66 lines
1.9 KiB
C++
66 lines
1.9 KiB
C++
#ifndef _RESAMPLER_H_
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#define _RESAMPLER_H_
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class Resampler {
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public:
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/* Constructor for rational sample rate conversion
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* @param p numerator of resampling ratio
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* @param q denominator of resampling ratio
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* @param filt_len length of each polyphase subfilter
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*/
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Resampler(size_t p, size_t q, size_t filt_len = 16);
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~Resampler();
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/* Initilize resampler filterbank.
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* @param bw bandwidth factor on filter generation (pre-window)
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* @return false on error, zero otherwise
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*
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* Automatic setting is to compute the filter to prevent aliasing with
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* a Blackman-Harris window. Adjustment is made through a bandwith
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* factor to shift the cutoff and/or the constituent filter lengths.
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* Calculation of specific rolloff factors or 3-dB cutoff points is
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* left as an excersize for the reader.
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*/
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bool init(int type = FILTER_TYPE_SINC, float bw = 1.0f);
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/* Rotate "commutator" and drive samples through filterbank
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* @param in continuous buffer of input complex float values
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* @param in_len input buffer length
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* @param out continuous buffer of output complex float values
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* @param out_len output buffer length
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* @return number of samples outputted, negative on error
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*
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* Input and output vector lengths must of be equal multiples of the
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* rational conversion rate denominator and numerator respectively.
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*/
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int rotate(float *in, size_t in_len, float *out, size_t out_len);
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/* Get filter length
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* @return number of taps in each filter partition
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*/
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size_t len();
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enum {
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FILTER_TYPE_SINC,
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FILTER_TYPE_RRC,
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};
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private:
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size_t p;
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size_t q;
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size_t filt_len;
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size_t path_len;
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size_t *in_index;
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size_t *out_path;
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float **partitions;
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float *history;
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bool initFilters(int type, float bw);
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void releaseFilters();
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bool computePaths(int len);
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bool checkLen(size_t in_len, size_t out_len);
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};
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#endif /* _RESAMPLER_H_ */
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