So I spent a little bit of time playing with myth last night. I’m now using Matt Zimmerman’s debs to get around compiling things. I used Debian’s module-assistant to compile the nVidia kernel modules that I need for TV-out, a wonderful tool that does all the tricky stuff for you. There’s even a recent enough release of lirc in Debian now that supports kernel events interface; although, setting it up was a nightmare, much harder than last time. The configuration file format seems to have changed, but there were no parsing errors, just silent failure. And the walk-through setup wizard output incorrect configuration information… The web interface needed a tiny patch to work, a call to intval() around the port parameter passed to the fsockconnect call that connects to the backend, no idea what’s going on there. I also had to hack the database a fair bit, it had metadata about hundreds of recordings made last year that had long been deleted from the filesystem, listing the recorded programs was taking an age as it attempts to get a keyframe of each and every missing recording. The new version has much better DVB support than previous versions, though the channel input dialog is a big finicky (add a transport for each station frequency, then do a scan on all existing transports). Channel Seven doesn’t seem to play ball here, but I haven’t tried recording anything yet. As for playback, colours look off, I’m not sure why yet. Panning and scrolling look horrible, not enough grunt maybe, I’m yet to look at the load of the box during playback. The speedup on playback option rocks, Kevin Rudd almost speaks as quickly as a normal person using it.

I’ve now extended my D1 parser to grab channel icons. There’s a winding path to follow to get mythtv to use channel icons, I think it’s to do with non .au networks having multiple channels per network. Instead of just using the icon element in the channel description, there’s an icon mapping file that needs to be imported into mythtv. My parser generates that file, the user imports it, then mythtv takes care of the rest. Oh well, it works.

The folks at D1 make commercial myth boxes, they’ve got program data up that I wrote a tv_grab_d1 script for use with myth. I’m gonna wash that XSLT right outa my hair..

Finally got around to buying a two dollar cable splitter so it’s not necessary to do any cable switching; there doesn’t seem to be any interference between PC and TV.

One of the data streams that can be pumped out in parallel to the TV signal is an electronic program guide (epg). tv_grab_dvb parses this information and outputs an XMLTV format file for use with myth. The program worked just fine, but it seems that the Queensland broadcasters only transmit a program guide that’s a few hours ahead, rather than a seven guide day that Sydney siders get.

Now that I’m getting close to having a working mythtv setup, it behoves me to write up my experiences in the hope that it helps someone else out there. My guide is a work in progress, but hopefully there’s that useful bit of information to save people scratching their heads for hours on end.

Without actually knowing what XVMC actually is, XVMC is the X11 interface to MPEG playback hardware on modern video cards. NVidia is the only brand of cards that people talk about using it with, I’m not sure if that’s just because NVidia are the only people to write drivers for it or what. I finally got around to getting xvmc working with mythtv, and on my woefully underpowered system it makes all the difference in the world: live TV is stutter free (the front end no longer pauses to buffer input) and the CPU usage is down to around 40% when displaying a 460x480 picture. There was a fair bit of stuffing around involved as I eventually discovered that XVMC and TwinView (an NVidia configuration option that allows the Monitor and TV to display the same image) don’t work together, only one display can use the MPEG hardware at one time. The NVidia documentation came to the rescue again, however, and walked me through setting up the TV and Monitor to be separate screens on the same display, such that the TV is :0.0 and the Monitor is :0.1, which lets the myth frontend use the MPEG hardware. I also setup the NVidia AGP driver, it seems to provide some marginal improvements. All in all, the current setup is almost usable. The picture on the TV is not full sized, or particularly smoothly rendered.

Filed Debian bug 241449 initial scan data not packaged. Sent some Brisbane data for the dvb utility scan upstream. My current problem is getting the myth front end to use the ALSA sound driver, configuring mythfrontend using ALSA:hw:0,0 just doesn’t work, the gui just ignores that device string, with no reason.

All I’d done was plug in the wrong value for the sound ID, how silly of me. The remote setup is *finally* there. Unfortunately I have to use a pre release version of lirc for it to work, but oh well. I still had to stuff around with the lircd.conf to add scan codes for half my remote’s buttons, and then muck around with Mythtv’s lircrc file to map the keys to something sensible, but now that I know how to do it, it’s not so bad.

I’ve upgraded to the 1.1.1 dvb drivers, if anything, it feels slower :/ On the other hand, after a *lot* of futzing around with the new mythtv channel picker I finally was able to watch some TV (sans sound) through Myth. Why oh why is it so darn hard to import tzap’s channels.conf file into Mythtv, surely someone has wanted to do that before? There’s very little docco out there on either configuration format. At least I’m learning, through bitter experience, all those things which make a program easier to use. For example, if you spit out a critical error saying such and such isn’t configured, you damn well better mention such and such in the documentation.

..mythtv would write a blog entry everytime I taped/watched a show!

So the first suggestion that MPlayer makes for slow computers is to use the ALSA sound drivers. These drivers are included in later kernels, but not the 2.4.x series. Instead of taking the sensible course of action of downloading the source tarball and compiling them myself, I took what I thought would be the easy way out and started using the Debian pre-compiled kernel and ALSA modules. Except that mkinitrd wasn’t producing an init image and I had to make it by hand. Except that I now had to recompile the NVidia driver (ugh) and the linuxtv modules (argh). Once I’d done all that however I could watch digital TV on the PC with no problems…until I actually wanted to do something on the computer that is. It’s then that I noticed that MPlayer wasn’t using the NVidia video output driver, that’s my next problem.

Compiled the latest MPlayer today and I could actually watch some digital TV on the PC, yay! It got out of sync and gave up after fifteen seconds, MPlayer helpfully spits out a list of things to do in order to improve the situation, so that’s where to from here. The S video cable has arrived too, it’s scarily attractive for a cable.

Straight forward job to install and configure them for X, though I’m still yet to understand how to setup the TV-out interface.

So I’ve got yet another expensive toy to play with, a digital TV recorder setup. I’ve purchased a HauppaugeTV Nova-t digital TV tuner card, as well as a new video card with a TV-out socket, and an 80gig HDD to store stuff on. My home setup already has the television sitting next to the computer, so I don’t need a fancy box. And I’m not fussed about noise either; if I can hear it, great. The only bit of the puzzle I’m waiting on is the S video cord to arrive. There are two goals I’d like to achieve, remote web based recording, for me and the flatmate; and predictive recording, probably based around tvfreak.com.au. The hard drive was pretty simple, though I’m mildly grumpy that you still have to move pins around. The video card wasn’t too much of a pain to install; it required X 4.3, which is in Debian, albeit the experimental section. Unfortunately, to be able to setup the TV-out slot it looks like the binary drivers from Nvidia are required, so there’s still some more work to do here. The TV tuner card is still a work in progress. I’ve downloaded the dvb driver, only came across one weird compilation problem (that I’m yet to understand my fix for) and according to the test program I seem to be decoding the digital TV signals just fine. However, I haven’t yet been able to get xine to show me a picture.