I'm have the same problem as @jimcor101, with Mythtv and HDPVR, but I'm not getting that ioctl error as @somsn. I very recently tried to upgrade a operational Mythtv setup from a PVR USB2 encoder to the HD-PVR encoder. With the HD-PVR, I'm able to successfully 'cat /dev/video1' to a file or fifo, I can change HD-PVR configuration using v4l2-ctl, and I can also confirm that mythtv-backend does, in fact, configure the HD-PVR properly (i.e. setting proper input connection), but I'm not able to capture any content using LiveTV or recording mode: mythtv simply times out.
When setting up card type via mythtv-setup, I tried both the 'HD-PVR H.264' as well as 'V4L2 encoder' card types. I also tried both the Component and Composite inputs. When trying to start live TV viewing, using either card-type settings, the HD-PVR unit does light up, indicating encoding in progress, but mythtv insists that there is no signal (Signal 0%) and times out. Upon further investigation, I did notice a problem when setting up using HD-PVR (but not with V4L2) card type: there were absolutely no Recording Profiles created (i.e. no "Default", no "Live TV", no "High Quality", etc) automatically, so I manually created at least Default and Live TV. Unfortunately, this did not help. Moreover, I'm NOW having the same 'signal loss' problem when I return to using the pvrusb2 encoder, which prior to all this was not a problem (for years), suggesting that the problem lies in MythTV or my configuration and not a OS or hardware problem.
@jimcor101, let me know if, when you setup capture card, there were any recording profiles automatically configured for you. And if not, can you check if creating the "Default" and/or "Live TV" profiles makes a difference. Maybe we can tag-team this problem. On the other hand, as a fallback, since I'm able to cat /dev/video1, I'm thinking about just setting up a local, live stream server and having MythTV record off that streaming server.
my config is:
Linux 4.8.0-58-generic #63~16.04.1-Ubuntu SMP Mon Jun 26 18:08:51 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux