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

[Henry Barton]

This sounds interesting; I too have been wondering how IQ files worked. I thought it must be alternating I bytes and Q bytes, or with >8-bit radios, I words and Q words. But maybe the packed byte system is right, since I can feed IQ recordings in WAV format directly into GNUradio without stripping the headers.

> To: ralph@schmid.xxx; discuss-gnuradio@gnu.org
> From: marcus.mueller@ettus.com
> Date: Wed, 16 Mar 2016 10:24:02 +0100
> Subject: Re: [Discuss-gnuradio] lack of understanding the different formats to store samples
>
> Ok, let "I" and "Q" be single bits each, so each byte would then be
>
> IQIQIQIQ
>
> if I had to take a guess.
>
> You can get get back something that GR commonly deals with by doing
>
> packed to unpacked (type=B, bits per chunk = 1, endianness=your machine)
> -> IChar to Complex
>
> Best regards,
> Marcus
> On 16.03.2016 08:13, Ralph A. Schmid, dk5ras wrote:
> > Each byte seems to contain 4 1 bit I/Q samples. This is the text from the
> > readme:
> >
> > "The output file size can be reduced by using "-b 1" option to store four
> > 1-bit I/Q samples into a single byte."
> >
> > Ralph.
> >
> >> -----Original Message-----
> >> From: discuss-gnuradio-bounces+ralph=schmid.xxx@gnu.org
> >> [mailto:discuss-gnuradio-bounces+ralph=schmid.xxx@gnu.org] On Behalf Of
> >> Marcus Müller
> >> Sent: Friday, March 11, 2016 2:53 PM
> >> To: discuss-gnuradio@gnu.org
> >> Subject: Re: [Discuss-gnuradio] lack of understanding the different
> > formats
> >> to store samples
> >>
> >> In what format are your 1bit samples? I'd assume they are just the fact
> >> whether a byte is 0x00 or 0x01; in that case, just use unpacked to packed.
> >>
> >> On 03/11/2016 10:24 AM, Ralph A. Schmid, dk5ras wrote:
> >>> Hi,
> >>>
> >>> 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...
> >>> Ralph.
> >>>
> >>>
> >>> _______________________________________________
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> >>
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