feature: option for %(ext)s to be "weba" for audio-only webm files

[bughit]

.weba is not an official but a de facto extension for audio/webm

http://svn.apache.org/repos/asf/httpd/httpd/trunk/docs/conf/mime.types
https://datatypes.net/open-weba-files
https://www.google.com/search?q=weba+webm&num=100&tbs=li:1

having the right extension is useful for some programs that make decisions only by extension

with such an option, youtube-dl -f worstaudio -o "%(title).%(ext)", would produce a title.weba file if it chose to download webm

[clsid2]

I would also like to have this option. An alternative compatible extension is .mka (matroska audio).

MPC-HC player already has the ability to stream content using youtube-dl. I want to add a basic download option as well to store the best quality audio/video. Having audio in a separate file is no issue for MPC-HC. It can load such a file automatically, provided that it has an audio specific extension, and that its base file name is identical to the opened video file.