From 60 To Zero

I seem to be falling behind a bit in my TV-watching. Which is okay; the whole point of having the PVR is to let me watch things when I have the opportunity and not by a fixed schedule, after all. Except that I’m already running out of disk space…

So, as the free space counter edges ever-closer towards 0%, what are my options?

1) Transcode to MPEG-4

Although the tuner card captures in MPEG-2, MythTV has a built-in option to convert recordings to MPEG-4 afterwards. Using the general guideline of keeping around 0.25 bits per pixel for good MPEG-4 quality, the original 2.2Mbps stream could be reduced down to around 1.3Mbps, trimming off over 40% of the file size.

There are downsides, though. Transcoding is slow, taking about 10 hours for every hour recorded, on this system. If I’m recording more than two hours a day, it wouldn’t even be able to catch up.

Transcoding also reduces the quality slightly, as all lossy reencodes do, though it doesn’t seem too bad to my eyes (e.g., in these before and after frames I can see some blurring after the reencoding, but it’s not too noticeable when actually playing the clip). This could be mitigated by raising the bitrate of the original capture so that there’s a higher quality source to work with, at the cost of some extra temporary disk space and a longer wait (a higher bitrate stream won’t play at full speed on this system. But then again I could play it on the iBook, too…)

And finally, the MythTV wrapper around MPEG-4 files doesn’t seem to be supported by MPlayer, so I would have to play it back within MythTV only, or extract it to a separate MPEG-4-compliant file format before viewing it. This won’t be such a big deal once I get the TV-Out working properly and/or a faster processor, but in the meantime I still want to be able to use MPlayer.

2) Manually edit out the commercials

Although MythTV tries to automatically detect commercial breaks and skip them, it doesn’t actually remove them from the file unless you have it transcode as above. It just keeps the start/end information in a table and uses that to skip over the appropriate sections of the file. Instead I can use something like ‘gopdit’ to manually edit the original stream without transcoding and cut the commercials out completely, freeing up some space. Doing this to a movie I recorded recently reduced its file size from 3.2G to 2.3G from this alone.

The biggest problem here is that this manual editing is tedious, and not really worth the effort for every single little thing that gets captured. I’ll reserve this for the things I’ll be more likely to keep permanently, like movies and favourite episodes.

3) Burn to media

And of course, I can always just put the files somewhere else. Again, primarily for those things I want to keep permanently, since there’s now a monetary cost involved.

There are a lot of options available here, though. I’ve burned VCDs before, but that’s not really good enough now that I’m recording at a higher resolution. SVCD matches the resolution and bitrate I’m capturing already, but my DVD player doesn’t support SVCD and the capacity would be a lot lower at only 30-40 or so minutes per CD, unless I start reducing the bitrate. Or I could just put MPEG-4 files on the CD and get over an hour, at the cost of having to play it back only on the computers.

Plus, I have a DVD burner on the way. Things I know I want to keep I can capture at the full 720×480 DVD resolution, and at 5Mbps I could fit two hours per single-layer DVD. Or transcode down to 3Mbps MPEG-4 (some players are supporting MPEG-4 files on burned discs now as an extra feature) and get over three hours. Or just keep it at 480×480 at 1.3Mbps MPEG-4 and get over 7 hours. It’s not like recorded TV shows need full DVD quality anyway. But then again, keeping it in the plain MPEG-2 DVD profile would have the best compatibility, and I could burn movies for my mother… (She keeps asking if I have anything she might want to borrow and watch, but our tastes don’t overlap much. :-)

4) Delete stuff

Do I really need to keep *every* episode of CSI that MythTV runs across? Probably not. Even if I haven’t watched them all yet, shows in syndication will be repeating soon enough…