[mythtv-users] 0.24 upgrade, audio buffer underruns

[James Orr]

On Mon, Jan 23, 2012 at 4:30 PM, Jean-Yves Avenard <jyavenard at gmail.com>wrote:

> Hi
>
> On 24 January 2012 04:36, James Orr <james.orr7 at gmail.com> wrote:
> > I just upgraded from 0.23 fixes to 0.24.1.  If I have my audio set to
> 5.1 I
> > get buffer underruns, setting it to stereo the audio is ok.
> >
> > This was not happening in 0.23.
> >
> > Here's the output from the frontend log, any ideas?
> >
> > 2012-01-23 12:25:34.921 AFD: Opened codec 0x90fc720, id(MPEG2VIDEO)
> > type(Video)
> > 2012-01-23 12:25:34.921 AFD: codec AC3 has 6 channels
> > 2012-01-23 12:25:34.922 AFD: Opened codec 0x9103520, id(AC3) type(Audio)
> > 2012-01-23 12:25:35.039 AO: Opening audio device
> 'iec958:CARD=SI7012,DEV=0'
> > ch 6(6) sr 48000 sf signed 16 bit reenc 1
>
> something is not right here...
>
> it is trying to open the iec958 device in 6 channels mode, when a
> iec958 is 2 maximum.
>
> As there's no error when trying to open it, the issue is most likely
> in the ALSA driver reporting this device has having 6 channels...
>
> How did you select this audio device?
>
> Go into the Settings -> General -> Audio Settings, and press the Scan
> Audio Device button.
> Browse the list generated. What does it say in the comment text when
> you select iec958:CARD=SI7012,DEV=0
>

In 0.23 it said something like ALSA:spdif.

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?

>
> To get around this ALSA issue, go into A
>
> > 2012-01-23 12:25:35.047 ALSA, Error: Unable to sufficiently increase
> ALSA
> > hardware buffer size - underruns are likely
>
> Well, the log does tell you you're going to get uderruns !
>
> My guess is that this audio cards has only 64kB of hardware buffer,
> and it's already set to 64kB
>

/proc/asound/card0/pcm0p/sub0/prealloc is set to 128
prealloc_max is also 128


> run mythfrontend with -v audio
>
> re-run the settings, scan the audio devices, select iec958, then try
> to play some audio and post the whole log here.
>
> If you have selected that audio device through the generated audio
> device list, and it is indeed configuring iec958 as a 6 channels, then
> go into the Advanced Settings page, and check "StereoPCM"
>
> This should fix all your issues..
> Then raise a bug with ALSA, that the iec958 port on the SI7012 audio
> card let you open it in 6 channels mode when it shouldn't.
>

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.

Thanks for the help!
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