OC app is enabled but do not work

Hello guys! I have OC 9.1 server, running on Debian jessie.
i have acidently installed, enabled and then disabled HTML5 video player.
actually i was bad reader and did not knew that OC 9 has files_videoplayer bu default up and running!
so i installed HTML5 videoplayer, enabled it (it did not work). And tried the files videoplayer: no luck. Not in chrome not in firefox...
i even do not have thumbnails of videfiles any more.
in the administration app tab files_videoplayer is enabled so i assume that something wrong somewhere in configs.
i tried to disable/enable files_videoplayer, with web interface and with occ - no luck.
please help)
Steps to reproduce
1. install and enable HTML5 videoplayer
2. disable and delete HTML5 videoplayer
3. try to play video via web ui
4. get sad

Expected behaviour
video should play in files_videoplayer

Actual behaviour
files are downloaded

Server configuration
Operating system: debian jessie
Web server: apache 2
Database: MarinaDB
PHP version: 5.6.29
ownCloud version (see ownCloud admin page): 9.1
Updated from an older ownCloud or fresh install: nope
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption): nope

ownCloud log (data/owncloud.log)
very long what should i grep?
Please paste possible errors in the following code block, see https://central.owncloud.org/t/how-to-find-webserver-or-oc-logfile-enable-php-logfile/808 for more info

no errors in apache log only some http acces ones

Integrity status for oC9+

Login as admin user into your ownCloud and access
paste the results here. 
No errors have been found.

Can you try with a video testfile that is known to work (some codecs just don't work properly)?

Logfiles would be interesting at the time you try to access the video.

Oh my bad. never read the description properly...
Test files played perfectly!
Before i tried to play avi files! Shame on my dumb self...
So, little research showed that there are some plugins for video.js to play avi files and even mov files. how can i implement it to my oc setup? little advice would be nice. Thnx again.