[mythtv] LAME quality fallback

[Matthew Middleton]

In two recordings out of over 100, the lame quality has seemed to fall 
back to an insanely low level in frame #64, and stay that way for the 
duration of the recording.  The frame size stays locked at its constant 
size of compression ratio 1:11.  (is there any reason why this is 
hardcoded?)

A 13-second rip of the mp3 stream from one of the recordings can be 
heard here:  https://matthewmiddleton.com/badsound.mp3

No errors appear in the mythtv log, except for the (lame) "strange error 
flushing buffer" one.  I have tried to reproduce it, but I haven't been 
successful.  The latest time this behavior occurred was in mythtv 0.19 
(the svn version corresponding to it) with lame 3.96.1.  (the previous 
time was in pre-0.19 development code)  I have tried purposefully 
straining my backend's resources (Sempron 2800+, x86_64, 512MB ram), but 
none of this has resulted in such fallback.  Both cases occurred in a 
recording profile set to a Lame quality setting of 6.

I've been going through Lame's code to try to find a case where the 
quality would drop off like this, but I haven't yet found such a case.  
Is anyone aware of such behavior, or how to fix it?

-Matthew Middleton