After three nights of debugging various issues, I now have the analog side of the HVR-950Q working properly with MythTV.
Special thanks go out to Janne Grunau for promptly merging my patch providing UYVY support to MythTV:
I will be setting up a tree this weekend with the 950q fixes. In the end, we had a power management bug in the au8522, the MythTV issue described above, and the saturation/hue controls not being implemented causing spurious errors in the mythbackend log. There is also a popping in the audio that occurs when changing channels (because I’m not controlling the au8522’s softmute properly), but that is a minor issue and I will take care of it.
Thanks go out to both Zaphod Beeblebrox and Nate Goergen for providing logs/traces as well to them and everybody else for their patience in waiting for me to finally get an environment setup to debug the problem.