RS-tracker/demod/iq_svcl

IQ server/client

receive IF stream from baseband IQ via TCP, default PORT=1280 (iq_svcl.h)

Compile

gcc -Ofast -c iq_base.c
gcc -O2 iq_server.c iq_base.o -lm -pthread -o iq_server
gcc -O2 iq_client.c -o iq_client

Usage/Examples

• T1$ ./iq_server [--port <pn>] <iq_baseband.wav>
T2$ ./iq_client [--ip <ip_adr>] [--port <pn>] --freq <fq>

• Ex.1
  [terminal 1]
  T1$ ./iq_server --bo 32 <iq_baseband.wav>    (or   $ ./iq_server --bo 32 - <sr> <bs> <iq_baseband.raw>)
  [terminal 2]
  T2$ ./iq_client --freq <fq> | ./rs41mod -vx --IQ 0.0 --lp - <if_sr> <bo>
  where
       -0.5 < fq < 0.5: (relative) frequency, fq=frequency/sr
     <if_sr>: IF sample rate
       <bo>=8,16,32: output/IF bits per (real) sample (u8, s16 or f32)
  down-converts up to MAX_FQ=(4+1) (iq_base.h) channels/signals. (On older CPUs, more signals than number of CPU cores is not recommended.)
  (Note: If the baseband sample rate has no appropriate factors (e.g. if prime), the IF sample rate might be high and IF-processing slow.)
  One channel can be used for scanning, e.g. ./iq_server --fft_avg <m> <fft_avg.csv> makes m rows of avg-FFT (FFT_AVG=2 seconds average), and this channel will be reused for client FFT requests. Only one channel/thread can be used for FFT/scanning. A client can request a new FFT, if the last FFT has finished.
  There are two kinds of FFTs, fft_all and fft_avg. fft_avg integrates over FFT_AVG=2 seconds and can be used for signal peak scanning. For waterfall display, --fft_all <m> <fft_all.csv> produces m*FFT_AVG*FFT_FPS/2 rows of FFT (FFT_AVG seconds, FFT_FPS/2 per sec). The FFT is saved in <fft.csv> as
     sec.ms,freq_min,freq_max,Hz/bin,N_bins, db_1,...,db_N
  approx. 200 Hz per bin. Choose filename="-" for stdout.
  If no output bps is chosen (--bo [8,16,32]), the IF bps is equal to the baseband bps. It is recommended to use --bo 32 (i.e. float32) output, then no quantization noise is introduced when converting from internal float32 samples.
  

• Ex.2
  [terminal 1]
  T1$ rtl_sdr -f 403.0M -s 1920000 - | ./iq_server --fft_avg 1 fft_server.csv --bo 32 - 1920000 8
  [terminal 2]
  T2$ ./iq_client --freq -0.3125 | ./m10mod -c -vv --IQ 0.0 - 48000 32
  [terminal 3]
  T3$ ./iq_client --freq 0.0 | ./rs41mod -vx --IQ 0.0 - 48000 32
  [terminal 4]
  T4$ ./iq_client -1    (close channel 1)
  T4$ ./iq_client --stop    (close all clients and stop server)
  

• The iq_server FFT options immediately start reading the IQ stream (so buffering is reduced).
  ./iq_client <fft_opt> <m> <fft_cl.txt>, where <fft_opt>=--fft_avg_cl or --fft_all_cl, requests FFT from the server.
  (<fft_opt>=--fft_avg_sv/--fft_all_sv would save the FFT at the server, but only if ./iq_server --enable_clsv_out.)
  The IF sample rate if_sr is at least 48000 and such that the baseband sample rate sr is a multiple of if_sr.

• Ex.3
  [terminal 1]
  T1$ rtl_sdr -f 404550k -s 2048000 - | ./iq_server --fft_avg 1 fft_avg.csv --bo 32 - 2048000 8
  (scan FFT: ./scan_fft fft_avg.csv)
  [terminal 3]
  T3$ ./iq_client --fft_all_cl -1 - | python plot_fft_ani.py 3 -