Re: [Discuss-gnuradio] Occasional choppiness/underruns (aUaU) with FCDPP->GRC->Pulse

[Martin Braun]

On 04/08/2014 10:42 AM, Marcus Müller wrote:
> [...]
> Ok, to be completely frank here:
> It looks like your computer is not up to the task of mixing pulse
> streams while simultaneously doing signal processing and watching
> Flash movies. Or maybe this is an irregularity in pulse, or pulse
> starts to internally resample other streams from 44.1kHz to 48 or very
> many other things...
> I'd say: try using dmix, if you really need to mix your GNU Radio
> output and your system sounds.
> 
> [...]
>> I am using a Phenom II X3 running at ~2.8GHz. 4GB ram.
> 
>> Under normal circumstances the overhead of pulseaudio is very low.
>> Using a graph to reproduce the issue consumes about 10% of one core
>> using sysdefault (direct to ALSA) in the output block, and when
>> using 'pulse' in the output block, the same 10% of one core. In all
>> cases, the FCDPP is accessed directly as hw:3 because using pulse
>> and routing it doesn't work - it just gives silence and "aUaUaU".
> 
> Seems like pulse is simply just not up to the task on your PC.

Hm, I don't really think Pulse is the issue. "High rate audio streams"
don't really exist (what is 48 kHz compared to our radio stuff)?

Chuck, I know you say it's not a two-clock problem, but I'm not
convinced, despite your great problem description. It takes little
difference to cause lots of underruns. One way you can figure that out
is by resampling a bit above the audio rate (say, 48100 or 48200 Hz) and
piping that into a Pulse that expects 48000 Hz. If you get less Us
(maybe some Os), that's the problem.

Martin