HTPC and firewire to cable box

Friday, June 13, 2008

Things are progressing nicely on my HTPC and it is time to move on to my next task, integrating the Rogers HD cable box with the HTPC over firewire. I stopped into one of the local stores and picked up a new Scientific Atlanta (SA) 4250HD, which is Rogers latest and greatest, for use in my office while I put the HTPC together. I could have temporarily moved the 3250HD that we already have in the living room but since this box may be in my office for awhile that wasn't an option, after all my family can only go so long without their TV fix.

Once I got the new box all hooked up and connected to the HTPC through firewire I ran plugreport which gives you some basic information about the firewire connection. I could see the 4250HD was connected so the next step was testing the connection. I compiled and ran the firewire_tester program and here is where I started having issues, no matter what I did I could not get a valid firewire connection to the 4250HD. After searching around for a bit it appeared that a few other people were having the same issue with the Rogers 4250HD box. It may be a driver or kernel issue because one person said his Mac didn't have any trouble interfacing with the 4250HD.

Unfortunately I'm using Linux so I needed an alternative. I knew the 3250HD would probably work as I had tried it under Windows previously and while the quality of the video was awful the connection was definitely there. So I disconnected both boxes and swapped them around and connected the 3250HD to the HTPC. When I fired up firewire_tester this time I still did not get a connection, however after moving the firewire cable to the second port on the 3250HD it made a connection right away. Next I configured the various sources in the MythTV backend setup and subscribed to schedule listings at SchedulesDirect. I was quite excited to see that it all worked the first time out of the gate with the exception of a couple of minor glitches.

The first issue is that MythTV would not change the channel on the SA3250HD box. After googling around I found that Mythbuntu includes a small program called SA3250HD that you can compile and setup with MythTV to handle the channel changing. Compiling it was quite trivial, I did it using the following commands:

sudo apt-get install libraw1394-dev libavc1394-dev
gunzip sa3250ch.c.gz
cc -o sa3250ch sa3250ch.c -lrom1394 -lavc1394 -lraw1394

I then copied the resulting binary to /usr/local/bin and configured MythTV to use it. After a quick test it was working like a charm. The second glitch was that whenever I went to the guide in MythTV with the live TV preview my CPU utilization would shoot up to 100% making the guide unuseable. Using the top command I was able to see that the xorg process was chewing up the CPU for some reason. I am using the NVidia drivers for the 8500GT card in the HTPC so using the default drivers was not the issue. After more googling I found the NVidia X configuration options here and saw there was an option called RenderAccel listed as experimental.

I modified my /etc/X11/xorg.conf to include this option and restarted X with the Ctrl-Alt-Backspace combo. Once X restarted I fired up MythTV and went into the guide again and sure enough CPU utilization dropped to a more sedate 20%.

Updated: I didn't have much time to play with the setup once I got it going so I will post some screen grabs and results of using the Rogers box this way during the weekend.

So now that MythTV is working with the cable box I need to setup the analog cable and ATSC tuners next. The ATSC tuner using OTA should be an interesting experience because my house is on the side of a hill towards the lower end of the hill, I suspect my line of site to Toronto and Buffalo is pretty impaired as I give up 20 to 30 feet of elevation with the hill. Anyways I'll have more on that next week.

Posted by Gerald Nunn at 12:39 PM | Categories: Home Theater | Permalink