Blackmagic Decklink Target v4

Introduction

The Blackmagic Decklink Target v4 sends the composed scene out through a Blackmagic Decklink card over SDI or HDMI — to a vision mixer, studio monitor, broadcast recorder, IRD / encoder hand-off point, or any other professional piece of kit on the SDI/HDMI side of the production chain. It's the inverse of the BlackMagic DeckLink Capture v3 input: same family of cards, same (card, channel) selection model, same multi-card support — but the data flows the other way.

The v4 generation supersedes the original target, v2, and v3 (all still ship for backwards compatibility but are hidden from the docs); new projects should always use v4. For latency-sensitive plant where a fixed-buffer scheduled-playback model is required (genlock-tight broadcast, RP188 timecode, master-control playout), there's a separate scheduling variant that's not covered here — talk to RealSprint Support if you think you need it.

Multiple Decklink cards on one host

Composer fully supports running multiple Decklink cards in the same host, with as many output targets as the cards collectively expose channels. Each Decklink Target binds to a single (card, channel) pair selected from the dropdowns in the property panel; drop another instance on the scene for each additional channel you need to drive. Composer enumerates every Decklink-recognised channel on the host at startup, regardless of how many physical cards back them.

Practical guidance for multi-card output setups:

Mind the PCIe budget. Each Decklink card consumes lanes; multi-card hosts on consumer-class CPUs run out of lanes faster than you'd expect, and the motherboard then silently downgrades the GPU's slot from x16 to x8, cutting the bandwidth available for cudaMemcpy frame transfers and showing up as dropped frames under load. See Operations & Tuning → PCIe bandwidth considerations for lane budgets per card and slot-allocation advice.
Pick a card that gives you channels per slot. A Decklink Quad 2 (4 × 3G-SDI), Quad HDMI Recorder (4 × HDMI 2.0), or Decklink Duo 2 yields multiple channels per single PCIe slot — substantially better lane economics than a stack of single-channel cards.
Set a capture card as the sync source in the Settings → General tab when running both Decklink inputs and outputs in the same project. Taking the sync from a genlocked input keeps capture and playout on the same render tick.
Composer Runtime supports the same multi-card setup headlessly — projects move between Desktop and Runtime without changes. For a production playout host with several output cards, the Runtime is typically the right deployment target.

Common use cases

Program output to a vision mixer — clean program feed from Composer's compositor into the studio's SDI router or vision mixer, alongside camera feeds.
Studio confidence monitor — a downstream-of-everything hardware-decoder feed for an operator's monitor, showing exactly what's going to air.
Master-control hand-off — provide a finished mixed feed to a master-control room, IRD, or downstream encoder rack over baseband.
Recorder feed — drive an SDI recorder for an archive copy of the live program output.
Multi-language broadcasts — the 8-channel audio mode unlocks the Channel Strip Inspector's MAPPING tab, useful for embedded multi-language audio over SDI to downstream distribution.
Backup chain — run the SDI output in parallel with RTMP / SRT targets so a network-side outage doesn't take the studio chain off air.

Driving from outside

Every command (Start, Stop) is invokable from the property panel, the HTTP API (/api/invokecommand?targetname=Decklink+Target&command=StartCommand), a Connector, or the Script Engine via ExecuteCommand / ExecuteCommandById. The current device name and runtime statistics are surfaced as readable properties so dashboards and scripts can monitor the output without polling the SDI side directly.

BlackMagic DeckLink Capture v3 — the input counterpart. Use it on the same host to receive SDI / HDMI signals; the same multi-card guidance applies.