%(extractor)s for the provider (youtube, metacafe,
etc), %(id)s for the video id and %% for a literal
percent. Use - to output to stdout.
+ --restrict-filenames Restrict filenames to only ASCII characters, and
+ avoid "&" and spaces in filenames
-a, --batch-file FILE file containing URLs to download ('-' for stdin)
-w, --no-overwrites do not overwrite files
-c, --continue resume partially downloaded files