I recently ran into an interesting problem with my MythTV audio. When I played back a program, it would play back with varying degrees of echo in the audio. Usually the echo would be around 100 ms behind, but if I skipped forward or back I could get it up to 3 seconds behind. This problem did not happen outside of MythTV.
First I started with alsa-mixer. There I determined that there was no level I could change to affect the echo. Changing the level always changed both the first audio and the echo.
Next I tried reinstalling the AC97 sound driver, because I saw a website that noted when the driver was corrupt you could get an echo. No dice.
Finally, I happened to be running top, and I saw this:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4273 myth 20 0 220m 85m 3588 S 12 8.5 11:55.43 mythfrontend.re
4257 myth 20 0 245m 85m 3700 S 12 8.5 10:20.79 mythfrontend.re
I had two copies of mythfrontend.real running! Both were getting the lirc keypresses and acting on them. This meant everything (including the player) was being run twice… hence an echo slightly behind the main audio.
Somehow the Gnome session state had been saved with a mythfrontend.real running, and when it was restored it would restore with that mythfrontend.real as well as start a new one. I made sure the session state wasn’t being saved (under Settings), killed all the running mythfrontend.real instances, and then logged out saving the session. Next I logged in and out but unchecked the button to save session on logout. That seems to have done the trick.