Pwelch

The Welch method estimates the power spectral density of a modified periodogram. It windows data, calculates the power spectral density of the data in the windows, and then averages the obtained values.

The function interface declaration is as follows:

HmppResult HMPPS_Pwelch_32f(const float* src, const float* window, float* dst, int32_t len, double overLap, int32_t nfft, int32_t windowLen);

HmppResult HMPPS_Pwelch_64f(const double* src, const double* window, double* dst, int32_t len, double overLap, int32_t nfft, int32_t windowLen);

HmppResult HMPPS_Pwelch_32fc(const Hmpp32fc* src, const float* window, float* dst, int32_t len, double overLap, int32_t nfft, int32_t windowLen);

HmppResult HMPPS_Pwelch_64fc(const Hmpp64fc* src, const double* window, double* dst, int32_t len, double overLap, int32_t nfft, int32_t windowLen);

Parameters

Parameter	Description	Value Range	Input/Output
src	Pointer to the array that stores the source signal vector	The value cannot be NULL.	Input
window	Pointer to the array that stores the window vector	This parameter can be NULL. If this parameter is left empty, the default value is 1. The length is windowLen.	Input
dst	Estimated array of power spectral density	The value cannot be NULL.	Output
overlap	Ratio of the overlapping part between two adjacent segments to the window length	(0, 0.95]	Input
nfft	Number of FFT points	The value is within the range [INT_MIN, windowLen]. If the value is less than 0, the default value of windowLen is used.	Input
len	Length of the source signal vector	(0, INT_MAX]	Input
windowLen	Length of the window vector	(0, len]	Input

Return Value

Success: HMPP_STS_NO_ERR
Failure: An error code is returned.

Error Codes

Error Code	Description
HMPP_STS_NULL_PTR_ERR	The value of src or dst is NULL.
HMPP_STS_SIZE_ERR	The value of len is less than or equal to 0.
HMPP_SYS_MALLOC_FAILED	The malloc function fails to be executed.

Example

#define  BUFFER_SIZE_T 5
#define  NFFT 2
#define  WINDOWLEN 2
#define  OVERLAP 0.5
void PwelchExample()
{
    float src[BUFFER_SIZE_T] = {1, 2.5, 3.3, 1, 5};
    float window[2] = {1,1};
    float dst[BUFFER_SIZE_T];
    HMPPS_Zero_32f(dst, BUFFER_SIZE_T); //Initialize all elements of dst to 0.
    HmppResult result = HMPPS_Pwelch_32f(src, window, dst, BUFFER_SIZE_T, OVERLAP, WINDOWLEN, NFFT);
    if (result == HMPP_STS_NO_ERR) {
        printf("dst = ");
        for (int32_t i = 0; i < (NFFT + 1) / 2; i++) {
            printf("%.2f ", dst[i]);
        }
        printf("\n");
    }
}

Output:

dst = 0.97 0.18

Parent topic: Basic and Common Calculations