[Discuss-gnuradio] "Frame Rate" in log_power_fft (and other blocks)

[John Ackermann N8UR]

I am trying to figure out the "frame rate" as used in log_power_fft and 
"update period" used in the QT GUI sinks.

I'm trying to generate one output from both QT waterfall and 
log_power_fft every 60 seconds.  I've tried setting the "frame rate" in 
log_power_fft to both 60 and the reciprocal 0.016.  In each case the 
actual output seems to be upon completion of each FFT (here, about 25 
seconds).  I've tried with the QT waterfall as well, but it's hard to 
see and time each update there.

How are the "frame rate" and "update period" defined?  The block 
documentation doesn't describe either, and a google search doesn't turn 
up any on-point references.

Thanks,
John