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ggwave : add filter function

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Currently support the following filter:

- Hann window
- Hamming window
- First-order high-pass
This commit is contained in:
Georgi Gerganov
2022-07-12 22:31:15 +03:00
parent 1341b3d80e
commit 0ab93dfad3
2 changed files with 117 additions and 12 deletions
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43
include/ggwave/ggwave.h
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@@ -72,6 +72,12 @@ extern "C" {
GGWAVE_PROTOCOL_COUNT,
} ggwave_ProtocolId;
typedef enum {
GGWAVE_FILTER_HANN,
GGWAVE_FILTER_HAMMING,
GGWAVE_FILTER_FIRST_ORDER_HIGH_PASS,
} ggwave_Filter;
// Operating modes of ggwave
//
// GGWAVE_OPERATING_MODE_RX:
@@ -770,14 +776,41 @@ public:
//
// src - input real-valued data, size is N
// dst - output complex-valued data, size is 2*N
// ip - work buffer, with size 2*N
// w - work buffer, with size 3 + sqrt(N/2)
// wi - work buffer, with size 2*N
// wf - work buffer, with size 3 + sqrt(N/2)
//
// First time calling thid function, make sure that ip[0] == 0
// This will initialize some internal coefficients and store them in ip and w for
// First time calling this function, make sure that wi[0] == 0
// This will initialize some internal coefficients and store them in wi and wf for
// future usage.
//
static bool computeFFTR(const float * src, float * dst, int N, int * ip, float * w);
// If wi == nullptr - returns the needed size for wi
// If wi != nullptr and wf == nullptr - returns the needed size for wf
// If wi != nullptr and wf != nullptr - returns 1 on success, 0 on failure
//
static int computeFFTR(const float * src, float * dst, int N, int * wi, float * wf);
// Filter the waveform
//
// filter - filter to use
// waveform - input waveform, size is N
// N - number of samples in the waveform
// p0 - parameter
// p1 - parameter
// w - work buffer
//
// Filter is applied in-place.
// First time calling this function, make sure that w[0] == 0 and w[1] == 0
// This will initialize some internal coefficients and store them in w for
// future usage.
//
// For GGWAVE_FILTER_FIRST_ORDER_HIGH_PASS:
// - p0 = cutoff frequency in Hz
// - p1 = sample rate in Hz
//
// If w == nullptr - returns the needed size for w for the specified filter
// If w != nullptr - returns 1 on success, 0 on failure
//
static int filter(ggwave_Filter filter, float * waveform, int N, float p0, float p1, float * w);
// Resample audio waveforms from one sample rate to another using sinc interpolation
class Resampler {