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?

>From:  Johnathan Corgan 
>Subject:  Re: [Discuss-gnuradio] Scope hangs 
>Date:  Mon, 29 Oct 2007 11:20:38 -0700 
>User-agent:  Thunderbird 2.0.0.6 (X11/20071022) 
>
>-----------------------------------------------------------------------
---------
>
>Tommi Rouvali wrote:
>
>> This is probably stupid question, but I ask it anyway:
>
>Not stupid :)
>
>> Now a litle change:
>> 66c66
>> <       self.src = audio.source (sample_rate, options.audio_input)
>> ---
>>>       self.src = gr.sig_source_f (sample_rate, gr.GR_SIN_WAVE, 650,
100)
>> 
>> And again I run it with -S to get the scope view. But this time the
>> scopes user interface is hang. Buttons do not do anything, and even
when
>> trying to close window linux tells me 'Program not responding' and I
>> have to force quit this app. The sin wave is scope runs there just
fine.
>> But user interface is 'locked' and cpu usage rises.
>
>What's happening here is that the signal source block is running at
>maximum CPU speed and preventing the GUI from updating or reacting to
>user events.  This doesn't happen with the audio source block as it is
>rate limited to the sample_rate parameter.
>
>You need to insert a gr.throttle(gr.sizeof_float, sample_rate) block to
>the flowgraph right after the signal source.
>
>-- 
>Johnathan Corgan
>Corgan Enterprises LLC
>http://corganenterprises.com

Thanks,

Rob Walker 
Crane Division, Naval Surface Warfare Center (NSWC Crane) 
Harnessing the Power of Technology for the Warfighter
300 Highway 361 
Crane, IN  47522-5001 
Ph:  (812) 854-3921 (DSN 482)
Cell:  (812) 617-1217
Email:  [EMAIL PROTECTED]

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