1

Setup: Matlab Student 2014, Psychtoolbox 3.0.12, GStreamer 1.4.3, ATI Radeon 69xx, all on Windows 7, all 64bit.

Screen works with different arguments, only at Screen('OpenMovie' the whole Program (Matlab) crashes - sometimes with Error (unable to synchronize framerate), sometimes no error at all.

I know it is quite specific and I think it is somehow in my configuration (the code will work on a different system (lab)).

What I've tried so far:

  • Psychtoolbox 3.0.11, GStreamer SDK, GStreamer 1.4.1
  • renewed ATI drivers (complete catalyst control center,..)
  • removed multi-monitor setting (makes it harder to debug then..)
  • Matlab itself works, GStreamer too (tried playing movie with playbin)
  • anything SyncTrouble states: wait for vertical synch, triple buffering off
  • overriding sync-tests or skipping at all (also crash)
  • looking for missing dlls (for Screen.mexw64)
  • VBLSyncTest and PerceptualVBLSyncTest look fine and have results (for me)

It has to be either something very simple, or very specific - I'm somehow out of ideas. My guess would be that the Radeon vertical sync on setting does not work - for what reason ever.

ANY guesses, tips are apreciated. (even other ways to test Screen or vertical sync in Matlab/Psychtoolbox)

definitely undefinable
  • 883
  • 1
  • 20
  • 34

1 Answers1

1

after hours of search, I think I've found a solution - oh Windows! (and oh, one simple line of code)

Screen('Preference', 'ConserveVRAM', 4096);

4096 == kPsychUseBeampositionQueryWorkaround Tell PTB to always use the workaround for broken beamposition queries in VBL on MS-Windows, even if the automatic startup test does not detect any problems. This for rare cases where the test fails to detect broken setups. [Psychtoolbox Docs]

I will do a recheck after some Videocache action and restarts.

edit: well, that did only work once, and randomly a second time - it seems like the ATI Radeon driver behave not quite deterministically - I also checked on a Linux (Ubuntu 14.04.1). Specifically, the VSync rate seems to behave somehow strangely.

It generally works on that specified Linux with the open source radeon drivers (instead of the fglrx ones) though. -> The Problem on that Linux system: it can only be configured as one Screen (two monitor setup would be nice for debug on one Screen). (Yes, I've tried: Unity, Gnome, Xmonad, Gnome+Xmonad - but I guess that is another story)

Alright, I've written enough, my solution: use a Linux distro (quite unsatisfying though, as I could not accomplish for everything to work).

definitely undefinable
  • 883
  • 1
  • 20
  • 34