After The Great TV Transition To Digital, Comcast for a while kept transmitting everything in analog NTSC, so I was able to use my Hauppauge WinTV PVR-250 for cable, and occasionally watched over-the-air ATSC with HVR-950. It was clear that this was not going to last, and recently all but few NTSC channels disappeared. On top of that, when HVR-950 didn't get a sufficiently strong signal or was otherwise confused, a combination of its hardware, driver and MythTV 0.21 ended up in some weird state that prevented all further tuning until full driver reload, so over the air reception was quite far from the painless experience that I remembered from pre-cable, pre-digital days. Upgrade to MythTV 0.22 gave me some improved HDTV output modes, but didn't do anything to reliable ATSC reception, and definitely didn't turn PVR-250 into a digital decoder -- something had to be done. My 40th birthday was an acceptable excuse to buy another device, so after some research I went to Fry's and brought home HDHomeRun -- a networked dual-tuner digital TV receiver.
Not surprisingly, installation and configuration were quite painless -- receiver got its address from DHCP, MythTV detected the receiver and its two tuners, ran a scan on both, and found a bunch of channels. Just as not-surprisingly, SchedulesDirect produced a channels list full of mis-identified channels (apparently radio stations that were recognized as TV), so the list required some tweaking before becoming usable.
The surprising part was playback. For a completely unrelated reason I have recently upgraded my NVIDIA graphics card, and the new card supports VDPAU. Before installing HDHomeRun I have spent some time tweaking MythTV to make HDTV play on a 1680x1050 monitor with my old AMD Athlon XP 3200+ and HVR-950. In the end everything up to 720x576 was set to ffmpeg decoder, Xv output, Yadif deinterlacer, denoise3d filter, everything above -- NVIDIA VDPAU, Temporal deinterlacer. Most channels played smooth, however it seemed like the time spent getting the high-resolution frames from HVR-950 was sufficient to cause some choppiness -- or maybe it only looked like that due to some dropped or corrupt data because I only tested it with over-the-air reception. With HDHomeRun this problem disappeared -- flawless playback on cable channels regardless of resolution, occasional visibly corrupt frames on some over-the-air channels, but no choppiness.
For some reason closed captions (and only closed captions, not other forms of overlays) on some resolutions cause massive slowdown and dropped frames. Low resolution (with all-software decoding and Xv output) is fine, high resolution (hardware decoding and high-resolution overlay) is fine, medium resolution (apparently higher-resolution text overlay on lower-resolution hardware-decoded video) has problems. Other than that, I have a fully-functional TV and DVR that receives cable and over-the-air TV, on a box with Athlon XP 3200+ CPU and a five years old motherboard.
Obviously, the whole thing only works with non-encrypted channels -- if by any chance Comcast will decide that they should DRM the Hell out of their network, everything will be broken again. Hopefully sanity will prevail, and the amount of breakage that it would inflict on all other existing subscribers will keep them from going into that direction. PVR-250 still receives some NTSC channels, and HVR-950 is still connected for its analog video input and may potentially be used as a backup tuner -- if I (or driver developers) will find out how to keep it from getting stuck.