williamp/osmocom-analog
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

common code: Sample rate conversion now supports any rate above 8000 Hz

Browse Source
This commit is contained in:
Andreas Eversberg
2016-04-17 15:17:38 +02:00
parent 05402283df
commit 9de121109d
6 changed files with 33 additions and 80 deletions
Download Patch File Download Diff File Expand all files Collapse all files

93
src/common/samplerate.c
View File

@@ -21,21 +21,21 @@
#include <stdint.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include "samplerate.h"
/* generally use filter, but disable for test using quick and dirty replacement */
#define USE_FILTER
/* NOTE: This is quick and dirtry. */
int init_samplerate(samplerate_t *state, int samplerate)
int init_samplerate(samplerate_t *state, double samplerate)
{
#if 0
if ((samplerate % 8000)) {
fprintf(stderr, "Sample rate must be a muliple of 8000 to support MNCC socket interface, aborting!\n");
return -EINVAL;
}
#endif
memset(state, 0, sizeof(*state));
state->factor = samplerate / 8000;
state->factor = samplerate / 8000.0;
biquad_init(&state->up.bq, 4000.0, samplerate);
biquad_init(&state->down.bq, 4000.0, samplerate);
@@ -46,10 +46,9 @@ int init_samplerate(samplerate_t *state, int samplerate)
/* convert input sample rate to 8000 Hz */
int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output)
{
#ifdef USE_FILTER
int output_num, i, j;
int factor = state->factor;
double spl[input_num];
int output_num, i;
double factor = state->factor, step;
double spl[input_num + 10]; /* add some safety */
int32_t value;
/* convert samples to double */
@@ -58,62 +57,42 @@ int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, in
/* filter down */
biquad_process(&state->down.bq, spl, input_num, 1);
output_num = input_num / factor;
output_num = (int)((double)input_num / factor);
/* resample filtered result */
for (i = 0, j = 0; i < output_num; i++, j += factor) {
value = spl[j] * 32768.0;
for (i = 0, step = 0.5 / (double)output_num; i < output_num; i++, step += factor) {
value = spl[(int)step] * 32768.0;
if (value < -32768)
value = -32768;
else if (value > 32767)
value = 32767;
*output++ = value;
}
return output_num;
#else
int output_num = 0, i;
double sum;
int factor, sum_count;
//memcpy(output, input, input_num*2);
//return input_num;
sum = state->down.sum;
sum_count = state->down.sum_count;
factor = state->factor;
for (i = 0; i < input_num; i++) {
sum += *input++;
sum_count++;
if (sum_count == factor) {
*output++ = sum / (double)sum_count;
output_num++;
sum = 0;
sum_count = 0;
}
if ((int)(step - factor) >= input_num) {
fprintf(stderr, "Error: input_num is %d, so step should be close to 0.5 below that, but it is %.4f. Please fix!\n", input_num, step);
abort();
}
state->down.sum = sum;
state->down.sum_count = sum_count;
return output_num;
#endif
}
/* convert 8000 Hz sample rate to output sample rate */
int samplerate_upsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output)
{
#ifdef USE_FILTER
int output_num, i;
int factor = state->factor;
double spl[input_num * factor];
double factor = 1.0 / state->factor, step;
double spl[(int)((double)input_num / factor + 0.5) + 10]; /* add some fafety */
int32_t value;
output_num = input_num * factor;
output_num = (int)((double)input_num / factor + 0.5);
/* resample input */
for (i = 0; i < output_num; i++)
spl[i] = input[i / factor] / 32768.0;
for (i = 0, step = 0.5 / (double)output_num; i < output_num; i++, step += factor)
spl[i] = input[(int)step] / 32768.0;
if ((int)(step - factor) >= input_num) {
fprintf(stderr, "Error: input_num is %d, so step should be close to 0.5 below that, but it is %.4f. Please fix!\n", input_num, step);
abort();
}
/* filter up */
biquad_process(&state->up.bq, spl, output_num, 1);
@@ -129,31 +108,5 @@ int samplerate_upsample(samplerate_t *state, int16_t *input, int input_num, int1
}
return output_num;
#else
int output_num = 0, i, j;
double last_sample, sample, slope;
int factor;
last_sample = state->up.last_sample;
factor = state->factor;
for (i = 0; i < input_num; i++) {
sample = *input++;
slope = (double)(sample - last_sample) / (double)factor;
//int jolly = (int)last_sample;
for (j = 0; j < factor; j++) {
// if (last_sample > 32767 || last_sample < -32767)
// printf("%.5f sample=%.0f, last_sample=%d, slope=%.5f\n", last_sample, sample, jolly, slope);
*output++ = last_sample;
output_num++;
last_sample += slope;
}
last_sample = sample;
}
state->up.last_sample = last_sample;
return output_num;
#endif
}