Re: [Discuss-gnuradio] Which block is causing dropped samples?

[Marcus D. Leech]

On 03/17/2015 07:06 PM, Anderson, Douglas J. wrote:

Hi all,

I just finished writing a flowgraph with a few custom C++ blocks, but when I connect it to a USRP N210 at about 25MS/s it's not too hard to find a combo of parameters that will cause a sea of DDDDDDDDDDs to come flooding into the term.

I think there are some areas I can improve in my blocks but I want to make sure I'm focusing on the worst-performing areas first.

So my question is, is there an easy (or hard, I don't really care) way to figure out which block in a flowgraph is causing the dropped samples? I already checked that it's not an internet issue.

Thanks in advance!

-Doug

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The 'D' message is coming from the UHD driver itself--long before it gets to the guts of your flow-graph.  That happens, though, when the app layer cannot
  "keep up" with the sample stream coming from the kernel, because its average offered load is higher than the average available compute and
  memory bandwidth.

If you're on Linux have you set the recommended buffering parameters in the network stack:

http://files.ettus.com/manual/page_transport.html#transport_udp