ALC662 audio card causes underruns and overruns

Hi,

I have a flow graph that receives, demodulates and filters a signal
before
sending it to the audio card. It’s been working in a single board,
single
core, computer with an audio card ALC888 for months. I occasionally had
underrun messages, specially when changing filter parameters. This
messages
were normally less than 10 and very spread, about every 30 seconds. It
didn’t cause any noticeable noise or problems.

Recently I moved to a better computer with better CPU, 4 cores and a
ALC662
audio card. The Python script works fine, with no visible bottlenecks in
the processor. However, I now get constant overruns and underruns
reported,
making the audio noisy.
The audio card is able to work correctly when using the speaker-test
command so, there isn’t a fault in the hardware. It’s also capable of
running at the required sample rate.

Is there any test I could make to understand and fix this issue? Has
anyone
had a bad experience using this audio card with GnuRadio?

Thanks,
Murray

Make sure you’re using ‘plughw:’ for the audio device so the driver does
resampling (check ALSA docs). Without looking at the flowgraph, I’d
guess this is a clock domain problem and your new computer (and audio
card) clocks are somehow different than your old ones.

Also make sure that the ALC662 also supports the audio sampling rate
you’re using – 44100 is the only rate I’ve been able to use on any
platform [1].

Best regards,
Marcus

[1] http://gnuradio.org/redmine/projects/gnuradio/wiki/ALSAPulseAudio

Thank you for your suggestions.
The card supports 96 KHz and I’m using hw. I’ll try to use plughw.
I’ve solved this problem upgrading to the latest kernel in 12.04 which
is
3.13.0-62.

Regards,
Murray

Wow, 12.04 (though still supported by GNU Radio!) feels ancient. Any
particular reason you stick with that?

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