[mythtv-users] RE: Re: ALSA: Cannot mute Capture

[Randy.Tidd at charter.net]

> Date: Wed, 03 Nov 2004 12:16:07 -0800
> From: Bruce Markey <bjm at lvcm.com>
> Subject: Re: [mythtv-users] ALSA: Cannot mute Capture
> To: Discussion about mythtv <mythtv-users at mythtv.org>
> Message-ID: <41893C87.50703 at lvcm.com>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> Randy.Tidd at charter.net wrote:
> > 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:
> 
> "Capture" should not be allowed to mute and even if it was, it
> should be unmuted. I've always wondered about this. This has been
> there for a long time but it appears to be inert.
> 
> > 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.
> 
> Check what happens when you press Pause. The realtime analog
> passthrough may continue while the playback of the recorded
> date would stop.
> 
> >   If I disable "capture" from the
> > Capture control, suddenly both audio streams are lost.
> 
> That's clearly not what should happen...
> 
> >   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.
> 
> This is what should happen. For yucks, can you try connecting it
> to AUX rather than CD? Or use the external patch cord to connect
> to Line? Possibly there is a card/driver quirk with the CD input.
> 
> > 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.
> 
> Again, not the correct behavior.
> 
> > 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.
> 
> Never heard of it. Agreed that this is an alsa problem so you
> should probaly do some digging at their site and Google. FWIW
> I have an "Creative Labs SB Live! 5.1 Model SB0100" and have used
> emu10k1 for every version of alsa 1.0.x and never saw this problem.
> 
> --  bjm
> 
> -------------- next part --------------
> Index: docs/mythtv-HOWTO.sgml
> ===================================================================
> RCS file: /var/lib/mythcvs/mythtv/docs/mythtv-HOWTO.sgml,v
> retrieving revision 1.246
> diff -u -r1.246 mythtv-HOWTO.sgml
> --- docs/mythtv-HOWTO.sgml	19 Oct 2004 06:37:28 -0000	1.246
> +++ docs/mythtv-HOWTO.sgml	3 Nov 2004 19:50:16 -0000
> @@ -1867,7 +1867,7 @@
>  <tscreen><verb>
>  $ amixer set Master,0 100%,100% unmute
>  $ amixer set Line,0 75%,75% mute captur
> -$ amixer set Capture,0 100%,100% mute captur
> +$ amixer set Capture,0 100%,100% captur
>  $ su
>  # alsactl store
>  # exit
> 
> ------------------------------
> 

Bruce, thanks for your reply.  I appreciate the effort.

I thought I'd post what seemed to fix the problem for me in case anyone else
as the same trouble.

At:  http://alsa.opensrc.org/index.php?page=emu10k1

I found a comment from "Jared 20020910" describing his experience setting up
capture from a line in.  He stated he set the AC97 volume to zero, but
wasn't sure if this fixed anything.  Well it seems to solve the problem for
me.  

Setting AC97 volume to 0 in the mixer rid me of the problem above.  Turning
the volume back up recreates the problem.  Not sure why this fixed it, but
sound now works as expected.

Thanks,

-Randy