http://www.vmixhd.com/knowledgebase/

I tried it twice and searching on sound finds not one article

searching om mp4 finds three articles, so it is not completely down. But is does seem that it has to be missing many articles with word sound in it. There are no options for find in title or title and text. It just says Search.

It would be nice if the Knowledge base brought up articles that were closest to what you search on, even if not exact. Google is very good at doing that.

Cheers