I finally found a few hours to sit down and debug the issue people were reporting where switching back and forth between analog and digital modes under MythTV would intermittently fail with the hvr-950q. It turns up there were a couple of race conditions related to the power management of the chip.
There was also a neat bug where the first tuning request after switching from analog mode back to digital would *always* get dropped on the floor. This would cause users to see the first tuning request fail, or there would be cases where if you had been watching analog TV and then later the backend went to record a digital program, that recording would fail.
These changes are not heavily tested yet (they do appear to fix the issues found in my environment), so I am looking for people who have seen problems to try them out and report their results in the comments.
Once I’ve gotten some feedback, I will issue a PULL request to get these fixes merged upstream.