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Re: [Discuss-gnuradio] lack of understanding the different formats to st

From: Ralph A. Schmid, dk5ras
Subject: Re: [Discuss-gnuradio] lack of understanding the different formats to store samples
Date: Wed, 16 Mar 2016 08:18:39 +0100

OK, I will give this a try :) I hoped that there would be some overview, explaining the different interconnect formats when connecting gnuradio blocks...






From: Jacob Gilbert [mailto:address@hidden
Sent: Friday, March 11, 2016 3:50 PM
To: Ralph A. Schmid, dk5ras
Cc: GNURadio Discussion List
Subject: Re: [Discuss-gnuradio] lack of understanding the different formats to store samples




If I understand this, each 8-bit byte of data contains four two-bit IQ samples, in which case the "Unpack K Bits" block is likely what you are looking for. It will treat each bit in a byte (from Byte File Source in this case) as an individual item, which can then be type-converted and interleaved to give you complex data. There are a couple other tools under the category of "Byte Operators" that may be helpful.




On Fri, Mar 11, 2016 at 2:24 AM, Ralph A. Schmid, dk5ras <address@hidden> wrote:


Being an RF guy I must admit that I am somehow lost in the different ways
how samples are stored in files. I stumbled over this question when I
experimented with https://github.com/osqzss/gps-sdr-sim. It works great when
using 16 bit samples and using a simple two-block grc file, feeding them
directly from a file source to the UHD sink. However the 1 bit variant
sounds promising, as the files are much smaller this way and also the
generation of them runs much faster.

It must only be a matter of finding the right blocks and the right settings
to convert this, but my google search was highly confusing, most probably
due to different names for the same thing.

So I do not only ask for how to use "four 1-bit I/Q samples into a single
byte" (taken from the readme of the gps-sdr-sim), but for a more general
overview how this stuff is done, to be prepared for other upcoming questions
of this kind :) Up to now I solved those issues by an educated guess or even
by try and error, what is not very satisfying...


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