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Remove the resampler. #95

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Oct 27, 2017
Merged

Remove the resampler. #95

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2 changes: 0 additions & 2 deletions src/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,6 @@ add_executable (
sync.c

firdecim_q15.c
firdes_kaiser.c
resamp_q15.c
math.c

conv_dec.c
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100 changes: 21 additions & 79 deletions src/acquire.c
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Expand Up @@ -27,16 +27,16 @@ void acquire_process(acquire_t *st)
{
float complex max_v = 0;
float angle, max_mag = -1.0f;
unsigned int samperr = 0, i, j;
unsigned int samperr = 0, i, j, keep;
unsigned int mink = 0, maxk = FFTCP;

if (st->idx != FFTCP * (M + 1))
return;

if (st->ready && fabsf(st->slope) < 1 && st->samperr > 10)
if (st->input->sync.ready)
{
mink = st->samperr - 10;
maxk = st->samperr + 10;
mink = FFTCP / 2 - 25;
maxk = FFTCP / 2 + 25;
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I had to widen the search range here to account for ppm error. Each invocation of acquire_process processes 64 * 2160 samples, so 100 ppm error causes a 14-sample offset between invocations.

}

memset(st->sums, 0, sizeof(float complex) * FFTCP);
Expand Down Expand Up @@ -74,81 +74,30 @@ void acquire_process(acquire_t *st)
angle = 0.5 * st->prev_angle + 0.5 * angle;
}
st->prev_angle = angle;
st->samperr = samperr;

// compare with previous timing offset
if (abs((int)samperr - (int)st->history[(st->history_size-1) % ACQ_HISTORY]) > FFT/2)
for (i = 0; i < M; ++i)
{
// clear the history if we "rolled over"
st->history_size = 0;
}

st->history[st->history_size % ACQ_HISTORY] = samperr;
if (++st->history_size > ACQ_HISTORY)
{
float avgerr, slope;
int sum = 0;
for (i = 0; i < ACQ_HISTORY; i++)
sum += st->history[i];
avgerr = sum / (float)ACQ_HISTORY;
slope = ((float)samperr - avgerr) / (ACQ_HISTORY / 2 * SYMBOLS);
st->ready = 1;
st->slope = slope;

if ((st->history_size % ACQ_HISTORY) == 0)
log_debug("Timing offset: %f, slope: %f", avgerr, slope);

// avoid adjusting the rate too much
if (fabsf(slope) > 1.0)
{
log_info("Timing offset: %f, slope: %f (adjust)", avgerr, slope);

input_rate_adjust(st->input, (-slope / BLKSZ) / FFTCP);

// clear the history so we don't overadjust
st->history_size = 0;
}
// we don't want the samperr to go < 0
else if (slope < 0)
int j;
for (j = 0; j < FFTCP; ++j)
{
input_rate_adjust(st->input, (-slope / BLKSZ / 8) / FFTCP);
st->history_size = 0;
int n = i * FFTCP + j;
float complex sample = fast_cexpf(angle * n / FFT) * st->buffer[i * FFTCP + j + samperr];
if (j < CP)
st->fftin[j] = st->shape[j] * sample;
else if (j < FFT)
st->fftin[j] = sample;
else
st->fftin[j - FFT] += st->shape[j] * sample;
}

// skip samples instead of having samperr > FFT
// NB adjustment must be greater than FFT/2
if (samperr > 7*FFT/8)
{
input_set_skip(st->input, 6*FFT/8);
st->samperr = 0;
}
fftwf_execute(st->fft);
fftshift(st->fftout, FFT);
sync_push(&st->input->sync, st->fftout);
}

if (st->ready)
{
for (i = 0; i < M; ++i)
{
int j;
for (j = 0; j < FFTCP; ++j)
{
int n = i * FFTCP + j;
float complex sample = fast_cexpf(angle * n / FFT) * st->buffer[i * FFTCP + j + samperr];
if (j < CP)
st->fftin[j] = st->shape[j] * sample;
else if (j < FFT)
st->fftin[j] = sample;
else
st->fftin[j - FFT] += st->shape[j] * sample;
}

fftwf_execute(st->fft);
fftshift(st->fftout, FFT);
sync_push(&st->input->sync, st->fftout);
}
}

memmove(&st->buffer[0], &st->buffer[st->idx - FFTCP], sizeof(float complex) * FFTCP);
st->idx = FFTCP;
keep = FFTCP * 3 / 2 - samperr;
memmove(&st->buffer[0], &st->buffer[st->idx - keep], sizeof(float complex) * keep);
st->idx = keep;
}

unsigned int acquire_push(acquire_t *st, float complex *buf, unsigned int length)
Expand All @@ -172,9 +121,6 @@ void acquire_init(acquire_t *st, input_t *input)
st->buffer = malloc(sizeof(float complex) * FFTCP * (M + 1));
st->sums = malloc(sizeof(float complex) * (FFTCP + CP));
st->idx = 0;
st->ready = 0;
st->samperr = 0;
st->slope = 0;
st->prev_angle = 0;

st->shape = malloc(sizeof(float) * FFTCP);
Expand All @@ -189,10 +135,6 @@ void acquire_init(acquire_t *st, input_t *input)
st->shape[i] = cosf(M_PI / 2 * (i - FFT) / CP);
}

st->history_size = 0;
for (i = 0; i < ACQ_HISTORY; ++i)
st->history[i] = 0;

st->fftin = malloc(sizeof(float complex) * FFT);
st->fftout = malloc(sizeof(float complex) * FFT);
st->fft = fftwf_plan_dft_1d(FFT, st->fftin, st->fftout, FFTW_FORWARD, 0);
Expand Down
7 changes: 0 additions & 7 deletions src/acquire.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,6 @@
#include <complex.h>
#include <fftw3.h>

#define ACQ_HISTORY 16

typedef struct
{
struct input_t *input;
Expand All @@ -15,12 +13,7 @@ typedef struct
float *shape;
fftwf_plan fft;

float samperr;
float slope;
unsigned int idx;
int ready;
int history[ACQ_HISTORY];
unsigned int history_size;
float prev_angle;
} acquire_t;

Expand Down
3 changes: 0 additions & 3 deletions src/firdes.h
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This file was deleted.

124 changes: 0 additions & 124 deletions src/firdes_kaiser.c
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This file was deleted.

19 changes: 1 addition & 18 deletions src/input.c
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Expand Up @@ -24,12 +24,6 @@

#define INPUT_BUF_LEN (2160 * 512)

#ifdef USE_FAST_MATH
#define RESAMP_NUM_TAPS 8
#else
#define RESAMP_NUM_TAPS 16
#endif

static float filter_taps[] = {
#ifdef USE_FAST_MATH
/*
Expand Down Expand Up @@ -143,11 +137,6 @@ void input_pdu_push(input_t *st, uint8_t *pdu, unsigned int len, unsigned int pr
output_push(st->output, pdu, len, program);
}

void input_rate_adjust(input_t *st, float adj)
{
st->resamp_rate += adj;
}

void input_set_skip(input_t *st, unsigned int skip)
{
st->skip += skip;
Expand Down Expand Up @@ -264,7 +253,6 @@ void input_cb(uint8_t *buf, uint32_t len, void *arg)
}
}
new_avail = st->avail;
resamp_q15_set_rate(st->resamp, st->resamp_rate);
#ifdef USE_THREADS
pthread_mutex_unlock(&st->mutex);
#endif
Expand All @@ -278,7 +266,6 @@ void input_cb(uint8_t *buf, uint32_t len, void *arg)

for (i = 0; i < cnt; i++)
{
unsigned int nw;
cint16_t x[2], y;

x[0].r = U8_Q15(buf[i * 4 + 0]);
Expand All @@ -287,9 +274,7 @@ void input_cb(uint8_t *buf, uint32_t len, void *arg)
x[1].i = -U8_Q15(buf[i * 4 + 3]);

firdecim_q15_execute(st->filter, x, &y);
resamp_q15_execute(st->resamp, &y, &st->buffer[new_avail], &nw);

new_avail += nw;
st->buffer[new_avail++] = y.r / 32768.0 + _Complex_I * y.i / 32768.0;
}

#ifdef USE_THREADS
Expand Down Expand Up @@ -318,7 +303,6 @@ void input_reset(input_t *st)
st->avail = 0;
st->used = 0;
st->skip = 0;
st->resamp_rate = 1.0f;
st->cfo = 0;
st->cfo_idx = 0;
st->cfo_used = 0;
Expand All @@ -339,7 +323,6 @@ void input_init(input_t *st, output_t *output, double center, unsigned int progr
st->snr_cb_arg = NULL;

st->filter = firdecim_q15_create(2, filter_taps, sizeof(filter_taps) / sizeof(filter_taps[0]));
st->resamp = resamp_q15_create(RESAMP_NUM_TAPS / 2, 0.45f, 60.0f, 16);
st->snr_fft = fftwf_plan_dft_1d(64, st->snr_fft_in, st->snr_fft_out, FFTW_FORWARD, 0);

input_reset(st);
Expand Down
4 changes: 0 additions & 4 deletions src/input.h
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Expand Up @@ -13,7 +13,6 @@
#include "firdecim_q15.h"
#include "frame.h"
#include "output.h"
#include "resamp_q15.h"
#include "sync.h"

typedef int (*input_snr_cb_t) (void *, float, float, float);
Expand All @@ -24,8 +23,6 @@ typedef struct input_t
FILE *outfp;

firdecim_q15 filter;
resamp_q15 resamp;
float resamp_rate;
float complex *buffer;
double center;
unsigned int avail, used, skip;
Expand Down Expand Up @@ -55,7 +52,6 @@ typedef struct input_t
void input_init(input_t *st, output_t *output, double center, unsigned int program, FILE *outfp);
void input_cb(uint8_t *, uint32_t, void *);
void input_set_snr_callback(input_t *st, input_snr_cb_t cb, void *);
void input_rate_adjust(input_t *st, float adj);
void input_cfo_adjust(input_t *st, int cfo);
void input_set_skip(input_t *st, unsigned int skip);
void input_wait(input_t *st, int flush);
Expand Down
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