Neurobs Presentation: Difference between revisions
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== Screen synchronization issue on 120 Hz screens == | == Screen synchronization issue on 120 Hz screens == | ||
There is a serious synchronisation issue where the picture.present() method returns one frame too early. It can be detected by measuring the time between two consecutive present() calls returning: | There is a serious synchronisation issue where the picture.present() method returns one frame too early. It can be detected by measuring the time between two consecutive present() calls returning: | ||
< | |||
<pre> | |||
wait_interval(220) | |||
picture1.present() | picture1.present() | ||
int t0 = clock.time(); | int t0 = clock.time(); | ||
| Line 79: | Line 81: | ||
int t1 = clock.time(); | int t1 = clock.time(); | ||
int dt = t1-t0; | int dt = t1-t0; | ||
</ | </pre> | ||
One would expect ''picture1'' to be shown for 1 frame (1/120 s) and time ''dt'' to show this. Sometimes this is not the case. The image will be shown for one frame (1/120 s), but ''dt'' will be 2/120 s: | |||
[[File:Timeline.svg|none|thumbnail]] | |||
The fact that ''picture1'' is shown for only 1/120 s was confirmed with a light sensor connected to an oscilloscope. | |||
The chance of this issue occurring is highly dependant on the waiting time | |||