[Discuss-gnuradio] New GR-SQL Module

[Ghost Op]

Hi everyone,

Back from GRCon2017 (one of the best conferences I've been to) and had
some time for some more module development.  During the conference in
one of the working sessions there was a suggestion for a module that
would allow you to query really large IQ files with a SQL-like syntax.

Made sense, 500 GB file but you only want a minute or two of the
sample rather than having to go through the whole thing.  So I put one
together and posted up on github
(https://github.com/ghostop14/gr-sql).

Basic to start.  Has a command-line tool called grsql (the readme has
some examples) to extract portions to a new file, and a flowgraph
block to play excerpt directly.

Basic syntax:

Get the total time length of a file:
grsql "select TIMELENGTH FROM '/tmp/myrecording_593MHz_6.2MSPS.raw'
ASDATATYPE complex SAMPLERATE 6.2M"

Extracting data from 45.2 seconds to 80 seconds into the save to a new file:
grsql "SELECT * FROM '/tmp/myrecording_593MHz_6.2MSPS.raw' ASDATATYPE
complex SAMPLERATE 6.2M STARTTIME 45.2 ENDTIME 80.0 SAVEAS
'/tmp/extracted.raw'"

In the flowgraph block, saveas doesn't apply but you can play specific
time ranges back directly from the flowgraph without needing to
extract from the file (if you're looking for a signal in the
recording).

If you're working on some blind analysis, if you extract a sample to a
new file, you may want to use the gr-filerepeater block up on my
github too.  It'll let you put delays between replays so that any
blocks looking for signal continuity won't get too "confused" by going
directly from the end of a sample immediately to the first sample
creating a weird signal discontinuity as it "jumps".  gr-filerepeater
will let it go "quiet" for a specified period of time so the blocks
can settle before trying to decode / demod again.

Anyway it's alpha/beta but it works.  If you run into any bugs or are
working with some big files and want any particular features, drop me
a note.  If all looks pretty solid and there's interest I can set up a
pull to integrate it into pybombs for an easier install.

Mike