Re: GRC max sample rate

[Paul Boven]

Hi Koyel,

On 7/25/20 9:19 AM, Koyel Das (Vehere) wrote:
> Will there be packet drops if USRP source is set at 32 bit complex float 
> in grc when receiving at 100 MSPS each from two channels? That makes 
> 2*100e6*64 (32 bit I and 32 bit Q) = 12800e6 or 12.8 gbps. I am unable 
> to set usrp source block to 16 bit complex as then the usrp source block 
> is not compatible with file sink which doesn’t have option for 16 bit 
> complex.

The USRP block is (as far as I could find) the only block in all of GNU 
Radio that uses the 'Complex Int16' type. Which is a bit confusing, but 
it is just a vector with a length of 2, alternating the I and Q channels 
as 16 bit shorts.

You can simply convert it to interleaved int16 by using a 'Vector to 
Stream' block, with these settings:

io_type: short
num_items: 2
vec_length: 1

These 16 bit integers can then be written to disk (if it can keep up), 
memory, transferred over the network, or turned into floats for further 
processing.

We use this to efficiently stream raw samples over the internet using a 
ZMQ Pub Sink.

Regards, Paul Boven.