[mythtv-users] 0.24 upgrade, audio buffer underruns

James Orr james.orr7 at gmail.com
Tue Jan 24 02:16:26 UTC 2012


On Mon, Jan 23, 2012 at 6:21 PM, Jean-Yves Avenard <jyavenard at gmail.com>wrote:

> Hi
>
> On 24 January 2012 08:48, James Orr <james.orr7 at gmail.com> wrote:
> >
> > After the upgrade and experiencing this problem I did do a scan audio
> device
> > and that option disappeared.  The comments for iec958 say ...
> >
> > SiS SI7012, SiS SI7012
> > IEC958 (S/PDIF) Digital Audio Output
> > Device supports up to 5.1 (digital output, AC3, DTS, multi-channels LPCM)
> >
> > This was the only item that mentioned S/PDIF, so it's the one I chose.
> >  Should I pick something else?
>
> If you are connected via digital coax or optical, then yes, this is
> the device to use.
>
> That it reports multi-channels LPCM indicates a bug in ALSA, myth goes
> by what ALSA allows: and multi-channels LPCM should never be there
> with iec958 device
>

Interesting.  I'm connected with HDMI using the S/PDIF pass through from
the onboard sound.


>
> > /proc/asound/card0/pcm0p/sub0/prealloc is set to 128
> > prealloc_max is also 128
>
> ok.. that's good
> > StereoPCM resulted in no sound at all, but I seem to have it working now.
> >
> > I changed my device to ALSA:default:CARD=SI7012 and everything seems to
> be
> > working now.  I guess I did pick the wrong one.  Thrown off by it not
> > mentioning S/PDIF I guess.
>
> You should be using ALSA:iec958 ; with StereoPCM checked to prevent
> the issue of ALSA reporting incorrectly 6 channels PCM.
>
> With ALSA:default, it's likely you will not get digital audio working
> properly.
>

My sound system does report Dolby Digital with all 5 speakers lit up.  On a
stereo recording (upscaling disabled) it stays on Dolby PL with two
speakers lit up.

I'd be interested in reading the logs when you select the iec958 one,
> with stereoPCM checked.


It's getting into TV viewing time now, so I'll mess around with it again
tomorrow and get those logs to you then.
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