Millisecond Forums

hello, 

i would like to play a video (mp4) in my experiment (code below), and it has been running on my computer (and others), but on some it just shows a blank screen (for example on MacOS Big Sur version 11.1). Is there anything I could do to prevent this from happening? (I tried to upload a zipped folder with the video but I think it's too large to upload to this post). 

thank you for your help!!
nina

*************************************************
DEFAULTS
*************************************************

<defaults>
/ minimumversion = "6.1.0.0"
/ fontstyle = ("Arial", 3%, false, false, false, false, 5, 1)
/ txcolor = white
/ txbgcolor = black
/ screencolor = black
/ canvasaspectratio = (4,3)
</defaults>

<shape blank>
/ color = black
/ shape = rectangle
/ size = (100%, 100%)
</shape>

*************************************************
EXPERIMENT
*************************************************

<expt>
/ blocks = [1=wof_spin]
</expt>

*************************************************
INSTRUCTIONS
*************************************************

<htmlpage instructions_wof_win>
/file = "intro_wof_win.htm"
</htmlpage>

<htmlpage instructions_wof_spin>
/file = "intro_wof_spin.htm"
</htmlpage>

<htmlpage instructions_wof_win_out>
/file = "intro_wof_win_out.htm"
</htmlpage>

*************************************************
BLOCK WHEEL OF FORTUNE
*************************************************

<block wof_spin>
/ preinstructions = (instructions_wof_win,instructions_wof_spin)
/ trials = [1 = wheel]
/ postinstructions = (instructions_wof_win_out)
</block>

<trial wheel>
/ stimulustimes = [0=wof]
/ timeout = 22000
</trial>

*************************************************
Stimuli Presentation
*************************************************

// lottery
<video wof>
/ items = ("wof_win.mp4")
/ playthrough = true
/ position = (50, 50)
</video>