A Simple and Efficient Audio Resampler Implementation in C.
uint64_t Resample_f32(const float *input, float *output, int inSampleRate, int outSampleRate, uint64_t inputSize,
uint32_t channels
) {
if (input == NULL)
return 0;
uint64_t outputSize = inputSize * outSampleRate / inSampleRate;
if (output == NULL)
return outputSize;
double stepDist = ((double) inSampleRate / (double) outSampleRate);
const uint64_t fixedFraction = (1LL << 32);
const double normFixed = (1.0 / (1LL << 32));
uint64_t step = ((uint64_t) (stepDist * fixedFraction + 0.5));
uint64_t curOffset = 0;
for (uint32_t i = 0; i < outputSize; i += 1) {
for (uint32_t c = 0; c < channels; c += 1) {
*output++ = (float) (input[c] + (input[c + channels] - input[c]) * (
(double) (curOffset >> 32) + ((curOffset & (fixedFraction - 1)) * normFixed)
)
);
}
curOffset += step;
input += (curOffset >> 32) * channels;
curOffset &= (fixedFraction - 1);
}
return outputSize;
}
uint64_t Resample_s16(const int16_t *input, int16_t *output, int inSampleRate, int outSampleRate, uint64_t inputSize,
uint32_t channels
) {
if (input == NULL)
return 0;
uint64_t outputSize = inputSize * outSampleRate / inSampleRate;
if (output == NULL)
return outputSize;
double stepDist = ((double) inSampleRate / (double) outSampleRate);
const uint64_t fixedFraction = (1LL << 32);
const double normFixed = (1.0 / (1LL << 32));
uint64_t step = ((uint64_t) (stepDist * fixedFraction + 0.5));
uint64_t curOffset = 0;
for (uint32_t i = 0; i < outputSize; i += 1) {
for (uint32_t c = 0; c < channels; c += 1) {
*output++ = (int16_t) (input[c] + (input[c + channels] - input[c]) * (
(double) (curOffset >> 32) + ((curOffset & (fixedFraction - 1)) * normFixed)
)
);
}
curOffset += step;
input += (curOffset >> 32) * channels;
curOffset &= (fixedFraction - 1);
}
return outputSize;
}
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