[mythtv] mpg2 corruption

[Ken Mandelberg]

I run a recent version of the trunk against an HDHomerun. I find that 
many of the mpg2 captured recordings have bad audio and video dropouts 
and artifacts for extended periods. In fact this is bad enough that when 
the frontend hits one of these segments, it often segfaults.

I separately poll the HDHomerun every few minutes to log debug info on 
the active tuner/streams, and the log shows nothing abnormal when I 
correlate it with the bad captures.

The backend log (at least at default debug settings) shows nothing 
corresponding the to the bad captures.

Linux messages/dmesg shows nothing.

THe HDHomerun is capturing clear QAM off cable. I also record on the 
Comcast DVR which doesn't show any of this problem on the same recordings.

I see the same corruption playing back the myth files in 
vlc/xine/mpalyer, so it is not the frontend.

I've had this problem for some time, and precedes the recent ffmpeg sync 
in the trunk.

Any suggestions on how to debug this?