Liquid-dsp

synchronization process in liquid, allowing for both detection and channel
impairment correction with a simplified interface. Additionally, code
coverage has been increased to 85% across the entire project, with numerous
bug fixes, stability improvements, and massive testing enhancements. From
an "architectural" standpoint, objects have been migrated to use standard
methods for consistency.

* build
- increased code coverage to 85% globally across entire project. This
is the single largest effort included in this version and touches
most modules in some way, most particularly the framing objects
- cleaning build to remove compiler warnings (e.g. unused variables)
- stripped version number off archive
* dotprod
- added support for AVX512-F (thanks, vankxr!)
* framing
- added numerous tests to increase coverage to 84%
- framesync64: using new qdsync object for simplified operation
- qdsync: new frame detector and synchronizer to much more easily
support frame processing. The object not only detects the frame, but
also provides an initial carrier frequency, phase, and timign offset,
and also corrects for these impairments, passing the results to the
user in a clean callback function.
* modem
- cpfskmod: increasing phase stability for long runs
* multichannel
- added numerous tests to increase coverage to 88%
* optim
- added numerous tests to increase coverage to 92%
* sequence
- msequence: extended support for state variables up to m=31, reversed
order for generator polynomial and internal state definition to be
more consistent with literature and readily-available genpolys

This release includes substantially improved testing coverage, deep copy()
methods for nearly all objects, improved speed, and resolves a number of
issues and pull requests.

* build
- added support for PlatformIO (https://platformio.org) for embeedded
development (thanks, jcw!)
- incorporated recursive copy() methods to objects to facilitate c++ copy
constructors for bindings; now all objects can be deep copied to a new
object with their entire memory and state preserved
- added convenience method to malloc and copy memory arrays
- improved support for error codes across objects and methods
- cleaned up spelling errors across project (thanks, nowls!)
- scrubbed function argument variable names to avoid underscore followed
by a capital letter, causing trouble with pre-compiler processing
- added basic test to check linking to installed library, incorporating
into CI/CD pipelines
- added more example programs
* autotest
- increased coverage testing (81% across entire project)
- added the ability to "hammer" a particular test by running repeatedly on
incremental seeds to assess specific edge cases (e.g. with random data)
- added timer to show execution time for each test and identify areas for
speed improvements
- added methods for testing spectral response of various fields
- added special directory for storing output logs: autotest/logs/
* benchmark
- replacing old C-based benchmark comparison with simpler python version
* dotprod
- added support for AVX SIMD in vector dot products (thanks, vankxr!)
* fft
- adding macro to allow for aligned memory allocation if FFTW is used
(thanks, nowls!)
* filter
- added new halfband filter design using Parks-McClellan algorithm and
qs1dsearch method to provide as exact a specification as possible
- added method to retrieve filter response from coefficients array
- dds: adding methods to get/set scale
- firhilb, iirhilb: added block processing method
- msresamp, resamp: adding method to provide the exact number of output
samples with provided input size
- msresamp2, resamp2: using better halfband filter design for exact user
specifications
- resamp: adding methods to get/set scale, fixing filter bank resolution
(was hard-coded, now respects user configuration)
* framing
- framesync64: added methods to set callback and userdata (context)
fields, adding support for exporting debugging files for post-analysis
as well as python script for processing, adding better estimate of
error vector magnitude
- msource: added convenience method to recall number of samples generated
by each source
- ofdmflexframesync: added methods to set callback and userdata (context)
fields
- qpacketmodem: returning much better estimate of error vector magnitude
- qsource: fixed issue with carrier frequency adjustment
* optim
- added qs1dsearch object to perform quad-section 1-dimensional search:
similar to bisection search, but to find potentially non-continuous
minimum/maximum of function

* autotest
- automated code coverage testing (72%)
* build
- incorporated error handling in most methods with integer-based return value
* agc
- added interface to check if AGC is locked or not
* buffer
- cbuffer: added method to check if buffer is empty
* dotprod
- included methods to create/recreate object in reverse order
* equalization
- eqlms: added convenience methods for copying coefficients and running as
a decimator
* fft
- spgram: adding convenience methods for getting/setting properties
- spwaterfall: adding convenience methods for getting/setting properties
* filter
- new direct digital synthesis (DDS) family of objects which allows
cascaded half-band interpolation/decimation with arbitrary frequency
translation
- new fractional delay (fdelay) family of objects which allow for
adjustable large fractional delays
- firdecim: adding convenience method to get decimation rate
- firfilt: adding convenience methods to get/copy coefficients as well as
create object using firdespm algorithm
- firinterp: adding convenience methods for new ways to create object as
well as getting object properties
- firpfb: adding convenience methods to create default object, write
samples
- resamp2: adding methods to get/set output scale
- rresamp: adding methods to operate with block execution
* framing
- new arbitrary rate symstreamr object (derived from symstream family)
- framesync64: adding methods for getting/resetting frame data statistics
as well as getting/setting detection threshold
- gmskframegen/gmskframesync: extending methods to support easier
operation, getting/resetting frame data statistics, more control over
parameters in create methods
- ofdmflexframesync: adding methods to get/reset frame data statistics
- qdetector: adding method to get threshold
- qpilotsync: adding method to get error vector magnitude
- symstream: adding convenience methods for getting properties
- symtrack: adding convenience methods for getting/setting properties
* math
- adding `liquid_` prefix to winodowing functions while supporting backwards
compatibility with older methods
- adding `liquid_` prefix to internal polynomial functions, using
common double-precision method for finding polynomial roots
* multichannel
- firpfbch2: adding convenience methods to get object properties
* modem
- modem: adding type extension for more consistency: `modem` -> `modemcf`,
supporting backwards compatibility with API shim

* improved selection of SSE/MMX extension flags for gcc
* agc
- adding squelch functionality back into gain control object
* filter
- adding callback function for Parks-McClellan algorithm to allow generic
filter prototyping
- fixed double-free bug in iirfilt
* fft
- adding new spwaterfall family of objects for generating waterfall plot
and automatically down-size as input sample size grows
* sequence
- fixed issue with order of operations causing inconsistent behavior across
different platforms

* New MIT/X11 license (https://opensource.org/licenses/MIT)
* agc (automatic gain control)
- major code scrub, improved reliability, simplified interface
- block-level operation
* buffer
- new cbuffer objects for dynamic-sized circular buffering
* channel
- new module to define certain channel emulation objects
- new functionality includes carrier frequency/phase offsets,
(time-varying) multi-path, shadowing, and additive noise
* dotprod
- adding method to compute x^T * x of a vector (sum of squares)
* equalization
- improved interface for LMS and RLS equalizers
- simplified methods to support blind operation
* fec (forward error correctino)
- interleaver and packetizer moved from the framing to the fec module
- packetizer now includes data whitening
* fft (fast Fourier transform)
- general speed improvements for one-dimensional FFTs
- completely reimplemented spgram (spectral periodogram) objects to
include both complex and real-values amples with simpler interface
- reimplemented asgram (ASCII spectral periodogram) objects
* filter
- additional prototype create methods, block execution
- added new fftfilt family of objects to realize linear filter
with fast Fourier transforms
- interp family renamed to firinterp, new iirinterp family
- decim family renamed to firdecim, new iirdecim family
- add linear interpolation for arbitrary resamp output
- new multi-stage half-band resampler family
- symsync: improved stability, added rate adjustment to help pull in
sample rate offsets
- added autotests for validating performance of both the
resamp and msresamp objects
* framing
- added `framedatastats` object for counting statistics across different
framing objects (e.g. number of total bytes received)
- adding generic callback function definition for all framing
structures
- qpacketmodem: new object to easily combine modulating and encoding;
buffer of data in, modulated and encoded samples out
- qpilotgen/qpilotsync: new objects to add and synchronize pilot symbols
to modulated symbols to recover carrier frequency/phase, and gain
- framing objects: frame64, flexframe now use qpacketmodem, qpilotgen, and
qpilotsync objects for unified interface and vastly improved performance
- flexframe: vastly simplified interface
- qdetector: new family for pre-demodulator synchronizion and detection
- moved interleaver and packetizer objects to `fec` module
- symstream: new family for generating random stream of modulated samples
- msource: new family for generating multiple signals for a single source,
including tones, noise, modulated symbols
- symtrack: new family for tracking a stream of symbols and recovering
signal level, timing, carrier frequency/phase without pilots
* math
- new windowing methods (e.g. 7-term Blackman-harris window)
* matrix
- adding smatrix family of objects (sparse matrices)
- improving linear solver methods (roughly doubled speed)
* modem
- re-organizing internal linear modem code (no interface change)
- freqmod/freqdem: new interface, block-level execution for analog FM
- cpfskmod/cpfskdem: new family for generic non-linear continuous-phase
frequency-shift modulation (e.g. minimum-shift keying)
- fskmod/fskdem: new family for non-coherent frequency-shift keying
modulation, often with many samples per symbol (e.g. 256-FSK)
* multicarrier
- adding OFDM framing option for window tapering
- simplfying OFDM framing for generating preamble symbols (all
generated OFDM symbols are the same length)
- adding run-time option for debugging ofdmframesync
- adding method for initializing subcarriers with frequency range
* nco (numerically-controlled oscillator)
- general performance improvements, adding block-level execution
* optim
- gradsearch (gradient search) uses internal linesearch for
significant speed increase and better reliability
- gradsearch interface greatly simplified
* utility
- build no longer auto-generates tables at compile time (helps with cross
compilation)
* vector
- new module to simplify basic vector operations
* miscellany
- documentation moved from core repository to website
- global header file (`liquid.h`) include more structured source
- consistent naming of reset() methods for most objects

* dotprod
- leveraging SIMD extensions for vector operations (SSE2, SSE3)
* fft
- completely re-structured internal transform strategy including
Cooley-Tukey mixed-radix algorithm, Rader algorithm for FFTs of
prime length, and specific codelets for small-size transforms.
* math
- new modular arithmetic methods (prime factor, totient, etc.)
* modem
- new API creates linear modem objects with one argument, e.g.
LIQUID_MODEM_QAM16
- new type definitions for analog modems