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OpenGL render in conjunction with JACK and "AV Sync" causes progressive slow down
Closed, ResolvedPublic


Kubuntu 17.10 with NVIDIA GTX 1060 6GB
Focusrite 18i8 through qjackctl
i4770k, 16GB RAM

Blender 2.79b

To reproduce:

  • start Blender 2.79b with fresh config directory
  • in user prefs, change audio device to JACK, save user prefs
  • open attached demo .blend file
  • click button to do OpenGL render: observe that green cursor moves in sync with render, and render speed is normal
  • if render is not finished, cancel it
  • remove PNGs from /tmp
  • click somewhere in graph editor away from frame 1, then shift-ctrl-down-arrow to return cursor to frame 1
  • click OpenGL render button again and observe bug:

The second time the render is started, it slows down progressively until it is crawling, and the green cursor does not track the render as it happens (the images are rendered fine). Once this slow-down has happened, I can not render normally, regardless of what I try. If I open the .blend and render without moving the cursor, it renders normally.

Except: disabling "AV Sync" in the timeline, or changing from the JACK driver, causes it to render normally. This seems to happen with Cycles or Blender render, IIRC.

I tried to make a simpler .blend demo with the default cube but could not, so that implies that there is either an additional relevant setting in the project, or that a base level of complexity is required to exhibit the bug.



Event Timeline

Philipp Oeser (lichtwerk) triaged this task as Needs Information from User priority.

I can confirm with attached file.
This seems to be a "two-window" issue for me though.

Could you confirm it is not happening in a "one-window" setup like


Marking as incomplete until we have that question out of the way

Thanks -- with me the gradual slow down in rendering speed happens with both the one-window setup and the original demo project two-window setup, but in the one-window setup the green cursors move as expected in both the "good" and "bad" renders, where with the two-window setup the green cursors do not move in the bad render.

Wanted to follow up -- is this in fact still "incomplete" somehow? Meaning, should I be supplying anything else? Thanks!

Philipp Oeser (lichtwerk) raised the priority of this task from Needs Information from User to Needs Triage by Developer.May 31 2018, 9:37 AM

Cant reproduce with the "one-window" setup, but maybe someone else can?
Going back to "Needs Triage" for the time being...

Sebastian Parborg (zeddb) triaged this task as Waiting for Developer to Reproduce priority.

I don't think any of the core devs is runing JACK. So it might take a while until this is looked on.

I can not reproduce this in 2.80, so it's probably safe to close (unless 2.79 bugs are still considered valid?)

But there do still seem to be JACK and AV Sync related OpenGL bugs; I filed a new report here:

Sebastian Parborg (zeddb) closed this task as Resolved.Jun 11 2019, 9:30 AM
Sebastian Parborg (zeddb) claimed this task.