How to set the video/audio MIME types

I’m attempting to use the Video and Audio classes and need to be able to specify the MIME types. For instance, in video if I try to use a webm file, the type is always set to ‘application/octet-stream’ instead of ‘video/webm’. If possible I’d like to not resort to writing straight HTML to achieve this.

Thanks and best regards as always,

Steve Thompson