[mythtv] errors, sound drops in dvb recordings

[Johnny Graettinger]

I've got a pvr-250 and pchdtv-3000 configured for dvb & qam stations.
Outside of myth, these cards work flawlessly--I've captured hours of
HD several times over via azap without problem. Within myth, the
pvr-250 is fine.

The hdtv-3000 however exhibits a large number of errors in the stream.
Further, on a couple of stations about 2-3 minutes into a capture,
playback freezes (both watching recorded and live tv). Restarting
playback and skipping over the freezing point enables watching the
rest of the recording, however the audio is no longer present. To be
clear, by freezing I mean that the backend stops providing data; I see
messages like "10 seconds without data from backend" printed by the
frontend.

Here's the really strange part: It used to be a lot worse. The streams
would initially capture just fine, but errors would increase until the
stream was unwatchable. I thought this might be a heat issue, and even
went as far as to replace the card, to no effect. However, what did
improve the situation to it's current status was disabling commercial
flagging processes.

This caught me by suprise, and I supposed from it that it could be a
process starvation issue. I wrote a simple infinite loop test program
and tried to reproduce the results outside of myth (via azap) by
renicing the test program, but capture showed no ill effects. Further,
the backend is a capable machine (1.7 p4), and only runs mythbackend.

I'm running a recent subversion build, and do not mind digging through
the source, but need more direction before I do.

Some relevant questions which might help are:

What are the differences between how mythtv tunes/captures from the
hd-3000 and how azap -r ..., cat /dev/dvb/.../dvr0 does?

Are there any likely buffer overflow situations which could cause bits
from the stream to be dropped when saving to the recording? Could
these be related to/triggered by mythcommercialflag?

And of course, anybody else experienced problems like this ? ; )

thanks a ton
Johnny