[mythtv-users] mythmusic iec958 help

Nick Rout nick.rout at gmail.com
Wed Jul 2 02:58:04 UTC 2008


On Wed, Jul 2, 2008 at 2:41 AM, Joe Henley <joehenley at kc.rr.com> wrote:
> Gregg,
>
> I assume (from the alsa file names) you're running Fedora Core 8.  If
> that's correct, then the first couple of "Info" boxes on the wiki you
> reference are saying to NOT use a modified .asoundrc file.  So go back
> to the original from the FC8 distribution.
>
> Also, are you using PukeAudio?  If so, gert rid of it.  It's still too
> "bleeding edge" to use.  (There are _lots_ of notes around about how to
> do that.)
>
>  From your note, it sounds like you want to take the CDRom info, output
> it thru the SPDIF connector to a separate amp/receiver/home theater
> receiver/etc.  If that's correct, then you want alsa plus the sound card
>  to do nothing to the signal; only stuff it into the SPDIF connector.
> You want your receiver to decode and then push it to the speakers.
>
> Most receivers these days, if they can handle (digital) SPDIF at all,
> can figure out the underlying sample frequency (44.1KHz or 48 KHz), and
> decode it correctly.  The problem often comes when the sound card gets
> in the middle and insists on re-coding the CDRom (native) signal as
> being 48 KHz.  The result is that the sound is then shifted upward in
> frequency about 10% when the receiver decodes it.
>
> Now the bad news.  IIRC, most soundblaster cards cannot output a 44.1KHz
> signal.  So they code everything as 48KHz.  I don't like Creative stuff
> so I'm not familiar with the specifics of their cards these days.  You
> should be able to google "Soundblaster Live 5.1" and "bit perfect audio"
> and get some useful info on your card's output capabilities.  I fear you
> may be in the market soon for a replacement card.
>
> I had a similar problem awhile back and ended up getting a Turtle Beach
> Riviera card.  It was 20 or 30 bucks and "just works" in Linux.
>
> Once you go back to the original .asoundrc file, get rid of PukeAudio,
> get a soundcard which can output a proper 44.1KHz signal on the SPDIF
> connector (or hopefully find a setting on SB Live card if possible),
> then your MythTV settings above should be OK.
>
> Good luck and come back here if you have questions.
>
> Joe Henley

Nice post Joe, I think I have been confusing the abilities of my sound
card and the abilities of my surround sound system.

Thanks.


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