Use with -use_localtime, and set -hls_segment_filename to a path which
contains a subdirectory i.e. /some/path/%Y%m%d/%Y%m%dT%H%M%S-%s.ts
This will mkdir the %Y%m%d-part of the path if it does not already
exist.
In addition, each filename in the playlist output will be prefixed with
this subdirectory (if playlist and segment shares the same base path).
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>