[mythtv-users] Odd audio issue (bt878 tuner, SB audigy2zs, FC7)

Bryan Thorne bthorne at vt.edu
Fri Nov 9 15:15:32 UTC 2007

When forced to switch Mythtv to schedules direct, I took the opportunity 
to upgrade my stable FC4 mythtv system to FC7 and the newest version of 
MythTV.  Since then, I have encountered this rather odd audio issue.  
When watching live tv or recording using MythTV, I get no audio from my 
tuner card unless Xawtv is also running in the background.  If I start 
mythtv and select watch live tv, for example, I get no audio.  If I then 
open a terminal and start xawtv, a few seconds later I get audio in sync 
with Mythtv's video stream.  If I close xawtv, the audio disappears 
after a short delay.  Running xawtv alone without mythtv produces no 
audio, as I have the analog mix muted and capture from analog mix 
selected.  Aplay /dev/dsp produces the expected output (audio slightly 
delayed from xawtv window, some underrun's).  I have dealt with this for 
the past few weeks by keeping xawtv running in the background on another 
workspace, enabling mythtv to record properly, but I would like to avoid 
doing this.  Settings in alsamixer do not change on starting xawtv, and 
a comparison of loaded modules from lsmod shows no differences between 
mythtv running alone and mythtv running after starting xawtv.  My best 
guess is that xawtv is initializing something in the tv tuner card that 
mythtv is not, but I have no idea what that would be or how to get 
mythtv to do it.  Any help would be appreciated, as I'm a bit confused.  
System configuration is below.  I can send any requested outputs this 
afternoon on my return home from work.

Thanks for your assistance,

Hardware config:
Sound card:  sound blaster audigy 2 zs
Tuner card: Kworld KW-tv878fm
Video card: ATI Radeon x1600 pro (currently using vesa drivers for xorg, 
but that's another story)
Processors: 2 AMD athlon mp2400+, tyan tiger motherboard
Fedora Core 7
Mythtv 0.20.2

modprobe.conf lines to initialize bt878 drivers (these were working 
before my reinstall)
alias char-major-89 i2c-dev
options i2c-algo-bit bit_test=1
alias char-major-81 videodev
alias char-major-81-0 bttv
alias char-major-81-1 tvaudio
options bttv card=78 radio=1 pll=1 tuner=2

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