[mythtv-users] Audio - PCM, Master

[R]

From:	"Brian Wood" <beww at beww.org>
Date:	Fri, 3 Mar 2006 18:13:09 -0700
To:	"Discussion about mythtv" <mythtv-users at mythtv.org>
Subject:	Re: [mythtv-users] Audio - PCM, Master

On Mar 3, 2006, at 6:01 PM, R wrote:

> In MthTV we have:
> MythTV->Main->Utilities->Setup->General->Audio->Mixer Controls->
> PCM or Master
>
> In Fedora Core 4 we have:
> KMenu->Sound & Video-KMix->Current Mixer->Input->PCM
>
> Pardon my ignorance.
>
> What is PCM?
> What is the difference between PCM and Master?
>
> Given that my MythTV box:
> 1.  Runs both frontend and backend.
> 2.  Has 1 TV Tuner card.
> 3.  Has 1 sound card.
>
> When should I use PCM?
> When should I use Master?


Your system has a sound mixer. "Master" controls the output of the
(virtual) mix bus. "PCM" is an input to that mixer, controlling it
controls only the level of that input going to the mix bus.

Both will control the ultimate output level, and if the PCM input is
the only one you are using (common for a MythTV system) then it
really doesn't matter which one you use, although you probably don't
want to run either one too high if you can avoid it.

_________________________________________________________________


Date:	 Fri, 03 Mar 2006 22:32:52 -0500
From:	"Michael T. Dean" <mtdean at thirdcontact.com>
To:	"Discussion about mythtv" <mythtv-users at mythtv.org>
Subject:	Re: [mythtv-users] Audio - PCM, Master

On 03/03/2006 08:01 PM, R wrote:
> In MthTV we have:
> MythTV->Main->Utilities->Setup->General->Audio->Mixer Controls-> PCM
or Master
>
> In Fedora Core 4 we have:
> KMenu->Sound & Video-KMix->Current Mixer->Input->PCM
>
> Pardon my ignorance.
>
> What is PCM?
>

In short, it's similar to what Windows calls "Wave" (or "Wav"?).
Technically, it's Pulse-Code Modulation

> What is the difference between PCM and Master?
>

Master typically controls the volume across multiple controls
(including
CD and PCM and ...).  However, note that on some sound cards, it does
*not* affect surround volumes (i.e. Center, Surround, LFE).

If you can't tell a difference in functionality on your system, it
doesn't matter which you use.  However, it's often nice to make sure
you
set Myth to use the same controls used by other applications (like xine
or MPlayer) otherwise, you'll end up adjusting Master in one then PCM
in
others, so where you leave one and enter another determines the maximum
volume range you have available...  (I.e. don't let apps "fight" each
other or you'll constantly be using external programs, like alsamixer,
to "reset" your volumes.)

Mike

_________________________________________________________________

Brian, Mike:
Thanks for the info.  This helps.

A couple of follow up question - below.

My current TV tuner card has:
1 coax input
1 RCA video out
1 audio out

My sound card has:
1 Microphone-in
1 Line-in
1 Line-out (Front Speakers)
1 Rear-out (Rear Speakers)

The TV tuner card audio out is hard-wired to the sound card Line-in.

If I add a 2nd TV tuner card to this box:
a.  How do I wire it to this sound card?
b.  Do I need to get a second sound card?