TraxDeck

Video Sync

Video output is available on Professional and Enterprise plans. Stem Director outputs video that is frame-locked to the audio engine clock — the video and audio share a single timeline and never drift apart.

Output methods

NDI (network video)

NDI (Network Device Interface) transmits video over a standard Ethernet network. Use this to:

  • Feed a dedicated media server (Resolume, Disguise, Notch, MadMapper)
  • Drive LED processors with NDI input (Brompton, Novastar)
  • Send to an IMAG confidence monitor on a separate machine
  • Distribute to multiple destinations simultaneously (broadcast mode)

Requirements:

  • Gigabit Ethernet recommended (NDI video is ~100–200 Mbps per stream)
  • NDI Tools installed on receiving machines (free from ndi.tv)

Enable NDI output in Preferences → Video → Output Method → NDI.

Direct display output

Stem Director can drive a connected display directly via HDMI or DisplayPort. Use this for:

  • An LED wall driven directly from the Stem Director machine
  • A confidence monitor on stage
  • A simple single-screen video setup without an external media server

Enable in Preferences → Video → Output Method → Display, then select the target display from the dropdown.

On Apple Silicon Macs, Thunderbolt → HDMI/DisplayPort adapters are supported. On Windows, ensure your GPU driver is up to date for best display performance.

Supported video formats

| Format | macOS | Windows | Notes | |---|---|---|---| | MP4 (H.264) | ✓ | ✓ | Most compatible — recommended for cross-platform shows | | MP4 (H.265/HEVC) | ✓ | ✓ | Better quality at same bitrate; requires hardware decoding | | MOV (H.264) | ✓ | ✓ | Same as MP4, Apple container | | ProRes 422 | ✓ | — | macOS only; highest quality for LED wall output | | ProRes 4444 | ✓ | — | macOS only; with alpha channel support | | HAP | ✓ | ✓ | GPU-decoded; lowest CPU load for high-resolution content | | HAP-Alpha | ✓ | ✓ | HAP with transparency |

Recommended for most productions: HAP for high-resolution LED wall content (best performance), H.264 MP4 for confidence monitors and IMAG (most compatible).

Frame rates

| Frame rate | Use case | |---|---| | 23.976 fps | Film / cinema content | | 25 fps | PAL regions; broadcast in Europe, Australia | | 29.97 fps | NTSC; US broadcast-aligned | | 30 fps | Common for LED wall content | | 50 fps | High-motion content in PAL | | 60 fps | High-motion content in NTSC / LED walls |

Configure in Preferences → Video → Frame Rate. The frame rate must match your video files — Stem Director does not transcode on the fly.

Sync accuracy

Stem Director synchronises video to the audio engine clock at the hardware level. On Apple Silicon, the synchronisation accuracy is typically within ±1 frame (at 30 fps, that is ±33 ms). On Intel and Windows hardware, accuracy depends on driver quality and is typically ±2 frames.

For LED wall work where sub-frame accuracy matters:

  • Use HAP format (GPU decoded, deterministic decode time)
  • Set your OS display refresh rate to match the video frame rate
  • Disable any system compositor GPU effects that might add a frame of buffering
  • Test with a high-frame-rate camera before the production

Playback modes

| Mode | Behaviour | |---|---| | One-shot | Video plays from start to end and stops on the last frame | | Loop | Video loops seamlessly while the track plays | | Timecode-chased | Video position is driven by the audio engine's bar/beat position (useful for non-linear shows) |

Set per-track in the track editor under Video → Playback Mode.

Linking video to a track

  1. Select a track in the track list
  2. Click the Video tab in the track editor
  3. Click Choose Video File and select your video
  4. Set playback mode, start offset if needed, and output destination
  5. The video thumbnail appears — click the preview icon to check sync

Video files do not need to be the same duration as your stems. If the video is shorter, it stops on the last frame. If longer, the excess is not played.

Troubleshooting video output

Video is out of sync with audio: Check that your video file's frame rate matches the configured output frame rate. A mismatch of even 0.1% (e.g. 29.97 vs 30 fps) will cause drift over time.

NDI stream not visible on receiving machine: Confirm both machines are on the same subnet. Check that firewall rules allow UDP traffic on ports 5353 (mDNS) and the NDI stream port range (49152–65535).

HAP video stuttering: HAP requires a GPU for decoding. On machines without a dedicated GPU (e.g. Mac mini), H.264 may perform more consistently.

Black frame on display output: On macOS, check System Settings → Privacy & Security → Screen Recording and ensure Stem Director has permission.