Tvheadend

I have a directory with many video files.
I serve this directory through HTTP by using webfs server.
And I've written a .m3u8 file with these files playlist.

In TVHeadend web interface, (version 4.3) I add a "Network" (type "IPTV Network) and next I add a "Mux" associated with it. There I specify URL:
http://192.168.1.40/subdir/video-podcast.m3u8

But all time "Scan result" becomes "FAIL", and I get nothing when I try the 'play' button and open it with VLC media player.

• I've tried both with full URL entries and only file names in m3u8 playlist.