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Backend Capabilities: Mythtv or other?

post #1 of 16
Thread Starter 
I'm drilling down into the capabilities of Mythtv, and having trouble differentiating between the frontend capabilities and those of the backend.

Can mythtv automatically whack the commercials on the backend, or is this just a function of the frontend? If so, is there a howto (I haven't found one yet)? If not, is there any other linux-based app/distro that can handle it?

I plan on using XBMC as my frontends due to WAF and prior experience with it. I would like to use mythtv to record shows for later watching.

Thanks.
post #2 of 16
The recording backend usually flags the commercials and the frontend skips them. Uh, if you set it up this way. I have no clue about XBMC. Never tried it. MythTV does everything I want, or more.
post #3 of 16
To clarify: The backend does not remove the commercials. It just flags them, and the frontend will detect the flags and skip over them. You need to set it to do this, as it won't do it by default.

As for XBMC. My experience is that it does not do deinterlacing. I found that I needed deinterlacing to watch 1080i recorded shows. I am not sure if it will honor the commercial flagging either, as my shows were unwatchable without deinterlacing.
post #4 of 16
Well, you can set it up to automatically remove commercials on the backend. http://www.mythtv.org/wiki/Removing_Commercials

Backends handle all non-user-interface functions. They record shows, do commercial flagging and transcode jobs, etc. The frontend, in it's most basic form, plays back the recorded shows. If the recording has commercials flagged, you can set the front end to automatically jump over the commercials.
post #5 of 16
Actually removing commercials involves re-encoding the file. It will use the commercial flagging file to generate a commercial cut list. This will take time and processing power.

It is my experience that the commercial flagging is not perfect. Before you actually cut the commercials, you should review the file and adjust the sections to be removed.

Removing commercials automatically means not reviewing the files first. Some commercials could be left in, and some of the actual show could be removed.

This is my experience with removing commercials. I only do this when I want to make a DVD of some shows, and I find the result would be unsatisfactory if I didn't review the cutlist first.
post #6 of 16
Quote:
Originally Posted by waterhead View Post

It is my experience that the commercial flagging is not perfect. Before you actually cut the commercials, you should review the file and adjust the sections to be removed.

This is my experience as well. Some programs are flagged with extremely high accuracy; others... well, the flagger struggles. Especially with very dark shows (like Battlestar Galactica, or Stargate Universe). I find that the flagger can struggle with basketball games, especially near the end of the game where frequent commercial breaks can mean there is more commercial than game.

My actual practice is to run the flagger on non-sports shows, and watch non-transcoded programs. I run my frontends with auto-skip, but notify me of how much time was skipped. If I notice an over-skip, I can back up and watch the part of the show that was erroneously flagged as a commercial. If it under-skips, it's easy to hit the 30 second skip button. I've got just over a TB of space (which used to be a lot, back when the big drives were 250GB!), and I'm only using about half of that, so I'm not worried about transcoding to save space. IMO, it just uses processing resources that are better allocated to commercial flagging ASAP. If the job scheduler was more sophisticated than a simple FIFO queue, I might consider automatically transcoding my old saved recordings (like, if it's been watched but not deleted, let's transcode to a smaller "archival" size), but right now it's not worth it.

Looking at the XBMC wiki, I see that MythTV is supported natively ( http://wiki.xbmc.org/index.php?title=MythTV ), which is good since by default the filenames are not human-friendly. The frontend displays the metadata pulled from the database, not the file names from the filesystem. You'll have to use mythweb (the web interface) to schedule shows, which is my preferred method anyway, since a mouse and keyboard is faster and more flexible than a remote control.
post #7 of 16
All great information here.

Only thing I would like to add is that at some point XBMC is supposed to release a "PVR plugin API" so it can act more like a PVR interface that you expect to use. What I mean by that is that it will support those functions that are needed for a PVR - scheduling shows etc. I think several plugins are in the works including one for myth TV.

I think the current downside of using XBMC today for myth recordings is that commercial skipping is not as slick. And someone mentioned earlier a script or plugin for XBMC as a frontend for mythtv exists - I have tried it and found it fairly buggy. Of course that was a few months ago so things could have improved by now. I would definitely give it a try since you want to use XBMC.

I believe this "PVR plugin API" project was a Google Summer of Code project a year or two ago. But I might not be remembering that correctly. Here is a thread that discusses it:

http://forum.xbmc.org/showthread.php?t=28918
post #8 of 16
Thread Starter 
Thanks to all for the information. If I were to miss a frame or two of a show, that would be acceptable. If I were to miss entire segments, I would probably throw something at the tv (in my mind of course).

I'll probably try out the MythTV front end just to gauge what the WAF is and see how acceptable the comskip is. Alternatively, since I won't use this for live TV, I may just use the backend for all of the scheduling & recording, then manually edit the programs. I had prior experience with VideoReDo, and may look at using that again.
post #9 of 16
Quote:
Originally Posted by waterhead View Post

As for XBMC. My experience is that it does not do deinterlacing. I found that I needed deinterlacing to watch 1080i recorded shows.

XBMC does indeed deinterlace, but it's turned off by default for whatever reason, so you either have to set it to auto detect in the video settings or manually activate it each time you play a video.
post #10 of 16
To clarify, there are options for deinterlacing, but they don't work. It is well known that deinterlacing is broken in XBMC.

I was trying it on an Intel video chip, in my netbook. I was trying to watch my MythTV recordings of OTA HDTV.

YMMV.
post #11 of 16
Has the VDPAU hardware deinterlacing broken too in XBMC? I haven't used it in a while.
post #12 of 16
I was referring to software deinterlacing. I haven't tried hardware deinterlacing with VDPAU.
post #13 of 16
I've been using XBMC for months and interlacing/scaling are very good. I admit I did read the wiki before I went out and bought hardware and ended up with a IONITX MB which not only works for SD, it also plays full 1080P too.
post #14 of 16
Thread Starter 
Quote:
Originally Posted by mythmaster View Post

Has the VDPAU hardware deinterlacing broken too in XBMC? I haven't used it in a while.

I know the VDPAU hardware *acceleration* works. I wasn't sure that there was a separate setting for hardware/software deinterlacing.
post #15 of 16
It's in advancedsettings.xml.

This is all pretty much outdated anyway. The next release (which is imminent) uses shading and will allow HW acceleration under most HW/OS platforms.
post #16 of 16
Quote:
Originally Posted by zimdba View Post

Thanks to all for the information. If I were to miss a frame or two of a show, that would be acceptable. If I were to miss entire segments, I would probably throw something at the tv (in my mind of course).

Sometimes it's quite a bit more than a frame or two. CBS seems to be the worst channel for me and sometimes skips 30 seconds before the actual commercial. As soon as you notice it you just have to hit the back button which disables the autoskip. As far as XBMC...I use it pretty much for all viewing and find that it actually works better than Myth in that the commskip is a lot smoother and with some shows you barely know a commercial should have been there. Since XBMC uses the same skip file whatever errors are in Myth will also be in XBMC. You can always turn off autoskip and use the 30 sec skip function.

The built in Mythtv interface can be used but it is nothing like myth in that there's not a real guide. You have to select a channel then it will show what's on in the next few hours so if you have 100 channels you have to do 100 lookups. Mythbox is a 3rd party frontend that although better than the official XBMC frontend still has some issues. It has a guide similar to Myth and allows you to setup recordings. I use it occasionally when the mood strikes me. My current process is to use a program called MythicalLibrarian which takes the Mythtv recordings, renames the files to SxxExx if a TV series then moves or links them to my XBMC library. If it's a movie then it's moved to the XBMC movie folder.
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