[Discuss-gnuradio] Underruns using the simplest gnuradio-companion flow graph

[Olof Tangrot]

Hi.
I have tried the simplest possible flow-graph. A sine-source->Throttle->Audio-sink. But I get about 1 Hz drop outs and the message pane keeps writing aU.
Using top the  process seems to laod the system less than 2 % and the total load on both processor kernels is well below 20 %. The samling rate is 48k. It does not seem to
be possible to lover the sampling rate due to limitations of my sound card (which probably sucks anyway). I am using Fedora 16 on an AMD 64-bit machine.

So is this really a processor capacity issue. I have sort of hard to believe that the the processor wont be able to compute 48000 sines per second and feed it to the sound card but there are of course a lot of layers in between. Any way rtl_fm seem to be able to feed data to aplay from a RTL2832U DVB-T recieiver without any problems so my machine is not totally slow. 

Isn't there anything I can do to improve the real-time performance of gnuradio-companion? 

Some kind of buffer to add to the flow-graph or something that is possible to tune in the operating system?

Regards 

Olof