WebSDR

ShinySDR

OpenWebRX

How to set up your own server?

#!/bin/bash
git clone https://github.com/simonyiszk/openwebrx.git
git clone https://github.com/simonyiszk/csdr.git
cd csdr
make
sudo make install
cd ../openwebrx
vim config_webrx.py #edit config or leave defaults
./openwebrx.py

Story

minidemod.c

#include <math.h>
#include <stdio.h>

int main()
{
	double i, q, i_last=q_last=0, s;
	for(;;)
	{
		i=((unsigned char)getchar()-127); 
		q=((unsigned char)getchar()-127);
		// s = ???
		putchar((unsigned char)(s+127));
		i_last=i; q_last=q;
	}
}

minidemod.c

#include <math.h>
#include <stdio.h>

int main()
{
	double i, q, i_last=0, q_last=0, s;
	for(;;)
	{
		i=((unsigned char)getchar()-127); 
		q=((unsigned char)getchar()-127);
		s=100*(atan2(i,q)-atan2(i_last,q_last)); 
		putchar((unsigned char)(s+127));
		i_last=i; q_last=q;
	}
}

minidemod.c

#include <math.h>
#include <stdio.h>

int main()
{
	double i, q, i_last=0, q_last=0, s;
	for(;;)
	{
		i=((unsigned char)getchar()-127); 
		q=((unsigned char)getchar()-127);
		s=70*((i*(q-q_last)) - (q*(i-i_last)))/(i*i+q*q);
		putchar((unsigned char)(s+127));
		i_last=i; q_last=q;
	}
}

Running minidemod

#!/bin/bash
rtl_sdr -s 240000 -f 89500000 -g 20 - | \  # taking I/Q samples
tcc -lm -run minidemod.c | \           # FM demodulation 
sox -t raw -r 240000 -e unsigned -b 8 \	   # decimation
   -c 1 - -t raw - rate 48000 | \
mplayer -quiet -rawaudio \                 # sound card output
   samplesize=1:channels=1:rate=48000 
   -demuxer rawaudio -

https://github.com/simonyiszk/minidemod/

libcsdr

#!/bin/bash

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - |

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \
csdr shift_addition_cc -0.145833 | \ #shift by -0.350 MHz

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \
csdr shift_addition_cc -0.145833 | \
csdr fir_decimate_cc 50 0.005 HAMMING | \

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \
csdr shift_addition_cc -0.145833 | \
csdr fir_decimate_cc 50 0.005 HAMMING | \
csdr fmdemod_quadri_cf |

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \
csdr shift_addition_cc -0.145833 | \
csdr fir_decimate_cc 50 0.005 HAMMING | \
csdr fmdemod_quadri_cf | csdr limit_ff |

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \
csdr shift_addition_cc -0.145833 | \
csdr fir_decimate_cc 50 0.005 HAMMING | \
csdr fmdemod_quadri_cf | csdr limit_ff | csdr deemphasis_nfm_ff 48000 | \

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \
csdr shift_addition_cc -0.145833 | \
csdr fir_decimate_cc 50 0.005 HAMMING | \
csdr fmdemod_quadri_cf | csdr limit_ff | csdr deemphasis_nfm_ff 48000 | \
csdr fastagc_ff |

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \
csdr shift_addition_cc -0.145833 | \
csdr fir_decimate_cc 50 0.005 HAMMING | \
csdr fmdemod_quadri_cf | csdr limit_ff | csdr deemphasis_nfm_ff 48000 | \
csdr fastagc_ff | csdr convert_f_i16 |

#!/bin/bash
rtl_sdr -s 2400000 -f 145000000 -g 20 - | csdr convert_u8_f | \
csdr shift_addition_cc -0.145833 | \
csdr fir_decimate_cc 50 0.005 HAMMING | \
csdr fmdemod_quadri_cf | csdr limit_ff | csdr deemphasis_nfm_ff 48000 | \
csdr fastagc_ff | csdr convert_f_i16 | mplayer -cache 1024 -quiet \
   -rawaudio samplesize=2:channels=1:rate=48000 -demuxer rawaudio -

- Small

- Fast to build

- Allows using multiple cores

Acceleration

SIMD

GPGPU

FPGA

Image by Gareth Halfacree, flickr user ghalfacree [CC BY-SA 2.0], via Wikimedia Commons

SIMD

SSE

NEON

Using SIMD

Auto-vectorization (-O3)

C intrinsics

Hand-coded assembly

sdr.js

libcsdr compiled to ASM.js

Just one last crazy idea...

Audio: 1D vector of samples

Waterfall: 1D vector of dBm values

...compress both with ADPCM?

Acknowledgement

János Selmeczi, PhD (HA5FT)

Péter Horváth, PhD (HA5CQA)