Re: working with WFM sample data

hi Marcus,

thanks for this tip, it pushed me the the right direction. i guess
this capture file isn’t the standard “complex” datatype, and a
conversion was the answer. i found the answer on the gnuradio.org
Octave page that said the magic word, short. i use this graph to render
on an FFT scope:

[ File Source (short) ]
-> [ Throttle (complex, 25M) ]
-> [ IShort to Complex ]
-> [ FFT Scope (complex, rate 25M) ]

using IShort to Complex was just a result of experimentation, as Short
to Complex seemed to output only half the captured band. now i get to
delve in to the world of filters, oof!

i’m surprised this isn’t listed on the gnuradio.org Sample Data page (
http://gnuradio.org/redmine/projects/gnuradio/wiki/SampleData ), as i’ve
come across messages from other folks confused about the data types and
semantics of these USRP capture files. i suggest an addition to that
page that mentions the necessity of an IShort conversion.

thanks again!

  • emilio
    KI6NVO

On 02/15/2012 02:05 PM, emilio gonzalez wrote:

-> [ IShort to Complex ]

addition to that page that mentions the necessity of an IShort
conversion.

You can capture any of the native sample formats in Gnu Radio, so it’s
not the case that disk-resident samples are necessarily recorded
in “complex short” format. It depends on what the program that
recorded them asked for, and you have to understand what the
program that recorded them intended.

Gnu Radio doesn’t use file headers or any other such technique–the file
sinks records raw samples in whatever format they’re presented
in.


Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

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