Adding syphon support to impress to allow access to the rendered output from other applications

Thorsten Behrens thb at
Mon Sep 30 10:49:54 PDT 2013

James Sheridan wrote:
> Currently we do what you mention via displaying the slideshow across
> 3 monitors linked into one display (via and AMD eyefinity card) and
> then using hardware capture (via a blackmagic declink quad capture
> card) to capture this into our warping solution (which runs on OSX).
> We would like to move away from needing a second computer for this
> though and creating an extension/plugin for Libre that just sends
> the output texture to our warping solution.....or any other syphon
> apps, mad mapper, resolume, vdmx etc.
Hi James,

so there is no ready-to-run texture for you, at least not now, and not
in the general case. If a slideshow contains animations, naturally
even when using opengl, you'd have a number of time-varying textures
composited over another.

I wonder where the need for textures as such comes from - in the end
you want the pixel, no?

The stuff that gets blitted to screen is composited here:

 canvas/source/vcl/spritecanvashelper.cxx, method
 SpriteCanvasHelper::updateScreen() - look into maVDev there

(but sure, on a Mac, that ends up in a texture eventually before
reaching the display - at least the method above gets called exactly
when new content arrives, and cobbles the pixel together)


-- Thorsten
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