I think this is an issue with how the app is triggered.
I'm only using Rstudio IDE , not any server but still.
If the app has the code to create the app object like so :
shinyApp(ui, server)
then
if I launch the app via runApp() or the IDE's green run app button, I can get an iframe playing a mp4 from a video subfolder of www.
However if I launch the app via selecting the app.R code and submitting it into console, the src is not found.
If I select and submit all the app.R code, *except for * shinyApp(ui, server) , and then follow up by submitting shinyAppDir(".") again it works.