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


From: Marcus Müller
Subject: Re: [Discuss-gnuradio] lack of understanding the different formats to store samples
Date: Wed, 16 Mar 2016 10:24:02 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

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: address@hidden
>> [mailto:address@hidden On Behalf Of
>> Marcus Müller
>> Sent: Friday, March 11, 2016 2:53 PM
>> To: address@hidden
>> 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.
>>>
>>>
>>> _______________________________________________
>>> Discuss-gnuradio mailing list
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>>
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