title: r shiny tags$video not showing video
body: <p>I want to play an mp4 video in a shiny output. It plays fine on my computer when I double click on the file name. I copied the file to the www folder below the main app folder. I have tried variations on the following code.</p>
  
  <pre><code>library(shiny)
  library(shinyjs)
  ui &lt;- fluidPage(
    useShinyjs(debug = TRUE),
    mainPanel(
      "video test",
      uiOutput('ozoneVideo'), id = "mainPanel")
  )
  
  server &lt;- function(input, output, session) {
    output$ozoneVideo &lt;- renderUI({
     h6("ozone video", tags$video(src = "MesaCountyOzone2017_07_10.mp4",  type = "video/mp4", width = "1080px", height = "480px", controls = "controls", autoplay = NA))
    })
  }
  shinyApp(ui = ui, server = server)
  </code></pre>
  
  <p>The web page that is generated shows the text elements (video test, ozone video) and horizontal bar with a video play button and the word "Error" with no explanation. No error appears in the javascript console. </p>
  
  <p>When I add www/ to the filename, the javascript console has an error message "Failed to load resource: the server responded with a status of 404 (Not Found) and a url of <code>http://127.0.0.1:4817/www/MesaCountyOzone2017_07_10.mp4</code></p>
  
  <p>Any help clarifying this greatly appreciated!</p>
  
  <p>Update: July 11, 2017. 
  I am now pretty sure this is a problem with Safari. I run the app with run external chosen. The web page that opens up in Safari has an error message in the video control section. If I copy the url and past to a Chrome web page, the video plays fine. </p>
  
  <p>So my question is now what do I do to make this play in Safari???</p>