[PD] pushing gem pix_video I/O

hi joson.android at googlemail.com
Fri Apr 17 16:30:04 CEST 2020

Hi Marco,

i tested a couple of years ago with a MacPro 2013 and a blackmagic card connected through thunderbolt. The minimum latency was ~200ms and was about the same with quicktime and Pd/Gem (i used the quicktime plugin anyway).
If your SDI out is not visible as a monitor output you would need an extra tool to send it there, maybe something exists with syphon?
If you need to work with OpenGL maybe shaders could help you (check [glsl_program]).
all the best,


> Am 17.04.2020 um 02:34 schrieb Marco Schretter <mco at zimt.at>:
> dear all,
> unfortunately i'm forced to work with a mediaserver that is not capable to do a live-cam freeze. now i'm trying to solve this by building a osc-controlled blackbox with GEM (pix_buffer[read/write]).
> test-setup:
> decklink quad 2-8 capturecard https://www.blackmagicdesign.com/de/products/decklink/techspecs/W-DLK-30 in sonnet frame
> macbookpro (2013)
> this testpatch works ok, but with 500-1000ms latency ...
> https://zimt.at/cam_freeze_v01.jpeg
> question:
> how can i push the latency and make it more "real-time" (whether with pix_buffer or several pix_buffers or other objects)
> do you have experience how to push the GEM output to the decklink sdi-out? i guess the rendering is done on the graphics card and not on the decklink (?not openGL capable?) so mabe this is useless? so is the macbookpro graphic card the bottleneck?
> merci
> marco
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