[Discuss-gnuradio] More Options for Working with Sample Data Sets

[Ghost Op]

I've been updating a number of modules following up on the GRCon
working sessions around working with large and sample data sets.

Yesterday I pushed another update to the new gr-sql module on github
that incorporates HackRF and rtlsdr 8-bit streams to either convert
with the command-line or directly play in a gnuradio flowgraph by
transparently handling the conversion (for those working with either
of those two SDR's).

While gr-sql is meant to help extract portions of signals out of a
very large sample stream, the other half of the issue for testing
could be to combine individual signal isolated sample recordings into
a more complex "real-world" signal for analysis, say for determining
if an algorithm could distinguish individual signals in an overlapping
environment by combining two prerecorded signals in a manner that you
control.

To that end, I updated the gr-filerepeater module with more control
over playback.  You can now add a delay before starting playback of a
signal (would output zero's until the delay is hit), as well as have
it transition back to outputting zero's after playback without
stopping the flowgraph.  This way you could say "for signal two, start
injecting after 3 seconds, and when it finishes just output zeros as
if the signal was gone but allow the rest of the flowgraph to
continue".