[mythtv-users] Dual tuners - how does the sound work?

[Joe Votour]

It depends on the capture card that is being used.

The PVR-x50/AverMedia M179, and other cards supported
by the ivtv driver do not require a seperate cable for
audio because the the sound is captured as part of the
MPEG-2 stream.

However, cards controlled by the bttv driver (which
are essentially frame grabbers) require some sort of
sound capture.  Some cards work with btaudio, which
generates a sound device (/dev/dspx, where x is a
number) that MythTV can read from for the sound.

Cards that don't support btaudio require a connection
to a sound card, so for every bttv card you have that
does not support btaudio, you require a sound card,
with a cable connecting the capture card to the sound
card (on the Line-In port).

It is possible to have multiple sound cards in a PC,
as long as you have enough PCI slots for them.  This
tends to be a problem for people with bttv cards,
since you wind up with two problems - bttv cards
require a lot more CPU than a PVR-x50 card, and you'll
run out of PCI slots quickly.

-- Joe

--- Robin Smith <1canuck2 at gmail.com> wrote:

> I have no cable from my tuner card to my soundcard.
> The tuner card
> "captures" the audio along with the video. The
> soundcard is only for
> playback.
> 
> 
> On Thu, 13 Jan 2005 14:15:52 +1100, Phill Edwards
> <philledwards at gmail.com> wrote:
> > I currently have a bt878 chip tuner card and I
> want to buy a 2nd one
> > but I don't understand how the sound recording can
> possibly work on
> > this setup. From what I understand at the moment,
> the sound gets
> > recorded by connecting a lead from the sound out
> from the tuner card
> > to the line in of the sound card (which in my case
> is  on-board). If
> > that lead is not connected in this way then I'll
> get a video recording
> > with no sound. Am I right so far?
> > 
> > So, when I put a 2nd tuner card in how do I
> connect the sound out to
> > the line in of the sound card when it's already
> been taken up by the
> > 1st tuner card? Is this when you need btaudio? I
> believe not all tuner
> > cards support btaudio. How can I determine which
> do and which don't -
> > from what I've seen it seems to just be some
> Hauppauges and WinTV
> > Radio?
> > 
> > Are my options as follows:
> > 
> > 1) Buy a sound card when I buy a tuner card, OR
> > 2) Buy a tuner card that supports btaudio (very
> limited choice and
> > expensive, I believe)
> > 
> > Lastly, my mobo has a S/PDIF connector which I
> currently have no idea
> > how to use but I do want to get Dolby digital
> working in the future
> > for DVD playback. Does this have any bearing on
> what sort of sound
> > card I should buy if I go for option 2?
> > 
> > Regards,
> > Phill
> > 
> > 
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> >
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> > 
> > 
> >
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