How to include a forward slash in the value of a dropdown option

When defining a shortcode with an attribute of type “dropdown”, I add an option like this:

video/mp4|mp4

The inserted code is HTML and is this:

{ type: “{{type}}”, src: “{{content}}” },

I would expect the text “video/mp4” would be inserted in the post, but the forward slash is removed. The following versions also doesn’t work:
video\/mp4|mp4
video//mp4|mp4
video%2Fmp4|mp4

If anyone has any idea how I can get the value inserted as “video/mp4” that would be greatly appreciated.