Hey Giacomo
well, what can i say, a few weeks ago i asked @momocampo what feature he wants to have next in the webui,
1) a player
2) farm controlling
He decided for farm controlling
(just kidding Benjamin, you know)
OK, so a player on the webui is something thats really complicated but doable after all.
Let me ask you some questions @ArsenioV
Are you aware that:
1) A browser cannot access any local file, so the files would need to be retrieved via http from the client to the webinterface server
2) A browser can only play certain containers and codecs, e.g. h264, so either we can only play formats that the browser supports OR
3) the server would need to "live transcode" the played video for the browser
Usually this is done using live transcoding on the server using Graphics card encoder, e.g. Intel Quicksync or Nvidia NVENC.
The problem is that the webinterface is usually hosted on the same server where FFAStrans is running and consuming all resources. So we'd need to control how many users view videos over the webinterface at the same time.
Alternatively, we could just have a "rightclick->openin player" and open a local video player. But again, the user would need to have direct access to where the files are and at least read access to that location.
What you think?
he never runs out of ideas! 
But i'll finish the metrics stuff before looking into this.