[mythtv] Transcoder can not find codec (mythtv version 0.12)

[Florian Winterstein]

Hello there!

I am using a PVR 250 and mythtv version 0.12. If I hit 'x' in play mode 
the file does not get transcoded. 
The following messages are logged:

2003-11-08 22:03:28 Transcoding from /store3/media/mythtv/1009_20031101160000_20031101170000.nuv to /store3/media/mythtv/1009_20031101160000_20031101170000.nuv.tmp
Input #0, mpeg, from '/store3/media/mythtv/1009_20031101160000_20031101170000.nuv':
  Stream #0.0: Video: mpeg2video, 480x480, 29.97 fps, 16000 kb/s
  Stream #0.1: Audio: mp2, 48000 Hz, stereo, 384 kb/s
Unknown video codec: (null)
Unknown audio codec: (null)
strange error flushing buffer ... 

Obviously the transcoder does not know what the target format is and I don't know where I can configure which transcoding profile should be used. Any help is greatly appreciated.
Thanks in advance,
Florian