SLAY Cart — touch-friendly VJ clip player for OBS

What it does

SLAY Cart is a clip-trigger media player for live streaming and broadcast. Build scenes from video and audio (local files, YouTube, Vimeo, direct URLs), set in and out points, and launch them on cue from a touch-friendly grid, a StreamDeck, or any HTTP or WebSocket client.

Its output goes into OBS over SLM, the SLAY Media protocol: shared memory when the player and OBS share a machine (zero-copy, no socket limits, no kernel tuning), and UDP across the network, both at once and discovered automatically. The status bar lights an SHM, UDP or NDI indicator per active receiver. In our tests the added latency measures about 1 ms over shared memory and around 3 ms to a laptop receiving over WiFi with hardware H.264; uncompressed NV12 across a gigabit LAN lands near 20 ms.

Every clip starts and ends clean, with no frozen frame and no A/V drift; audio-only clips run a native, gapless retrigger path, so hitting the same pad twice just restarts it. NDI output runs alongside SLM, so the same triggers also feed vMix, TriCaster, or anything else on the network.

Highlights

Touch-friendly scene grid with configurable columns and instant retrigger.
Any source: local video and audio, plus YouTube, Vimeo, and direct URLs via yt-dlp.
Manage Clip preview with in/out markers and waveforms that never touch the live output.
SLM output over shared memory (~1 ms) and UDP (~3 ms over WiFi with H.264), with zero configuration.
GPU H.264/H.265 over WiFi or raw NV12 on gigabit, with FEC for lossy links.
REST + WebSocket control for StreamDeck, Bitfocus Companion, or your own scripts.

See it in action

SLAY Cart Stream Info panel showing the H.264 encoder and per-receiver latency of 1 to 3 ms. — Stream Info: live per-receiver latency — ~1 ms over SHM, ~3 ms over WiFi with H.264.

SLAY Cart Manage Clip view previewing a video with a seek bar, in/out markers, transport controls, and a filmstrip of clips. — Manage Clip: preview and trim without touching the live output.

SLAY Cart Manage Clip view for an audio clip showing a full-width waveform with in/out markers. — Real-peak waveforms with in/out markers for audio clips.

SLAY Cart showing a scene of short sample clips in the grid. — Scenes for stingers, samples, and reaction clips.

SLAY Cart main grid mixing video and audio clips with live output indicators. — Video and audio together, with live SHM / UDP / NDI output.

Quick start

Get the pieces

Download SLAY Cart and the SLM Wire for OBS Studio. If you want NDI, install the NDI Runtime on the SLAY Cart machine (optional).
Set up OBS

Drop the plugin into your OBS plugins folder, restart OBS, then add a SLM Receiver (video) and SLM Audio Receiver (for audio-only) sources to your scene.
Add some clips

Launch SLAY Cart and drag in video or audio files, or paste a YouTube link to download and add it to the grid.
Hit play

Click a clip to fire it. It appears in OBS instantly over shared memory. Watch the latency readout and the SHM badge light up in the status bar.

Trigger it from anything (optional)

SLAY Cart exposes a REST API on port 7878 for StreamDeck, Bitfocus Companion, or your own scripts:

# Play a clip by scene and name
curl http://localhost:7878/start/General/Get_in_the_Van

# Stop all playback
curl http://localhost:7878/stop

# List scenes and their clips
curl http://localhost:7878/list/scene

Requirements

Linux or Windows 10+.
OBS Studio with SLM Wire for OBS Studio, to receive the output.
ffmpeg and ffprobe available (bundled in the Windows download; sudo apt install ffmpeg on Linux).
yt-dlp on your PATH for YouTube and Vimeo downloads (optional).
The NDI runtime if you want NDI output (optional).

Setup help

SLAY Cart checks for its helper tools when it starts and drops a note in the Messages panel if anything needed for the full experience is missing. Here is how to fix each one.

ffmpeg and ffprobe required

Used for clip metadata, thumbnails, waveforms, proxies and playback. Without them most of SLAY Cart will not work.

Windows: both ship inside the SLAY Cart download. If the check still fails, re-download the full ZIP and keep ffmpeg.exe and ffprobe.exe in the same folder as slay-cart.exe.
Linux: install from your package manager, e.g. sudo apt install ffmpeg on Debian/Ubuntu. One package provides both binaries.

yt-dlp optional

Only needed to add clips from YouTube, Vimeo and similar links. Local files work without it.

Windows: grab yt-dlp.exe from the yt-dlp releases page and put it next to slay-cart.exe, or anywhere on your PATH.
Linux: sudo apt install yt-dlp, or pip install -U yt-dlp for the newest build (streaming sites change often, so keep it current).

SLM video codec fell back to raw heads-up

If you set the SLM codec to H.264 or H.265 but no matching hardware encoder is available, SLAY Cart keeps working but sends uncompressed raw video, which uses far more bandwidth. Install or enable a GPU encoder (NVENC on NVIDIA), or set the SLM codec back to raw in Settings to silence the warning.

NDI runtime required for NDI output

If you want SLAY Cart to produce an NDI output, you need to install the free NDI Tools / NDI Runtime on that machine. If you don't have it installed, SLAY Cart will warn you at start-up (once). SLM output does not depend on NDI.