How to cope with frame loss

I have no idea why my computer would lose some frames. Athough it may cost little influence on my experiment, I’d better fix it. Any help would be greatly appreciated. :star_struck:

The error code is as follows:

22.9845     WARNING     Couldn't measure a consistent frame rate.
  - Is your graphics card set to sync to vertical blank?
  - Are you running other processes on your computer?

24.8179     WARNING     Couldn't measure a consistent frame rate.
  - Is your graphics card set to sync to vertical blank?
  - Are you running other processes on your computer?

25.3718     WARNING     t of last frame was 554.39ms (=1/1)
25.4103     WARNING     t of last frame was 38.53ms (=1/25)
25.4332     WARNING     t of last frame was 22.95ms (=1/43)
25.5288     WARNING     t of last frame was 20.45ms (=1/48)
25.5504     WARNING     Multiple dropped frames have occurred - I'll stop bothering you about them!
Generating PsychoPy script...


what graphic card are you using? Which operating system?

Best wishes Jens

Thanks sincerely. :star_struck:
To be honest, I am not so familiar with my computer configuration.
It seems that my computer has two graphic cards. One is “Intel® UHD Graphics”, the other is “NVIDIA GeForce MX250”. The operating system is “64-bit”.

Best wishes.

Hello Cheer,

which of the two graphics card are you using in the experiment? The NVIDIA is more powerful than the Intel one. If you are using the NVIDIA try to change the G-Sync option via the NVIDIA control panel.

Do you use “large” visual stimuli in fast succession? Do try to present visual stimuli faster than the refresh rate?

See here.

Best wishes Jens

Hello Jens,

Even though I turn on the G-Sync option via the NVIDIA control panel, the problem has not been solved. Frame loss situation still happens.

In my experiment, participants first learn many object pictures, and then have a memory test(pick the learned one in four pictures).

Besides, I have no idea how to caculate the presentation rate of visual simuli. Therefore I am not sure whether the speed of visual stimuli presentation is faster than the refresh rate.

Thanks for your time and patience. :star_struck:

Best wishes Cheer

The presentation rate of your stimuli would be the number of pictures you attempt to present per second.
In other words: 1 divided by the duration of your stimulus in seconds.

If you try to present stimuli very short e.g. 10 milliseconds, this will cause issues since your screen probably has a refresh rate of 60hz, meaning that you can’t present stimuli shorter than 16.666 milliseconds. The same problem occurs when the pictures are very large files which may take longer to load.


did try to run your experiment with G-Sync turned off? G-Sync is a technique to synchronize your monitor’s refresh rates to the refresh rates your GPU is using (see here for an explanation).

The refresh rate of your monitor determines the duration with which a stimulus can be presented. Most monitors nowadays are 60 Hz monitors. They refresh the monitor 60 times per seconds or every 16.667 ms. So, you can present a stimulus for 16.667 ms, and multiples 16.667. Imagine a masking experiment in which you want to present a mask for 35 ms on a 60 Hz monitor. This is impossible. Two screen refreshes take 33,334. So, you probably end up with three screen refreshes or approx. 50,00 ms presentation (not good in a masking experiment). If your monitor (and your graphics card) were capable to use a refresh rate to 5 ms or 200 Hz, you could use 35 ms. Most gaming monitors are capable of using a 100 hz, 120 Hz or 144 hz refresh rate.

G-Sync is a technique that allows variable refresh rates. A feature that PsychoPy does not like too much. Do you plan to run your experiment on-line? Then you don’t have to care about this too much. Most of your participants won’t have a computer with G-Sync GPU and monitor

If you have rather larger (or many) stimuli, this will delay the onset of the stimuli because the computer has to load the stimuli into memory for presentation. Thus, stimuli will be presented later than you programmed. If you set the stimulus presentation to a fixed duration, a later onset will result in a shorter presentation time. However, PsychoPy allows you to preload your images to overcome this problem.

Best wishes Jens