An active recording is a WTV file, and although XBMC can play WTV files, it bugs out when the WTV file is still being written to - XBMC only plays it up to the size it was, when playback started. Eg if a recording has been going for 10 minutes and you watch the WTV file in XBMC, then at the 10 minute mark, XBMC will stop playing the file, eventhough by that stage it is 20 minutes long etc. So just like with live TV, we remux an active recording's WTV file to a TS file and send that to XBMC (because XBMC is able to play a growing TS file and re-evaluates the file size as it goes etc), if the user wants to watch the recording while it is in progress. There are no extra tuners used or anything like that, it is all about being able to watch an active recording to the end without the playback stopping etc.
I should also mention that this is the way that ServerWMC has always worked for a long time.
There is one draw back to the remux to TS of an active rcording, which is that if an active recording has been going for say 45 minutes, and you start viewing it, we start remuxing the TS file when you start viewing, but you cant immediatley skip to the 30 minute or 45 minute point etc (because the TS file remuxer only just got started and the TS file doesnt have all that data in it yet). Ultimately we think the TS remux should catch up pretty quickly but certainly you cant skip ahead a much/as soon as you want etc. One user on here was having issues where even after pausing things, the remuxer didnt seem to catch up. Behaviour here seems odd and we need to test more, there could be a problem with XBMC or our stuff where even if we wait for the remuxer to catch up, we still cant skip nicely etc. As an aside, we are looking at developing an option to have active recordings automatically remuxed to TS immediately, rather than only when a user starts trying to view one. Ie "remux active recordings incase the user wants to view them" type thing. Perhaps every recording or perhaps a way to flag certain recordings (series recordings etc) to enable this pre-emptive remux. I also suggested having times of day where it would and wouldnt do this (no point doing it if its 3am and the users are asleep etc). Of course the remuxed TS file will be deleted whenever the user isnt watching it anymore or the recording actually completes (at this stage, it is a completed recording and watching the normal WTV file works fine).
The reason it can now be disabled is that as of the latest build (and on GOTHAM only!) we now support Resume playback on recordings. Given this fact, when watching an active recording in WTV format, when playback stops at the "size when XBMC started viewing" point, you can simply play the file again, and it will offer to resume from that point. Krusty thought this was an interesting workflow that some users might prefer, so he made the remuxing of active recordings to TS, be an option.
To sum up that whole lot of drivel, essentially there are 2 behaviours
- The default (and long standing behaviour) of remuxing active recordings to TS - meaning they can play right the way through but with some difficulties skipping/fast forwarding etc
- An alternative behaviour of playing the raw WTV file, being able to skip around to your heart's content, but playback stopping prematurely, with the Resume functionality making it less painful to get the playback going again
Regading your thing about Pi clients, you are confusing another thing which was that they seem to have issues playing large WTV files, so another option "remux all recordings" can be used so that even completed recordings will be remuxed to TS and hopefully work on a Pi (when normally a completed recording, we just play the WTV file)
Sorry for the rambling post, I have no idea how you could even attempt to make sense of this and put it in the wiki!
Im actually interested in the whole "XBMC playing active WTV file stopping at the filesize when playback started" thing... I wonder if it's just a simple bug in XBMC and if we raised a Trac ticket, we might end up with XBMC able to play live WTV files. That would reduce alot of complexity for us, as we wouldnt need to remux live TV or active recordings, to TS anymore...