The only available in main portage tree version of media-video/kino-1.3.4 creates incompatible with current stable version media-video/dvdauthor-0.7.0 xml DVD index.
So, declared function of writing video DVDs really is inoperable.
There are two rather simple workarounds, solving this issue.
As described in http://ru.gentoo-wiki.com/wiki/Home_Video_Howto
media-video/dvdauthor-0.7.0 requires to be set the output format (PAL or NTSC).
It can be done either in xml file, or as environment variable (VIDEO_FORMAT) or in ~/.config/video_format config file.
To my mind warning in elog and postinstall message will be enough.