Output buffer size is adjustable - set_min_output_buffer(min_items) will give a buffer that is at least num_items in size, but is often larger due to alignment requirements. I wouldn't use vectors just to get around buffer sizes. Very large buffers may not work due to the way they are allocated. Give this a try first.
On Tue, Aug 16, 2022 at 9:24 PM Carl Laufer <ad...@rtl-sdr.com> wrote: > Thanks. I think it has to be a vector output. > > It seems that if I'm using a stream output, and have decimation blocks > downstream, output_items in the source is always smaller than cpi_size, and > I can't fit the 2^20 array into output_items. I think it expects the source > to adjust its output buffer size? I'd have to throw away data as there's no > way to tell heimdall at runtime to reconfigure to use a smaller cpi_size. > > Unless, is there any way to force output_items to always be [5, cpi_size] > when using a stream output in the source block? > > On Wed, Aug 17, 2022 at 2:13 AM Jeff Long <willco...@gmail.com> wrote: > >> Hi Carl, >> >> Use vectors only if data always needs to be grouped in exact quantities, >> e.g., if the GR flowgraph needs to always handle blocks of 2^20 items. In >> general, a 5-channel stream would be more flexible. The variation in the >> number of items would be due to the output buffer sometimes being empty and >> sometimes not. This depends on what is happening in downstream blocks, and >> also on random scheduling of threads. Hope that answers some of your >> questions. >> >> On Tue, Aug 16, 2022 at 9:49 AM Carl Laufer <ad...@rtl-sdr.com> wrote: >> >>> Hi All, >>> >>> I'm currently working on a GNU Radio source block for the KrakenSDR. So >>> far my block mostly seems to work as expected, but I'm having some minor >>> issues and questions. >>> >>> If you didn't know, the KrakenSDR is 5 RTL-SDR receivers, on the same >>> clock with a noise source for coherence calibration of the channels. We're >>> using it for applications like radio direction finding and passive >>> radar, and mostly write our own code in Python. But having a GNU Radio >>> source would be useful for others. >>> >>> With KrakenSDR there is a DAQ software called "heimdall" which handles >>> all the coherent calibration automatically. In my source block, I'm able to >>> successfully receive the data in the GNU Radio source block from heimdall >>> via a socket connection. >>> >>> First so you know, the heimdall DAQ buffers an array of "cpi_size" (cpi >>> = coherent processing interval) IQ data per channel, and outputs those >>> arrays on the socket when it's filled. By default the cpi_size = 2^20. So >>> in my GNU Radio source I'm receiving five, 2^20 long arrays of coherent >>> complex IQ data every ~400ms. >>> >>> I believe in GNU Radio this is considered a vector? So should I make the >>> output of the source block five port vectors, with out_sig=[(np.complex64, >>> cpi_size)] * numChannels and set vlen to cpi_size in the yaml? >>> >>> Or instead should I have it as an output stream out_sig=[np.complex64] * >>> numChannels, and be using Stream->Vector blocks when needed, with num_items >>> set to cpi_size? >>> >>> I've tried both methods, and they both work. But I don't understand why >>> when using the vector output implementation, the shape of output_items >>> keeps flipping between (5, 2, 1048576) and (5, 1, 1048576)? >>> >>> Code is all at https://github.com/krakenrf/gr-krakensdr if anyone would >>> care to take a look. Everything in Python. If anyone has any tips or >>> comments please let me know. Thanks to anyone for your insights. >>> >>> Regards, >>> Carl Laufer >>> >>
