Deltacast Video Device Out - "Failed to start video" when using two TouchDesigner instances

Hardware
1

Hi everyone,

I’m having an issue with the Deltacast Video Device Out TOP and would like to know if this is an expected limitation or if there is a workaround.

Environment

  • TouchDesigner: 2023.32820

  • Deltacast board: DELTA-12G-e-h 8c

  • Windows: Same PC, same Windows user

  • One Deltacast board

Issue

When I launch two separate TouchDesigner instances, each project contains one Video Device Out TOP configured to output a 4K signal through the Deltacast board.

The first TouchDesigner instance starts output normally, but the second instance always fails with the following error:

Failed to start video

However, if I combine both outputs into a single TouchDesigner project, I can output two independent 4K signals simultaneously without any issues.

So the behavior is:

  • :white_check_mark: One TouchDesigner instance → Two 4K outputs → Works

  • :cross_mark: Two TouchDesigner instances → One 4K output each → Second instance reports “Failed to start video”

This makes me think the issue is related to multiple TouchDesigner processes accessing the same Deltacast board, rather than a hardware bandwidth limitation.

Questions

  1. Is this a known limitation of the Deltacast implementation in TouchDesigner?

  2. Does the Video Device Out TOP exclusively lock the entire Deltacast board per process?

  3. Is there any recommended way to share a single Deltacast board between multiple TouchDesigner instances?

Any advice or confirmation would be greatly appreciated.

Thank you!