MythTV

In the summer of 2005, I put together a computer, connected it to my television, and made it operate as a DVR (digital video recorder, a.k.a. a TiVo). I have been running it ever since (albeit after replacing the motherboard when it died). Although there was certainly some effort involved, by and large it was not that difficult.

• The computer uses a Hauppauge PVR-150 card to record analog television. This card includes a built-in MPEG-2 encoder, relieving the computer from the hardest part of recording TV.
• I chose an nVidia graphics card for several reasons. One, they offer TV-out (over S-Video) support in Linux. Two, if you use the proprietary drivers you also get XvMC, i.e. hardware MPEG-1 and -2 decoding.
• Beyond those two items, the rest of the computer does not particularly matter. 512 MB of memory is the minimum to get by efficiently. Plenty of hard drive space is also a must.
• The Hauppauge card comes with a remote control; if you do not have a remote, I encourage getting one so you can use your rig like a purpose-built DVR.

I use MythTV, an extremely complete Linux-based DVR software which does just about anything you would want it to.

• MythTV has a backend/frontend architecture: the backend records TV, and the frontend plays it. You may have multiple computers running backends cooperatively, and each backend may run multiple capture cards. A frontend can be run on any computer, so I can watch TV on my desktop computer.
• MythTV can be set up to automatically detect and skip commercials. (This is perhaps one of the most compelling reasons to run your own OSS DVR, in my opinion.) The commercial detection is not perfect, but 99% of the time it is spot on or only fails to skip past a short bumper ad. My 1.4 GHz system can run commercial detection significantly faster than real-time, and commercial detection is ordinarily run in parallel with the recording.
• Like any competent DVR, MythTV obtains advance TV listings (two weeks worth is standard in North America) and uses this to schedule recordings. In most cases, I simply tell it "Record this show at any time on this channel" and it does the right thing without any intervention. It remembers which episodes have been recorded and does not record duplicates. Conflict resolution is handled automatically by optionally assigning priorities to shows, stations, capture cards, and recording types; you can of course also override it manually.
  • Since September 2007, there are no free listings available in the U.S./Canada (without resorting to screen scraping). A new OSS collaboration now provides listings at $20/year, which is still a bargain.
• MythTV also comes with many plug-ins. I have plugins to:
  • Play video files not recorded from TV. I have it use MPlayer to play all files.
  • Play, rip, and transcode DVDs. I have it use Xine to play DVDs; the transcoding is very automated but I think depends on ffmpeg to do the work.
  • Play music. (Good for parties, especially with the trippy visualizations turned on.)
  • Show pictures.
  • Launch games/emulators. This works particularly well with ZSNES; other emulators are not as cooperative.
  • Display the current weather.

Aside from MythTV, I also run the following on my system.

• LIRC, to handle the remote control. (This works with MythTV, MPlayer, Xine, and a handful of other things.)
• Apache, to host a web interface to MythTV (used to manage the backend and schedule recordings, not watch TV (although that is in the development pipeline!)).
• NFS and Samba, to share the non-TV video directories over the network. (MythTV streams recorded TV from the backend to the frontend on its own, but the external video plugin does not have this capability.)
• NTP, to keep my clock correct automatically. (Not that millisecond accuracy is important, since most stations are not so well-timed. I choose to keep my clock correct, and ask MythTV to add a 15-second buffer on either end of recording.)

My only complaint is that while MythTV handles digital television with just as much elegance, my unfriendly cable provider does not: they encrypt all their streams, and there is not yet a computer capture card that has a way to decrypt them. Although the problem is technologically trivial, untested legal issues abound, and it remains to be seen whether someone will produce and sell such a card that will work with OSS. (There is already a daring company that produces an HDTV capture card which ignores the broadcast flag, but they do not have one that decrypts encrypted streams yet.)