[mythtv-users] sound buffers

Nick knowledgejunkie at gmail.com
Mon Jun 27 23:53:31 UTC 2005

On 6/28/05, Nick Rout <nick at rout.co.nz> wrote:
> I am having stutter problems with livetv.
> Hardware: epia m9000, pvr-150, inbuilt sound card with alsa enabled
> through the kernel, kernel is 2.6.11
> Symptoms: every few seconds the tv freezes momentarily, there are a few
> bluish artifacts on the screen, sound also freezes.
> Investigations: Cannot give the exact error message at the moment as the system is at home and I am at work. However when I run mythfrontend -v
> all (so as to get full diagnostics) I get lots of audio buffer error
> messages.
> Crawling through the list archives, along with the reference to audio in
> the verbose output, leads me to believe this is an audio issue. However
> i am not sure where to go from here. Options seem to be:
> *use alsa instead of the oss/alsa emulation - but I have seen list posts
> that claim the alsa support in myth is crap and to be avoided

Not true.

> *find some way of giving the sound driver (or the oss emulation layer)
> more buffering space - how would I do this?

Options in frontend setup.

> *try the independent alsa drivers instead of what is in the kernel

Easily doable - download the drivers, lib and utils archives from

> Any suggestions would be gratefully received.

Frontend setup allows you to use aggressive soundcard buffering
(general setup) and another audio buffering setting in TV settings.

You could check whether using ALSA devices (you may have OSS emulation
running, using /dev/dsp and /dev/mixer) makaes things better.
ALSA:default and default are the typical equivalent devices to use. I
don't have any problems with ALSA at all, other than the fact that
mythmusic still uses OSS.

The one time I have had audio issues was on my Pentium M laptop (over
wireless g), when I had borked the powersave options and throttled the
CPU too low when unplugged. Setting the throttling to a more sensible
level cured all the problems. I had at the time already installed ALSA
1.0.9b, but another system using 1.0.8 is also fine.

I'd also look into running the frontend with root privileges to get
better performance and access to real-time threading, which may
improve performance.


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