[mythtv] readAdjust -> UI unresponsiveness.

[Daniel Kristjansson]

I was trying to reproduce #942 I ran into a problem with readAdjust.
It appears it is set correctly after the first ringbuffer switch, but
then goes further and further out of sync after each ringbuffer switch.

After the ringbuffer is given a new file the TV class ignores
keypress eventshile the pkt->pos pointer in avformatdecoder is
less than readAdjust. So after several ringbuffer switches the
UI becomes permanently unresponsive as the readAdjust pointer
grows much faster than the pkt->pos pointer...

I'm going to sleep soon, but thought someone in a different
timezone might want to look at this.

Also attached is my dbg942.patch, it adds a lot of debugging
statements, and fixes a bug with the ringbuffer switching
debugging code in TVRec. The old debug code itself breaks sometimes
when dealing with seamless ringbuffer switches; it does back to
back switches when curRecording isn't initialized in time, this
gives us a zero length recording, which the frontend rightfully
balks at (by exiting gracefully :).

The frontend log attached also shows me successfully reproducing
#942, but I still need to add more debugging to figure out what
is going on there; it seems to only occur with my PVR-350 and not
very often, but it is reproducible.

-- Daniel

NOTE: I had to remove the front end log due to size constraints
basically:

2006-02-04 19:10:46.876 SwitchToProgram(void) -- end normal
2006-02-04 19:10:46.877 pkt->pos: 3494544 readAdjust: 3668068
2006-02-04 19:11:30.711 SwitchToProgram(void) -- end normal
2006-02-04 19:11:30.713 pkt->pos: 8290612 readAdjust: 8693120
2006-02-04 19:11:48.561 SwitchToProgram(void) -- end normal
2006-02-04 19:11:48.562 pkt->pos: 11471384 readAdjust: 11894384
2006-02-04 19:12:28.729 SwitchToProgram(void) -- end normal
2006-02-04 19:12:28.730 pkt->pos: 18784772 readAdjust: 38642344
2006-02-04 19:12:48.520 SwitchToProgram(void) -- end normal
2006-02-04 19:12:48.522 pkt->pos: 22922912 readAdjust: 61979420
2006-02-04 19:13:07.902 SwitchToProgram(void) -- end normal
2006-02-04 19:13:07.903 pkt->pos: 26811880 readAdjust: 89201328

As you can see the first few are ok, and then all of a sudden
readAdjust is way off and getting worse with each switch.

-- Daniel
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