You almost never want to use a gr_throttle block. It was primarily
created to test some GUI code.
Ah. I use it with a GUI to take samples I've captured off air to feed them at the same rate the USRP would (post-decimation). The idea is the user gets to save their 'recordings' which they can then 'replay' as though they were live. Its been quite useful to do that.
I suspect that if you remove the gr_throttle that the code will work
fine. In the case of the USRP, you've got the "two clock problem".
That is, there are two clocks in the system (usrp and audio) and they
are not synchronized and are running at different rates.
I could see how that would lead to occasional aU reports but not the constant stream I currently have. I shall test with the USRP and see if I can remove the throttle (although I suspect it could make things a little rapid).
If you are using portaudio, you might try specifying False for the
third parameter to the audio_source constructor. (I'm not sure what
kind of shape the portaudio source/sink is in.)
Portaudio?! Thankfully not.