Hello Tim,
It's great to have you onboard. I'm more of an "implimenter", by no means good
at C or C++.
So I can't help to that depth.
I can compile code on ARM and Intel Linux platforms here and with transceivers,
give it a go.
So, if I can be useful.
My SDR here in western Sydney, Australia can do Codec2 decode though currently
in one mode.
(easily changeable in a script file) Web browse 110.143.195.8:8073
You may notice the M17 project has chosen the Codec2 modes 1600 and 3200 to
"replace" AMBE
in an open source transceiver project.
Welcome
Alan VK2ZIW
On Tue, 3 Aug 2021 17:14:15 -0500, Tim Meehan wrote
> Hi - I'm not extremely versed in digital modes, but I am well versed in
> optimization. I think that HAM radio should be something open source, which
> is why Codec2 appeals to me.
>
> Before I post a large blob of C code, I wanted to mention that I have a
> program that I have written a genetic optimizer to move spline knots around -
> and I'd be happy to run the optimizer based on BER/PER ... however ... I need
> someone to explain to me how I might generate quantities to optimize on. I
> don't need bunches of help, just enough so that I can write it myself.
>
> I found that the 16-sample clamped endpoint spline with log-spaced samples
> worked the best, so I'll chop out the higher sample density parts of the
> code. My hope was faster AND more accurate, but I think all I got was faster
> and LESS accurate. Perhaps wiser eyes than mine can help me out.
>
> The test script that I was using was:
> #!/bin/sh
> ./ldpc_enc /dev/zero - --sd --code HRA_112_112 --testframes 100 \ |
> ./ldpc_noise - - 1 \
> | ./ldpc_dec - /dev/null --code HRA_112_112 --sd --testframes
>
> The code is (simply replace phi0.c with this):// phi0.c
> #include <stdint.h>
> #include <stddef.h>
>
> float coeffs_clamped_16[16] = {
> 7.93223341e+07, 1.55433768e+07, 3.60871810e+06, 7.33752374e+05,
> 1.65434845e+05, 3.44055511e+04, 7.62050634e+03, 1.60695364e+03,
> 3.52218272e+02, 7.50245180e+01, 1.64584579e+01, 3.63755151e+00,
> 8.75888035e-01, 1.72673513e-01, 6.76273536e-03, -7.75296180e-03};
>
> float x_16[16] = {
> 1.00000000e-04, 2.15443469e-04, 4.64158883e-04, 1.00000000e-03,
> 2.15443469e-03, 4.64158883e-03, 1.00000000e-02, 2.15443469e-02,
> 4.64158883e-02, 1.00000000e-01, 2.15443469e-01, 4.64158883e-01,
> 1.00000000e+00, 2.15443469e+00, 4.64158883e+00, 1.00000000e+01};
>
> float y_16[16] = {
> 9.90348755e+00, 9.13595919e+00, 8.36843084e+00, 7.60090254e+00,
> 6.83337448e+00, 6.06584753e+00, 5.29832570e+00, 4.53082768e+00,
> 3.76344015e+00, 2.99656512e+00, 2.23206146e+00, 1.47840690e+00,
> 7.71936833e-01, 2.32985688e-01, 1.92853284e-02, 9.07998596e-05};
>
> static size_t
> bisect(float x, float *restrict x_data, size_t size)
> {
> size_t left = 0;
> size_t right = size - 1;
> int max_iterations = 32; /* waay higher than we need */
>
> while (right - left > 1 && max_iterations--) {
> size_t middle = left + (right - left)/2;
> float xm = x_data[middle];
> if (x < xm)
> right = middle;
> else if (xm < x)
> left = middle;
> }
>
> return left;
> }
>
> static float
> spline_interpolate(float x,
> float *restrict x_data,
> float *restrict y_data,
> float *restrict M,
> size_t size) {
> size_t i = bisect(x, x_data, size);
> float h = x_data[i + 1] - x_data[i];
> float z = (x - x_data[i])/h;
> float h2 = h * h;
>
> float c1 = (M[i + 1] - M[i]) * h2 / 6.0;
> float c2 = M[i] * h2 / 2.0;
> float c3 = y_data[i + 1] - y_data[i] - (M[i + 1] + 2.0 * M[i]) * h2 / 6.0;
>
> return ((c1 * z + c2) * z + c3) * z + y_data[i];
> }
>
> extern float
> phi0(float x) {
> if (x <= x_16[0])
> return 10.0f;
> if (x >= x_16[15])
> return 0.0f;
>
> return spline_interpolate(x, x_16, y_16, coeffs_clamped_16, 16);
> }
---------------------------------------------------
Alan VK2ZIW
Before the Big Bang, God, Sela.
OpenWebMail 2.53, nothing in the cloud.
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