongside the video, with the channel layout selectable per input:

• Stereo (2-channel) — the default, sufficient for single-language programmes, monitoring feeds, and most camera returns.
• 8-channel — captures the full eight-channel embedded audio group, useful for multi-language broadcasts (programme bus + several language commentary mixes), discrete-mic captures from a stage feed, or any production that ships more than a stereo pair down the SDI cable. Switching to 8-channel mode unlocks the Channel Strip Inspector's MAPPING tab so each incoming channel can be routed independently into Composer's master audio bus.

The channel-count switch is a single property on the input (Audio channels) — pick the layout that matches the upstream device and Composer captures from there. Genlock and frame timing of the audio follows the host's sync source the same way the video does.

Multiple capture cards on one host

Composer fully supports running multiple Decklink cards in the same host, with as many capture inputs as the cards collectively expose channels. Each BlackMagic DeckLink Capture v3 input binds to a single (card, channel) pair selected from the dropdowns in the property panel; drop another instance on the project for each additional channel you need to ingest. Composer enumerates every Decklink-recognised channel on the host at startup, regardless of how many physical cards back them, and the per-input channel dropdown lists every available (card, channel) pair.

Practical guidance for multi-card setups:

• Mind the PCIe budget. Each capture card consumes lanes, and consumer-class CPUs can run out of lanes faster than you'd expect — a Decklink Quad 2 plus an RTX-class GPU at full lanes is already pushing a 24-lane Ryzen platform. The motherboard then silently downgrades the GPU's slot from x16 to x8, which directly cuts the bandwidth available for cudaMemcpy frame transfers and shows up as dropped frames under load. See Operations & Tuning → PCIe bandwidth considerations for the full sizing guide, lane budgets per card, and motherboard-slot-allocation advice.
• Pick a card that gives you channels per slot. A Decklink Quad 2 (4 × 3G-SDI) and a Decklink Quad HDMI Recorder (4 × HDMI 2.0) each yield four capture channels from a single card slot; multi-channel cards are a substantially better fit than four single-channel cards on a host where PCIe lanes are tight.
• Set one capture card as the sync source in the Settings → General tab when running several cards together. With genlocked cameras feeding the capture cards, taking the sync from one of those captures keeps every input on the same render tick — see the input's Capture is genlocked to sync source advanced option for the per-input switch.
• Composer Runtime supports the same multi-card setup headlessly — the same project moves between Desktop and Runtime without changes. For production hosts with several cards, the Runtime host is typically the right deployment target.

Common use cases

• Multi-camera live productions — one capture input per physical camera, mixed and switched in scene logic or via the Connectors / Script Engine surfaces.
• SDI / HDMI signal monitoring — bring a downstream feed back into Composer for on-screen verification, scoping, or recording.
• Hardware-player ingest — capture from a tape deck, ProRes player, or external graphics machine without re-encoding.
• Multi-language audio ingest — the v3 input supports either stereo (2-channel) or 8-channel audio. Use 8-channel mode to capture a programme bus plus several language commentary feeds from the same SDI source.
• Reference / fallback graphics — the on-board still store can hold a reference frame or fallback graphic, automatically swapped in if the live signal disappears.

What you can control

• Device + channel selection — pick the Decklink card and channel to capture from. Composer enumerates every channel on every installed Decklink card at startup.
• Audio channels — choose between stereo (2-channel) and full 8-channel modes; the latter unlocks the Channel Strip Inspector's MAPPING tab for per-channel routing.
• Auto-start on load — start capturing immediately when the project opens, or wait for an explicit Start command.
• Freeze-frame on pause / lost input — hold the last good frame instead of going to black during a brief signal interruption.
• Black-video detection — automatic detection with an optional Script Engine callback to react when the source goes dark (cut to a fallback scene, log the event, page operations).
• Still store — load a reference frame or fallback graphic from disk; useful as a known-good substitute when the live signal drops.
• Capture statistics — frame arrival timing, queue depth, format-mismatch counters, and other diagnostic readouts; useful both during commissioning and for ongoing monitoring.

For property-by-property reference, see the auto-generated table below.

BlackMagic DeckLink Capture v3 - Settings

Input device and channel

Input device and channel — pick which Decklink card and physical port to capture from.

Options

Options — capture behaviour and resilience settings.

Log

Log — recent capture events and status messages from the input.

Black video detection

Black video detection — react when the captured picture goes (almost) entirely black.

Still store

Still store — a reference image that can stand in for the live capture.

Performance and properties

Performance and properties — runtime stats and capture diagnostics.

Inherits from: AbstractInput, AbstractAudioProcessing, AbstractAudioMetering.

See also: BlackMagic DeckLink Capture v3 in Script Engine Objects.

Shared input properties

Every input — regardless of source type — exposes the following property groups. They are surfaced in the property panel only when Show advanced options is enabled on the input.

Icon

• Icon text — short text shown on the input's icon in the Inputs list. Useful as a quick visual label (channel number, mic name, camera position) to tell otherwise-similar inputs apart at a glance. Empty by default; has no effect on rendering or routing.

Audio mixer

• Hide in audio mixer — when on, hides the input from the audio mixer view without disabling its audio. Useful for de-cluttering the mixer while keeping the audio routed (e.g. fixed background music, ambient beds, pre-aligned playout). [default=false]

Render Options

• Invisible (Do not render in scene) — when on, the input is skipped during rendering and produces no picture on any layer or scene. Audio routing is unaffected. Toggle from a script for cued-in / cued-out behaviour during a show. [default=false]
• Do not render input — disables the input's internal render entirely (no decode or capture work is done). Stronger than Invisible: that one renders but doesn't display; this one stops the input from doing any work at all. Useful for reducing CPU / network load on heavy sources (e.g. high-bitrate RTMP / SRT streams, large media files) when the input is temporarily not needed. Audio meters are cleared while disabled. [default=false]
• Do not render input controller — chooses what drives the Do not render input flag. Let Composer decide (the default) hands control to the project-level Render Tuning optimiser, which automatically pauses inputs that aren't used by any active scene. Manual Configuration ignores Render Tuning and lets the Do not render input toggle control the flag directly — use this to keep a network source warm even when it's currently off-air, or to take a heavy input down by hand regardless of scene activity. [default=Let Composer decide]

Optional TAGS

• TAGS — one or more free-form tag words used to classify this input (typically space- or comma-separated). Picked up by Composer's Smart Search to filter or find inputs by category — e.g. camera, music, interview, sponsor. Has no effect on rendering.

Audio configuration and processing options

For inputs capable of processing audio, additional audio configuration and processing options are available through the audio mixer and the Channel Strip Inspector.

• Audio mixer — monitor levels, adjust gain and pan, mute / solo inputs, and configure auxiliary sends to Audio Channel Strip submix buses, all from a centralised mixer-style interface.
• Channel Strip Inspector — advanced per-strip audio processing for the selected input:
  • Input trim, stereo remapping, and audio delay
  • Channel mapping (8-channel mode unlocks the full MAPPING tab)
  • Gate
  • Low-cut filter
  • Equaliser (5-band parametric)
  • Compressor
  • Sidechain ducking (a second compressor whose gain reduction is driven by another input's level — e.g. dipping music under a voice-over)
  • Limiter

For the full audio signal flow, see Audio processing workflow.