Since I got back into the MythTV project a few days ago, I’ve scarcely come up for air. It’s been a long, winding and especially rocky road, but we’re finally reaping some of the fruits of those labours.
The good news is that our MythTV box now basically works, which is to say that we can record and watch programmes, both from live TV and previously scheduled recordings.
On the other hand, although I’ve put a lot of work into the system already, I still have quite a way to go before it becomes really useful. For example, only one TV tuner is active and it’s receiving analogue cable input. This means a lot of our favourite channels, such as BBC3, BBC4, BBC Prime and the Travel Channel are missing from the feed. Furthermore, the coaxial input providing the analogue signal is chained through a couple of other devices before it gets to the MythTV box, so the signal quality suffers. Most of all, though, the poor quality is down to the TV cards, which, truthfully, just aren’t that great.
To get things up and working as quickly as possible, I followed the excellent HOWTO put together by Jarod Wilson. It’s a little out of date and some of the information is no longer accurate, but that didn’t cause any major headaches.
I bought a second tuner card a couple of days ago, a PVR-500, with the intention of making this a triple tuner box (the PVR-500 has two tuner inputs), but this particular card turned out to have the latest Samsung chipset on it, which won’t be supported for a little while yet. Even if I had the patience to wait, I don’t want to have to update the kernel or the ivtv drivers, since these are fragile software components that currently work. Messing with them is just asking for trouble.
So, I took the PVR-500 back to the shop yesterday and exchanged it for a second PVR-350. It’s only a single tuner card, but the chipset is well known and superbly supported by Linux. Besides, two tuners should be plenty in practice.
The idea behind the second tuner is that it will receive its input from our digital cable box, enabling us to record in higher quality and, more importantly, record from the channels that are absent from the standard analogue cable package. I’ll be working on getting that part working in the coming days. The hardest part will be trying to get an IR blaster to change the channel on the digital cable box, since that brainless thing has no serial port or other civilised way to externally control it.
In fact, not only is the cable box missing useful inputs, it only has SCART outputs, which is a problem, because the PVR-350 wants either coax or S-Video + a 3.5 mm stereo jack for the input. I bought a lead today that gives SCART to S-Video + 2 RCA phono jacks, plus an adapter to convert the two RCA plugs to a single 3.5 mm stereo jack. It’s not ideal, but beggars can’t be choosers.
The hardest thing to figure out so far has been the really poor picture quality coming out of the PVR-350. I couldn’t understand why the MythTV menus looked great, but the TV picture showed lots of discolouration and wavy lines. In the end, it turned out that MythTV’s channel scanner is buggy: it doesn’t fine-tune the channels it finds, so if you look at the frequency that each channel has been tuned to and compare that to the one given in UPC’s table of channel frequencies for the Amsterdam cable network, you see that the tuning is off my a few hundred kilohertz every time; enough to really screw up the picture. The solution is thus to enter each channel’s frequency by hand from this table.
Even after fixing that, though, the picture is nothing to write home about, certainly when you’ve become accustomed to digital cable; and one of the PVR-350s suffers significantly worse from interference than the other. I played around with both cards, swapping them from one PCI slot to another to ascertain whether this was truly the case, and it is.
Another annoying problem was having an off-centre picture, with the left and bottom edges of the picture running off the screen. I’m not using a normal video card at all, having instead opted to set up a frame buffer and an X server for the PVR-350’s TV-Out. This allows the card”s hardware-based video decoder to be used for playback, which reduces the load on the main CPU. I’d actually like to remove the nVIDIA video card altogether, as it was needed only for installing the operating system, but the system won’t boot without a card in the AGP slot.
Anyway, the off-centre picture problem was puzzling. I was using a perfect X modeline for a PAL television’s 720×576 resolution, so that couldn’t be it. Eventually, I mostly fixed the problem by telling MythTV to run its GUI in a window rather than full screen, and to offset the window.
In the coming days, I’ll be trying to make a number of improvements to the system. Most importantly, we need to be able to record from the digital cable box. The remote control also needs some minor tuning, as its current configuration is not all that intuitive. Also on the list is the housing of the system. It has a VFD display, which currently displays the unwavering message “Welcome to HTPC”. Ideally, I’d like that to display details of what’s currently being viewed or recorded, but it remains to be seen to what extent I can drive that device in Linux, which connects internally to the motherboard via USB.
Apart from that, both Sarah and I need to become more familiar with the system, as it’s a bit rough around the edges and doesn’t come with a manual as such, just the Installing and Using MythTV document. There are a lot of complicated settings that I currently don’t understand, so I’m leaving them well alone.
But there you have it. Some six months later than originally envisaged, our MythTV box is finally a reality, which is very pleasing, indeed. We even have MythWeb running, so we can use a Web browser to schedule the recording of programmes: handy when you’re away on holiday and hear about a great programme you’d like to see.
This will be an ongoing project, though. There have been a couple of kernel oopses, hangs during channel scanning and strange video freezes, which all need to be cleared up if the system is to truly become a useful appliance, rather than just an interesting hobby project. It’s certainly a lot of fun to play with, though.