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authorAndreas Eversberg <jolly@eversberg.eu>2016-04-17 15:17:38 +0200
committerAndreas Eversberg <jolly@eversberg.eu>2016-04-17 16:49:39 +0200
commit9de121109db5ca60462d35e4e45b7e5219f28503 (patch)
treee0aaf1d5ce770b5f0a5494b3319b4aa00ea32bbb /src/common/samplerate.c
parent05402283dfd4da630c254cd1e3852ac3900abd3e (diff)
common code: Sample rate conversion now supports any rate above 8000 Hz
Diffstat (limited to 'src/common/samplerate.c')
-rw-r--r--src/common/samplerate.c93
1 files changed, 23 insertions, 70 deletions
diff --git a/src/common/samplerate.c b/src/common/samplerate.c
index 9f01bce..43b2fe7 100644
--- a/src/common/samplerate.c
+++ b/src/common/samplerate.c
@@ -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
}