[mythtv-users] ALSA: Cannot mute Capture

[Randy.Tidd at charter.net]

HI,

I hope you can help.  I'm trying to setup the mixer as described in the
documentation:

http://www.mythtv.org/docs/mythtv-HOWTO-7.html#ss7.2

$ amixer set Master,0 100%,100% unmute
$ amixer set Line,0 75%,75% mute captur
$ amixer set Capture,0 100%,100% mute captur
$ su
# alsactl store
# exit
$

I'm having trouble with the 3rd command.  amixer set Capture,0 100%,100%
mute captur

Capture will not mute.  It does not seem to have this property.  Before
running this command:

$amixer get Capture,0

Simple mixer control 'Capture',0
  Capabilities: cvolume cswitch cswitch-joined
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 15
  Front Left: Capture 5 [33%] [off]
  Front Right: Capture 5 [33%] [off]


Then:

$amixer set Capture,0 100%,100% mute captur
$amixer get Capture,0

Simple mixer control 'Capture',0
  Capabilities: cvolume cswitch cswitch-joined
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 15
  Front Left: Capture 15 [100%] [on]
  Front Right: Capture 15 [100%] [on]

The off value to the right of "Front Left:" and "Front Right:" change to on
because of the 'captur' part of the command issued.  There does not seem to
be a corresponding value for mute.  Similarly checking alsamixer, I find the
Capture control, but when I highlight it and press the m key the control
does not get the typical 'mm' above the volume levels that other mutable
controls do.

I believe this is the cause of the two streams of audio I hear when watching
live tv.  I hear both the "live" audio and the delayed audio that is in sync
with the delayed video Myth generates.  If I disable "capture" from the
Capture control, suddenly both audio streams are lost.  If I then unmute the
CD control(the TV tuner is connected to the CD input of the soundcard) I
then hear the "live" audio which is out of sync with the delayed video as
expected.  

Similarly xawtv has the same problem.  Despite the CD control being muted, I
hear live audio.  If I disable "capture" on the Capture control, this live
audio stops.  If I then unmute the CD control, I can again hear live audio
as I would expect.

If I'm crazy and there is another cause of this symptom please feel free to
point that out. :)

I realize this is more of an alsa problem, but hoping someone has run into
the same thing here and can help me out.  This is a gentoo system running
the 2.6.9-r1 kernel with a Soundblaster Live! using the emu10k1 alsa driver.

Thanks for any insight you can provide.

-Randy