Fully high definition

I’m happy to report that, other than a fun weekend with the family, I do have one success story to report: I’ve successfully switched all of our televisions to ATSC-only reception. For the analog Sony that of course is the Channel Master CM-7000 converter box. For our den big-screen TV, that is the built-in tuner. For our MythTV box, that is a new Avermedia MCE A180 HDTV tuner card.

The main thing that happened this weekend was wiring up our broadcast antenna in the attic. I’d initially pointed the antenna to the tower cluster in Auburn, NC where most of Raleigh’s TV stations transmit. This left the channel we watch the most, PBS on Chapel Hill’s WUNC, weak and fading. Then I realized that being in downtown Raleigh, we’re already well-covered by the Auburn antennas. Thus, I could point the antenna to WUNC’s tower (31 miles away) and get a good signal from all the stations.

Our Myth box, on the other hand, has been a bit ornery as far as this goes. The AverMedia card works fine with the latest Mythbuntu kernel but the same kernel breaks the drivers for our existing analog capture card. Since I wanted to make a clean break from analog, I figured it was an easy sacrifice. However, while the A180’s drivers load, the output is blocky and pixellated. And slow: a few frames trickle out at a time. The load on my Myth backend rises considerably as well.

I’m confused as to why this is as I thought the card would simply dump the received ATSC MPEG stream to disk rather than process it. This apparently isn’t the case, even with SD channels. And the box’s load average doesn’t indicate any I/O waits, so the bottleneck doesn’t seem to be disk.

The analog AverMedia PVR-150 card has a built-in MPEG encoder and has been working fine in this admittedly-ancient 1GHz system, but not the new card which supposedly has less to do. Since both cards are spitting out MPEG frames (one received and one created), I am puzzled as to why the digital card is not keeping up. In the meantime, I am turning my attention to getting the PVR-150 card working with the new kernel so that I’m at least back where I started.