How to retrieve the hashcode of any designative content?

I have done some tests of upload and download on ipfs with ipfs desktop application. But I found that only can we use is the hashcode of the content. For example, if I want to watch a video, I need to search the Internet or call for someone to get its hash. It is not convenient to get content which we don’t kown its hashcode. So, shall we already have a content search engine or portal site to provide the mapping between content and hash?

Discovery is usually done out of band but you could also build a system using PubSub.