It is currently impossible (or completely undocumented) how you would actually return the file name for results in the Wikimedia Commons query service. This is something you would expect to be a very common need, just as how in the WDQS it is very common to output labels in most queries, since the Q-id is not human-meaningful, just like the MediaInfo M-id.

Users have developed a workarounds for this issue, which require using schema:url and then doing a series of string manipulations and decoding the URI, such as: BIND(CONCAT("File:", STRAFTER(wikibase:decodeUri(STR(?url)), "http://commons.wikimedia.org/wiki/Special:FilePath/")) AS ?fileTitle).

This is not very user-friendly. In the entity JSON, this is already available in title. What would be much easier for users would be if the title were accessible in a straightforward way, such as schema:name (which doesn't seem to do anything for MediaInfo entities yet).