common code: Fix sample rate conversion
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@ -46,9 +46,9 @@ int init_samplerate(samplerate_t *state, double samplerate)
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/* convert input sample rate to 8000 Hz */
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int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output)
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{
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int output_num, i;
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double factor = state->factor, step;
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double spl[input_num + 10]; /* add some safety */
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int output_num = 0, i, idx;
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double factor = state->factor, in_index;
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double spl[input_num];
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int32_t value;
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/* convert samples to double */
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@ -57,21 +57,36 @@ int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, in
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/* filter down */
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biquad_process(&state->down.bq, spl, input_num, 1);
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output_num = (int)((double)input_num / factor);
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/* resample filtered result */
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for (i = 0, step = 0.5 / (double)output_num; i < output_num; i++, step += factor) {
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value = spl[(int)step] * 32768.0;
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in_index = state->down.in_index;
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for (i = 0; ; i++) {
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/* convert index to int */
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idx = (int)in_index;
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/* if index is outside input sample range, we are done */
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if (idx >= input_num)
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break;
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/* copy value from input to output */
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value = spl[idx] * 32768.0;
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if (value < -32768)
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value = -32768;
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else if (value > 32767)
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value = 32767;
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*output++ = value;
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/* count output number */
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output_num++;
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/* increment input index */
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in_index += factor;
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}
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if ((int)(step - factor) >= input_num) {
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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);
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abort();
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}
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/* remove number of input samples from index */
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in_index -= (double)input_num;
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/* in_index cannot be negative, excpet due to rounding error, so... */
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if ((int)in_index < 0)
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in_index = 0.0;
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state->down.in_index = in_index;
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return output_num;
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}
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@ -79,21 +94,36 @@ int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, in
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/* convert 8000 Hz sample rate to output sample rate */
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int samplerate_upsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output)
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{
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int output_num, i;
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double factor = 1.0 / state->factor, step;
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int output_num = 0, i, idx;
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double factor = 1.0 / state->factor, in_index;
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double spl[(int)((double)input_num / factor + 0.5) + 10]; /* add some fafety */
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int32_t value;
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output_num = (int)((double)input_num / factor + 0.5);
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/* resample input */
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for (i = 0, step = 0.5 / (double)output_num; i < output_num; i++, step += factor)
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spl[i] = input[(int)step] / 32768.0;
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if ((int)(step - factor) >= input_num) {
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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);
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abort();
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in_index = state->up.in_index;
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for (i = 0; ; i++) {
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/* convert index to int */
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idx = (int)in_index;
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/* if index is outside input sample range, we are done */
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if (idx >= input_num)
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break;
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/* copy value */
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spl[i] = input[idx] / 32768.0;
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/* count output number */
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output_num++;
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/* increment input index */
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in_index += factor;
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}
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/* remove number of input samples from index */
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in_index -= (double)input_num;
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/* in_index cannot be negative, excpet due to rounding error, so... */
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if ((int)in_index < 0)
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in_index = 0.0;
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state->up.in_index = in_index;
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/* filter up */
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biquad_process(&state->up.bq, spl, output_num, 1);
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@ -3,13 +3,12 @@
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typedef struct samplerate {
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double factor;
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struct {
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double sum;
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double sum_count;
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biquad_low_pass_t bq;
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double in_index;
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} down;
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struct {
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double last_sample;
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biquad_low_pass_t bq;
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double in_index;
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} up;
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} samplerate_t;
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