A problem with H.264 video (DVB-T)

Hi!
  I have the following problem with playing H.264 (MPEG4) video from DVB-T
stream:
  When the channel is tuned, the video is played perfectly, without any
problems. However, about 30 - 60 seconds later, the video starts to skip.
At first, it stops momentarily and then skips the missing frames for about
every 2 - 3 seconds, so it is very annoying (it still plays smoothly between
the skips, every skip takes about 200 ms). The skip intervals decrease by the
time, and of course also the difference between picture contents before and
after the skip. After about a minute, it skips very often with very short
skips, so it looks as a low framerate (about 10 fps). This is the final state,
it continues to play this way until the channel is re-tuned, which resumes
smooth playing for the next 30 - 60 seconds and then it repeats the whole
process.
  The sound is played continuously, no skips, and it keeps approximately
in sync with the video.
  This is not a CPU performance problem - CPU load doesn't hit 1.00 and it
is a dualcore machine, so there is a big reserve in the CPU power.
  Using kaffeine as a frontend. Formerly used xine-lib-1.1.15 and ffmpeg svn
from the beginning of September, now tried with current hg snapshot of
xine-lib and svn snapshot of ffmpeg. Still the same. I've been also playing
extensively with various xine engine settings (quality of postprocessing,
deinterlacer type, codecs priority etc.), and it didn't influence anything,
the problem appears always in the same manner.
  There isn't any debug/error output from xine-lib/ffmpeg. 
  Any help, what to fix ?
    With regards, Pavel Troller

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