[Discuss-gnuradio] How to capture fixed length burst of samples (to avoid overflow)

[Rickard Radio]

Hi list,

Two questions:
a)  I would like to know the easiest way (of low complexity) to capture a 
certain length/number of samples (or time period), preferably in gnuradio, and 
then automagically turn off the uhd-reception (and save received samples to 
disk) ?! 

b)  Are there any other (kernel, uhd, gnuradio) buffers and settings than 
"net.core.wmem_max" and "net.core.rmem_max"  (set with "sysctl" command in 
Linux) which affect transmit and receive buffering for uhd/gnuradio ? 

Background: I am capturing bursts of samples at very high sampling rate (like 
25 MSPS @ 16 bit I&Q, or 50 MSPS @ 8 bit I&Q) and save them to disk for further 
offline processing. But for now I have to manually cancel the application 
(CTRL-C) after a few seconds to avoid overflow since writing to a normal HDD 
does not keep up for saving in continuos real time (which anyway quickly 
creates too large files). Also, I have tried to maximize receive (and transmit) 
buffering (through mentioned buffers) in order to capture (and buffer) as long 
sequences as possible in RAM before saving them to disk and get the inevitable 
overflows (resulting in loss of received samples). However, to avoid overflow 
without manual interception I would like to capture just as much as the 
RAM-buffers can hold (or less) and then automatically turn off the reception so 
that the burst of samples can be saved to disk without any overflows and loss 
of samples.  Feels like it should be an easy way to accomplish this but how ?!  
 FYI: Hardware is USRP N210.

Any help appreciated!

/ Rickard