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authorAndreas Eversberg <jolly@eversberg.eu>2016-04-24 07:09:25 +0200
committerAndreas Eversberg <jolly@eversberg.eu>2016-04-24 15:18:59 +0200
commit4b3e3385b5d7e4017e699a6fe399db2bcae064cf (patch)
treeac068acb2a92d160aa5a65c5c800579122949b0a /src/common/samplerate.c
parent4356c93afa77734ce880651a2b0333378267e165 (diff)
common code: Fix sample rate conversion
Diffstat (limited to 'src/common/samplerate.c')
-rw-r--r--src/common/samplerate.c68
1 files changed, 49 insertions, 19 deletions
diff --git a/src/common/samplerate.c b/src/common/samplerate.c
index 43b2fe7..630ba5d 100644
--- a/src/common/samplerate.c
+++ b/src/common/samplerate.c
@@ -46,9 +46,9 @@ int init_samplerate(samplerate_t *state, double samplerate)
/* convert input sample rate to 8000 Hz */
int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output)
{
- int output_num, i;
- double factor = state->factor, step;
- double spl[input_num + 10]; /* add some safety */
+ int output_num = 0, i, idx;
+ double factor = state->factor, in_index;
+ double spl[input_num];
int32_t value;
/* convert samples to double */
@@ -57,21 +57,36 @@ 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 = (int)((double)input_num / factor);
/* resample filtered result */
- for (i = 0, step = 0.5 / (double)output_num; i < output_num; i++, step += factor) {
- value = spl[(int)step] * 32768.0;
+ in_index = state->down.in_index;
+
+ for (i = 0; ; i++) {
+ /* convert index to int */
+ idx = (int)in_index;
+ /* if index is outside input sample range, we are done */
+ if (idx >= input_num)
+ break;
+ /* copy value from input to output */
+ value = spl[idx] * 32768.0;
if (value < -32768)
value = -32768;
else if (value > 32767)
value = 32767;
*output++ = value;
+ /* count output number */
+ output_num++;
+ /* increment input index */
+ in_index += factor;
}
- 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();
- }
+
+ /* remove number of input samples from index */
+ in_index -= (double)input_num;
+ /* in_index cannot be negative, excpet due to rounding error, so... */
+ if ((int)in_index < 0)
+ in_index = 0.0;
+
+ state->down.in_index = in_index;
return output_num;
}
@@ -79,21 +94,36 @@ int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, in
/* convert 8000 Hz sample rate to output sample rate */
int samplerate_upsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output)
{
- int output_num, i;
- double factor = 1.0 / state->factor, step;
+ int output_num = 0, i, idx;
+ double factor = 1.0 / state->factor, in_index;
double spl[(int)((double)input_num / factor + 0.5) + 10]; /* add some fafety */
int32_t value;
- output_num = (int)((double)input_num / factor + 0.5);
-
/* resample input */
- 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();
+ in_index = state->up.in_index;
+
+ for (i = 0; ; i++) {
+ /* convert index to int */
+ idx = (int)in_index;
+ /* if index is outside input sample range, we are done */
+ if (idx >= input_num)
+ break;
+ /* copy value */
+ spl[i] = input[idx] / 32768.0;
+ /* count output number */
+ output_num++;
+ /* increment input index */
+ in_index += factor;
}
+ /* remove number of input samples from index */
+ in_index -= (double)input_num;
+ /* in_index cannot be negative, excpet due to rounding error, so... */
+ if ((int)in_index < 0)
+ in_index = 0.0;
+
+ state->up.in_index = in_index;
+
/* filter up */
biquad_process(&state->up.bq, spl, output_num, 1);