Screentest

1
Hi

I downloaded the latest release of PTB [Psychtoolbox OS X C Source Release 1.0.5 (11 April
2005)], and do not find Screentest.m in the unpacked toolbox.

I was wondering if this had been phased out, for some other testing program.

Much thanks

Lu Lesmes
Salk Institute
2
--- In psychtoolbox@yahoogroups.com, "sosy" wrote:
>
> Hi.I'm new in psychtoolbox.I'm using window 7 ,32 bits and matlab 2011 and installed psychtoolbox 3 ..and make a screentest..however,the output is questionable..below is the result :
>
> >> ScreenTest
>
> ***** ScreenTest: Testing Screen 0 *****
>
>
> PTB-INFO: This is Psychtoolbox-3 for Microsoft Windows, under Matlab (Version 3.0.10 - Build date: Oct 27 2012).
> PTB-INFO: Type 'PsychtoolboxVersion' for more detailed version information.
> PTB-INFO: Most parts of the Psychtoolbox distribution are licensed to you under terms of the MIT License, with
> PTB-INFO: some restrictions. See file 'License.txt' in the Psychtoolbox root folder for the exact licensing conditions.
>
> PTB-INFO: Will disable DWM because a regular fullscreen onscreen window is opened -> We want best timing and performance.
> PTB-INFO: The detected endline of the vertical blank interval is equal or lower than the startline. This indicates
> PTB-INFO: that i couldn't detect the duration of the vertical blank interval and won't be able to correct timestamps
> PTB-INFO: for it. This will introduce a very small and constant offset (typically << 1 msec). Read 'help BeampositionQueries'
> PTB-INFO: for how to correct this, should you really require that last few microseconds of precision.
> PTB-INFO: Btw. this can also mean that your systems beamposition queries are slightly broken. It may help timing precision to
> PTB-INFO: enable the beamposition workaround, as explained in 'help ConserveVRAM', section 'kPsychUseBeampositionQueryWorkaround'.
>
>
> PTB-INFO: OpenGL-Renderer is NVIDIA Corporation :: GeForce 9100M G/PCI/SSE2/3DNOW! :: 2.1.2
> PTB-INFO: VBL startline = 768 , VBL Endline = 768
> PTB-INFO: Measured monitor refresh interval from beamposition = 17.008407 ms [58.794455 Hz].
> PTB-INFO: Will use beamposition query for accurate Flip time stamping.
> PTB-INFO: Measured monitor refresh interval from VBLsync = 16.660104 ms [60.023634 Hz]. (288 valid samples taken, stddev=0.351685 ms.)
> PTB-INFO: Reported monitor refresh interval from operating system = 16.666667 ms [60.000000 Hz].
> PTB-INFO: Small deviations between reported values are normal and no reason to worry.
> PTB-INFO: Support for fast OffscreenWindows enabled.
>
> ***** ScreenTest: Done With Screen 0 *****
>
> Questions : 1. Is the result saying that psychtoolbox will not working well?
>
> 2.Do i need to install back the toolbox?
>
> Need your advice.Thank you
>

It says:

PTB-INFO: for it. This will introduce a very small and constant offset
(typically << 1 msec). Read 'help BeampositionQueries'
PTB-INFO: for how to correct this, should you really require that last few microseconds of precision.

If you don't care about stimulus onset timestamps which are up to 1 msec off, then it's likely fine. You can always run VBLSyncTest and PerceptualVBLSyncTest for some more checks.

The only thing i see is that system timing seems to be quite a bit noisy, but sometimes that's an outlier and then you use Windows-7 which is famous for noisy timing, so often expected.

-mario