I tried Tommi Rouvali's mod to audio_fft.py with the throttle added as
suggested by Johnathan Corgan but my CPU usage still went to 100% and
the fft window locked up. This is on a MingW/Windows XP system with a
1.8GHz Pentium M with 512MB RAM.
As a further experiment, I added an audio.sink instead of the throttle
and I got the tone as well as a working FFT display and CPU usage
dropped to 13-15%.
I then tried running fftsink.py since it has throttle statements in the
standalone test app at the end and once again the window locked up with
100% CPU usage after displaying the first of the two fft screens in that
app. After some experimenting, I changed both gr.sig_source statements
to audio.source and got rid of the throttles and everything worked fine
with CPU usage around 35-50%.
It appears the throttles aren't working the way I think they are
supposed to. Any advice?