If you want to set multiple sources dinamically (e.g. .mp4 & .ogg at runtime), you could add:
edittime.js, line 34:
---
AddStringParam("Source2", "The location (URL) of the video file", '""');
AddAction(0, 0, "Set source", "Setting", "Set video source to <i>{0}</i> <i>{1}</i>", "Set video source.", "SetSource");
---
runtime.js, line 202:
---
Acts.prototype.SetSource = function (src,src2)
{
this.elem.src = src;
this.elem.src = src2;
};
---
You could also add .webm this way as source3, for me two were enough.