All these meta fields must be borrowed from final extractor that actually performs extraction.
This commit fixes extractor id in download archives for url_transparent downloads. Previously, 'transparent' extractor was erroneously
used for extractor archive id, e.g. 'eggheadlesson 4n8ugwwj5t' instead of 'wistia 4n8ugwwj5t'.
If someone is running youtube-dl on a server to deliver files, the user could input 'file:///some/important/file' and youtube-dl would save that file as a video giving access to sensitive information to the user.
'file:' urls can be filtered, but the user can use an URL to a crafted m3u8 manifest like:
#EXTM3U
#EXT-X-MEDIA-SEQUENCE:0
#EXTINF:10.0
file:///etc/passwd
#EXT-X-ENDLIST
With this patch 'file:' URLs raise URLError like for unknown protocols.
When using 'bestvideo/best,bestaudio', 'bestvideo/best' must be set as the current_selector (instead of appending it to the selectors), otherwise when it gets the ',' it would append 'None' to the selectors.
'bestvideo+bestaudio/best' was incorrectly interpreted as 'bestvideo+(bestaudio/best)', so it would fail if 'bestaudio' doesn't exist instead of falling back to 'best'.
The spec string is processed using 'tokenize.tokenize' to split it in words and operators, the filters are still processed using regular expressions.
This should make easier to allow grouping operators with parens.
Otherwise it's impossible to only download non-DASH formats, for example `best[height=?480]/best` would download a DASH video if it's the only one with height=480, instead for falling back to the second format specifier.
For audio only urls (soundcloud, bandcamp ...), the best audio will be downloaded as before.
It doesn't work well with 'bestvideo' and 'bestaudio' because they are usually before the max quality.
Format filters should be used instead, they are more flexible and don't require the requested quality to exist for each video.
dirkf