[mythtv-users] mencoder oddity checking for QAM channels

[Bob]

When I scan for channels using mythtv-setup I do not always get *all* 
the unencrypted channels.  I typically use mencoder as described here:

http://www.mythtv.org/wiki/Adding_QAM_Channels_For_HDTV_Tuner_Cards#Verifying_channel_tuning

However, I've also noticed that sometimes mencoder will not output a 
file while the backend is perfectly capable of recording from that channel.

I tried the test_dvr mentioned in the wiki with the same luck.  Any 
other suggestions?