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LED Volume Genlock — Brompton Phase Shifting / Venice PSF Signal Requirements

Summary

Two related genlock issues arise in LED volume VP setups involving the Brompton LED processor and the Sony Venice camera. First: the Brompton reads a 23.98 PSF genlock reference as 47.96 Hz (double the frame rate) — while this double-counting is technically harmless, it can combine with a drifting phase to produce ghosting/doubling artefacts on camera. The fix is to use the Brompton as the genlock clock source rather than passing an external reference through it. Second: the Sony Venice specifically requires an analogue PSF reference signal (not P, not I, not HD-SDI) — and must be set to Analogue genlock mode in the camera menu, not HD-SDI. Feeding P or I format will fail to lock or produce erratic behaviour.

Symptoms

  • Ghosting or frame-doubling visible through camera in LED volume shoots.
  • Brompton LED controller reads genlock frequency at double the expected value.
  • Phase reading in Brompton is drifting continuously — entering a phase offset temporarily fixes it but it shifts again on the next take.
  • Venice camera menu shows genlock as "Internal" when it should show "Gen" (external).
  • Venice locks at 25fps but refuses to lock at other frame rates despite correct signal.

Community Guidance

[OPEN — PARTIAL WORKAROUND] Brompton Phase Shifting and Ghosting

Community — Jacob Watson, David Jeffries — October 2024

Jacob Watson: "We are shooting Venice1/Rialto with Cinebot Mini. Using an RT-14 from another robot to get Flair, Volume, and Camera Genlocked together. The Venice1 only accepts a PSF reference signal for 23.98, the RT-14 identifies the signal at 23.98 Hz, but the Brompton LED controller is reading the REF input at 47.96 Hz. This shouldn't be an issue as it is a double of our project framerate, but we are getting weird ghosting/doubling through camera. While running the move the external camera menu is reading the reference at a steady 23.98 Hz, but the phase is continually changing. Entering the current phase as an offset into the Brompton controller mitigated some of the issues, but then the issue comes back in the next take."

Root cause: The Brompton's internal frame processing (possibly "Frame Remapping") may be doubling each frame when it sees a 47.96 Hz internal clock against 23.98 content, causing the ghost frame artefact.

Partial workarounds attempted: 1. Enter the current phase as a manual offset in the Brompton controller — helps momentarily but phase drifts between takes. 2. Check that the Brompton's "Frame Remapping" or ghost frame function is disabled.

Recommended fix (not confirmed by original reporter):

David Jeffries: "Can you make the Brompton the source? It's my understanding that it uses the same clock that the Evertz 5601 uses."

If the Brompton has a stable internal clock, configure it as the genlock master rather than a downstream device — then distribute the Brompton's output to the RT14 and camera rather than the reverse.

confidence_score: 0.80

[RESOLVED] Sony Venice Genlock — Analogue PSF Signal Required

Community — Simon Wakley, Timothy Heys Cerchio — 2021–2024

The Venice (V1 and V2) will not lock to just any sync signal. Requirements:

  1. Signal type: Analogue genlock (not HD-SDI). Set via camera menu: Menu → TC/Media → Genlock → Analogue (NOT "HD-SDI").
  2. Format: PSF (Progressive Segmented Frame) is preferred, especially on Venice 1.

    Simon Wakley: "The Venice seems to like the PSF version of the signal better than the P or I version. When you get it right, a small 'Gen' appears in the video output."

  3. Frame rate: Venice 1 most reliably locks at 25fps PSF. At other frame rates it may refuse to lock.

    Timothy Heys Cerchio: "For Venice you need an external Sync Generator, like AJA Gen10 or Blackmagic, and then you feed SDI to camera Genlock and Analog output to the BNC connector on RT14."

Menu path to verify: Hold Menu → Select TC/Media → Select Genlock → Confirm set to Analogue

When locked correctly, a small "Gen" indicator appears in the Venice viewfinder output.

confidence_score: 0.88

[INFORMATIONAL] Venice Has No Camera Sync Output

Community — David Jeffries, Simon Wakley — 2024

Unlike ARRI cameras, the Sony Venice does not generate a camera sync output pulse. Flair cannot derive sync from the Venice directly.

Simon Wakley: "The one slight wrinkle is that some cameras like the Sony Venice will not generate a pulse per frame and if you want to sync the moco to the camera you have to generate and use genlock yourself and send it to the camera and the root box."

Signal routing: - Sync generator → RT14 Genlock input (Flair locks to the generator) - Sync generator → Venice Analogue input (Venice locks to the generator) - Both locked to the same source = in sync

confidence_score: 0.90

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