Hi Koyel,
I was attempting to explain why the output of the USRP block (Complex
Int16) doesn't directly connect to other blocks. Although no other block
in GNU radio seems to use the type 'Complex Int16', it is actually just
a vector of size 2, containing the I and Q samples as 16 bits int.
It is possible to connect the USRP source block directly to the File
Sink block: you just need to set Vec Length to 2 in the File Sink block,
and set the data type to 'short'.
Other blocks in GNU Radio can use either the 'Short' or the 'IShort'
data type, where the latter stands for 'Interleaved Short'. Using the
'Vector to Stream' block as described in my previous mail, you can
convert the vector shorts from the USRP block into interleaved shorts
which can then be converted into e.g. floats.
Regards, Paul Boven.
On 7/25/20 10:22 AM, Koyel Das (Vehere) wrote:
Hi Paul,
Thanks for your help. Can you please give an example? Like if usrp
source outputs 16 bit complex as I Q I Q I Q I Q for 4 IQ samples where
I and Q are 16 bit complex then what will be the change in the format
after vector to stream conversion? I understood that usrp source block
already gives binary file where I and Q are written alternately as above
or interleaved. So I am unable to understand when you say vector to
stream will interleave I and Q samples.
Regards,
Koyel
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------------------------------------------------------------------------
*From:* Discuss-gnuradio
<discuss-gnuradio-bounces+koyel.das=vehere....@gnu.org> on behalf of
Paul Boven <p.bo...@xs4all.nl>
*Sent:* Saturday, July 25, 2020 1:31:20 PM
*To:* discuss-gnuradio@gnu.org <discuss-gnuradio@gnu.org>
*Subject:* Re: GRC max sample rate
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.
