Since my latest post about mythtv I set up my channels using a combination of scanning using my tv-card and a channels list that mythtv downloaded. Most of the channels are set up now.
But the audio was echoing when I watched live-tv. As I couldn’t find the solution using Google, I’ll post it here in case somebody has the same problem: My tv-card (a Pinnacle PCTV Pro) uses the analog-M input of my soundcard for the audio data. Using alsamixer I needed to mute the analog-M channel in Playback mode and mute the PCM channel in Capture mode.
Next up: recording.