[pulseaudio-discuss] Pulseaudio-equalizer module crackling with libao

Sean Greenslade sean at seangreenslade.com
Sun May 4 15:13:08 PDT 2014

On Fri, May 02, 2014 at 01:08:49AM -0700, Jason Newton wrote:
> Hi Sean,
> I'll add libao to the list of things to investigate down the line,
> flash is another thing that can exhibit this crackling characteristic.
> It probably has to do with buffering and how often how much audio a
> client is willing to give to pulse within the period of time
> pulse/equalizer asks for the audio before the render calls starts
> filling in zeros but that is just a starting point of investigation.

Thanks for the reply. It would seem that way, given that the buffer
actually does absorb ~20 seconds of audio before blocking. It seems to
be post-EQ, but I need to double-check that.

> If the problem is indeed like flash, currently one thing you can do is
> see if changing toggling tsched helps but that's just a work around at
> best.   Another less-than-work-around is just to not use the equalizer
> for that particular client - pavucontrol lets you accomplish this.

I've tried tsched, it doesn't change anything. And yeah, I currectly
route those apps straight to the card sink manually. Less than ideal.
(My workaround for my desktop is a couple of vintage hardware
 equalizers. Nice, but not exactly a laptop-able solution. =P )

> Unfortunately I don't really have time to work on the equalizer for a
> few more months due to some project deadlines and I really can't be
> missing those :-).  I will remember to look into libao though.  If you
> want to look into the guts of the equalizer, it's fairly self
> contained in the src/modules/module-equalizer-sink.c , however I think
> to debug this interaction you may want to get familiar with the core
> libraries, and source/sinks.

I might (if I'm feeling adventurous) take a dive into the code this
summer. I also don't have much free time now, either. Thanks for the


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